Vitamin C

Evidence-based effects and studies

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Effects
2206
Total evidences
2667

Effects and Evidences

Detailed analysis of research findings

melanin index (skin lightness)

1 evidences

In 50 middle-aged Thai women, nightly topical serum containing 20% vitamin C (plus vitamin E and raspberry extract) applied to one side of the face for 8 weeks improved skin lightness, elasticity and radiance versus the untreated side and was well tolerated.

Trust comment: Split-face randomized trial with objective instrument measures and clear effects, moderate sample size (50) though single-blinded and combined-actives limit isolation of vitamin C alone.

Study Details

PMID:31975502
Participants:50
Impact:-7.7% melanin index at 8 weeks (treated side vs baseline; treated: 226.7 → 209.3)
Trust score:4/5

skin elasticity (R2 ratio)

1 evidences

In 50 middle-aged Thai women, nightly topical serum containing 20% vitamin C (plus vitamin E and raspberry extract) applied to one side of the face for 8 weeks improved skin lightness, elasticity and radiance versus the untreated side and was well tolerated.

Trust comment: Split-face randomized trial with objective instrument measures and clear effects, moderate sample size (50) though single-blinded and combined-actives limit isolation of vitamin C alone.

Study Details

PMID:31975502
Participants:50
Impact:+14% R2 (elasticity) at 8 weeks (treated side: 0.63 → 0.72)
Trust score:4/5

skin radiance (gloss DSC)

1 evidences

In 50 middle-aged Thai women, nightly topical serum containing 20% vitamin C (plus vitamin E and raspberry extract) applied to one side of the face for 8 weeks improved skin lightness, elasticity and radiance versus the untreated side and was well tolerated.

Trust comment: Split-face randomized trial with objective instrument measures and clear effects, moderate sample size (50) though single-blinded and combined-actives limit isolation of vitamin C alone.

Study Details

PMID:31975502
Participants:50
Impact:+24% gloss DSC (radiance) at 8 weeks (treated: 4.09 → 5.08)
Trust score:4/5

hemoglobin increase

3 evidences

In 440 adults with iron-deficiency anemia, adding oral vitamin C (200 mg every 8 hours) to standard oral iron did not improve hemoglobin recovery or iron stores compared with iron alone over 8 weeks (equivalence trial).

Trust comment: Large, randomized, controlled equivalence trial (n=440) with predefined margins and objective lab outcomes, high internal validity.

Study Details

PMID:33136134
Participants:440
Impact:No meaningful difference; 2-week change: +2.00 g/dL (vitamin C+iron) vs +1.84 g/dL (iron only); between-group difference 0.16 g/dL (within equivalence margin)
Trust score:5/5

Ferrous ascorbate raised hemoglobin and cured more children of anemia than colloidal iron over 12 weeks.

Trust comment: Randomized trial in children with a clear primary outcome (Hb) and significant results, moderate sample size.

Study Details

PMID:23180405
Participants:73
Impact:+3.59 ± 1.67 g/dl (ferrous ascorbate) vs +2.43 ± 1.73 g/dl (colloidal iron) at 12 wk
Trust score:4/5

In children with iron‑deficiency anemia, ferrous ascorbate produced larger and faster improvements in hemoglobin and other hematologic indices over 3 months compared with iron polymaltose complex.

Trust comment: Randomized controlled trial with a substantial sample (N=125) and consistent, statistically significant hematologic improvements favoring ferrous ascorbate.

Study Details

PMID:31520309
Participants:125
Impact:FA: +3.13 g/dL at 1 mo vs IPC: +2.00 g/dL (P=0.017); at 3 mo FA +4.88 vs IPC +3.33 (P=0.001)
Trust score:4/5

serum ferritin (iron stores)

2 evidences

An intensive dietary program that increased vitamin C intake (among other changes) improved iron intake and produced modest increases in iron stores compared with placebo, while iron supplementation produced larger increases.

Trust comment: Randomized controlled 16‑week intervention with objective iron outcomes, but vitamin C was part of a multi-component dietary change so effects are indirect.

Study Details

PMID:11601562
Participants:75
Impact:increased 59% in Supplement group (p=0.001) and 26% in Diet group (p=0.068) vs placebo
Trust score:3/5

In 440 adults with iron-deficiency anemia, adding oral vitamin C (200 mg every 8 hours) to standard oral iron did not improve hemoglobin recovery or iron stores compared with iron alone over 8 weeks (equivalence trial).

Trust comment: Large, randomized, controlled equivalence trial (n=440) with predefined margins and objective lab outcomes, high internal validity.

Study Details

PMID:33136134
Participants:440
Impact:No significant difference at 8 weeks; change ~35.75 vs 34.48 ng/mL (between-group diff 1.27 ng/mL)
Trust score:5/5

transferrin saturation / TIBC

1 evidences

In 440 adults with iron-deficiency anemia, adding oral vitamin C (200 mg every 8 hours) to standard oral iron did not improve hemoglobin recovery or iron stores compared with iron alone over 8 weeks (equivalence trial).

Trust comment: Large, randomized, controlled equivalence trial (n=440) with predefined margins and objective lab outcomes, high internal validity.

Study Details

PMID:33136134
Participants:440
Impact:No clinically important improvement with vitamin C (parameters comparable between groups at wk 8)
Trust score:5/5

dermis density

1 evidences

16‑week randomized double‑blind trial (90 enrolled, 87 completed) in women: 5 g/day collagen (± HA + vit C) increased dermal density and reduced roughness and wrinkle severity versus placebo.

Trust comment: Randomized, double-blind, placebo-controlled trial with objective measurements and good completion rate (87/90), moderate sample size.

Study Details

PMID:38931263
Participants:87
Impact:+16.3% dermis density at 16 weeks (CP group vs placebo)
Trust score:4/5

skin roughness (Ra)

1 evidences

16‑week randomized double‑blind trial (90 enrolled, 87 completed) in women: 5 g/day collagen (± HA + vit C) increased dermal density and reduced roughness and wrinkle severity versus placebo.

Trust comment: Randomized, double-blind, placebo-controlled trial with objective measurements and good completion rate (87/90), moderate sample size.

Study Details

PMID:38931263
Participants:87
Impact:-9.6% roughness at 16 weeks (CP group vs placebo)
Trust score:4/5

wrinkle volume

1 evidences

16‑week randomized double‑blind trial (90 enrolled, 87 completed) in women: 5 g/day collagen (± HA + vit C) increased dermal density and reduced roughness and wrinkle severity versus placebo.

Trust comment: Randomized, double-blind, placebo-controlled trial with objective measurements and good completion rate (87/90), moderate sample size.

Study Details

PMID:38931263
Participants:87
Impact:-13.8% wrinkle volume at 16 weeks (CP group vs placebo)
Trust score:4/5

serum vitamin C concentration

4 evidences

In autologous SCT patients, vitamin C supplementation raised serum vitamin C but did not shorten time to neutrophil recovery; transient higher cytotoxic T cells and a lower (non-significant) bacteremia rate were observed.

Trust comment: Well-designed triple-blind randomized trial (44 patients) with appropriate endpoints; limited size reduces power for some clinical outcomes.

Study Details

PMID:36432471
Participants:44
Impact:significantly higher at multiple time points in vitamin C group (expected pharmacokinetic effect)
Trust score:4/5

Randomized double-blind trial of vitamin C (1000 mg/day) vs placebo in young adults with low vitamin C; not a vitamin D study — included here for completeness but does not test vitamin D.

Trust comment: Double-blind, placebo-controlled RCT in vitamin C–insufficient young adults (n=50, 46 analyzed) with objective and subjective cognitive endpoints, moderate sample size.

Study Details

PMID:34476568
Participants:46
Impact:Mean increase Δ = +45.17 ± 18.90 μmol/L after 4 weeks (vitamin C group)
Trust score:4/5

Patients with acute pancreatitis or colorectal cancer had lower serum vitamin C than healthy controls; antioxidant depletion accompanied increased oxidative stress markers.

Trust comment: Prospective descriptive clinical study with small groups; measurements appear reliable but limited sample size reduces generalizability.

Study Details

PMID:15723737
Participants:52
Impact:decreased in acute pancreatitis and colorectal cancer patients vs healthy controls (P<0.05)
Trust score:3/5

Five-year randomized supplementation (50 vs 500 mg/day) showing larger increases in serum vitamin C with high-dose without changing dietary intake.

Trust comment: Large, long-term randomized trial with clear biochemical outcomes though some dropouts and early termination of beta-carotene arm.

Study Details

PMID:12805247
Participants:244
Impact:High-dose (500 mg/day) ↑38.5% (95% CI 27.0–49.9) vs low-dose (50 mg/day) ↑13.0% (95% CI 5.1–20.9) after 5 years
Trust score:4/5

attention (subjective score)

1 evidences

Randomized double-blind trial of vitamin C (1000 mg/day) vs placebo in young adults with low vitamin C; not a vitamin D study — included here for completeness but does not test vitamin D.

Trust comment: Double-blind, placebo-controlled RCT in vitamin C–insufficient young adults (n=50, 46 analyzed) with objective and subjective cognitive endpoints, moderate sample size.

Study Details

PMID:34476568
Participants:46
Impact:+1.9 points attention score change (vitamin C group baseline 7.1 → 9.0) vs +0.3 in placebo; between-group p=0.03
Trust score:4/5

cognitive processing speed (Stroop reaction time)

1 evidences

Randomized double-blind trial of vitamin C (1000 mg/day) vs placebo in young adults with low vitamin C; not a vitamin D study — included here for completeness but does not test vitamin D.

Trust comment: Double-blind, placebo-controlled RCT in vitamin C–insufficient young adults (n=50, 46 analyzed) with objective and subjective cognitive endpoints, moderate sample size.

Study Details

PMID:34476568
Participants:46
Impact:Shorter reaction time on incongruent Stroop task (vitamin C vs placebo; p=0.04)
Trust score:4/5

rate of force development (RFD)

1 evidences

In 50 male athletes over 3 weeks of strength training, daily hydrolysed collagen (20 g) plus 50 mg vitamin C restored rate of force development (RFD) to baseline by study end versus continued depression in the placebo group and improved some eccentric jump metrics.

Trust comment: Double-blind, parallel trial in athletes with objective performance measures but short duration (3 weeks) and sport-specific population limits broader applicability.

Study Details

PMID:34808597
Participants:50
Impact:RFD recovered to baseline by Test 3 in HC+C group (between-group improvement at Test 3, p = 0.036)
Trust score:3/5

eccentric deceleration impulse / RFD (countermovement jump)

1 evidences

In 50 male athletes over 3 weeks of strength training, daily hydrolysed collagen (20 g) plus 50 mg vitamin C restored rate of force development (RFD) to baseline by study end versus continued depression in the placebo group and improved some eccentric jump metrics.

Trust comment: Double-blind, parallel trial in athletes with objective performance measures but short duration (3 weeks) and sport-specific population limits broader applicability.

Study Details

PMID:34808597
Participants:50
Impact:Improved eccentric deceleration impulse (p = 0.008) and eccentric deceleration RFD (p = 0.04) in HC+C group
Trust score:3/5

swallowing function (WST)

1 evidences

Among 120 stroke patients with dysphagia, vitamin C stimulation improved swallowing, nutrition markers, and immune markers versus routine care.

Trust comment: Single-center randomized prospective study with clear outcomes but limited detail on blinding and effect sizes.

Study Details

PMID:35362717
Participants:120
Impact:decreased (improved) — significant
Trust score:3/5

swallowing function (VFSS) score

1 evidences

Among 120 stroke patients with dysphagia, vitamin C stimulation improved swallowing, nutrition markers, and immune markers versus routine care.

Trust comment: Single-center randomized prospective study with clear outcomes but limited detail on blinding and effect sizes.

Study Details

PMID:35362717
Participants:120
Impact:increased — significant
Trust score:3/5

nutritional and immune markers (hemoglobin, albumin, total protein, IgA/IgM/IgG)

1 evidences

Among 120 stroke patients with dysphagia, vitamin C stimulation improved swallowing, nutrition markers, and immune markers versus routine care.

Trust comment: Single-center randomized prospective study with clear outcomes but limited detail on blinding and effect sizes.

Study Details

PMID:35362717
Participants:120
Impact:increased — significant
Trust score:3/5

time alive and vasopressor-free (day 7)

1 evidences

In a multicenter RCT of septic shock patients, adding IV vitamin C (with hydrocortisone and thiamine) did not speed resolution of shock versus hydrocortisone alone.

Trust comment: Large, multicenter, randomized clinical trial with prespecified outcomes and robust methodology.

Study Details

PMID:31950979
Participants:211
Impact:median difference −0.6 hours (95% CI −8.3 to 7.2); not significant (P=0.83)
Trust score:5/5

90-day mortality

2 evidences

In a multicenter RCT of septic shock patients, adding IV vitamin C (with hydrocortisone and thiamine) did not speed resolution of shock versus hydrocortisone alone.

Trust comment: Large, multicenter, randomized clinical trial with prespecified outcomes and robust methodology.

Study Details

PMID:31950979
Participants:211
Impact:intervention 28.6% vs control 24.5% (HR 1.18; 95% CI 0.69–2.00); not significant
Trust score:5/5

Early combined hydrocortisone, high-dose IV vitamin C, and thiamine did not reduce 90-day or 28-day mortality or improve shock reversal in septic shock patients.

Trust comment: Large, randomized, double-blind trial with robust design and low loss to follow-up; found no mortality or clinically meaningful benefit.

Study Details

PMID:36171582
Participants:408
Impact:No significant change (40.4% vs 39.0%; p=0.77)
Trust score:5/5

systolic blood pressure (SBP)

1 evidences

One week of 2 g/day vitamin C in healthy young adults reduced inflammatory markers and modestly lowered blood pressure and improved antioxidant enzyme activity under high PM exposure.

Trust comment: Randomized double-blind crossover with biomarker and BP measures; short intervention (1 week) limits inference on long-term effects.

Study Details

PMID:35689890
Participants:58
Impact:−3.37% (significant)
Trust score:4/5

plasma Cmax

1 evidences

In a randomized, double-blind crossover study (n=27) a single 500 mg dose of liposomal vitamin C produced higher plasma and leukocyte vitamin C levels than standard vitamin C or placebo.

Trust comment: Randomized, double-blind, placebo-controlled crossover with intensive pharmacokinetic sampling but small sample size (n=27).

Study Details

PMID:39237620
Participants:27
Impact:LV-VIT C 8610 ng/mL vs VIT C 6271 ng/mL and PLA 379 ng/mL; LV vs VIT +27% (LV vs PLA +2174%) — significant
Trust score:4/5

plasma AUC0–24

1 evidences

In a randomized, double-blind crossover study (n=27) a single 500 mg dose of liposomal vitamin C produced higher plasma and leukocyte vitamin C levels than standard vitamin C or placebo.

Trust comment: Randomized, double-blind, placebo-controlled crossover with intensive pharmacokinetic sampling but small sample size (n=27).

Study Details

PMID:39237620
Participants:27
Impact:LV 72,358 ng·h/mL vs VIT 57,152 vs PLA 4,242; LV vs VIT +21% — significant
Trust score:4/5

leukocyte Cmax / AUC0–24

1 evidences

In a randomized, double-blind crossover study (n=27) a single 500 mg dose of liposomal vitamin C produced higher plasma and leukocyte vitamin C levels than standard vitamin C or placebo.

Trust comment: Randomized, double-blind, placebo-controlled crossover with intensive pharmacokinetic sampling but small sample size (n=27).

Study Details

PMID:39237620
Participants:27
Impact:leukocyte Cmax LV 6,369 ng/mL vs VIT 5,088 vs PLA 315; leukocyte AUC LV 53,277 vs VIT 48,922 vs PLA 3,439; LV vs VIT ≈+20% — significant
Trust score:4/5

malondialdehyde (MDA)

13 evidences

In iron-deficient non-anemic girls, iron therapy with or without added vitamin C improved oxidative stress markers; adding vitamin C did not further change TAC or MDA but raised serum vitamin C levels more.

Trust comment: Double-blind randomized controlled trial with 60 participants; biochemical endpoints well measured though modest sample size.

Study Details

PMID:23686563
Participants:60
Impact:decrease from baseline in both groups (P time <0.001); no additional effect of vitamin C vs iron alone
Trust score:4/5

In this pilot RCT of postmenopausal women with insulin resistance (n=42 completers), vitamin C alone or combined with resveratrol reduced oxidative stress markers and increased total antioxidant capacity but did not change insulin resistance.

Trust comment: Randomized, double-blind pilot with objective biochemical endpoints but small sample and limited power to compare groups.

Study Details

PMID:39519608
Participants:42
Impact:decrease: vitamin C group −38%; resveratrol + vitamin C −32%; resveratrol alone −26% (intra-group significant)
Trust score:3/5

Vitamin C (1000 mg/day) reduced lipid peroxidation markers and increased some antioxidant enzymes and certain hematological parameters in power plant workers.

Trust comment: Double‑blind randomized trial with objective biochemical measures but small per‑arm sample sizes and some inconsistent reporting.

Study Details

PMID:32191586
Participants:91
Impact:-significant decrease (vitamin C group)
Trust score:3/5

In hyperlipidemic patients, 500 mg vitamin C daily for 10 weeks increased blood vitamin C and was associated with reductions in total cholesterol, apo-B, and MDA versus baseline.

Trust comment: Randomized placebo-controlled trial but small total sample and short duration and multiple arms reduce per-group power.

Study Details

PMID:12847992
Participants:68
Impact:decrease vs baseline (P=0.015)
Trust score:3/5

Two-week vitamin C+E supplementation increased plasma vitamins and reduced exercise-induced protein oxidation in trained adults.

Trust comment: Randomized, controlled supplementation trial with repeated measures and objective biomarkers; moderate quality though group sizes modest.

Study Details

PMID:16775552
Participants:48
Impact:no change
Trust score:4/5

A 12-week trial of combined antioxidants including vitamin C (100 mg/day) reduced oxidative damage markers and prevented micronucleus increases versus placebo, with effects influenced by folate status.

Trust comment: Randomized trial but vitamin C was given as part of a multinutrient antioxidant combination, so effects cannot be attributed to vitamin C alone.

Study Details

PMID:15548759
Participants:86
Impact:decreased in supplemented myocardial infarction survivors (P = 0.001)
Trust score:3/5

Daily vitamin C (1000 mg) plus vitamin E (800 IU) for 8 weeks reduced oxidative stress markers and improved pain scores in women with endometriosis versus placebo.

Trust comment: Triple-blind randomized placebo-controlled trial with moderate sample size (n=60); baseline imbalance in some markers was addressed by ANCOVA.

Study Details

PMID:34122682
Participants:60
Impact:decrease with vitamin C+E vs placebo (ANCOVA adjusted, P=0.002)
Trust score:4/5

In zinc-deficient hemodialysis patients, three months of zinc supplementation increased serum zinc, improved red blood cell osmotic fragility and reduced lipid peroxidation (MDA), but some side effects occurred with zinc.

Trust comment: Randomized study with clear biochemical outcomes but small, specific (zinc-deficient) population limits generalizability.

Study Details

PMID:11979503
Participants:34
Impact:decreased
Trust score:3/5

Radioiodine therapy increased oxidative stress markers; vitamin C given before therapy reduced some oxidative enzyme responses versus control.

Trust comment: Small randomized patient groups (n=58) with biomarker endpoints; human but moderate sample and limited detail on randomization/blinding.

Study Details

PMID:29860661
Participants:58
Impact:significant increase after RAIT in all groups (vitamin C did not prevent the increase)
Trust score:3/5

In HNC patients on cisplatin, the control group given vitamins C+E showed increases in SOD and decreases in MDA, but astaxanthin produced larger MDA reductions.

Trust comment: Small double-blind randomized trial with clear pre/post biochemical measures, but small sample (n=42) and comparison was against astaxanthin rather than placebo.

Study Details

PMID:39487992
Participants:42
Impact:decrease in vit C+E group: Δ -51.6 pg/mL (pre→post), pre vs post p=0.028 (astaxanthin produced a larger decrease)
Trust score:3/5

Vitamin A+C given for 1 month produced mixed effects on oxidative-stress markers: some markers improved in HIV-only patients but worsened or did not improve in HIV-TB co-infected patients.

Trust comment: Moderate-quality non-blinded clinical supplementation study with short duration and mixed/contradictory biomarker results.

Study Details

PMID:29062324
Participants:90
Impact:↓ with supplementation in HIV mono-infected vs no-supplement; ↑ after supplementation in HIV/TB co-infected vs baseline
Trust score:3/5

Three months of community yoga lowered oxidative stress (MDA) and improved BMI, waist, systolic BP and fasting glucose but did not change vitamin C levels.

Trust comment: Small RCT with objective oxidative stress measures; vitamin C was measured as an antioxidant but showed no effect.

Study Details

PMID:24280463
Participants:29
Impact:decrease — significant (p<0.001)
Trust score:3/5

A 4-month high-antioxidant diet (designed to raise vitamins A, C and E) increased plasma and leukocyte vitamin C, boosted antioxidant enzyme activities, and lowered lipid oxidative markers in women with endometriosis.

Trust comment: Randomized diet intervention with objective biochemical endpoints and moderate completion rates, but unblinded and with some dropouts.

Study Details

PMID:19476631
Participants:72
Impact:−20% (at 3 months)
Trust score:3/5

protein carbonylation

2 evidences

In this pilot RCT of postmenopausal women with insulin resistance (n=42 completers), vitamin C alone or combined with resveratrol reduced oxidative stress markers and increased total antioxidant capacity but did not change insulin resistance.

Trust comment: Randomized, double-blind pilot with objective biochemical endpoints but small sample and limited power to compare groups.

Study Details

PMID:39519608
Participants:42
Impact:decrease: resveratrol + vitamin C −39% (largest intra-group change)
Trust score:3/5

Patients given n‑3 PUFA plus antioxidant vitamins (including 1 g/day vitamin C) before and around cardiac surgery showed reduced oxidative stress and inflammation markers in atrial tissue and blood.

Trust comment: Clinical intervention in surgical patients with clear biochemical endpoints; reasonably powered (n=95) though trial design details (blinding/randomization) are not fully described.

Study Details

PMID:21138533
Participants:95
Impact:-24%
Trust score:4/5

total antioxidant capacity (TAC)

4 evidences

In iron-deficient non-anemic girls, iron therapy with or without added vitamin C improved oxidative stress markers; adding vitamin C did not further change TAC or MDA but raised serum vitamin C levels more.

Trust comment: Double-blind randomized controlled trial with 60 participants; biochemical endpoints well measured though modest sample size.

Study Details

PMID:23686563
Participants:60
Impact:increase from baseline in both groups (P time <0.001); no additional effect of vitamin C vs iron alone
Trust score:4/5

In patients with prior nonmelanoma skin cancer, 60 days of antioxidant supplementation including zinc produced modest reductions in oxidative stress biomarkers (notably 15-F2t-isoprostane) but differences versus placebo were not statistically significant.

Trust comment: Double-blind, randomized, placebo-controlled design but small sample and short (60-day) supplementation limit power to detect effects.

Study Details

PMID:26509174
Participants:60
Impact:-0.2 mmol/L (2.3 → 2.1 mmol/L; not significant)
Trust score:3/5

In this pilot RCT of postmenopausal women with insulin resistance (n=42 completers), vitamin C alone or combined with resveratrol reduced oxidative stress markers and increased total antioxidant capacity but did not change insulin resistance.

Trust comment: Randomized, double-blind pilot with objective biochemical endpoints but small sample and limited power to compare groups.

Study Details

PMID:39519608
Participants:42
Impact:increase: resveratrol + vitamin C +30%; vitamin C alone +28% (intra-group significant)
Trust score:3/5

Resistance training with whey increased some antioxidant markers (including vitamin C) and improved some lipid/HDL measures in overweight young men.

Trust comment: Small randomized study (n=30) with objective measures but limited sample size and short duration.

Study Details

PMID:22889987
Participants:30
Impact:increased (significant in RW group)
Trust score:3/5

umbilical vein Doppler velocity (Vmax)

1 evidences

In pregnant smokers randomized to 500 mg/day vitamin C (ancillary analyses of an RCT), umbilical vein blood flow measures were restored toward nonsmoker values and placental gene-expression changes associated with vascular development were partially normalized.

Trust comment: Nested, placebo-controlled RCT with Doppler and transcriptomic analyses and qPCR validation, though some analyses use subset samples and nominal p-values.

Study Details

PMID:39461975
Participants:88
Impact:placebo 23.49 cm/s vs nonsmokers 28.00; vitamin C 27.88 cm/s (restored to nonsmokers; p=0.04 vs placebo)
Trust score:4/5

umbilical vein volume blood flow (cQUV)

1 evidences

In pregnant smokers randomized to 500 mg/day vitamin C (ancillary analyses of an RCT), umbilical vein blood flow measures were restored toward nonsmoker values and placental gene-expression changes associated with vascular development were partially normalized.

Trust comment: Nested, placebo-controlled RCT with Doppler and transcriptomic analyses and qPCR validation, though some analyses use subset samples and nominal p-values.

Study Details

PMID:39461975
Participants:88
Impact:placebo 209.4 mL/min vs nonsmokers 254.9; vitamin C 249.2 mL/min (partially restored; p≈0.09 vs placebo)
Trust score:4/5

placental gene expression normalization

1 evidences

In pregnant smokers randomized to 500 mg/day vitamin C (ancillary analyses of an RCT), umbilical vein blood flow measures were restored toward nonsmoker values and placental gene-expression changes associated with vascular development were partially normalized.

Trust comment: Nested, placebo-controlled RCT with Doppler and transcriptomic analyses and qPCR validation, though some analyses use subset samples and nominal p-values.

Study Details

PMID:39461975
Participants:88
Impact:164 overlapping genes altered by smoking, 160/164 shifted ≥40% toward nonsmoker expression with vitamin C (nominal significance)
Trust score:4/5

inflammatory response profile (subtypes)

1 evidences

In a biomarker sub-study of the LOVIT sepsis trial (n=457 with plasma samples), three inflammatory subtypes were identified and no subtype showed clear benefit from IV vitamin C; treatment did not produce discernible anti-inflammatory effects.

Trust comment: Well-powered biomarker sub-study with blinded analyses nested in a randomized trial, but inference limited to available plasma subset.

Study Details

PMID:39774855
Participants:457
Impact:three subtypes identified: subtype-2 highest inflammation, subtype-3 lowest
Trust score:4/5

anti-inflammatory effect of vitamin C

1 evidences

In a biomarker sub-study of the LOVIT sepsis trial (n=457 with plasma samples), three inflammatory subtypes were identified and no subtype showed clear benefit from IV vitamin C; treatment did not produce discernible anti-inflammatory effects.

Trust comment: Well-powered biomarker sub-study with blinded analyses nested in a randomized trial, but inference limited to available plasma subset.

Study Details

PMID:39774855
Participants:457
Impact:no discernible anti-inflammatory effect in paired samples; effects related to time and hydrocortisone, not vitamin C
Trust score:4/5

treatment effect on clinical outcome by subtype

1 evidences

In a biomarker sub-study of the LOVIT sepsis trial (n=457 with plasma samples), three inflammatory subtypes were identified and no subtype showed clear benefit from IV vitamin C; treatment did not produce discernible anti-inflammatory effects.

Trust comment: Well-powered biomarker sub-study with blinded analyses nested in a randomized trial, but inference limited to available plasma subset.

Study Details

PMID:39774855
Participants:457
Impact:ORs (95% CI): subtype-1 1.04 (0.63–1.73); subtype-2 1.33 (0.53–3.36); subtype-3 1.95 (0.85–4.49); heterogeneity p=0.002 (no subgroup benefit)
Trust score:4/5

Plasma L-ascorbic acid AUC0-24

1 evidences

In 30 healthy adults, a 1000 mg vitamin C gummy and caplet produced similar blood absorption and were safe; caplet had a higher peak concentration and gummy had a slower time-to-peak.

Trust comment: Randomized, examiner-blind crossover in healthy adults with complete PK sampling; small sample but appropriate design.

Study Details

PMID:31747355
Participants:30
Impact:no significant difference
Trust score:4/5

Cmax (plasma peak)

1 evidences

In 30 healthy adults, a 1000 mg vitamin C gummy and caplet produced similar blood absorption and were safe; caplet had a higher peak concentration and gummy had a slower time-to-peak.

Trust comment: Randomized, examiner-blind crossover in healthy adults with complete PK sampling; small sample but appropriate design.

Study Details

PMID:31747355
Participants:30
Impact:caplet > gummy (significantly higher)
Trust score:4/5

Tmax (time to peak)

1 evidences

In 30 healthy adults, a 1000 mg vitamin C gummy and caplet produced similar blood absorption and were safe; caplet had a higher peak concentration and gummy had a slower time-to-peak.

Trust comment: Randomized, examiner-blind crossover in healthy adults with complete PK sampling; small sample but appropriate design.

Study Details

PMID:31747355
Participants:30
Impact:gummy longer (p=0.012)
Trust score:4/5

Plasma norepinephrine (96 h)

1 evidences

In 58 septic shock patients, intravenous vitamin C (high and low dose) increased norepinephrine concentrations and NE‑synthesis enzyme markers and reduced required exogenous norepinephrine dose, but did not significantly improve clinical scores or mortality.

Trust comment: Double-blind RCT with mechanistic biomarkers and clinical endpoints but single-center and modest sample size limits power for mortality/clinical outcomes.

Study Details

PMID:38608046
Participants:58
Impact:group A 318.72 ± 40.95 vs control 227.06 ± 43.17 ng/L (significantly higher)
Trust score:4/5

Exogenous norepinephrine dosage (96 h)

1 evidences

In 58 septic shock patients, intravenous vitamin C (high and low dose) increased norepinephrine concentrations and NE‑synthesis enzyme markers and reduced required exogenous norepinephrine dose, but did not significantly improve clinical scores or mortality.

Trust comment: Double-blind RCT with mechanistic biomarkers and clinical endpoints but single-center and modest sample size limits power for mortality/clinical outcomes.

Study Details

PMID:38608046
Participants:58
Impact:reduced in vitamin C groups (group A 0.11 ± 0.09 vs control 0.26 ± 0.11 μg/kg·min; P=0.038)
Trust score:4/5

Organ dysfunction / mortality

1 evidences

In 58 septic shock patients, intravenous vitamin C (high and low dose) increased norepinephrine concentrations and NE‑synthesis enzyme markers and reduced required exogenous norepinephrine dose, but did not significantly improve clinical scores or mortality.

Trust comment: Double-blind RCT with mechanistic biomarkers and clinical endpoints but single-center and modest sample size limits power for mortality/clinical outcomes.

Study Details

PMID:38608046
Participants:58
Impact:no significant improvement in APACHE/SOFA/MODS or 28-day mortality
Trust score:4/5

Total urine output (24 h)

1 evidences

In 30 septic shock patients, a single 60 g sodium ascorbate infusion markedly raised plasma ascorbate, increased cumulative urine output, decreased vasopressor requirements and SOFA score over time, but had small-sample safety signals (hypernatremia, possible hemolysis).

Trust comment: Well-blinded randomized pilot with physiological endpoints; small single-center study and protocol amendments limit generalizability.

Study Details

PMID:37828547
Participants:30
Impact:mean 2948 vs 2056 ml (difference 891 ml, p=0.051; cumulative UO over time significantly greater, p<0.001)
Trust score:4/5

Vasopressor requirement

1 evidences

In 30 septic shock patients, a single 60 g sodium ascorbate infusion markedly raised plasma ascorbate, increased cumulative urine output, decreased vasopressor requirements and SOFA score over time, but had small-sample safety signals (hypernatremia, possible hemolysis).

Trust comment: Well-blinded randomized pilot with physiological endpoints; small single-center study and protocol amendments limit generalizability.

Study Details

PMID:37828547
Participants:30
Impact:greater decrease over time with NaAscorbate (−0.04 μg/kg/min greater decrease; p<0.001)
Trust score:4/5

SOFA score over time

1 evidences

In 30 septic shock patients, a single 60 g sodium ascorbate infusion markedly raised plasma ascorbate, increased cumulative urine output, decreased vasopressor requirements and SOFA score over time, but had small-sample safety signals (hypernatremia, possible hemolysis).

Trust comment: Well-blinded randomized pilot with physiological endpoints; small single-center study and protocol amendments limit generalizability.

Study Details

PMID:37828547
Participants:30
Impact:greater decrease over first 72 h (p=0.042)
Trust score:4/5

SOFA score

2 evidences

In 83 sepsis patients randomized to standard care ± vitamin C, the vitamin C group had lower SOFA scores, reduced inflammatory and myocardial injury markers, and lower combined morbidity/mortality (9.52% vs 29.27%).

Trust comment: Randomized study with positive results but limited methods detail and unclear blinding/centering raises risk of bias.

Study Details

PMID:38401077
Participants:83
Impact:lower after treatment (P < .05)
Trust score:3/5

In sepsis patients, IV ascorbic acid combined with thiamine and hydrocortisone shortened time on vasopressors but did not change organ-failure scores or mortality.

Trust comment: Randomized, double-blind, placebo-controlled ICU RCT with moderate sample size and clinically relevant endpoints.

Study Details

PMID:32194058
Participants:137
Impact:no significant change (P = .17)
Trust score:4/5

Inflammatory markers (hs-CRP, TNF, HMGB1)

1 evidences

In 83 sepsis patients randomized to standard care ± vitamin C, the vitamin C group had lower SOFA scores, reduced inflammatory and myocardial injury markers, and lower combined morbidity/mortality (9.52% vs 29.27%).

Trust comment: Randomized study with positive results but limited methods detail and unclear blinding/centering raises risk of bias.

Study Details

PMID:38401077
Participants:83
Impact:significantly lower after treatment (P < .05)
Trust score:3/5

Morbidity/mortality

1 evidences

In 83 sepsis patients randomized to standard care ± vitamin C, the vitamin C group had lower SOFA scores, reduced inflammatory and myocardial injury markers, and lower combined morbidity/mortality (9.52% vs 29.27%).

Trust comment: Randomized study with positive results but limited methods detail and unclear blinding/centering raises risk of bias.

Study Details

PMID:38401077
Participants:83
Impact:9.52% vs 29.27% (study vs control; P < .05; ~−19.75 percentage points)
Trust score:3/5

Plasma vitamin C (24 h)

1 evidences

A 75-person feasibility RCT of IV then oral vitamin C for moderate–severe CAP showed large increases in plasma vitamin C but no statistically significant differences in mortality or clinical endpoints; trends favored faster clinical stability and shorter hospital stay but the study was underpowered.

Trust comment: Randomized, placebo-controlled feasibility trial with good execution but small and not powered for clinical endpoints.

Study Details

PMID:37482552
Participants:75
Impact:median 226 vs 19 μmol/L (vitamin C vs placebo; p<0.0001)
Trust score:4/5

Mortality (in-hospital / 30 day)

1 evidences

A 75-person feasibility RCT of IV then oral vitamin C for moderate–severe CAP showed large increases in plasma vitamin C but no statistically significant differences in mortality or clinical endpoints; trends favored faster clinical stability and shorter hospital stay but the study was underpowered.

Trust comment: Randomized, placebo-controlled feasibility trial with good execution but small and not powered for clinical endpoints.

Study Details

PMID:37482552
Participants:75
Impact:no significant difference (0 vs 2 in-hospital deaths; p=0.494)
Trust score:4/5

Time to clinical stability / length of stay

1 evidences

A 75-person feasibility RCT of IV then oral vitamin C for moderate–severe CAP showed large increases in plasma vitamin C but no statistically significant differences in mortality or clinical endpoints; trends favored faster clinical stability and shorter hospital stay but the study was underpowered.

Trust comment: Randomized, placebo-controlled feasibility trial with good execution but small and not powered for clinical endpoints.

Study Details

PMID:37482552
Participants:75
Impact:trends favor vitamin C (shorter), not statistically significant
Trust score:4/5

Vasopressor duration

2 evidences

In this pilot RCT of septic shock patients, high‑dose IV vitamin C raised plasma vitamin C markedly but did not significantly change vasopressor dose or duration, SOFA scores, ICU/hospital mortality or most inflammatory markers; neutrophil counts were higher at 72 h in the vitamin C group.

Trust comment: Pilot double‑blind RCT with appropriate methods but small sample (n=40), limiting power for clinical endpoints.

Study Details

PMID:35073968
Participants:40
Impact:No significant difference; between-group difference −6 h (95% CI −25 to 13; p=0.54)
Trust score:3/5

In 71 patients with vasoplegic shock, IV vitamin C (1.5 g every 6 h) did not significantly reduce duration of vasopressor use or other clinical outcomes compared with placebo.

Trust comment: Double-blind RCT with adequate methods and sample size for primary endpoint but narrowly missed significance and showed no other clinical benefit.

Study Details

PMID:37478532
Participants:71
Impact:median 44 h (vitamin C) vs 55 h (placebo); p=0.057 (not significant)
Trust score:4/5

ICU/hospital length of stay and mortality

1 evidences

In 71 patients with vasoplegic shock, IV vitamin C (1.5 g every 6 h) did not significantly reduce duration of vasopressor use or other clinical outcomes compared with placebo.

Trust comment: Double-blind RCT with adequate methods and sample size for primary endpoint but narrowly missed significance and showed no other clinical benefit.

Study Details

PMID:37478532
Participants:71
Impact:no significant differences
Trust score:4/5

28-day mortality

6 evidences

Early combined hydrocortisone, high-dose IV vitamin C, and thiamine did not reduce 90-day or 28-day mortality or improve shock reversal in septic shock patients.

Trust comment: Large, randomized, double-blind trial with robust design and low loss to follow-up; found no mortality or clinically meaningful benefit.

Study Details

PMID:36171582
Participants:408
Impact:No significant change (37.1% vs 36.2%; p=0.84)
Trust score:5/5

Early adjunctive high‑dose IV vitamin C in sepsis was associated with lower 28‑day mortality, lower early SOFA score change, and higher procalcitonin clearance versus control.

Trust comment: Randomized study reporting mortality and organ-failure score improvements, but excerpt lacks full methodological detail and may be single-center.

Study Details

PMID:33094466
Participants:117
Impact:42.97% -> 27.93% (absolute -15.04 percentage points with vitamin C)
Trust score:3/5

In septic shock patients, continuous IV vitamin C did not significantly lower 28-day mortality and was associated with higher use of renal replacement therapy.

Trust comment: Multicenter, randomized, double-blind placebo-controlled trial but modest sample size and underpowered for mortality endpoint.

Study Details

PMID:34982738
Participants:124
Impact:-13.9% (26.7% vs 40.6%; p=0.10)
Trust score:4/5

In ICU patients with sepsis on vasopressors, IV vitamin C increased the risk of death or persistent organ dysfunction at 28 days compared with placebo.

Trust comment: Large randomized, placebo-controlled ICU trial with clinically meaningful endpoints; high reliability.

Study Details

PMID:35704292
Participants:872
Impact:↑ (35.4% vitamin C vs 31.6% placebo; RR 1.17)
Trust score:5/5

In septic shock patients, adding vitamin C and thiamine to hydrocortisone did not significantly reduce 28-day mortality but shortened shock duration and vasopressor use and reduced some adverse renal and fever outcomes.

Trust comment: Randomised clinical trial in ICU patients with clear clinical endpoints, but vitamin C was given as part of a combined regimen so its isolated effect is uncertain.

Study Details

PMID:34003568
Participants:94
Impact:−8.5 percentage points (36.2% vs 44.7%; non-significant)
Trust score:3/5

In 60 children with septic shock, IV vitamin C plus hydrocortisone and thiamin was feasible to deliver but did not improve organ-dysfunction-free days and showed a numerically higher 28-day mortality.

Trust comment: Multicenter randomized open-label pilot RCT (n=60) with good data monitoring but underpowered for clinical efficacy and unblinded.

Study Details

PMID:38240537
Participants:60
Impact:+9% (15% intervention vs 6% control)
Trust score:4/5

ICU mortality

2 evidences

In a small RCT of sepsis patients, high‑dose IV vitamin C transiently improved early microvascular perfusion (PPV) and reduced a glycocalyx metric in the smallest capillaries, with no change in mortality.

Trust comment: Double-blind randomized pilot in critically ill patients with objective microcirculation measures but very small sample and heterogeneous sepsis sources.

Study Details

PMID:37700249
Participants:23
Impact:No significant difference (58.3% vs 54.5%, p=0.849)
Trust score:3/5

In septic shock patients, continuous IV vitamin C did not significantly lower 28-day mortality and was associated with higher use of renal replacement therapy.

Trust comment: Multicenter, randomized, double-blind placebo-controlled trial but modest sample size and underpowered for mortality endpoint.

Study Details

PMID:34982738
Participants:124
Impact:-7.8% (23.3% vs 31.1%; p=0.32)
Trust score:4/5

Renal replacement therapy requirement

1 evidences

In septic shock patients, continuous IV vitamin C did not significantly lower 28-day mortality and was associated with higher use of renal replacement therapy.

Trust comment: Multicenter, randomized, double-blind placebo-controlled trial but modest sample size and underpowered for mortality endpoint.

Study Details

PMID:34982738
Participants:124
Impact:+13.4% (16.7% vs 3.3%; p=0.02)
Trust score:4/5

Pain (VAS)

2 evidences

Double-blind RCT comparing PRP alone vs PRP+vitamin C in partial-thickness rotator cuff tears (two injections 3 weeks apart); both groups improved pain and function over 3 months with no significant difference between groups.

Trust comment: Single-center, double-blind randomized trial with adequate sample size for planned effect; 3-month follow-up but no radiologic endpoints.

Study Details

PMID:39044241
Participants:110
Impact:No significant additional benefit vs PRP alone (3-month values: 3.44 vs 3.15; p=0.389)
Trust score:4/5

A 6-month randomized trial found the product containing undenatured type II collagen (Artneo) improved pain, stiffness, and some MRI signs of synovitis and was not inferior to glucosamine+chondroitin.

Trust comment: Randomized small trial showing benefit of a combination product that includes vitamin C; the contribution of vitamin C alone cannot be determined.

Study Details

PMID:38785054
Participants:70
Impact:decreased in both groups with no significant intergroup difference
Trust score:3/5

Shoulder function (ASES)

1 evidences

Double-blind RCT comparing PRP alone vs PRP+vitamin C in partial-thickness rotator cuff tears (two injections 3 weeks apart); both groups improved pain and function over 3 months with no significant difference between groups.

Trust comment: Single-center, double-blind randomized trial with adequate sample size for planned effect; 3-month follow-up but no radiologic endpoints.

Study Details

PMID:39044241
Participants:110
Impact:No significant additional benefit vs PRP alone (3-month values: 71.24 vs 73.05; p=0.578)
Trust score:4/5

Constant score

1 evidences

Double-blind RCT comparing PRP alone vs PRP+vitamin C in partial-thickness rotator cuff tears (two injections 3 weeks apart); both groups improved pain and function over 3 months with no significant difference between groups.

Trust comment: Single-center, double-blind randomized trial with adequate sample size for planned effect; 3-month follow-up but no radiologic endpoints.

Study Details

PMID:39044241
Participants:110
Impact:No significant additional benefit vs PRP alone (3-month values: 85.02 vs 87.13; p=0.771)
Trust score:4/5

Symptom progression

1 evidences

Oral vitamin C 1000 mg daily did not alter symptom resolution or quality-of-life trajectory compared with placebo in mild-to-moderate COVID-19.

Trust comment: Small, double-blind pilot RCT with 98 completers; limited power to detect small effects.

Study Details

PMID:35896462
Participants:98
Impact:No difference vs placebo (vitamin C progressed at same rate as placebo)
Trust score:3/5

Quality of life

4 evidences

High-dose oral vitamin C for 12 months in children with CMT1A was safe but did not meaningfully improve nerve conduction, strength, function, or quality of life.

Trust comment: Large (for this condition), double-blind, randomized placebo-controlled pediatric trial with intention-to-treat analysis; high internal validity and clear null result.

Study Details

PMID:19427269
Participants:80
Impact:no measurable effect (no improvement)
Trust score:5/5

Oral vitamin C 1000 mg daily did not alter symptom resolution or quality-of-life trajectory compared with placebo in mild-to-moderate COVID-19.

Trust comment: Small, double-blind pilot RCT with 98 completers; limited power to detect small effects.

Study Details

PMID:35896462
Participants:98
Impact:No difference vs placebo (vitamin C similar to placebo)
Trust score:3/5

Small preliminary randomized, placebo-controlled trial of topical QR-333 (combination including vitamin D3) reported symptom improvements in diabetic neuropathy but attribution to vitamin D is unclear.

Trust comment: Small double-blind randomized safety/efficacy study; contains a vitamin C derivative but is a multi-component topical formulation.

Study Details

PMID:16112498
Participants:34
Impact:improved with QR-333
Trust score:3/5

A wound-specific oral supplement containing arginine, vitamin C and zinc was less effective for wound-healing than a standard nutrition supplement in patients with chronic wounds.

Trust comment: Small pragmatic randomized trial; vitamin C was part of a multi-nutrient formula so individual effect of vitamin C cannot be isolated.

Study Details

PMID:23627791
Participants:24
Impact:no significant effect
Trust score:3/5

Plaque index (PI)

1 evidences

Adding vitamin C to chlorhexidine mouthwash for 14 days did not improve plaque, gingival inflammation, or bleeding compared with chlorhexidine alone; staining patterns were similar between CHX formulations.

Trust comment: Randomized, blinded mouthwash trial but small sample, short 14-day follow-up, and exclusions for noncompliance reduce generalizability.

Study Details

PMID:39881161
Participants:51
Impact:No additional benefit of CHX+VitC vs CHX alone (no significant difference at day 14)
Trust score:3/5

Gingival index (GI)

2 evidences

Adding vitamin C to chlorhexidine mouthwash for 14 days did not improve plaque, gingival inflammation, or bleeding compared with chlorhexidine alone; staining patterns were similar between CHX formulations.

Trust comment: Randomized, blinded mouthwash trial but small sample, short 14-day follow-up, and exclusions for noncompliance reduce generalizability.

Study Details

PMID:39881161
Participants:51
Impact:No additional benefit of CHX+VitC vs CHX alone (no significant difference at day 14)
Trust score:3/5

A dentifrice containing an ascorbic acid derivative showed reduced gingival redness and higher salivary antioxidant activity; primary GI outcome was not significant in ITT but improved in per-protocol analysis.

Trust comment: Large multicenter randomized controlled trial with objective endpoints, but primary outcome not significant in ITT which reduces certainty.

Study Details

PMID:25277459
Participants:300
Impact:no significant difference ITT; decreased in per-protocol analysis (P=0.01)
Trust score:4/5

Tooth staining

1 evidences

Adding vitamin C to chlorhexidine mouthwash for 14 days did not improve plaque, gingival inflammation, or bleeding compared with chlorhexidine alone; staining patterns were similar between CHX formulations.

Trust comment: Randomized, blinded mouthwash trial but small sample, short 14-day follow-up, and exclusions for noncompliance reduce generalizability.

Study Details

PMID:39881161
Participants:51
Impact:CHX groups caused more staining than phenol; CHX+VitC similar to CHX alone
Trust score:3/5

Shock reversal

1 evidences

Early combined hydrocortisone, high-dose IV vitamin C, and thiamine did not reduce 90-day or 28-day mortality or improve shock reversal in septic shock patients.

Trust comment: Large, randomized, double-blind trial with robust design and low loss to follow-up; found no mortality or clinically meaningful benefit.

Study Details

PMID:36171582
Participants:408
Impact:No significant difference in reversal rate or time to reversal
Trust score:5/5

Gestational age at membrane rupture

1 evidences

Oral vitamin C starting at 14 weeks in women with prior PPROM modestly delayed membrane rupture and delivery and increased birth weight in the current pregnancy.

Trust comment: Randomized trial with 100 participants showing significant differences, but single-center and modest size limit external validity.

Study Details

PMID:36481988
Participants:100
Impact:+1.11 weeks (30.11 vs 29.00 weeks; p=0.033)
Trust score:3/5

Gestational age at birth

1 evidences

Oral vitamin C starting at 14 weeks in women with prior PPROM modestly delayed membrane rupture and delivery and increased birth weight in the current pregnancy.

Trust comment: Randomized trial with 100 participants showing significant differences, but single-center and modest size limit external validity.

Study Details

PMID:36481988
Participants:100
Impact:+1.27 weeks (33.31 vs 32.04 weeks; p=0.019)
Trust score:3/5

Birth weight

2 evidences

Oral vitamin C starting at 14 weeks in women with prior PPROM modestly delayed membrane rupture and delivery and increased birth weight in the current pregnancy.

Trust comment: Randomized trial with 100 participants showing significant differences, but single-center and modest size limit external validity.

Study Details

PMID:36481988
Participants:100
Impact:+458 g (2409 g vs 1951 g; p=0.019)
Trust score:3/5

Randomized double-blind trial in pregnant women: micronutrient supplement raised maternal vitamin levels, was associated with 10% higher birth weights and fewer low-birth-weight infants; maternal plasma zinc correlated with newborn height.

Trust comment: Double-blind RCT but substantial attrition (100 recruited → 65 completed) which reduces confidence in effect estimates.

Study Details

PMID:14679367
Participants:65
Impact:increased by ~10% in supplemented group
Trust score:3/5

Hospital mortality at 60 days

1 evidences

Open-label randomized trial of hydrocortisone, vitamin C, and thiamine versus standard care in septic shock found no significant reduction in 60-day/hospital mortality or other key clinical outcomes; trial stopped early.

Trust comment: Multicenter randomized but open-label and terminated early with small sample, limiting power and increasing risk of type II error.

Study Details

PMID:36870070
Participants:106
Impact:-7.5% (28.3% vs 35.8%; p=0.40; not significant)
Trust score:3/5

Duration of vasopressor therapy

1 evidences

Open-label randomized trial of hydrocortisone, vitamin C, and thiamine versus standard care in septic shock found no significant reduction in 60-day/hospital mortality or other key clinical outcomes; trial stopped early.

Trust comment: Multicenter randomized but open-label and terminated early with small sample, limiting power and increasing risk of type II error.

Study Details

PMID:36870070
Participants:106
Impact:No significant difference (median ~50 h vs 58 h; p=0.44)
Trust score:3/5

SOFA score at 72 h

1 evidences

Open-label randomized trial of hydrocortisone, vitamin C, and thiamine versus standard care in septic shock found no significant reduction in 60-day/hospital mortality or other key clinical outcomes; trial stopped early.

Trust comment: Multicenter randomized but open-label and terminated early with small sample, limiting power and increasing risk of type II error.

Study Details

PMID:36870070
Participants:106
Impact:No significant difference
Trust score:3/5

Interleukin-6 (immediate postoperative)

1 evidences

In adult cardiac-surgery patients, adding thiamine to high‑dose IV vitamin C reduced immediate postoperative myocardial injury markers and early IL‑6 and was associated with fewer arrhythmias and shorter dobutamine use; no differences in LVEF, CRP, lactate, or ICU/hospital stay.

Trust comment: Randomized, double‑blind RCT with clearly reported biomarkers but modest sample size (n=64) and some baseline medication imbalances.

Study Details

PMID:40290059
Participants:64
Impact:-44.8% (114.4 → 63.1 pg/mL; p=0.003)
Trust score:4/5

Troponin‑I (immediate)

1 evidences

In adult cardiac-surgery patients, adding thiamine to high‑dose IV vitamin C reduced immediate postoperative myocardial injury markers and early IL‑6 and was associated with fewer arrhythmias and shorter dobutamine use; no differences in LVEF, CRP, lactate, or ICU/hospital stay.

Trust comment: Randomized, double‑blind RCT with clearly reported biomarkers but modest sample size (n=64) and some baseline medication imbalances.

Study Details

PMID:40290059
Participants:64
Impact:-61.5% (1606.8 → 618 ng/mL; p=0.005)
Trust score:4/5

Troponin‑I (24 h)

1 evidences

In adult cardiac-surgery patients, adding thiamine to high‑dose IV vitamin C reduced immediate postoperative myocardial injury markers and early IL‑6 and was associated with fewer arrhythmias and shorter dobutamine use; no differences in LVEF, CRP, lactate, or ICU/hospital stay.

Trust comment: Randomized, double‑blind RCT with clearly reported biomarkers but modest sample size (n=64) and some baseline medication imbalances.

Study Details

PMID:40290059
Participants:64
Impact:-55.9% (3603.7 → 1589.5 ng/mL; p=0.005)
Trust score:4/5

CK‑MB (immediate)

1 evidences

In adult cardiac-surgery patients, adding thiamine to high‑dose IV vitamin C reduced immediate postoperative myocardial injury markers and early IL‑6 and was associated with fewer arrhythmias and shorter dobutamine use; no differences in LVEF, CRP, lactate, or ICU/hospital stay.

Trust comment: Randomized, double‑blind RCT with clearly reported biomarkers but modest sample size (n=64) and some baseline medication imbalances.

Study Details

PMID:40290059
Participants:64
Impact:-33.0% (22.1 → 14.8 IU/L; p=0.008)
Trust score:4/5

CK‑MB (24 h)

1 evidences

In adult cardiac-surgery patients, adding thiamine to high‑dose IV vitamin C reduced immediate postoperative myocardial injury markers and early IL‑6 and was associated with fewer arrhythmias and shorter dobutamine use; no differences in LVEF, CRP, lactate, or ICU/hospital stay.

Trust comment: Randomized, double‑blind RCT with clearly reported biomarkers but modest sample size (n=64) and some baseline medication imbalances.

Study Details

PMID:40290059
Participants:64
Impact:-38.3% (12.8 → 7.9 IU/L; p=0.048)
Trust score:4/5

Systolic blood pressure

8 evidences

In nulliparous pregnant women, combined vitamins C and E (with iron) from mid-pregnancy reduced the rate of preeclampsia compared with iron alone.

Trust comment: Moderate-sized clinical trial (n=160) with a large absolute reduction in preeclampsia but methods (randomization/blinding) and some reported BP data are unclear in text excerpt.

Study Details

PMID:32755100
Participants:160
Impact:overall improvement reported (authors state alleviation of blood pressure)
Trust score:3/5

In young healthy men, 12 weeks of vitamin C+E+folate reduced systolic blood pressure but showed no other clear cardiovascular changes.

Trust comment: Small randomized trial with objective measures but limited sample size and combined-vitamin intervention confounds vitamin C–specific attribution.

Study Details

PMID:15580811
Participants:31
Impact:decrease (statistically significant, p=0.03)
Trust score:3/5

In a long-term (5 year) randomized trial among participants taking vitamin C (50 mg or 500 mg daily), systolic blood pressure increased over time in all groups and high‑dose vitamin C did not reduce blood pressure.

Trust comment: Large randomized double‑blind long‑term trial with many completers in vitamin C arms, suitable for BP outcomes though cohort had atrophic gastritis limiting generalizability.

Study Details

PMID:12468560
Participants:244
Impact:increased in high-dose group from 125.4 → 131.7 mmHg (+5.88 mmHg over 5 years); similar increases in low-dose (+5.73 mmHg) and dropout groups (+4.52 mmHg)
Trust score:4/5

Eating two kiwifruit daily increased vitamin C intake and lowered systolic blood pressure by ~2.7 mmHg over 7 weeks, without changing fasting insulin or other metabolic markers.

Trust comment: Randomized controlled trial with objective measures and documented vitamin C intake increase; modest sample size and short duration limit generalizability.

Study Details

PMID:35807858
Participants:43
Impact:Decrease of 2.7 mmHg in kiwifruit group vs control (significant)
Trust score:4/5

Double-blind controlled trial in overweight older men compared 5 weeks of Enzogenol+vitamin C versus vitamin C alone; cognitive response speed improved with Enzogenol+vitamin C while vitamin C alone produced no improvements.

Trust comment: Randomized, double-blind controlled study but small (n=42); vitamin C was given to all participants as part of both arms, and vitamin C alone showed no cognitive benefit in this trial.

Study Details

PMID:18683195
Participants:42
Impact:Trend toward reduction with Enzogenol+vitamin C; no change with vitamin C alone
Trust score:3/5

In mildly hypertensive patients, oral vitamin C supplementation lowered systolic and diastolic blood pressure modestly (short‑term), with no durable lipid changes and no extra benefit from higher doses.

Trust comment: Randomized double‑blind trial but small sample (n≈31 randomized), low reported compliance (~48%), and short duration of observed effect.

Study Details

PMID:12115017
Participants:31
Impact:-4.5 ±1.8 mmHg (mean drop; P<0.05; effect significant at 1 month only)
Trust score:3/5

Eight-week randomized trial in 72 middle-aged subjects with cardiovascular risk factors: moderate berry consumption improved platelet function, raised HDL, and lowered systolic blood pressure in those with high baseline BP.

Trust comment: Randomized, placebo‑controlled trial (n=72) with objective platelet measures and clear between‑group differences; moderate sample size.

Study Details

PMID:18258621
Participants:72
Impact:decrease (significant overall; -7.3 mmHg in highest baseline tertile)
Trust score:4/5

Short-term high-dose combination antioxidants including vitamin C lowered systolic blood pressure (significantly in treated hypertensives) and increased circulating antioxidant levels.

Trust comment: Randomized double-blind crossover trial but small sample (n=38 completers) and multi-antioxidant intervention limits attribution to vitamin C alone.

Study Details

PMID:9176034
Participants:38
Impact:decreased (significant fall in patients on antihypertensive therapy, P<0.01; trend in normotensives P=0.067)
Trust score:3/5

Diastolic blood pressure

6 evidences

Controlled exposure to fine particulates (± ozone) increased diastolic blood pressure and, in one location, impaired endothelial function; high-dose vitamin C (2 g) pretreatment did not prevent the BP rise or endothelial impairment.

Trust comment: Randomized, double-blind, crossover human exposure study with objective vascular and BP measures; moderate sample size and clear negative finding for high-dose vitamin C as a mitigator.

Study Details

PMID:19620518
Participants:81
Impact:+2.5 to +4.0 mm Hg during exposures (increase not mitigated by 2 g vitamin C pretreatment)
Trust score:4/5

In adolescent girls with metabolic syndrome, 6 weeks of DASH recommendations increased vitamin C levels, lowered insulin and prevented rise in diastolic blood pressure versus usual advice.

Trust comment: Randomised crossover trial with objective biochemical measures but moderate sample size and short intervention period.

Study Details

PMID:23773316
Participants:60
Impact:prevented increase vs UDA (P=0.01)
Trust score:4/5

In young healthy men, 12 weeks of vitamin C+E+folate reduced systolic blood pressure but showed no other clear cardiovascular changes.

Trust comment: Small randomized trial with objective measures but limited sample size and combined-vitamin intervention confounds vitamin C–specific attribution.

Study Details

PMID:15580811
Participants:31
Impact:no statistically significant change (possible decrease indicated)
Trust score:3/5

In mildly hypertensive patients, oral vitamin C supplementation lowered systolic and diastolic blood pressure modestly (short‑term), with no durable lipid changes and no extra benefit from higher doses.

Trust comment: Randomized double‑blind trial but small sample (n≈31 randomized), low reported compliance (~48%), and short duration of observed effect.

Study Details

PMID:12115017
Participants:31
Impact:-2.8 ±1.2 mmHg (mean drop; P<0.05)
Trust score:3/5

In nulliparous pregnant women, combined vitamins C and E (with iron) from mid-pregnancy reduced the rate of preeclampsia compared with iron alone.

Trust comment: Moderate-sized clinical trial (n=160) with a large absolute reduction in preeclampsia but methods (randomization/blinding) and some reported BP data are unclear in text excerpt.

Study Details

PMID:32755100
Participants:160
Impact:overall improvement reported (authors state alleviation of blood pressure)
Trust score:3/5

In a long-term (5 year) randomized trial among participants taking vitamin C (50 mg or 500 mg daily), systolic blood pressure increased over time in all groups and high‑dose vitamin C did not reduce blood pressure.

Trust comment: Large randomized double‑blind long‑term trial with many completers in vitamin C arms, suitable for BP outcomes though cohort had atrophic gastritis limiting generalizability.

Study Details

PMID:12468560
Participants:244
Impact:no difference in change among groups
Trust score:4/5

Lipids

1 evidences

In mildly hypertensive patients, oral vitamin C supplementation lowered systolic and diastolic blood pressure modestly (short‑term), with no durable lipid changes and no extra benefit from higher doses.

Trust comment: Randomized double‑blind trial but small sample (n≈31 randomized), low reported compliance (~48%), and short duration of observed effect.

Study Details

PMID:12115017
Participants:31
Impact:No change after 6 months
Trust score:3/5

Mean vasopressor dose (0–96 h)

1 evidences

In this pilot RCT of septic shock patients, high‑dose IV vitamin C raised plasma vitamin C markedly but did not significantly change vasopressor dose or duration, SOFA scores, ICU/hospital mortality or most inflammatory markers; neutrophil counts were higher at 72 h in the vitamin C group.

Trust comment: Pilot double‑blind RCT with appropriate methods but small sample (n=40), limiting power for clinical endpoints.

Study Details

PMID:35073968
Participants:40
Impact:No significant difference; mean difference 0.28 units/min (95% CI −0.31 to 0.87; p=0.35)
Trust score:3/5

Neutrophil count (72 h)

1 evidences

In this pilot RCT of septic shock patients, high‑dose IV vitamin C raised plasma vitamin C markedly but did not significantly change vasopressor dose or duration, SOFA scores, ICU/hospital mortality or most inflammatory markers; neutrophil counts were higher at 72 h in the vitamin C group.

Trust comment: Pilot double‑blind RCT with appropriate methods but small sample (n=40), limiting power for clinical endpoints.

Study Details

PMID:35073968
Participants:40
Impact:Increase in vitamin C group (20 vs 9 ×10^9/L; p=0.01)
Trust score:3/5

Death or persistent organ dysfunction (28 days)

1 evidences

Bayesian reanalysis of a large randomized trial (LOVIT) found allocation to IV vitamin C was associated with a higher probability of harm: increased risk of death or persistent organ dysfunction at 28 days.

Trust comment: Large randomized trial reanalysis with robust Bayesian methods showing consistent signal of harm across priors.

Study Details

PMID:37026849
Participants:872
Impact:Risk Ratio +20% (RR 1.20; 95% CrI 1.04–1.39; high probability of harm)
Trust score:4/5

28‑day mortality

1 evidences

Bayesian reanalysis of a large randomized trial (LOVIT) found allocation to IV vitamin C was associated with a higher probability of harm: increased risk of death or persistent organ dysfunction at 28 days.

Trust comment: Large randomized trial reanalysis with robust Bayesian methods showing consistent signal of harm across priors.

Study Details

PMID:37026849
Participants:872
Impact:Trend toward increase (RR 1.17; 95% CrI 0.98–1.40; high probability of harm under neutral priors)
Trust score:4/5

Gingival Pigmentation Index (GPI) at 1 and 6 months

1 evidences

Local injectable vitamin C depigmentation produced comparable gingival pigmentation index outcomes to surgical depigmentation at 6 months and higher patient satisfaction (VAS); surgical method showed faster initial improvement at 1 month (objective image score), but long‑term results were similar.

Trust comment: Randomized single‑center trial with small sample (n=42) and potential operator/assessment bias (same investigator performing procedures and assessments).

Study Details

PMID:39781402
Participants:42
Impact:No significant difference between vitamin C and surgical groups (p>0.2)
Trust score:3/5

Skin Hyperpigmentation Index (SHI) at 1 month

1 evidences

Local injectable vitamin C depigmentation produced comparable gingival pigmentation index outcomes to surgical depigmentation at 6 months and higher patient satisfaction (VAS); surgical method showed faster initial improvement at 1 month (objective image score), but long‑term results were similar.

Trust comment: Randomized single‑center trial with small sample (n=42) and potential operator/assessment bias (same investigator performing procedures and assessments).

Study Details

PMID:39781402
Participants:42
Impact:Surgical group better at 1 month (p<0.001); no difference at 6 months (p=0.891)
Trust score:3/5

Patient satisfaction (VAS)

1 evidences

Local injectable vitamin C depigmentation produced comparable gingival pigmentation index outcomes to surgical depigmentation at 6 months and higher patient satisfaction (VAS); surgical method showed faster initial improvement at 1 month (objective image score), but long‑term results were similar.

Trust comment: Randomized single‑center trial with small sample (n=42) and potential operator/assessment bias (same investigator performing procedures and assessments).

Study Details

PMID:39781402
Participants:42
Impact:Higher with vitamin C group (mean 8.90 vs 6.29; ~+26% satisfaction; p<0.001)
Trust score:3/5

Average SOFA score (days 2–5)

1 evidences

In this multicenter double‑blind RCT of early IV vitamin C in ED patients with sepsis/septic shock, there was no significant improvement in the primary outcome (average SOFA day 2–5) or most secondary outcomes; a subgroup with baseline SOFA ≥6 showed a lower SOFA (exploratory). Overall no clear clinical benefit.

Trust comment: Large, multicenter, double‑blind RCT with prespecified primary outcome and adequate sample size; negative primary result with some exploratory subgroup signals.

Study Details

PMID:40269974
Participants:292
Impact:No significant difference; ratio 0.91 (95% CI 0.77–1.08); P=0.30
Trust score:4/5

28‑day mortality / secondary outcomes

1 evidences

In this multicenter double‑blind RCT of early IV vitamin C in ED patients with sepsis/septic shock, there was no significant improvement in the primary outcome (average SOFA day 2–5) or most secondary outcomes; a subgroup with baseline SOFA ≥6 showed a lower SOFA (exploratory). Overall no clear clinical benefit.

Trust comment: Large, multicenter, double‑blind RCT with prespecified primary outcome and adequate sample size; negative primary result with some exploratory subgroup signals.

Study Details

PMID:40269974
Participants:292
Impact:No significant differences overall (no survival benefit)
Trust score:4/5

SOFA in baseline SOFA ≥6 subgroup

1 evidences

In this multicenter double‑blind RCT of early IV vitamin C in ED patients with sepsis/septic shock, there was no significant improvement in the primary outcome (average SOFA day 2–5) or most secondary outcomes; a subgroup with baseline SOFA ≥6 showed a lower SOFA (exploratory). Overall no clear clinical benefit.

Trust comment: Large, multicenter, double‑blind RCT with prespecified primary outcome and adequate sample size; negative primary result with some exploratory subgroup signals.

Study Details

PMID:40269974
Participants:292
Impact:Lower average SOFA (ratio 0.76; P=0.042) — exploratory
Trust score:4/5

CRQ total score (patient-reported)

1 evidences

In stable COPD patients, oral L‑arginine plus liposomal vitamin C for 4 weeks improved patient‑reported outcomes (CRQ total and dyspnea domains) and activity‑of‑daily‑living scores versus placebo; more patients reached MCID. As the intervention combined two agents, attribution to vitamin C alone is uncertain.

Trust comment: Randomized multicenter study with moderate size, but intervention combined L‑arginine and liposomal vitamin C (single‑blind), so effects cannot be isolated to vitamin C alone.

Study Details

PMID:40316462
Participants:150
Impact:Median increase 3.5 points vs placebo (p=0.006)
Trust score:3/5

CRQ dyspnea domain

1 evidences

In stable COPD patients, oral L‑arginine plus liposomal vitamin C for 4 weeks improved patient‑reported outcomes (CRQ total and dyspnea domains) and activity‑of‑daily‑living scores versus placebo; more patients reached MCID. As the intervention combined two agents, attribution to vitamin C alone is uncertain.

Trust comment: Randomized multicenter study with moderate size, but intervention combined L‑arginine and liposomal vitamin C (single‑blind), so effects cannot be isolated to vitamin C alone.

Study Details

PMID:40316462
Participants:150
Impact:Median increase 3.0 points (p<0.001)
Trust score:3/5

LCADL total score (ADL)

1 evidences

In stable COPD patients, oral L‑arginine plus liposomal vitamin C for 4 weeks improved patient‑reported outcomes (CRQ total and dyspnea domains) and activity‑of‑daily‑living scores versus placebo; more patients reached MCID. As the intervention combined two agents, attribution to vitamin C alone is uncertain.

Trust comment: Randomized multicenter study with moderate size, but intervention combined L‑arginine and liposomal vitamin C (single‑blind), so effects cannot be isolated to vitamin C alone.

Study Details

PMID:40316462
Participants:150
Impact:Median change −1.0 (improvement) (p=0.005)
Trust score:3/5

female sexual function (FSFI)

1 evidences

Giving an oral combination that included vitamin C improved sexual function and urinary symptoms in people with recurrent UTIs over 3 months.

Trust comment: Randomized crossover trial in humans but small sample and co-administration of other supplements and short follow-up limit certainty.

Study Details

PMID:38721680
Participants:50
Impact:improved at 3 months vs control (higher FSFI; P < 0.001)
Trust score:3/5

urinary symptoms (IPSS)

1 evidences

Giving an oral combination that included vitamin C improved sexual function and urinary symptoms in people with recurrent UTIs over 3 months.

Trust comment: Randomized crossover trial in humans but small sample and co-administration of other supplements and short follow-up limit certainty.

Study Details

PMID:38721680
Participants:50
Impact:improved at 3 months vs control (lower IPSS; P = 0.03)
Trust score:3/5

seizure frequency

1 evidences

Adding vitamins C (100 mg/day) and E to standard care for 8 weeks reduced seizure frequency in drug-resistant children but did not change the oxidative stress marker (MDA) versus placebo.

Trust comment: Double-blind randomized placebo-controlled trial with clear clinical effect on seizures but short duration, limited biomarker assessment and some power issues for MDA.

Study Details

PMID:39280329
Participants:88
Impact:large reduction in treatment group (per-protocol: 95% decreased vs 35% placebo; P < 0.001; ITT: 80% vs 32%; P < 0.001)
Trust score:4/5

MDA (oxidative stress marker)

1 evidences

Adding vitamins C (100 mg/day) and E to standard care for 8 weeks reduced seizure frequency in drug-resistant children but did not change the oxidative stress marker (MDA) versus placebo.

Trust comment: Double-blind randomized placebo-controlled trial with clear clinical effect on seizures but short duration, limited biomarker assessment and some power issues for MDA.

Study Details

PMID:39280329
Participants:88
Impact:decreased within both groups but no between-group difference (median Δ -0.172 vs -0.131 nmol/mL; p = 0.181)
Trust score:4/5

moderate-or-greater catheter-related bladder discomfort (CRBD)

1 evidences

A single 1 g IV dose of vitamin C given after anesthesia reduced early catheter-related bladder discomfort and increased patient satisfaction after bladder tumor resection.

Trust comment: Well-conducted double-blind RCT with clear short-term clinical benefit; single-center and single perioperative dose limit generalizability.

Study Details

PMID:37356194
Participants:118
Impact:reduced immediately post-op (28.8% vs 67.8%; P < 0.001) and at 1h and 2h (P = 0.003 and P = 0.008); no difference at 6h
Trust score:4/5

patient satisfaction

2 evidences

A single 1 g IV dose of vitamin C given after anesthesia reduced early catheter-related bladder discomfort and increased patient satisfaction after bladder tumor resection.

Trust comment: Well-conducted double-blind RCT with clear short-term clinical benefit; single-center and single perioperative dose limit generalizability.

Study Details

PMID:37356194
Participants:118
Impact:increased (mean 5.0 ± 1.3 vs 4.4 ± 1.4; P = 0.009)
Trust score:4/5

PEG with ascorbic acid and sodium phosphate tablets achieved similar bowel-cleaning quality and detection rates, but patient satisfaction and compliance favored sodium phosphate tablets.

Trust comment: Multicenter randomized trial with 189 patients and objective colon-cleansing scoring, though patient-reported measures vary.

Study Details

PMID:25603851
Participants:189
Impact:higher with sodium phosphate tablets (7.9 vs 7.4; p=0.022)
Trust score:4/5

clinical remission of oral leukoplakia

1 evidences

One year of low-dose beta-carotene plus vitamin C did not produce higher clinical remission of oral leukoplakia or reduce long-term cancer risk versus placebo.

Trust comment: Randomized double-blind design but small sample and low event rates reduce power to detect clinically meaningful effects.

Study Details

PMID:25156040
Participants:46
Impact:no significant improvement (17.4% vs 4.3%; P = 0.346)
Trust score:3/5

malignant transformation (oral cancer)

1 evidences

One year of low-dose beta-carotene plus vitamin C did not produce higher clinical remission of oral leukoplakia or reduce long-term cancer risk versus placebo.

Trust comment: Randomized double-blind design but small sample and low event rates reduce power to detect clinically meaningful effects.

Study Details

PMID:25156040
Participants:46
Impact:no reduction over median 60-month follow-up (2 vs 3 cases; RR 0.77; P = 0.580)
Trust score:3/5

upper-body fat-free mass (hypertrophy)

1 evidences

In trained men over 10 weeks, combined vitamin C and E supplementation appeared to blunt some upper-body strength and hypertrophy gains but also reduced visceral fat gain compared with placebo.

Trust comment: Randomized double-blind trial but very small sample of trained men limits precision and generalizability.

Study Details

PMID:36283241
Participants:23
Impact:placebo showed significant increase; vitamin group showed no increase (vitamins appeared to blunt upper-body hypertrophy)
Trust score:3/5

dominant handgrip strength

1 evidences

In trained men over 10 weeks, combined vitamin C and E supplementation appeared to blunt some upper-body strength and hypertrophy gains but also reduced visceral fat gain compared with placebo.

Trust comment: Randomized double-blind trial but very small sample of trained men limits precision and generalizability.

Study Details

PMID:36283241
Participants:23
Impact:increased only in placebo group (significant in placebo; not in vitamin group)
Trust score:3/5

visceral adipose tissue gain

1 evidences

In trained men over 10 weeks, combined vitamin C and E supplementation appeared to blunt some upper-body strength and hypertrophy gains but also reduced visceral fat gain compared with placebo.

Trust comment: Randomized double-blind trial but very small sample of trained men limits precision and generalizability.

Study Details

PMID:36283241
Participants:23
Impact:increase seen in placebo but mitigated in vitamin group (vitamins reduced VAT gain)
Trust score:3/5

asthma control (FEV1, symptoms, peak flow, airway responsiveness)

1 evidences

Daily magnesium (450 mg) for 16 weeks did not improve asthma control outcomes compared with placebo.

Trust comment: Large randomized double-blind placebo-controlled trial in primary care with null results and good external validity.

Study Details

PMID:14519140
Participants:300
Impact:no improvement versus placebo across measured outcomes (no significant effect)
Trust score:4/5

depression severity (HDRS)

1 evidences

Adding up to 1,000 mg/day vitamin C to citalopram for 8 weeks did not improve depression scores or suicidal behavior compared with placebo.

Trust comment: Randomized double-blind trial but small sample and short duration; possible ceiling effect from concurrent citalopram.

Study Details

PMID:25873303
Participants:40
Impact:no additional benefit vs placebo over 8 weeks (HDRS decline similar between groups; P = NS)
Trust score:3/5

suicidal behavior score

1 evidences

Adding up to 1,000 mg/day vitamin C to citalopram for 8 weeks did not improve depression scores or suicidal behavior compared with placebo.

Trust comment: Randomized double-blind trial but small sample and short duration; possible ceiling effect from concurrent citalopram.

Study Details

PMID:25873303
Participants:40
Impact:no difference in decline between groups
Trust score:3/5

Plasma vitamin C concentration

29 evidences

In healthy older people, oral vitamin C raised blood vitamin levels but did not improve vascular dilation; a Mediterranean-type diet did improve vascular function.

Trust comment: Randomized, physiologic measurement study with moderate sample size (n=54) and objective vascular endpoints; clear negative result for vitamin C.

Study Details

PMID:12237172
Participants:54
Impact:increased (oral vitamin C and diet raised plasma vitamin C from ~83 to ~135 μmol/L)
Trust score:4/5

A three‑arm randomized trial (kiwifruit, vitamin C tablet, placebo) in adults with low vitamin C showed that kiwifruit improved mood and well‑being early; vitamin C tablets raised plasma vitamin C to saturation and reduced fatigue in participants with low baseline vitamin C.

Trust comment: Well‑designed, preregistered RCT with objective vitamin C measures, adequate sample and subgroup analyses; high internal validity.

Study Details

PMID:32971991
Participants:159
Impact:increased to saturation (>60 µmol/L) within 2 weeks (kiwifruit and vitamin C tablet)
Trust score:5/5

Oral 1 g vitamin C increased plasma vitamin C and attenuated exercise-induced oxidative stress markers in type 1 diabetic patients and healthy controls.

Trust comment: Randomized double-blind placebo-controlled trial but small sample size and mixed groups limit generalizability.

Study Details

PMID:18769906
Participants:26
Impact:Increased after supplementation (P < 0.05 vs pre-supplementation)
Trust score:3/5

Double-blind RCT of blackcurrant juice rich in vitamin C and polyphenols for 6 weeks: raised plasma vitamin C, lowered oxidative stress and improved endothelial function.

Trust comment: Well-conducted double-blind RCT with objective vascular and biochemical outcomes, but intervention combined vitamin C with polyphenols so effects of vitamin C alone are uncertain.

Study Details

PMID:24742818
Participants:66
Impact:increased significantly (low: 38.6→49.4 µmol/L; high: 34.6→73.8 µmol/L; P<0.001 vs placebo)
Trust score:4/5

In older women doing 6 weeks of moderate training, 1000 mg/day vitamin C raised blood vitamin C but did not produce clear changes in antioxidant balance or inflammatory gene expression.

Trust comment: Randomized, double-blind trial but very small sample (n=24) with baseline composition differences limiting generalizability.

Study Details

PMID:33653365
Participants:24
Impact:+4.5 mg/L (from 13.9 ± 4.2 to 18.4 ± 8.6 mg/L) p=0.04
Trust score:3/5

Two weeks of 500 mg/day oral vitamin C reduced anxiety scores and raised plasma vitamin C compared with placebo in high-school students.

Trust comment: Double-blind randomized placebo-controlled trial but small sample (n=42) and short duration (14 days).

Study Details

PMID:26353411
Participants:42
Impact:Increase vs placebo (significant)
Trust score:3/5

Single 10 g IV vitamin C reduced 'fatigue right now' scores vs placebo at 2 hours and persisted at 24 hours; plasma vitamin C rose markedly and oxidative stress fell.

Trust comment: Well-conducted double-blind RCT with adequate sample size, objective biochemical measures, and low dropout rate.

Study Details

PMID:22264303
Participants:141
Impact:Increased from 12.66 μg/ml to 267.90 μg/ml at 2 hours after 10 g IV
Trust score:5/5

In 56 healthy smokers randomized to 500 mg vitamin C daily or placebo for 4 weeks, plasma vitamin C increased but markers of lipid peroxidation and pulmonary function tests did not change.

Trust comment: Randomized double‑blind trial with complete follow‑up but small sample and short duration for clinical pulmonary endpoints.

Study Details

PMID:10052021
Participants:56
Impact:significant increase in supplemented group (p<0.005)
Trust score:3/5

In a 4-week double-blind crossover trial, combined high-dose vitamin C and E lowered urinary albumin excretion in Type 2 diabetic patients.

Trust comment: Randomised, double-blind crossover RCT with clear endpoints but small N and short duration limits generalizability.

Study Details

PMID:11606175
Participants:30
Impact:increased from 41.9 to 79.4 μmol/L
Trust score:4/5

After 2 years of daily antioxidant supplementation (including 120 mg vitamin C), plasma concentrations of vitamin C, vitamin E, beta-carotene, selenium and zinc were significantly higher than placebo in a 1000-person subsample.

Trust comment: Large randomized double-blind placebo-controlled trial with substantial sample and clear biomarker changes, though this report is preliminary on a subsample.

Study Details

PMID:11718454
Participants:1000
Impact:increased to 11.5 µg/mL (men) and 12.6 µg/mL (women) in intervention (significantly higher than placebo)
Trust score:4/5

Children given multiple micronutrients including vitamin C had higher plasma antioxidant levels and less oxidized DNA damage in lymphocytes.

Trust comment: Randomized trial in children showing biochemical benefits but was a multinutrient supplement and details on blinding/completion are limited.

Study Details

PMID:15941534
Participants:82
Impact:+46.9% versus control after 8 weeks
Trust score:3/5

Observational study showing higher fruit intake is associated with higher plasma vitamin C concentrations.

Trust comment: Large cross-sectional/observational study with strong sample size but susceptible to confounding and temporality issues.

Study Details

PMID:21729475
Participants:2031
Impact:positively associated with fruit intake (higher fruit → higher plasma vitamin C)
Trust score:3/5

In healthy men given endotoxin, high‑dose IV vitamin C restored endothelial-dependent forearm vasodilation that was suppressed by endotoxin.

Trust comment: Well-controlled, placebo crossover in healthy humans with objective vascular measures, but modest sample size (n=36).

Study Details

PMID:24512733
Participants:36
Impact:increased to mean 3.2–4.9 mmol/L after infusion
Trust score:4/5

Eating two SunGold kiwifruit daily (high in vitamin C) for 28 days improved mood, wellbeing, vitality and gut symptoms and raised plasma vitamin C in adults with mild–moderate mood disturbance.

Trust comment: Randomised crossover in humans with objective vitamin C measures; small sample and unblinded limit generalizability.

Study Details

PMID:40284237
Participants:23
Impact:increase +21.3 µmol/L at week 2 (57.9 → 79.2 µmol/L) and +15.9 µmol/L at week 4 (57.9 → 73.8 µmol/L)
Trust score:4/5

In 21 septic shock patients, 1.5 g IV vitamin C every 6 hours corrected deficiency and produced high plasma concentrations with a short half-life.

Trust comment: Prospective pharmacokinetic study in critically ill patients with clear measurements but small sample size.

Study Details

PMID:31778629
Participants:21
Impact:corrected deficiency; median 258 μmol/L post-dose (T0) in dosed patients
Trust score:4/5

In 35 people with type II diabetes, 1.5 g/day oral vitamin C raised plasma levels but did not change oxidative stress marker, blood pressure, or endothelial function after 3 weeks.

Trust comment: Randomized double-blind trial but small sample and short duration limit generalizability of negative findings.

Study Details

PMID:12241530
Participants:35
Impact:increased from 58 ±6 to 122 ±10 μmol/L
Trust score:3/5

In 40 septic shock patients, 3 days of high‑dose IV vitamin C raised blood vitamin C but did not reduce increases in protein oxidative damage.

Trust comment: Small randomized controlled trial in critically ill humans with objective biochemical endpoints but limited sample size (n=40).

Study Details

PMID:34818575
Participants:40
Impact:increased from 9.8 ± 1.4 to 456 ± 90 μmol/L after 3 days IV
Trust score:3/5

In this 2-year dietary trial (n=276), plasma vitamin C rose with increased fruit and vegetable intake but tended to plateau above higher intake levels.

Trust comment: Longitudinal randomized dietary intervention with biomarker measurements in free-living volunteers; good duration and objective biomarkers though not a supplement trial per se.

Study Details

PMID:19538812
Participants:276
Impact:increased with higher fruit and vegetable intake but showed limited further rise above ~500 g/day (association with intake r=+0.31 at baseline)
Trust score:4/5

Randomized placebo-controlled 2×2 factorial trial in healthy adults testing micronutrient mix (including vitamin C) and bovine colostrum over 10 weeks; micronutrient supplementation raised plasma vitamin C and other micronutrients and enhanced delayed-type hypersensitivity (DTH) responses, especially in older subjects; most other immune parameters unchanged.

Trust comment: Well-controlled randomized study with good compliance and relevant immune biomarkers, but effects were limited to DTH and concentrated in older subjects.

Study Details

PMID:17118191
Participants:131
Impact:increased >70% in micronutrient groups (P < 0.0001)
Trust score:4/5

In pregnant women with obesity, adding a supplement (includes 90 mg vitamin C plus other nutrients) raised some micronutrients but did not change vitamin C levels or markers of inflammation/oxidative stress.

Trust comment: Double-blind RCT in humans with adequate randomization and clinical outcomes, but vitamin C was given in a multinutrient supplement and vitamin C concentrations did not differ between groups.

Study Details

PMID:38396126
Participants:98
Impact:no difference by randomization group
Trust score:4/5

Irvingia gabonensis kernel extract (300 mg/day) in overweight/obese women for 12 weeks raised plasma vitamin C and maintained adiponectin but did not change fat oxidation, body composition, telomere length, or aerobic capacity.

Trust comment: Randomized, double-blind placebo-controlled RCT with appropriate methods and adequate completion (66), though single-sex sample and limited duration constrain generalizability.

Study Details

PMID:36364907
Participants:66
Impact:+23.45 μmol/L (IG vs placebo at 6 weeks); +16.95 μmol/L (IG vs placebo at 12 weeks) — IG group +28.8 to +31.0 μmol/L vs baseline
Trust score:4/5

Pilot randomized trial in 44 critically ill adults found enteral or parenteral alanyl-glutamine did not change plasma vitamin C, glutathione, markers of oxidative stress, lymphocyte subsets, gut permeability, or nitrogen balance compared to control by day 9.

Trust comment: Double-blind pilot RCT with direct biochemical measures but small sample and limited duration reduces confidence in null findings.

Study Details

PMID:18258342
Participants:44
Impact:no differences between enteral AG, parenteral AG, and control groups (no effect reported)
Trust score:3/5

More frequent hemodialysis did not significantly change predialysis plasma vitamin C concentrations or prevalence of deficiency in this small ancillary cohort.

Trust comment: Ancillary quasi-randomized analysis with small sample and some loss to follow-up, limiting power to detect differences.

Study Details

PMID:31101018
Participants:30
Impact:no significant treatment effect (adjusted treatment comparison at 12 months −2.5 μmol/L; P = 0.70)
Trust score:3/5

Alpha-tocopherol (vitamin E) supplementation with insulin infusion reduced lipid peroxides and was associated with increased plasma vitamin C concentrations.

Trust comment: Randomized supplement trial measuring vitamin C as a secondary outcome; vitamin C change is reported but was not the intervention.

Study Details

PMID:11916760
Participants:98
Impact:significant increase (no numeric value reported)
Trust score:3/5

Oral vitamin C supplementation markedly and reliably raised plasma vitamin C concentrations in healthy young men.

Trust comment: Randomized supplementation study with clear biochemical endpoints (n=64) and expected pharmacokinetic results; well measured but limited to healthy young males.

Study Details

PMID:20499024
Participants:64
Impact:In Combination group: increased from 2.86 mg/L to 10.37 mg/L (4 wks) and 15.63 mg/L (8 wks); Vitamin C group also showed significant increases
Trust score:4/5

In healthy volunteers, a 1-month high-heat-treated diet reduced insulin sensitivity and lowered plasma vitamins (including vitamin C) while increasing blood lipids.

Trust comment: Randomized crossover diet intervention with objective biochemical measures; moderate sample size limits precision.

Study Details

PMID:20335546
Participants:62
Impact:-8% (vs steamed diet)
Trust score:4/5

In dental students under exam stress, a daily micronutrient supplement including vitamin C modestly raised plasma vitamin C and showed small non-significant improvements in inflammatory and antioxidant markers.

Trust comment: Small randomized pilot study (40 completers) with objective lab measures but limited power and mostly non-significant differences.

Study Details

PMID:22027646
Participants:40
Impact:increased from 8.0 to 11.3 mg/L in supplement group (p=0.49)
Trust score:3/5

Eating gold kiwifruit daily increased plasma vitamin C and some antioxidants and reduced duration/severity of selected cold symptoms in older adults.

Trust comment: Randomized crossover human trial (n=32) with biologic measures and symptom outcomes; moderate-good quality though sample size is small.

Study Details

PMID:22172428
Participants:32
Impact:+significant increase
Trust score:4/5

Adults advised to eat more fruit and vegetables for eight weeks had higher plasma vitamin C and carotenoids but no change in lipids.

Trust comment: Randomized controlled trial with clear dietary intervention and measured plasma antioxidants, but exact vitamin C change not numerically reported in the summary.

Study Details

PMID:9224079
Participants:87
Impact:increased (mean increase not specified)
Trust score:4/5

Intraoperative blood loss

1 evidences

IV 2 g ascorbic acid given perioperatively did not reduce intraoperative blood loss or change operative outcomes in women undergoing laparoscopic myomectomy.

Trust comment: Randomized, double-blind placebo-controlled RCT but small sample (46 completers) limiting power to detect modest effects.

Study Details

PMID:26946313
Participants:46
Impact:no significant change (193±204 mL vs 159±193 mL; P=0.52)
Trust score:4/5

seasickness symptom severity

1 evidences

In a double-blind crossover trial, oral 2 g vitamin C before wave exposure reduced seasickness symptoms and fewer people wanted to leave the raft early; histamine and DAO rose after vitamin C.

Trust comment: Well-designed double-blind placebo-controlled crossover with clear p-values and n=63 analyzed, though habituation and some non-significant VAS differences temper certainty.

Study Details

PMID:25095772
Participants:63
Impact:reduced (less severe symptoms after vitamin C; p < 0.01)
Trust score:4/5

early raft exit

1 evidences

In a double-blind crossover trial, oral 2 g vitamin C before wave exposure reduced seasickness symptoms and fewer people wanted to leave the raft early; histamine and DAO rose after vitamin C.

Trust comment: Well-designed double-blind placebo-controlled crossover with clear p-values and n=63 analyzed, though habituation and some non-significant VAS differences temper certainty.

Study Details

PMID:25095772
Participants:63
Impact:fewer early exits (17 after placebo vs 6 after vitamin C; p < 0.03)
Trust score:4/5

histamine level

1 evidences

In a double-blind crossover trial, oral 2 g vitamin C before wave exposure reduced seasickness symptoms and fewer people wanted to leave the raft early; histamine and DAO rose after vitamin C.

Trust comment: Well-designed double-blind placebo-controlled crossover with clear p-values and n=63 analyzed, though habituation and some non-significant VAS differences temper certainty.

Study Details

PMID:25095772
Participants:63
Impact:increased after vitamin C (p < 0.01); DAO also increased (p < 0.001)
Trust score:4/5

common cold frequency

1 evidences

Five-year randomized trial in older adults with atrophic gastritis found higher-dose (500 mg) vitamin C reduced frequency of multiple colds but did not affect cold duration or severity.

Trust comment: Large long-term randomized trial but had protocol amendments and a specialized population (atrophic gastritis), limiting generalizability.

Study Details

PMID:16118650
Participants:244
Impact:reduced (total colds per 1000 person-months: 21.3 low-dose vs 17.1 high-dose; RR for ≥3 colds 0.34, 95% CI 0.12–0.97)
Trust score:3/5

cold duration

2 evidences

8-week RCT in young men with low-to-marginal vitamin C found supplementation (1000 mg/day) raised plasma vitamin C, reduced the number of participants who reported colds, tended to shorten cold duration and produced modest increases in reported physical activity.

Trust comment: Randomized double-blind trial with objective biomarkers, but small sample size, baseline activity imbalance, and limited generalizability to other populations.

Study Details

PMID:25010554
Participants:28
Impact:reduced (mean −3.2 days; ~59% reduction; p = 0.06)
Trust score:3/5

Five-year randomized trial in older adults with atrophic gastritis found higher-dose (500 mg) vitamin C reduced frequency of multiple colds but did not affect cold duration or severity.

Trust comment: Large long-term randomized trial but had protocol amendments and a specialized population (atrophic gastritis), limiting generalizability.

Study Details

PMID:16118650
Participants:244
Impact:no apparent effect on duration (no significant reduction)
Trust score:3/5

cold severity

1 evidences

Five-year randomized trial in older adults with atrophic gastritis found higher-dose (500 mg) vitamin C reduced frequency of multiple colds but did not affect cold duration or severity.

Trust comment: Large long-term randomized trial but had protocol amendments and a specialized population (atrophic gastritis), limiting generalizability.

Study Details

PMID:16118650
Participants:244
Impact:no apparent effect on severity
Trust score:3/5

Desulfovibrio abundance

1 evidences

In a 4-week RCT (500 mg twice daily) in young adults with low vitamin C, supplementation changed gut microbiota (notably reduced Desulfovibrio), reduced markers of endotoxemia/inflammation and correlated with improved mental vitality measures and BDNF increases in responders.

Trust comment: Randomized double-blind trial with mechanistic microbiome and biomarker analyses but small sample (n=40) limiting precision.

Study Details

PMID:40187667
Participants:40
Impact:decreased (reduction correlated with improved Stroop performance)
Trust score:4/5

BDNF level

1 evidences

In a 4-week RCT (500 mg twice daily) in young adults with low vitamin C, supplementation changed gut microbiota (notably reduced Desulfovibrio), reduced markers of endotoxemia/inflammation and correlated with improved mental vitality measures and BDNF increases in responders.

Trust comment: Randomized double-blind trial with mechanistic microbiome and biomarker analyses but small sample (n=40) limiting precision.

Study Details

PMID:40187667
Participants:40
Impact:increased in participants with substantial Desulfovibrio reduction (responders; magnitude not quantified)
Trust score:4/5

serum LPS (endotoxemia)/inflammation

1 evidences

In a 4-week RCT (500 mg twice daily) in young adults with low vitamin C, supplementation changed gut microbiota (notably reduced Desulfovibrio), reduced markers of endotoxemia/inflammation and correlated with improved mental vitality measures and BDNF increases in responders.

Trust comment: Randomized double-blind trial with mechanistic microbiome and biomarker analyses but small sample (n=40) limiting precision.

Study Details

PMID:40187667
Participants:40
Impact:decreased (suppressed inflammatory responses with lower serum LPS; responder-specific decreases in IL-10 and classical monocytes)
Trust score:4/5

bleeding on probing (BOP)

2 evidences

Randomized controlled trial (three arms, n=15 each) found that adding VitC-loaded I-PRF to non-surgical periodontal therapy did not significantly change bleeding on probing or most long-term clinical/radiographic outcomes versus controls, but it reduced early postoperative pain and showed transient better CAL at 3 months.

Trust comment: Registered, randomized trial with blinded outcome assessment and complete follow-up (n=45), but relatively small per-arm sample limits detection of modest effects.

Study Details

PMID:40410805
Participants:45
Impact:no significant difference between groups at 3 or 6 months (p=0.185 and p=0.301)
Trust score:4/5

In patients receiving non-surgical periodontal therapy, a 4‑week free-sugar avoidance led to greater reductions in bleeding on probing and periodontal inflamed surface area and increased dietary vitamin C intake compared with control.

Trust comment: Single-blinded randomized controlled exploratory trial with objective clinical endpoints but very small sample (n=22) and dietary change (not isolated vitamin C supplementation).

Study Details

PMID:39185702
Participants:22
Impact:−40.3% (SAG T1–T2) vs −34.0% (CG T1–T2); sustained (−39.6% vs −28.73% at 10 weeks)
Trust score:3/5

clinical attachment level (CAL)

1 evidences

Randomized controlled trial (three arms, n=15 each) found that adding VitC-loaded I-PRF to non-surgical periodontal therapy did not significantly change bleeding on probing or most long-term clinical/radiographic outcomes versus controls, but it reduced early postoperative pain and showed transient better CAL at 3 months.

Trust comment: Registered, randomized trial with blinded outcome assessment and complete follow-up (n=45), but relatively small per-arm sample limits detection of modest effects.

Study Details

PMID:40410805
Participants:45
Impact:PMPR+I-PRF/VitC showed better CAL at 3 months (p=0.029) but no significant difference at 6 months
Trust score:4/5

postoperative pain (VAS)

5 evidences

Randomized controlled trial (three arms, n=15 each) found that adding VitC-loaded I-PRF to non-surgical periodontal therapy did not significantly change bleeding on probing or most long-term clinical/radiographic outcomes versus controls, but it reduced early postoperative pain and showed transient better CAL at 3 months.

Trust comment: Registered, randomized trial with blinded outcome assessment and complete follow-up (n=45), but relatively small per-arm sample limits detection of modest effects.

Study Details

PMID:40410805
Participants:45
Impact:reduced in PMPR+I-PRF/VitC at 2 and 3 days (inter-group p=0.021 and p=0.001 respectively; significant within-group decrease)
Trust score:4/5

Randomized trial comparing memantine vs vitamin C after elective abdominal surgery; memantine reduced pain more than vitamin C.

Trust comment: Small single-center double-blind RCT on humans but very small sample limits precision.

Study Details

PMID:40497407
Participants:34
Impact:Vitamin C group mean 24h VAS 4.7 vs memantine 3.2 (vitamin C worse by +1.5 points)
Trust score:3/5

A single 2 g oral vitamin C given 1 hour before major abdominal surgery reduced pain scores, lowered morphine use, and decreased need for extra analgesic compared with placebo.

Trust comment: Prospective, double-blind randomized controlled trial with adequate sample size and clinically relevant endpoints.

Study Details

PMID:31465720
Participants:165
Impact:VAS scores lower vs placebo at most time points (p < 0.05)
Trust score:4/5

Vitamin C supplementation improved soft‑tissue healing after dental implant surgery in several patient subgroups but did not reduce pain.

Trust comment: Randomized controlled clinical trial with a substantial sample size and objective healing indices, though subgroup effects and blinding details are unclear.

Study Details

PMID:30039526
Participants:128
Impact:no significant change
Trust score:4/5

Peri- and postoperative vitamin C reduced subjective pain and analgesic use after hip fracture surgery but did not change hip function scores.

Trust comment: Prospective randomized full-scale study with objective consumption and pain measures; blinding not clearly reported.

Study Details

PMID:40355782
Participants:74
Impact:decreased (significantly lower at all follow-ups; p<0.05)
Trust score:4/5

cold incidence

1 evidences

8-week RCT in young men with low-to-marginal vitamin C found supplementation (1000 mg/day) raised plasma vitamin C, reduced the number of participants who reported colds, tended to shorten cold duration and produced modest increases in reported physical activity.

Trust comment: Randomized double-blind trial with objective biomarkers, but small sample size, baseline activity imbalance, and limited generalizability to other populations.

Study Details

PMID:25010554
Participants:28
Impact:reduced participants with colds (7 vs 11; RR = 0.55, 95% CI 0.33–0.94; p = 0.04)
Trust score:3/5

physical activity (METS)

1 evidences

8-week RCT in young men with low-to-marginal vitamin C found supplementation (1000 mg/day) raised plasma vitamin C, reduced the number of participants who reported colds, tended to shorten cold duration and produced modest increases in reported physical activity.

Trust comment: Randomized double-blind trial with objective biomarkers, but small sample size, baseline activity imbalance, and limited generalizability to other populations.

Study Details

PMID:25010554
Participants:28
Impact:increased (up to +39.6% vs placebo at weeks 7–8; p = 0.10; not statistically significant)
Trust score:3/5

Melasma severity (MASI/mMASI)

1 evidences

Topical multicomponent serum (contains a stabilized form of vitamin C) twice daily reduced melasma severity similar to 4% hydroquinone, improved skin hydration and was better tolerated.

Trust comment: Randomized single-center investigator-blind cosmetic trial with objective measures but modest sample size and relevant COI (industry employees), limiting certainty.

Study Details

PMID:40062688
Participants:60
Impact:MASI decreased ~−3.5 points at 3 months and ~−5.7 points at 5 months (Serum B3 group); similar reductions seen with HQ4% by month 5
Trust score:3/5

Erythema (IGA)

1 evidences

Topical multicomponent serum (contains a stabilized form of vitamin C) twice daily reduced melasma severity similar to 4% hydroquinone, improved skin hydration and was better tolerated.

Trust comment: Randomized single-center investigator-blind cosmetic trial with objective measures but modest sample size and relevant COI (industry employees), limiting certainty.

Study Details

PMID:40062688
Participants:60
Impact:Erythema decreased in Serum B3 group (early significant between-group advantage at Months 1–2 favoring Serum B3, p≤0.027)
Trust score:3/5

Skin hydration (Corneometry)

1 evidences

Topical multicomponent serum (contains a stabilized form of vitamin C) twice daily reduced melasma severity similar to 4% hydroquinone, improved skin hydration and was better tolerated.

Trust comment: Randomized single-center investigator-blind cosmetic trial with objective measures but modest sample size and relevant COI (industry employees), limiting certainty.

Study Details

PMID:40062688
Participants:60
Impact:Hydration maintained with Serum B3; HQ4% caused significant hydration decrease until switch (p≤0.01)
Trust score:3/5

Skin pigmentation (colorimeter L value)

1 evidences

Vitamin C delivered by iontophoresis to one side of the face reduced objective pigmentation compared with the control side at 12 weeks.

Trust comment: Randomized, double-blind, within-subject controlled trial with objective colorimetric outcome but small sample size.

Study Details

PMID:12771472
Participants:29
Impact:L value decreased from 4.60 to 2.78 on treated side at 12 weeks (change −1.82, p=0.002); control side change non-significant
Trust score:4/5

Reduced glutathione (GSH)

3 evidences

Yoga and sham-yoga produced similar improvements in many markers in T2DM; only reduced glutathione improved more with yoga, and vitamin C changed within groups but not between groups.

Trust comment: Single-blind pilot RCT with active control and small sample size; measured vitamin C but between-group differences were absent except for GSH.

Study Details

PMID:31283365
Participants:40
Impact:increase — significant in yoga vs sham
Trust score:3/5

Dietary changes (and mate tea) increased vitamin C intake and were associated with higher antioxidant capacity and glutathione in dyslipidemic subjects.

Trust comment: Randomized clinical trial with dietary interventions showing associations between increased vitamin C intake and antioxidant markers, but effects are from diet/tea interventions rather than isolated vitamin C supplementation.

Study Details

PMID:22578980
Participants:74
Impact:significant increase correlated with vitamin C intake
Trust score:3/5

Multivitamin/mineral supplements given to women undergoing IVF were associated with decreased oxidative stress markers and higher antioxidant vitamin levels in serum and follicular fluid.

Trust comment: Moderate-sized human study with biological measures but unclear blinding/controls and combined multivitamin intervention limits attribution to vitamin C alone.

Study Details

PMID:20226443
Participants:69
Impact:increased (strengthened antioxidant defense)
Trust score:3/5

GSH:GSSG ratio

1 evidences

Patients given n‑3 PUFA plus antioxidant vitamins (including 1 g/day vitamin C) before and around cardiac surgery showed reduced oxidative stress and inflammation markers in atrial tissue and blood.

Trust comment: Clinical intervention in surgical patients with clear biochemical endpoints; reasonably powered (n=95) though trial design details (blinding/randomization) are not fully described.

Study Details

PMID:21138533
Participants:95
Impact:+38.1%
Trust score:4/5

Incident type 2 diabetes

1 evidences

Long-term daily vitamin C (500 mg) did not significantly change risk of developing type 2 diabetes in women at high CVD risk over ~9 years (trend to modest reduction).

Trust comment: Large, long-term randomized trial with strong design and adequate power; null result with a non-significant trend reduces likelihood of a meaningful effect.

Study Details

PMID:19491386
Participants:8171
Impact:Relative risk 0.89 (11% relative reduction), 95% CI 0.78–1.02, P=0.09 (not statistically significant)
Trust score:5/5

Oxygen saturation (SpO2)

1 evidences

High-dose IV vitamin C (1.5 g q6h for 5 days) produced some early improvements in oxygenation on day 3 but did not change mortality or discharge SpO2; hospital stay was longer in the vitamin C group.

Trust comment: Randomized but open-label with small sample size and concurrent therapies; results are suggestive but underpowered for hard outcomes.

Study Details

PMID:33573699
Participants:60
Impact:Higher median SpO2 on day 3 in vitamin C group (90.5% vs 88.0%, P=0.014) but no difference at discharge
Trust score:3/5

Hospital length of stay

1 evidences

High-dose IV vitamin C (1.5 g q6h for 5 days) produced some early improvements in oxygenation on day 3 but did not change mortality or discharge SpO2; hospital stay was longer in the vitamin C group.

Trust comment: Randomized but open-label with small sample size and concurrent therapies; results are suggestive but underpowered for hard outcomes.

Study Details

PMID:33573699
Participants:60
Impact:Longer median stay with vitamin C (8.5 vs 6.5 days, P=0.028)
Trust score:3/5

Mortality

4 evidences

In septic patients, adding vitamin C (with/without thiamine) did not change mortality but combined vitamin C+thiamine was associated with greater improvement in SOFA score; oxidative stress markers were higher in sepsis than healthy controls.

Trust comment: Randomized groups of modest size (n=80) with measured biochemical outcomes; mortality endpoint underpowered for definitive conclusions.

Study Details

PMID:35438278
Participants:80
Impact:No additional mortality benefit with Vitamin C ± Thiamine (no difference vs control)
Trust score:3/5

In term infants with perinatal asphyxia, early intravenous ascorbic acid plus oral ibuprofen did not improve cytokines, mortality, neurologic discharge status, or 6-month developmental outcomes versus placebo.

Trust comment: Randomized neonatal trial but small sample and vitamin C was co-administered with ibuprofen; no benefit demonstrated.

Study Details

PMID:19242485
Participants:60
Impact:37% (intervention) vs 33% (control); no significant difference
Trust score:3/5

High-dose IV vitamin C (1.5 g q6h for 5 days) produced some early improvements in oxygenation on day 3 but did not change mortality or discharge SpO2; hospital stay was longer in the vitamin C group.

Trust comment: Randomized but open-label with small sample size and concurrent therapies; results are suggestive but underpowered for hard outcomes.

Study Details

PMID:33573699
Participants:60
Impact:No difference (3 deaths vs 3 deaths)
Trust score:3/5

Randomized, triple‑blind trial of perioperative ascorbic acid vs placebo in CABG patients; monitored postoperative atrial fibrillation and complications.

Trust comment: Randomized, triple‑blind trial with adequate sample and clear clinical endpoints; well‑reported negative finding.

Study Details

PMID:23022248
Participants:185
Impact:no difference (no effect on mortality)
Trust score:4/5

Serum vitamin C

20 evidences

A double-blind RCT of a micronutrient combination including vitamin D3 modestly improved common cold symptom scores and reduced the decline in 25(OH)D3 vs placebo.

Trust comment: Large double-blind randomized multicenter trial (n=192) with clinical and biochemical endpoints, but used a multi-nutrient preparation so vitamin C-specific causal effects cannot be isolated.

Study Details

PMID:22184801
Participants:192
Impact:increase (active vs placebo, p ≤ 0.001)
Trust score:4/5

Physically active men who practiced yoga for 3 months had improvements in antioxidant markers (including higher vitamin C) and some metabolic measures versus controls.

Trust comment: Controlled human study with objective biochemical endpoints, but non-blinded, lifestyle intervention and results reported without detailed effect sizes in the abstract.

Study Details

PMID:24834493
Participants:64
Impact:increased (statistically significant)
Trust score:3/5

Large observational cohort: heavier soup consumers had higher dietary vitamin C intake; serum vitamin C was slightly higher but not significantly.

Trust comment: Large cohort with repeated 24-h records supports dietary associations, but observational design limits causal inference.

Study Details

PMID:14639794
Participants:4988
Impact:higher (not statistically significant)
Trust score:3/5

In critically ill patients, supplementation with vitamins A, C and E reduced lipid peroxidation (MDA) and altered antioxidant vitamin levels but did not change clinical outcomes (ventilation, mortality, length of stay).

Trust comment: Small non-blinded dietary supplementation study with limited sample (n=34) and no demonstrated clinical benefit, limiting confidence in clinical relevance.

Study Details

PMID:24160231
Participants:34
Impact:trend toward increase in supplemented group (not clearly quantified)
Trust score:3/5

Randomized 8-week trial: adding fruit or nuts raised serum vitamin C in both groups; no change in hepatic fat; basal metabolic rate increased in the nut group.

Trust comment: Randomized human trial with objective biochemical and MRI outcomes but small sample size limits precision.

Study Details

PMID:26788923
Participants:30
Impact:Fruit: 16.3 → 28.7 μM (+12.4 μM, +76%, p=0.017 within-group); Nut: 8.7 → 17.2 μM (+8.5 μM, +98%, p=0.009 within-group); no significant difference between groups (p=0.53)
Trust score:4/5

Six months of a multivitamin (including 150 mg vitamin C) prevented the decline in serum vitamin C seen in the placebo group but did not raise vitamin C above baseline.

Trust comment: Large randomized double-blind placebo-controlled trial in elderly women with objective nutrient measurements, though vitamin C was given as part of a multivitamin.

Study Details

PMID:15255454
Participants:220
Impact:no change from baseline in supplemented group vs significant decrease in placebo after 6 months (placebo decreased; P=0.000)
Trust score:4/5

Four-week multi-antioxidant supplementation (including 1500 mg/day vitamin C) raised serum vitamin levels but did not change markers of oxidative stress, airway inflammation, or allergen-specific immune responses.

Trust comment: Randomized controlled trial with measured biochemical and functional endpoints; modest sample size and multi-nutrient supplement complicates attribution to vitamin C alone.

Study Details

PMID:17250690
Participants:54
Impact:significant increase (P<0.001) after supplementation
Trust score:4/5

Higher blood vitamin C was associated with lower odds of mild dementia in this cross-sectional case-control study of older adults.

Trust comment: Population-based case-control (cross-sectional) association with multiple adjustments but cannot establish causality.

Study Details

PMID:22710913
Participants:232
Impact:lower in demented vs controls (significant)
Trust score:3/5

Double-blind randomized trial in 106 alcohol-dependent inpatients comparing 21 days of micronutrient supplementation (including zinc 20 mg) versus placebo and measuring serum vitamin and trace element levels.

Trust comment: Randomized double-blind trial with moderate size but used a multi-nutrient supplement so vitamin C–specific effects are not isolated.

Study Details

PMID:12897045
Participants:106
Impact:significantly increased in supplement group vs placebo after 21 days
Trust score:3/5

Obese participants on a 3-month low-calorie, DRI-covering formula diet showed declines in cellular and serum vitamin C but an increase in leukocyte vitamin C; some vitamin C deficiency cases increased after the diet.

Trust comment: Human pilot study with well-described methods and intracellular measures but small subgroup sample sizes (serum n=14) limit precision.

Study Details

PMID:22657586
Participants:32
Impact:−37% (59.44 → 37.29 μmol/L; n.s.)
Trust score:3/5

Hemodialysis patients given 250 mg vitamin C every other day for 12 weeks had higher blood vitamin C, lower oxidative stress marker, and improved cholesterol/LDL measures.

Trust comment: Randomized double-blind RCT in a relevant patient group with clear biochemical endpoints but small sample (n=42).

Study Details

PMID:20533214
Participants:42
Impact:increase (significant vs baseline p=0.033; vs placebo p=0.001)
Trust score:4/5

Six-month double-blind RCT in institutionalized elderly: vitamin supplementation (including vitamin C) increased serum vitamin levels and improved enzymatic antioxidant activity.

Trust comment: Large randomized, double-blind, placebo-controlled trial with objective biochemical endpoints, though clinical outcomes limited.

Study Details

PMID:8862480
Participants:575
Impact:Increased (statistically significant; exact values not provided in excerpt)
Trust score:4/5

In 44 men with moderate-to-severe COPD, an 8-week fortified whey beverage containing 275 mg elemental magnesium improved inflammation, fat-free mass, muscle strength, and respiratory-quality-of-life measures versus control.

Trust comment: Single-blind RCT with low dropout showing multiple benefits, but multi-ingredient intervention (whey, magnesium, vitamin C) and lack of placebo beverage limit attribution specifically to vitamin C.

Study Details

PMID:32807165
Participants:44
Impact:+6.00 μM/L (intervention change); between-group P=0.004
Trust score:3/5

In zinc-deficient hemodialysis patients, three months of zinc supplementation increased serum zinc, improved red blood cell osmotic fragility and reduced lipid peroxidation (MDA), but some side effects occurred with zinc.

Trust comment: Randomized study with clear biochemical outcomes but small, specific (zinc-deficient) population limits generalizability.

Study Details

PMID:11979503
Participants:34
Impact:increased
Trust score:3/5

A single 500 g strawberry beverage (providing ~255 mg vitamin C) rapidly raised serum vitamin C and folate and modestly improved LDL antioxidant capacity without affecting postprandial glucose.

Trust comment: Randomized, placebo-controlled, double-blind crossover in healthy volunteers with objective biochemical endpoints but small sample size.

Study Details

PMID:37008410
Participants:23
Impact:Increased significantly postprandially, peaking at 15.0 ± 2.5 μg/ml at 2 hours
Trust score:4/5

In healthy adults, serum vitamin C concentrations differed by GST genotype and were associated with differences in oxidative stress biomarkers.

Trust comment: Large cross-sectional biomarker study with genotyping; observational associations cannot prove causation.

Study Details

PMID:21813807
Participants:383
Impact:higher in GSTM1‑0 genotype (P=0.006)
Trust score:4/5

High-dose vitamins C+E raised serum vitamin levels but unexpectedly increased markers of haemolysis without improving haemoglobin in sickle cell patients.

Trust comment: Randomized, double-blind, placebo-controlled trial with a moderate sample (n=83); clear and clinically important outcomes.

Study Details

PMID:23278176
Participants:83
Impact:significantly increased with supplementation
Trust score:4/5

Critically ill septic patients receiving an enteral supplement (including vitamin C) had faster improvement in organ dysfunction and serum vitamin C rose to normal range by day 3.

Trust comment: Randomized, double-blind clinical trial in humans, but vitamin C was part of a multi-nutrient supplement so specific attribution is limited.

Study Details

PMID:18007263
Participants:55
Impact:increased from 10.6 to 58.7 μmol/L by day 3 (to normal range)
Trust score:4/5

Drinking Concord grape juice daily for 9 weeks increased serum vitamin C, improved antioxidant measures, and increased certain immune cell measures versus placebo.

Trust comment: Randomized double-blind placebo-controlled trial (n=85) with objective immunologic and biochemical endpoints, but grape juice contains multiple bioactives so vitamin C-specific effects are not isolated.

Study Details

PMID:21138361
Participants:85
Impact:increase (significant, P<0.05)
Trust score:4/5

A 3-week fruit/vegetable concentrate raised blood vitamin C and some antioxidants but did not change markers of oxidative damage in male smokers.

Trust comment: Randomized crossover trial directly measured serum vitamin C with clear outcomes but had a small sample and used a complex concentrate, limiting attribution solely to vitamin C.

Study Details

PMID:11385058
Participants:22
Impact:increased
Trust score:3/5

LDL antioxidant capacity (lag time)

1 evidences

A single 500 g strawberry beverage (providing ~255 mg vitamin C) rapidly raised serum vitamin C and folate and modestly improved LDL antioxidant capacity without affecting postprandial glucose.

Trust comment: Randomized, placebo-controlled, double-blind crossover in healthy volunteers with objective biochemical endpoints but small sample size.

Study Details

PMID:37008410
Participants:23
Impact:Lag time prolonged (~+1.0 min at 1 h; significant)
Trust score:4/5

Postprandial blood glucose

1 evidences

A single 500 g strawberry beverage (providing ~255 mg vitamin C) rapidly raised serum vitamin C and folate and modestly improved LDL antioxidant capacity without affecting postprandial glucose.

Trust comment: Randomized, placebo-controlled, double-blind crossover in healthy volunteers with objective biochemical endpoints but small sample size.

Study Details

PMID:37008410
Participants:23
Impact:No significant difference versus placebo (no clinically meaningful increase)
Trust score:4/5

DOPI (pigmentation intensity)

1 evidences

Vitamin C injections into the gums reduced gum darkening but laser produced faster and larger improvements; pain was higher immediately after injections though satisfaction was similar.

Trust comment: Randomized double-blind (evaluator/statistician) RCT with complete follow-up but small sample (n=26) and operator/patient unblinding.

Study Details

PMID:37990224
Participants:26
Impact:−1.51 points (−61%) at 3 months (mean 2.46 → 0.95)
Trust score:4/5

GPI (pigmentation area)

1 evidences

Vitamin C injections into the gums reduced gum darkening but laser produced faster and larger improvements; pain was higher immediately after injections though satisfaction was similar.

Trust comment: Randomized double-blind (evaluator/statistician) RCT with complete follow-up but small sample (n=26) and operator/patient unblinding.

Study Details

PMID:37990224
Participants:26
Impact:−0.62 points (−24%) at 3 months (mean 2.54 → 1.92)
Trust score:4/5

Immediate postoperative pain (VAS)

1 evidences

Vitamin C injections into the gums reduced gum darkening but laser produced faster and larger improvements; pain was higher immediately after injections though satisfaction was similar.

Trust comment: Randomized double-blind (evaluator/statistician) RCT with complete follow-up but small sample (n=26) and operator/patient unblinding.

Study Details

PMID:37990224
Participants:26
Impact:Higher in Vitamin C mesotherapy vs laser (P=0.005)
Trust score:4/5

ΔSOFA (organ dysfunction change)

1 evidences

In septic patients, adding vitamin C (with/without thiamine) did not change mortality but combined vitamin C+thiamine was associated with greater improvement in SOFA score; oxidative stress markers were higher in sepsis than healthy controls.

Trust comment: Randomized groups of modest size (n=80) with measured biochemical outcomes; mortality endpoint underpowered for definitive conclusions.

Study Details

PMID:35438278
Participants:80
Impact:Greater improvement in ΔSOFA in Vitamin C + Thiamine group (statistically significant vs other groups)
Trust score:3/5

Malondialdehyde (oxidative stress)

2 evidences

Daily vitamins E+C for 1 year improved antioxidant biomarkers but did not improve cognitive test scores in elderly with mild cognitive impairment.

Trust comment: Large double-blind randomized placebo-controlled trial with objective biomarkers but no cognitive benefit observed.

Study Details

PMID:24326981
Participants:256
Impact:Significantly decreased (P < 0.001)
Trust score:4/5

In septic patients, adding vitamin C (with/without thiamine) did not change mortality but combined vitamin C+thiamine was associated with greater improvement in SOFA score; oxidative stress markers were higher in sepsis than healthy controls.

Trust comment: Randomized groups of modest size (n=80) with measured biochemical outcomes; mortality endpoint underpowered for definitive conclusions.

Study Details

PMID:35438278
Participants:80
Impact:Higher in sepsis vs healthy controls (1.81 ± 1.18 vs 0.78 ± 0.36 µmol/L)
Trust score:3/5

Anxiety (Beck Anxiety Inventory)

1 evidences

Two weeks of 500 mg/day oral vitamin C reduced anxiety scores and raised plasma vitamin C compared with placebo in high-school students.

Trust comment: Double-blind randomized placebo-controlled trial but small sample (n=42) and short duration (14 days).

Study Details

PMID:26353411
Participants:42
Impact:Decrease in anxiety scores vs placebo (significant)
Trust score:3/5

Mean heart rate

1 evidences

Two weeks of 500 mg/day oral vitamin C reduced anxiety scores and raised plasma vitamin C compared with placebo in high-school students.

Trust comment: Double-blind randomized placebo-controlled trial but small sample (n=42) and short duration (14 days).

Study Details

PMID:26353411
Participants:42
Impact:Between-group difference in mean heart rate (significant)
Trust score:3/5

CRPS incidence after TKA

1 evidences

Taking 1 g/day vitamin C for 40 days after knee replacement reduced the risk of complex regional pain syndrome compared with no vitamin C.

Trust comment: Prospective randomized study with substantial sample size and statistically significant effect on clinically meaningful endpoint.

Study Details

PMID:33438072
Participants:292
Impact:Reduced from 12.2% (control) to 3.9% (Vitamin C); relative risk 0.27 (95% CI 0.1–0.8); p=0.008
Trust score:4/5

Serum cortisol (post-etomidate)

1 evidences

Pre-treatment with IV vitamin C prevented the significant drop in serum cortisol seen after etomidate in the control group, suggesting protection against etomidate-induced adrenal suppression.

Trust comment: Randomized single-center trial with modest final sample (n=51) and baseline cortisol imbalance limiting certainty of effect size.

Study Details

PMID:37005585
Participants:51
Impact:No significant decrease with Vitamin C (median 40.8 → 39.4; P=0.564) vs significant decrease without Vitamin C (median 15.9 → 15.05; intragroup P=0.005)
Trust score:3/5

morphine consumption

1 evidences

Single 2 g oral vitamin C given before surgery reduced 24‑hr morphine use after laparoscopic cholecystectomy.

Trust comment: Randomized, double-blind, placebo‑controlled trial with a prespecified primary outcome and significant reduction in opioid use; limited to single perioperative dose and one surgical population.

Study Details

PMID:22402954
Participants:80
Impact:-6.6 mg (−29%) over 24 hr; P=0.02
Trust score:4/5

incisional pain scores

1 evidences

Single 2 g oral vitamin C given before surgery reduced 24‑hr morphine use after laparoscopic cholecystectomy.

Trust comment: Randomized, double-blind, placebo‑controlled trial with a prespecified primary outcome and significant reduction in opioid use; limited to single perioperative dose and one surgical population.

Study Details

PMID:22402954
Participants:80
Impact:no significant change
Trust score:4/5

side effects (nausea/vomiting, pruritus, sedation)

1 evidences

Single 2 g oral vitamin C given before surgery reduced 24‑hr morphine use after laparoscopic cholecystectomy.

Trust comment: Randomized, double-blind, placebo‑controlled trial with a prespecified primary outcome and significant reduction in opioid use; limited to single perioperative dose and one surgical population.

Study Details

PMID:22402954
Participants:80
Impact:no significant change
Trust score:4/5

C-reactive protein (CRP)

13 evidences

One week of 2 g/day vitamin C in healthy young adults reduced inflammatory markers and modestly lowered blood pressure and improved antioxidant enzyme activity under high PM exposure.

Trust comment: Randomized double-blind crossover with biomarker and BP measures; short intervention (1 week) limits inference on long-term effects.

Study Details

PMID:35689890
Participants:58
Impact:−34.01% (significant)
Trust score:4/5

In people with atrophic gastritis, a higher vitamin C dose raised serum ascorbic acid but did not change CRP or SAA over 5 years.

Trust comment: Population-based, double-blind RCT with long follow-up and adequate completion (120 and 124), but limited to biomarker outcomes.

Study Details

PMID:23167953
Participants:244
Impact:no significant difference between 50 mg and 500 mg groups (P=0.63)
Trust score:4/5

Oral vitamin C (250 mg thrice weekly for 2 months) restored plasma vitamin C but did not change markers of oxidative stress or inflammation in haemodialysis patients.

Trust comment: Randomized prospective open-label trial with objective biochemical endpoints but small sample size limits precision.

Study Details

PMID:15972322
Participants:33
Impact:no change
Trust score:3/5

Five-day IV antioxidant regimen (including high-dose vitamin C) did not improve early organ dysfunction (SOFA) or AKI overall, but reduced CRP (blunted inflammation) and showed some shorter hospital stay in trauma subgroup.

Trust comment: Well-designed randomized double-blind trial in critically ill patients with sufficient size, but single-center with protocol violations and multi-nutrient intervention limits attribution to vitamin C alone.

Study Details

PMID:18687132
Participants:200
Impact:significantly lower CRP trajectory in AOX group (blunted inflammatory response)
Trust score:4/5

In hemodialysis patients with refractory anemia, intravenous vitamin C (300 mg each dialysis) improved hemoglobin and iron availability and reduced inflammation markers over 6 months.

Trust comment: Randomized but open-label and moderate sample size; objective lab endpoints supportive but potential bias from unblinded design.

Study Details

PMID:16564942
Participants:41
Impact:−1.9 mg/dL (2.8 → 0.9 mg/dL)
Trust score:3/5

Increasing fruit and vegetable intake after surgery reduced CRP more than usual diet, with a correlation between vitamin C intake and CRP reduction.

Trust comment: Prospective controlled dietary intervention with objective CRP outcome but short duration and modest sample size limit generalizability.

Study Details

PMID:21336433
Participants:60
Impact:decreased more in high fruit/vegetable group (P=0.028)
Trust score:3/5

A multi-component nutraceutical (includes vitamin D among other ingredients) reduced lymphocyte counts, IL-6, and CRP and improved self-reported wellness in hospitalized elderly compared with untreated elderly controls.

Trust comment: Adequately sized study with randomized elderly treatment groups but multi-ingredient supplement and hospitalized sample make isolating vitamin C effects and generalizability limited.

Study Details

PMID:36079732
Participants:120
Impact:decrease (statistically significant)
Trust score:3/5

In dental students under exam stress, a daily micronutrient supplement including vitamin C modestly raised plasma vitamin C and showed small non-significant improvements in inflammatory and antioxidant markers.

Trust comment: Small randomized pilot study (40 completers) with objective lab measures but limited power and mostly non-significant differences.

Study Details

PMID:22027646
Participants:40
Impact:smaller CRP increase in supplement group (p=0.059)
Trust score:3/5

1000 mg/day vitamin C for 2 months lowered CRP among participants with elevated baseline CRP (≥1.0 mg/L).

Trust comment: Large randomized trial with significant subgroup effect in those with elevated baseline CRP, though overall cohort (low median CRP) showed no effect.

Study Details

PMID:18952164
Participants:396
Impact:median −25.3% vs placebo in CRP ≥1.0 mg/L subgroup (vitamin C within-group median −0.25 mg/L, −16.7%); P=0.02
Trust score:5/5

In septic shock patients, oral vitamin C (small group) restored vitamin C levels and improved organ dysfunction and some inflammation/oxidative markers.

Trust comment: Randomized, triple-masked clinical trial but small arm sizes (vitamin C n=18) limit power for clinical endpoints despite statistically significant biomarker/score changes.

Study Details

PMID:33213070
Participants:97
Impact:decreased during treatment (p ≤ 0.05)
Trust score:4/5

Two-month Mediterranean-style diet (which increased dietary vitamin C intake) showed within-group decreases in some inflammation markers but no significant between-group changes for most adhesion molecules.

Trust comment: Randomized dietary intervention in humans with modest sample size; vitamin C intake changed as part of a broader diet, and between-group differences were generally not significant.

Study Details

PMID:28361746
Participants:90
Impact:decreased within intervention group (between-group change not statistically significant)
Trust score:3/5

A 5-week multi-ingredient supplement (including vitamin C) modestly increased adiponectin and produced subtle omics-signals of reduced inflammation and oxidative stress in overweight men; CRP unchanged.

Trust comment: Well-controlled double-blind crossover but small sample (n=36) and effects cannot be attributed to vitamin C alone because of the multi-ingredient formulation.

Study Details

PMID:20181810
Participants:36
Impact:no change
Trust score:3/5

In 62 CKD patients randomized to three oral iron therapies, the group receiving ferric sodium EDTA combined with vitamin C and other micronutrients showed larger improvements in hemoglobin and iron parameters and reductions in inflammatory markers.

Trust comment: Randomized multicenter study with objective labs, but open-label design and multi-nutrient combination prevent attributing effects to vitamin C alone.

Study Details

PMID:35631257
Participants:62
Impact:-2.53 mg/dL (Group 2, 6 months)
Trust score:3/5

oxidative DNA damage (urinary 8‑OHdG)

1 evidences

500 mg/day vitamin C for ~2 months did not significantly change urinary 8‑OHdG (a marker of oxidative DNA damage) in nonsmoking adults.

Trust comment: Well‑conducted randomized, placebo‑controlled 2×2 factorial trial with moderate sample size and direct biomarker measurement yielding null results.

Study Details

PMID:10919732
Participants:184
Impact:no significant change (no main effect or interaction vs placebo)
Trust score:4/5

oxygen saturation

1 evidences

High‑dose IV vitamin C (2 g q6h for 5 days) was associated with improved oxygen saturation, reduced respiratory rate, and less lung involvement on CT versus standard care in this small trial.

Trust comment: Randomized clinical trial with significant physiologic and imaging signals but small, single‑center sample with unclear group sizes and limited reporting.

Study Details

PMID:34746999
Participants:54
Impact:increase from 86±5% to 90±3% (Δ +4 percentage points); P=0.02
Trust score:3/5

respiratory rate

1 evidences

High‑dose IV vitamin C (2 g q6h for 5 days) was associated with improved oxygen saturation, reduced respiratory rate, and less lung involvement on CT versus standard care in this small trial.

Trust comment: Randomized clinical trial with significant physiologic and imaging signals but small, single‑center sample with unclear group sizes and limited reporting.

Study Details

PMID:34746999
Participants:54
Impact:decrease from 27±3 to 24±3 breaths/min (Δ −3); P=0.03
Trust score:3/5

lung involvement on CT

1 evidences

High‑dose IV vitamin C (2 g q6h for 5 days) was associated with improved oxygen saturation, reduced respiratory rate, and less lung involvement on CT versus standard care in this small trial.

Trust comment: Randomized clinical trial with significant physiologic and imaging signals but small, single‑center sample with unclear group sizes and limited reporting.

Study Details

PMID:34746999
Participants:54
Impact:significantly lower extent of involvement vs control at end of treatment; P=0.02
Trust score:3/5

NOX2-dependent ROS generation

1 evidences

Single 1000 mg oral vitamin C dose in recovering COVID‑19 volunteers produced a transient inhibition of NOX2‑dependent ROS but did not significantly improve mitochondrial or iNOS‑dependent ROS or bioavailable NO compared with PB‑Blend.

Trust comment: Randomized, double‑blind, acute single‑dose study with real‑time mechanistic measures but small sample size and short observation period limiting clinical inference.

Study Details

PMID:40508019
Participants:28
Impact:transient reduction up to ~36% (max at ~30 min), effect diminished by ~3 hr
Trust score:3/5

iNOS-dependent ROS generation

1 evidences

Single 1000 mg oral vitamin C dose in recovering COVID‑19 volunteers produced a transient inhibition of NOX2‑dependent ROS but did not significantly improve mitochondrial or iNOS‑dependent ROS or bioavailable NO compared with PB‑Blend.

Trust comment: Randomized, double‑blind, acute single‑dose study with real‑time mechanistic measures but small sample size and short observation period limiting clinical inference.

Study Details

PMID:40508019
Participants:28
Impact:no reduction; tended to increase at later time points
Trust score:3/5

bioavailable NO (NOHb)

1 evidences

Single 1000 mg oral vitamin C dose in recovering COVID‑19 volunteers produced a transient inhibition of NOX2‑dependent ROS but did not significantly improve mitochondrial or iNOS‑dependent ROS or bioavailable NO compared with PB‑Blend.

Trust comment: Randomized, double‑blind, acute single‑dose study with real‑time mechanistic measures but small sample size and short observation period limiting clinical inference.

Study Details

PMID:40508019
Participants:28
Impact:no significant change
Trust score:3/5

opioid requirement

1 evidences

Randomized trial comparing memantine vs vitamin C after elective abdominal surgery; memantine reduced pain more than vitamin C.

Trust comment: Small single-center double-blind RCT on humans but very small sample limits precision.

Study Details

PMID:40497407
Participants:34
Impact:Vitamin C associated with higher opioid use vs memantine (memantine reduced use but not statistically significant)
Trust score:3/5

dietary vitamin C intake

9 evidences

Large observational cohort: heavier soup consumers had higher dietary vitamin C intake; serum vitamin C was slightly higher but not significantly.

Trust comment: Large cohort with repeated 24-h records supports dietary associations, but observational design limits causal inference.

Study Details

PMID:14639794
Participants:4988
Impact:higher in heavy soup consumers
Trust score:3/5

Daily fruit-and-vegetable puree drinks raised dietary vitamin C and plasma carotenoids and produced a trend toward improved endothelium-dependent vasodilation.

Trust comment: Randomized crossover with 39 completers and objective biochemical and vascular measures; reasonably reliable though vasodilation effect was borderline.

Study Details

PMID:22831286
Participants:39
Impact:significantly increased (P<0.001)
Trust score:4/5

An intensive dietary program that increased vitamin C intake (among other changes) improved iron intake and produced modest increases in iron stores compared with placebo, while iron supplementation produced larger increases.

Trust comment: Randomized controlled 16‑week intervention with objective iron outcomes, but vitamin C was part of a multi-component dietary change so effects are indirect.

Study Details

PMID:11601562
Participants:75
Impact:significantly increased in Diet group after counseling
Trust score:3/5

Five-year randomized supplementation (50 vs 500 mg/day) showing larger increases in serum vitamin C with high-dose without changing dietary intake.

Trust comment: Large, long-term randomized trial with clear biochemical outcomes though some dropouts and early termination of beta-carotene arm.

Study Details

PMID:12805247
Participants:244
Impact:No meaningful change in intake in supplement groups (~−2.31 mg/day, 95% CI −15.3–10.7)
Trust score:4/5

Increasing fruit and vegetable intake raised dietary and biomarker vitamin C levels in adults at increased CVD risk.

Trust comment: Randomized dietary intervention with objective biomarker verification and reasonable sample size.

Study Details

PMID:22476876
Participants:174
Impact:increase (significant vs control, P=0.0001)
Trust score:4/5

A mobile-technology education program (MyPinkMom) for anemic pregnant women increased dietary vitamin C intake substantially and improved hemoglobin versus routine counseling.

Trust comment: Cluster RCT with adequate sample size and clear, significant changes in dietary vitamin C intake and hemoglobin, though biochemical iron markers were not measured.

Study Details

PMID:36473006
Participants:104
Impact:+123.56 mg/day (mean difference intervention vs control at week 6; 244.31 vs 120.76 mg/day; p=0.001)
Trust score:4/5

In patients receiving non-surgical periodontal therapy, a 4‑week free-sugar avoidance led to greater reductions in bleeding on probing and periodontal inflamed surface area and increased dietary vitamin C intake compared with control.

Trust comment: Single-blinded randomized controlled exploratory trial with objective clinical endpoints but very small sample (n=22) and dietary change (not isolated vitamin C supplementation).

Study Details

PMID:39185702
Participants:22
Impact:+75.89 mg/day (mean difference T1–T2, significant)
Trust score:3/5

Large prospective cohort of male smokers found no link between dietary or serum antioxidant vitamins (including vitamin C) and colorectal cancer risk.

Trust comment: Large prospective cohort with adjustment for major confounders; high sample size supports reliability.

Study Details

PMID:12080400
Participants:26951
Impact:no significant association with colorectal cancer risk
Trust score:4/5

6-month randomized weight-loss program (partial meal replacements + exercise) in older obese adults improved diet quality and increased intake of key micronutrients despite reduced calories.

Trust comment: Randomized intervention with dietary records and objective weight outcomes; micronutrient increases reported but blood nutrient status not all measured.

Study Details

PMID:20617289
Participants:71
Impact:Higher in weight-loss (WL) group at 6 months versus weight-stable (WS) control (study reports micronutrient intakes were higher for WL; exact mg not provided)
Trust score:4/5

fatigue (current, 0-10)

1 evidences

Single 10 g IV vitamin C reduced 'fatigue right now' scores vs placebo at 2 hours and persisted at 24 hours; plasma vitamin C rose markedly and oxidative stress fell.

Trust comment: Well-conducted double-blind RCT with adequate sample size, objective biochemical measures, and low dropout rate.

Study Details

PMID:22264303
Participants:141
Impact:Vitamin C group decreased from 5.64 to 5.10 at 2h (−0.54) and to 4.97 at 24h (−0.67); difference vs placebo significant (p=0.004)
Trust score:5/5

oxidative stress (FORT)

1 evidences

Single 10 g IV vitamin C reduced 'fatigue right now' scores vs placebo at 2 hours and persisted at 24 hours; plasma vitamin C rose markedly and oxidative stress fell.

Trust comment: Well-conducted double-blind RCT with adequate sample size, objective biochemical measures, and low dropout rate.

Study Details

PMID:22264303
Participants:141
Impact:Decreased from 311.76 to 184.46 mmol/dl H2O2 at 2 hours (p<0.001)
Trust score:5/5

oxygen requirement at 36 weeks postmenstrual age

1 evidences

Randomized trial in very preterm infants comparing higher vs lower vitamin C intake for 28 days; no significant differences in primary clinical outcomes.

Trust comment: Randomized double-blind neonatal trial with clinically relevant outcomes but limited sample for detecting some differences.

Study Details

PMID:15724034
Participants:119
Impact:HH group 19% vs LL group 41% (p=0.06, trend but not statistically significant)
Trust score:4/5

primary clinical outcomes (oxygen at 28 days, days on oxygen, retinopathy)

1 evidences

Randomized trial in very preterm infants comparing higher vs lower vitamin C intake for 28 days; no significant differences in primary clinical outcomes.

Trust comment: Randomized double-blind neonatal trial with clinically relevant outcomes but limited sample for detecting some differences.

Study Details

PMID:15724034
Participants:119
Impact:No significant differences between supplementation protocols
Trust score:4/5

H2O2-induced DNA breakages (WBC)

1 evidences

Randomized placebo-controlled trial in stable COPD patients showing 12 weeks of vitamin C (250 mg/day) improved resistance of WBC DNA to oxidative challenge but did not change lung function.

Trust comment: Small randomized human study with a biologic surrogate endpoint showing antioxidant effects, but underpowered for clinical outcomes.

Study Details

PMID:18271282
Participants:35
Impact:Suppressed by ~52% in C250 group after 12 weeks (p<0.05)
Trust score:3/5

TBARS and spirometric parameters

1 evidences

Randomized placebo-controlled trial in stable COPD patients showing 12 weeks of vitamin C (250 mg/day) improved resistance of WBC DNA to oxidative challenge but did not change lung function.

Trust comment: Small randomized human study with a biologic surrogate endpoint showing antioxidant effects, but underpowered for clinical outcomes.

Study Details

PMID:18271282
Participants:35
Impact:No significant change after 12 weeks
Trust score:3/5

perfused small vessel density (sPVD)

1 evidences

Pilot randomized trial in septic shock patients showing hydrocortisone plus vitamin C and B1 improved sublingual microcirculation and renal perfusion vs hydrocortisone alone at 24 hours.

Trust comment: Randomized pilot study on humans with objective microcirculation endpoints but small single-center sample and combination therapy prevents isolating vitamin C effect.

Study Details

PMID:36911931
Participants:22
Impact:Mean difference +7.075 mm/mm² at 24h vs control (95% CI 2.39–11.76, p=0.008)
Trust score:3/5

sPPV, sTVD, MFI (microcirculation parameters)

1 evidences

Pilot randomized trial in septic shock patients showing hydrocortisone plus vitamin C and B1 improved sublingual microcirculation and renal perfusion vs hydrocortisone alone at 24 hours.

Trust comment: Randomized pilot study on humans with objective microcirculation endpoints but small single-center sample and combination therapy prevents isolating vitamin C effect.

Study Details

PMID:36911931
Participants:22
Impact:All significantly higher at 24h in treatment group (sPPV mean diff +13.49, p=0.019; sTVD mean diff +5.659, p=0.016; MFI mean diff +0.459, p=0.037)
Trust score:3/5

lactate

1 evidences

Pilot randomized trial in septic shock patients showing hydrocortisone plus vitamin C and B1 improved sublingual microcirculation and renal perfusion vs hydrocortisone alone at 24 hours.

Trust comment: Randomized pilot study on humans with objective microcirculation endpoints but small single-center sample and combination therapy prevents isolating vitamin C effect.

Study Details

PMID:36911931
Participants:22
Impact:Decreased at 24h in treatment group (mean difference 2.839 mmol/L, 95% CI 0.280–5.398, p=0.032)
Trust score:3/5

serum ferritin

11 evidences

A fortified drink given 6 days/week for 8 weeks reduced vitamin B12 deficiency prevalence and increased vitamin B12 concentration and hemoglobin in schoolchildren.

Trust comment: Checklist: confirmed Vitamin C included in the fortified drink; primary outcomes (vitamin C status, Hb, ferritin) identified; participant count confirmed—randomized double-blind placebo-controlled trial with strong internal validity.

Study Details

PMID:23232585
Participants:246
Impact:increase (significantly higher in intervention, P<0.001)
Trust score:4/5

Thirty-two hemodialysis patients with functional iron deficiency were randomized to IV ascorbic acid or placebo thrice weekly for 3 months; ferritin declined significantly in the vitamin C group while other labs were unchanged.

Trust comment: Randomized clinical trial with objective lab outcome but small single-center sample limits generalizability.

Study Details

PMID:35271495
Participants:32
Impact:decreased at study end (statistically significant, P<0.05)
Trust score:3/5

Hemodialysis patients receiving 300 mg IV vitamin C each session for 3 months showed improved hemoglobin and transferrin saturation and reduced reticulocyte hemoglobin content and serum ferritin compared with standard care.

Trust comment: Small clinical intervention in hemodialysis patients with measurable improvements, but randomization and full trial details are unclear from the summary.

Study Details

PMID:18974579
Participants:46
Impact:significant decrease in vitamin C group
Trust score:3/5

Increasing consumption of citrus fruit/juice (rich in vitamin C) after meals improved serum ferritin in iron-depleted preschool children over three months.

Trust comment: Randomized pilot study with small sample; results suggest association between increased vitamin-C-rich intake and ferritin but limited size and duration.

Study Details

PMID:15580808
Participants:62
Impact:Control: 8.9→6.9 µg/dL (−2.0); Diet modification: 9.5→11.2 µg/dL (+1.7); Nutrition education: 6.9→10.7 µg/dL (+3.8) — increases in intervention groups significant
Trust score:3/5

Kindergarten children received Sprinkles (contain vitamin C among other micronutrients) daily or weekly for 13 weeks; high consumption and no evidence of iron overload were observed.

Trust comment: Cluster-randomized trial with objective safety outcomes; vitamin C was included in the mix but not isolated, so effects cannot be attributed to vitamin C alone.

Study Details

PMID:16684385
Participants:415
Impact:median SF: daily 71 µg/L, weekly 55 µg/L, control 54 µg/L (overall difference P=0.06; daily vs control P=0.02)
Trust score:3/5

In 324 anemic adolescent girls, once- or twice-weekly multiple micronutrient supplements (including vitamin C) improved vitamin C status and several other micronutrients compared with iron+folic acid over 52 weeks; hemoglobin differences were minimal overall.

Trust comment: Checklist: Vitamin C measured as part of MMN vs IFA comparison; main outcomes (vitamin C status, Hb, ferritin) identified; participant count confirmed—large randomized double-blind trial with appropriate follow-up.

Study Details

PMID:20702745
Participants:324
Impact:reduced iron deficiency across treatments (all effective); once-weekly MMN produced lower ferritin than other treatments
Trust score:4/5

Daily low-dose MNP containing bioavailable iron and 2.5 mg zinc reduced iron and zinc deficiencies and modestly improved weight-for-age over 23 weeks.

Trust comment: Randomized double-blind trial (n=200) with clear effects on iron/zinc status, but vitamin C was a component of a combined formula so its isolated effect is not determined.

Study Details

PMID:21178093
Participants:200
Impact:Increased (P < 0.05)
Trust score:3/5

Adding iron plus ascorbic acid to household water increased hemoglobin and ferritin in children and adults over 4 months.

Trust comment: Small community intervention (88 people) with clear pre/post biochemical changes, but iron+ascorbic combination makes isolated vitamin C effect indirect.

Study Details

PMID:12362799
Participants:88
Impact:Children: 27.6±21.6 to 33.8±22.1 ng/dL; Adults: 74.8±41.3 to 106.2±93.9 ng/dL (p<0.05 for adults)
Trust score:3/5

Randomized 16-week trial showing that eating vitamin C–rich gold kiwifruit with iron-fortified cereal improves iron status in women with low iron stores.

Trust comment: Randomized controlled dietary trial with clear biomarker changes, moderate sample size (final n=69).

Study Details

PMID:20727238
Participants:69
Impact:median increase 10.0 μg/L (kiwifruit) vs 1.0 μg/L (banana)
Trust score:4/5

A 6-month school feeding intervention with cowpea-based food plus a vitamin C-rich drink increased hemoglobin and reduced anemia prevalence in children.

Trust comment: Randomized school feeding intervention with 150 children in a malaria-endemic setting; reasonable size though infectious disease confounding present.

Study Details

PMID:26385950
Participants:150
Impact:no significant difference among groups
Trust score:4/5

Fortified porridge given for 6 months raised hemoglobin and ferritin and improved motor development in infants.

Trust comment: Large randomized trial with good completion (292); includes ascorbic acid as part of a multi-micronutrient fortification so effects are attributable to the combined formulation, not vitamin C alone.

Study Details

PMID:16280435
Participants:292
Impact:+9.4 µg/L intervention effect (95% CI: 3.6 to 15.1 µg/L)
Trust score:4/5

total reactive oxygen species (ROS)

1 evidences

244 subjects with atrophic gastritis were randomized to 50 mg or 500 mg vitamin C daily for 5 years; high-dose vitamin C reduced plasma ROS compared with low-dose (between-group p=0.01).

Trust comment: Large long-term randomized trial with objective biomarker outcome and statistically significant difference.

Study Details

PMID:19003734
Participants:244
Impact:high-dose: −2.70 (≈ −1.26%); low-dose: +4.16 (≈ +3.79%); between-group p=0.01
Trust score:4/5

ICU survival at 14 days

1 evidences

Low-dose enteral vitamin C (500 mg/day) for 14 days increased short-term survival duration in critically ill COVID-19 patients; serum calcium and other electrolytes were unchanged.

Trust comment: Randomized clinical trial with clinical endpoint but modest sample size, short follow-up, and methodological/ dosing limitations.

Study Details

PMID:34975830
Participants:100
Impact:higher proportion survived in vitamin C group: 16.1% vs 2.9% (p=0.028)
Trust score:3/5

survival duration (days)

1 evidences

Low-dose enteral vitamin C (500 mg/day) for 14 days increased short-term survival duration in critically ill COVID-19 patients; serum calcium and other electrolytes were unchanged.

Trust comment: Randomized clinical trial with clinical endpoint but modest sample size, short follow-up, and methodological/ dosing limitations.

Study Details

PMID:34975830
Participants:100
Impact:positive association with supplementation duration B=1.66 days per supplementation day (p=0.001)
Trust score:3/5

serum potassium

1 evidences

Low-dose enteral vitamin C (500 mg/day) for 14 days increased short-term survival duration in critically ill COVID-19 patients; serum calcium and other electrolytes were unchanged.

Trust comment: Randomized clinical trial with clinical endpoint but modest sample size, short follow-up, and methodological/ dosing limitations.

Study Details

PMID:34975830
Participants:100
Impact:vitamin C group: essentially unchanged (3.92→3.93 mEq/L) vs control increase (3.75→4.21 mEq/L)
Trust score:3/5

common cold incidence

1 evidences

Randomized, double-blind, placebo-controlled trial in 1,444 army recruits given vitamin C 6000 mg/day during 30 days; vitamin C reduced the odds of medically recorded common cold.

Trust comment: Large randomized double-blind trial with medical-record outcome in a specific young military population; high dose and single-population limit broader applicability.

Study Details

PMID:32139409
Participants:1444
Impact:reduced odds (OR 0.80; ~20% lower odds vs placebo)
Trust score:4/5

serum ascorbic acid

5 evidences

Pilot 3-month factorial randomized trial (vitamin C 0, 50, 1000 mg/day) in 54 middle-aged subjects; high-dose vitamin C (1000 mg/day) raised serum ascorbic acid substantially and reached steady state by 1 month.

Trust comment: Well-conducted pilot RCT with objective biochemical endpoints but small sample and short duration limit inference.

Study Details

PMID:10835489
Participants:54
Impact:+88–95% increase with 1000 mg/day (steady by 1 month); low-dose 50 mg not significantly different from placebo
Trust score:3/5

In smokers, daily 1000 mg vitamin C raised blood vitamin C and produced a large (81%) drop in blood lead after one week; 200 mg had no effect on lead.

Trust comment: Randomized 3-arm trial with clear, large effect for 1000 mg group though limited to healthy young male smokers and short follow-up.

Study Details

PMID:10204833
Participants:75
Impact:significant increase after 1 week (p≤0.001)
Trust score:4/5

In people with atrophic gastritis, a higher vitamin C dose raised serum ascorbic acid but did not change CRP or SAA over 5 years.

Trust comment: Population-based, double-blind RCT with long follow-up and adequate completion (120 and 124), but limited to biomarker outcomes.

Study Details

PMID:23167953
Participants:244
Impact:higher in high-dose group (1.73 vs 1.49 μg/l; P<0.001)
Trust score:4/5

Community dietary education increased reported vitamin C intake modestly but produced only minimal change in serum ascorbic acid.

Trust comment: Randomized community trial with objective biomarkers but intake measured by questionnaire and biomarker changes were modest/non‑significant.

Study Details

PMID:14572428
Participants:550
Impact:no significant change (net +0.1 vs -0.5 mg/L; p = 0.07)
Trust score:3/5

Giving oral antioxidant capsules around ESWL reduced markers of oxidative stress and short-term kidney injury compared with no antioxidants.

Trust comment: Randomized clinical trial with 120 patients and objective biochemical endpoints, but antioxidants were a multi-component product so Vitamin C–specific effects are not isolated.

Study Details

PMID:18064446
Participants:120
Impact:significant increase in antioxidant groups (P<0.001)
Trust score:4/5

superimposed preeclampsia incidence

1 evidences

In pregnant women with essential hypertension, daily vitamin C+E did not prevent superimposed preeclampsia or small-for-gestational-age infants.

Trust comment: Randomized controlled trial in humans with 50 completers; small sample but randomized design gives moderate trust.

Study Details

PMID:21174586
Participants:50
Impact:no change (8% vs 12%, p=1.00)
Trust score:4/5

aggravation of hypertension

1 evidences

In pregnant women with essential hypertension, daily vitamin C+E did not prevent superimposed preeclampsia or small-for-gestational-age infants.

Trust comment: Randomized controlled trial in humans with 50 completers; small sample but randomized design gives moderate trust.

Study Details

PMID:21174586
Participants:50
Impact:no significant reduction (12% vs 32%, p=0.172)
Trust score:4/5

small for gestational age

2 evidences

In pregnant women with essential hypertension, daily vitamin C+E did not prevent superimposed preeclampsia or small-for-gestational-age infants.

Trust comment: Randomized controlled trial in humans with 50 completers; small sample but randomized design gives moderate trust.

Study Details

PMID:21174586
Participants:50
Impact:no change (4% vs 6%, p=1.00)
Trust score:4/5

Combined vitamin C (1000 mg) and vitamin E did not prevent pre-eclampsia and was associated with a higher rate of low birthweight infants.

Trust comment: Large multicenter randomized placebo-controlled trial with high participant number and intention-to-treat analysis.

Study Details

PMID:16616557
Participants:2395
Impact:no change
Trust score:5/5

total mood disturbance (TMD)

1 evidences

Eating two SunGold kiwifruit daily (high in vitamin C) for 28 days improved mood, wellbeing, vitality and gut symptoms and raised plasma vitamin C in adults with mild–moderate mood disturbance.

Trust comment: Randomised crossover in humans with objective vitamin C measures; small sample and unblinded limit generalizability.

Study Details

PMID:40284237
Participants:23
Impact:decrease −18.0 points (27.6 → 9.6 by week 4 in kiwifruit condition; treatment×time p<0.001)
Trust score:4/5

wellbeing score (WEMWBS)

1 evidences

Eating two SunGold kiwifruit daily (high in vitamin C) for 28 days improved mood, wellbeing, vitality and gut symptoms and raised plasma vitamin C in adults with mild–moderate mood disturbance.

Trust comment: Randomised crossover in humans with objective vitamin C measures; small sample and unblinded limit generalizability.

Study Details

PMID:40284237
Participants:23
Impact:increase +4.4 points (42.1 → 46.5 at week 4; treatment×time p=0.003)
Trust score:4/5

rhinitis symptoms

1 evidences

Eight weeks of aerobic exercise improved allergic rhinitis symptoms and nasal airflow; adding 2000 mg/day vitamin C did not show additional benefit given the small sample.

Trust comment: Randomized human trial but small groups (n=8–10 per arm) and limited power to detect vitamin C-specific effects.

Study Details

PMID:30118241
Participants:27
Impact:decreased after exercise (EX and EX+Vit.C) compared to pre-test (significant)
Trust score:3/5

peak nasal inspiratory flow (PNIF)

1 evidences

Eight weeks of aerobic exercise improved allergic rhinitis symptoms and nasal airflow; adding 2000 mg/day vitamin C did not show additional benefit given the small sample.

Trust comment: Randomized human trial but small groups (n=8–10 per arm) and limited power to detect vitamin C-specific effects.

Study Details

PMID:30118241
Participants:27
Impact:increased in EX and EX+Vit.C groups (significant vs pre-test)
Trust score:3/5

nasal secretion IL-4

1 evidences

Eight weeks of aerobic exercise improved allergic rhinitis symptoms and nasal airflow; adding 2000 mg/day vitamin C did not show additional benefit given the small sample.

Trust comment: Randomized human trial but small groups (n=8–10 per arm) and limited power to detect vitamin C-specific effects.

Study Details

PMID:30118241
Participants:27
Impact:decreased in EX and EX+Vit.C vs control (significant)
Trust score:3/5

body mass

1 evidences

In a large RCT, 12-week quercetin supplementation given with vitamin C and niacin did not change body mass or composition versus placebo.

Trust comment: Large randomized human trial but vitamin C was co-administered (not isolated), so attribution to vitamin C is unclear.

Study Details

PMID:21574787
Participants:941
Impact:no significant change between supplement and placebo groups after 12 weeks
Trust score:3/5

body composition

1 evidences

In a large RCT, 12-week quercetin supplementation given with vitamin C and niacin did not change body mass or composition versus placebo.

Trust comment: Large randomized human trial but vitamin C was co-administered (not isolated), so attribution to vitamin C is unclear.

Study Details

PMID:21574787
Participants:941
Impact:no significant change between groups after 12 weeks
Trust score:3/5

plasma quercetin

3 evidences

In a large RCT, 12-week quercetin supplementation given with vitamin C and niacin did not change body mass or composition versus placebo.

Trust comment: Large randomized human trial but vitamin C was co-administered (not isolated), so attribution to vitamin C is unclear.

Study Details

PMID:21574787
Participants:941
Impact:increased dose-responsively (confirming supplement uptake)
Trust score:3/5

A 10-week mixed flavonoid–fish oil supplement (which included 250 mg vitamin C/day) upregulated antiviral/interferon-related gene expression but did not change standard inflammatory or oxidative-stress biomarkers.

Trust comment: Randomized, double-blind RCT (n=48) with robust transcriptomic analysis showing consistent gene-expression changes though traditional biomarkers were unchanged.

Study Details

PMID:27187447
Participants:48
Impact:+500% (six-fold higher vs placebo at 10 weeks, p<0.001)
Trust score:4/5

In cyclists, regimens containing vitamin C (with flavonoids ± n-3) attenuated the immediate postexercise rise in F2-isoprostanes (oxidative stress marker) compared with placebo.

Trust comment: Randomized small study in athletes showing physiological effects on an oxidative stress marker, but multi-ingredient arms complicate attribution to vitamin C alone.

Study Details

PMID:21813916
Participants:39
Impact:significant increase in QC and QFO groups
Trust score:3/5

glutathione peroxidase (GSH-Px) activity

1 evidences

Children given multiple micronutrients including vitamin C had higher plasma antioxidant levels and less oxidized DNA damage in lymphocytes.

Trust comment: Randomized trial in children showing biochemical benefits but was a multinutrient supplement and details on blinding/completion are limited.

Study Details

PMID:15941534
Participants:82
Impact:significant increase after supplementation (P < 0.05)
Trust score:3/5

LDL cholesterol

10 evidences

Long-term micronutrient supplementation (capsules including 250 mg vitamin C plus vitamin E and selenium) was associated with small increases in total and LDL cholesterol after ~7.3 years.

Trust comment: Large randomized, placebo-controlled factorial trial but the exposure was a combined micronutrient supplement (vitamin C among others), so effects cannot be attributed to vitamin C alone.

Study Details

PMID:17023720
Participants:3411
Impact:+0.19 mmol/L (increase at 7.3 y; P = 0.02)
Trust score:4/5

Two small controlled studies in adults ≥70 showed statins lowered LDL but adding antioxidant vitamins (including vitamin C in one arm) did not improve brachial artery flow-mediated or nitroglycerin-mediated vasodilation.

Trust comment: Controlled, double-blind studies but small sample sizes and combined interventions limit ability to isolate vitamin C effects.

Study Details

PMID:11738278
Participants:54
Impact:decreased with statin therapy (P<0.001)
Trust score:3/5

Phlebotomy to reduce iron stores did not change CYP2E1 activity but was associated with lower LDL and vitamin E and a small but significant increase in plasma vitamin C.

Trust comment: Randomized trial (n=48) with clear biochemical endpoints; moderate sample size limits precision but findings on vitamin C are directly reported.

Study Details

PMID:17014579
Participants:48
Impact:decreased (mean change −0.15 vs +0.24; P=0.002)
Trust score:3/5

In subjects with resistant hypertension and dyslipidemia, 500 mg/day vitamin C for 8 weeks produced no significant improvements in blood pressure, LDL, or endothelial function.

Trust comment: Randomized trial but small sample and short duration; clear negative result for vitamin C arm while active comparator showed benefit.

Study Details

PMID:15609886
Participants:48
Impact:no significant change with vitamin C
Trust score:3/5

Providing 350 g/day vegetables and using water-free (multi-ply) cookware increased blood vitamin C and reduced oxidized LDL and LDL cholesterol over 2 weeks compared with ordinary cooking or usual diet.

Trust comment: Randomized study with objective biomarker changes (n=57) showing short-term increases in blood vitamin C and improvements in lipid/oxidative markers; moderate sample and short duration.

Study Details

PMID:22229802
Participants:57
Impact:Group A: 99.5 → 89.6 mg/dl (−9.9 mg/dl; P < 0.05); Group B: 98.3 → 87.8 mg/dl (−10.5 mg/dl; P < 0.01)
Trust score:4/5

Hemodialysis patients received vitamins; vitamin D3 group had reductions in triglycerides and TG/HDL ratio over 3 months.

Trust comment: Randomized allocation with measurable lipid outcomes (n=84) but small group sizes and short follow-up limit confidence.

Study Details

PMID:10757273
Participants:84
Impact:decreased after vitamin C therapy
Trust score:3/5

In a randomized trial of T2DM patients, combined vitamin C (500 mg) and chromium (200 µg) for the treatment group (n=30) improved glycemic control (HbA1c), lipid profile, liver enzymes and BMI versus placebo.

Trust comment: Small randomized controlled trial (n=60) testing a combined supplement (vitamin C + chromium) so effects cannot be attributed to vitamin C alone; limited methodological detail reported.

Study Details

PMID:38747270
Participants:60
Impact:Post-treatment LDL 105.1 ± 22.4 mg/dL (P=0.002 vs control; reported as significantly lower)
Trust score:3/5

In 40 older type II diabetic patients, chronic oral vitamin C (1 g/day) improved oxidative markers and reduced insulin and lipid concentrations.

Trust comment: Double-blind randomized cross-over in 40 elderly diabetics with multiple metabolic endpoints; moderate quality but older study and limited to one dose/population.

Study Details

PMID:8568117
Participants:40
Impact:decreased from 5.6→4.1 mmol/L (−1.5 mmol/L, p<0.05)
Trust score:3/5

A 3-month trial of a polyphenol-rich antioxidant supplement (pomegranate, green tea extracts, plus ascorbic acid) in type 2 diabetics lowered LDL and MDA and increased antioxidant markers compared with placebo.

Trust comment: Placebo-controlled human trial with 114 participants, but multi-ingredient supplement (includes ascorbic acid) prevents attributing effects solely to Vitamin C.

Study Details

PMID:19834314
Participants:114
Impact:decrease (statistically significant vs placebo, p<0.001)
Trust score:3/5

In a 75-day randomized double-blind trial, vitamin C (and vitamin E) reduced total and LDL cholesterol and raised HDL in healthy adults aged 50+; vitamin C group showed no significant triglyceride change.

Trust comment: Well-designed randomized double-blind placebo-controlled trial (n=120) showing favorable lipid changes with vitamin C, though duration was 75 days and full data detail is limited in abstract.

Study Details

PMID:12841306
Participants:120
Impact:significant decrease with vitamin C (vs placebo)
Trust score:4/5

HbA1c level

1 evidences

Randomized trial in healthy adults testing aspirin, vitamin C, vitamin E for 4 months; vitamins C/E did not change HbA1c.

Trust comment: Small randomized human trial (n=28) with multiple assay methods; limited sample size reduces confidence.

Study Details

PMID:16698007
Participants:28
Impact:no change (vitamin C group)
Trust score:3/5

Lipid peroxidation (TBARS)

2 evidences

In older adults undertaking regular exercise, a multi-ingredient antioxidant beverage (containing vitamin C among others) prevented exercise-induced increases in markers of lipid, protein and DNA oxidation and normalized glutathione and vitamin C levels.

Trust comment: Large, long-term intervention but used a multi-ingredient product (not isolated vitamin C), so effects cannot be attributed solely to vitamin C.

Study Details

PMID:19857542
Participants:400
Impact:Exercise ↑ TBARS +15%; supplementation prevented the exercise-induced increase
Trust score:3/5

In dialysis patients, high-dose vitamin C infusion (500 mg during dialysis) prevented increases in lipid peroxidation during sessions with a nonmodified membrane, but did not enhance the antioxidant effect of a vitamin E-modified membrane long-term.

Trust comment: Clinical dialysis study with both short-term and 12-week components and objective oxidative stress markers, but small samples and mixed protocols.

Study Details

PMID:11453871
Participants:24
Impact:vitamin C infusion prevented dialysis-associated increase in TBARS with nonmodified membrane (short-term); no added benefit over E-modified membrane long-term
Trust score:3/5

Morphine consumption (0–24 h)

2 evidences

A randomized double-blind trial found a single 3 g IV vitamin C dose at induction reduced 0–24 h morphine use, early VAS pain scores, early IL-6 and CRP, and improved early hip flexion after total hip arthroplasty.

Trust comment: Prospective, preregistered double-blind RCT with 100 patients and objective outcomes, though effect sizes are modest and clinical significance debated by authors.

Study Details

PMID:39487511
Participants:100
Impact:reduced (4.9 ± 2.6 mg vitamin C vs 5.8 ± 3.5 mg control; p = 0.043; absolute −0.9 mg)
Trust score:4/5

Double-blind RCT in 100 THA patients: multi-dose IV vitamin C perioperatively reduced opioid use, lowered pain scores, reduced inflammatory markers, and improved early function.

Trust comment: Well-conducted randomized double-blind trial (n=100) showing consistent reductions in opioid use, pain, and inflammation.

Study Details

PMID:40231193
Participants:100
Impact:reduced: 6.1±2.7 mg (control) vs 4.0±2.9 mg (vit C) (P<0.001)
Trust score:4/5

Postoperative VAS pain scores

1 evidences

Double-blind RCT in 100 THA patients: multi-dose IV vitamin C perioperatively reduced opioid use, lowered pain scores, reduced inflammatory markers, and improved early function.

Trust comment: Well-conducted randomized double-blind trial (n=100) showing consistent reductions in opioid use, pain, and inflammation.

Study Details

PMID:40231193
Participants:100
Impact:lower at multiple timepoints (e.g., motion at 2h: 5.56±0.48 vs 4.75±0.43, P<0.001)
Trust score:4/5

Inflammatory markers (IL-6, CRP)

1 evidences

Double-blind RCT in 100 THA patients: multi-dose IV vitamin C perioperatively reduced opioid use, lowered pain scores, reduced inflammatory markers, and improved early function.

Trust comment: Well-conducted randomized double-blind trial (n=100) showing consistent reductions in opioid use, pain, and inflammation.

Study Details

PMID:40231193
Participants:100
Impact:IL-6 and CRP lower in vitamin C group at 24–72 h (e.g., IL-6-24h 60.98±8.41 vs 53.61±9.75, P<0.001)
Trust score:4/5

Lower-back pain intensity (VAS) at 1 year

1 evidences

Prospective randomized double-blind trial (123 patients) giving oral vitamin C for 45 days after PLIF; pain improved in both groups but vitamin C did not change 1-year postoperative pain versus placebo.

Trust comment: Well-designed randomized double-blind trial with adequate sample (n=123); no effect on primary outcome at 1 year.

Study Details

PMID:28861199
Participants:123
Impact:no significant difference between vitamin C and placebo (both improved from baseline)
Trust score:4/5

Functional status (ODI)

1 evidences

Prospective randomized double-blind trial (123 patients) giving oral vitamin C for 45 days after PLIF; pain improved in both groups but vitamin C did not change 1-year postoperative pain versus placebo.

Trust comment: Well-designed randomized double-blind trial with adequate sample (n=123); no effect on primary outcome at 1 year.

Study Details

PMID:28861199
Participants:123
Impact:no long-term benefit; ODI at 3 months was slightly worse in vitamin C group (P=0.04), otherwise similar
Trust score:4/5

Fusion rate

1 evidences

Prospective randomized double-blind trial (123 patients) giving oral vitamin C for 45 days after PLIF; pain improved in both groups but vitamin C did not change 1-year postoperative pain versus placebo.

Trust comment: Well-designed randomized double-blind trial with adequate sample (n=123); no effect on primary outcome at 1 year.

Study Details

PMID:28861199
Participants:123
Impact:no difference (≈87% vs 86.9%)
Trust score:4/5

inhaled corticosteroid dose

1 evidences

In adults with asthma undergoing a corticosteroid-reduction protocol, oral magnesium supplementation (450 mg/day) did not meaningfully reduce the inhaled corticosteroid dose required to maintain control compared with placebo.

Trust comment: Randomized controlled design but modest sample size and only borderline statistical significance.

Study Details

PMID:16338599
Participants:92
Impact:-49 µg (geometric mean reduction with vitamin C; placebo -11 µg); relative reduction ratio 4.03, p=0.06 (borderline)
Trust score:3/5

LDL/HDL ratio

1 evidences

Hemodialysis patients received vitamins; vitamin D3 group had reductions in triglycerides and TG/HDL ratio over 3 months.

Trust comment: Randomized allocation with measurable lipid outcomes (n=84) but small group sizes and short follow-up limit confidence.

Study Details

PMID:10757273
Participants:84
Impact:decreased after vitamin C therapy
Trust score:3/5

premature rupture of membranes (PROM)

1 evidences

Daily 100 mg vitamin C from week 20 reduced the incidence of premature rupture of membranes compared with placebo.

Trust comment: Double-blind randomized trial with meaningful clinical outcome and clear effect sizes.

Study Details

PMID:15817864
Participants:109
Impact:7.69% (4/52) vs 24.5% (14/57) placebo; relative risk 0.26
Trust score:4/5

skin elasticity

1 evidences

Daily oral collagen tripeptide (3 g) improved skin hydration and elasticity and tended to reduce transepidermal water loss over 12 weeks compared with no supplement.

Trust comment: Randomized controlled trial but very small groups (n≈8 per arm) limiting confidence in vitamin C-specific conclusions.

Study Details

PMID:24131075
Participants:32
Impact:improved with collagen peptide; addition of vitamin C did not further enhance effect (no additional benefit reported)
Trust score:3/5

URI incidence

1 evidences

In competitive adolescent swimmers, 1 g/day vitamin C did not change URI incidence overall but shortened duration and reduced severity in males.

Trust comment: Randomized double-blind trial but small sample and subgroup (sex) findings require cautious interpretation.

Study Details

PMID:20689965
Participants:39
Impact:No effect (rate ratio = 1.01)
Trust score:3/5

URI duration in males

1 evidences

In competitive adolescent swimmers, 1 g/day vitamin C did not change URI incidence overall but shortened duration and reduced severity in males.

Trust comment: Randomized double-blind trial but small sample and subgroup (sex) findings require cautious interpretation.

Study Details

PMID:20689965
Participants:39
Impact:-47% (duration shortened in males; 95% CI -80% to -14%)
Trust score:3/5

URI severity in males

1 evidences

In competitive adolescent swimmers, 1 g/day vitamin C did not change URI incidence overall but shortened duration and reduced severity in males.

Trust comment: Randomized double-blind trial but small sample and subgroup (sex) findings require cautious interpretation.

Study Details

PMID:20689965
Participants:39
Impact:Reduced in males, no effect in females
Trust score:3/5

ΔSOFA at 72 h

1 evidences

Early adjunctive high‑dose IV vitamin C in sepsis was associated with lower 28‑day mortality, lower early SOFA score change, and higher procalcitonin clearance versus control.

Trust comment: Randomized study reporting mortality and organ-failure score improvements, but excerpt lacks full methodological detail and may be single-center.

Study Details

PMID:33094466
Participants:117
Impact:4.2 -> 2.1 (smaller SOFA change with vitamin C)
Trust score:3/5

procalcitonin clearance

1 evidences

Early adjunctive high‑dose IV vitamin C in sepsis was associated with lower 28‑day mortality, lower early SOFA score change, and higher procalcitonin clearance versus control.

Trust comment: Randomized study reporting mortality and organ-failure score improvements, but excerpt lacks full methodological detail and may be single-center.

Study Details

PMID:33094466
Participants:117
Impact:79.6% vs 61.3% (higher clearance with vitamin C)
Trust score:3/5

complex regional pain syndrome incidence

1 evidences

1 g/day vitamin C for 40 days after foot/ankle surgery reduced risk of CRPS.

Trust comment: Large prospective randomized study with objective CRPS diagnosis and significant effect, though group sizes were unbalanced.

Study Details

PMID:34347132
Participants:329
Impact:-81% risk (OR 0.19; 95% CI 0.05–0.8; p=0.021)
Trust score:4/5

common cold duration and severity

1 evidences

High-dose vitamin C (>1 g) started at cold onset did not reduce duration or severity of colds in adults.

Trust comment: Double-blind randomized trial but only 149 of 400 participants returned episode records, reducing completeness of outcomes.

Study Details

PMID:11700812
Participants:149
Impact:no significant change (no difference between 0.03 g, 1 g, 3 g, or 3 g Bio-C groups)
Trust score:3/5

supragingival calculus score

1 evidences

30 calculus-forming subjects chewed vitamin C gums; vitamin C gum reduced supragingival calculus and bleeding sites; iodine used only as titration reagent in release measurements (study not about iodine effects).

Trust comment: Controlled clinical chewing-gum study with modest sample size (n=30) showing clinically relevant reductions in calculus and bleeding.

Study Details

PMID:15693825
Participants:30
Impact:-33% total calculus score with vitamin C gum vs no gum
Trust score:3/5

bleeding sites

1 evidences

30 calculus-forming subjects chewed vitamin C gums; vitamin C gum reduced supragingival calculus and bleeding sites; iodine used only as titration reagent in release measurements (study not about iodine effects).

Trust comment: Controlled clinical chewing-gum study with modest sample size (n=30) showing clinically relevant reductions in calculus and bleeding.

Study Details

PMID:15693825
Participants:30
Impact:-37% bleeding sites with vitamin C gum
Trust score:3/5

IL-6

2 evidences

Runners given 500 mg/day vitamin C for 15 days had higher plasma vitamin C but vitamin C did not change exercise-induced IL-6 or IL-10 responses.

Trust comment: Double-blind randomized human trial with clear negative finding but small sample (n=31).

Study Details

PMID:24802951
Participants:31
Impact:↑ with exercise; no difference with vitamin C vs placebo
Trust score:4/5

Daily 1 g vitamin C for 8 weeks reduced inflammatory markers (hs-CRP, IL-6) and fasting blood glucose in hypertensive and/or diabetic obese adults versus control.

Trust comment: Randomized controlled trial with objective inflammatory/metabolic biomarkers but open-label design and modest sample size limit confidence.

Study Details

PMID:26170625
Participants:64
Impact:significant reduction (between-group difference at 8 wk, P=0.001)
Trust score:4/5

IL-10

1 evidences

Runners given 500 mg/day vitamin C for 15 days had higher plasma vitamin C but vitamin C did not change exercise-induced IL-6 or IL-10 responses.

Trust comment: Double-blind randomized human trial with clear negative finding but small sample (n=31).

Study Details

PMID:24802951
Participants:31
Impact:↑ with exercise; no difference with vitamin C vs placebo
Trust score:4/5

Oxidative stress markers / cortisol

1 evidences

Runners given 500 mg/day vitamin C for 15 days had higher plasma vitamin C but vitamin C did not change exercise-induced IL-6 or IL-10 responses.

Trust comment: Double-blind randomized human trial with clear negative finding but small sample (n=31).

Study Details

PMID:24802951
Participants:31
Impact:exercise-induced changes observed; no difference with vitamin C
Trust score:4/5

Triglycerides

1 evidences

In 91 power-plant workers, 1000 mg/day vitamin C for 3 months reduced several proinflammatory cytokines compared with control.

Trust comment: Double-blind randomized controlled trial with reasonable sample size and clear biochemical outcomes, though groups were modest in size and exposure-specific population limits generalizability.

Study Details

PMID:32931612
Participants:91
Impact:increased in the vitamin C group (statistically significant)
Trust score:4/5

Asthma control (C-ACT)

1 evidences

Supplementation including zinc (with omega-3 and vitamin C) improved asthma control, pulmonary function, and sputum inflammatory markers in children with moderate persistent asthma.

Trust comment: Randomized self-controlled pediatric study showing benefit, but multiple concurrent supplements limit attribution of effects specifically to vitamin C.

Study Details

PMID:19154523
Participants:60
Impact:Significant improvement with supplements (p<0.001)
Trust score:3/5

Pulmonary function tests

2 evidences

In 56 healthy smokers randomized to 500 mg vitamin C daily or placebo for 4 weeks, plasma vitamin C increased but markers of lipid peroxidation and pulmonary function tests did not change.

Trust comment: Randomized double‑blind trial with complete follow‑up but small sample and short duration for clinical pulmonary endpoints.

Study Details

PMID:10052021
Participants:56
Impact:no changes detected after supplementation
Trust score:3/5

Supplementation including zinc (with omega-3 and vitamin C) improved asthma control, pulmonary function, and sputum inflammatory markers in children with moderate persistent asthma.

Trust comment: Randomized self-controlled pediatric study showing benefit, but multiple concurrent supplements limit attribution of effects specifically to vitamin C.

Study Details

PMID:19154523
Participants:60
Impact:Significant improvement with supplements (p<0.001)
Trust score:3/5

Sputum inflammatory markers

1 evidences

Supplementation including zinc (with omega-3 and vitamin C) improved asthma control, pulmonary function, and sputum inflammatory markers in children with moderate persistent asthma.

Trust comment: Randomized self-controlled pediatric study showing benefit, but multiple concurrent supplements limit attribution of effects specifically to vitamin C.

Study Details

PMID:19154523
Participants:60
Impact:Significant improvement with supplements (p<0.001)
Trust score:3/5

Echo Comet Score (pulmonary oedema) day 1

1 evidences

In severe preeclampsia postpartum patients, repeated IV vitamin C did not reduce pulmonary oedema on day 1 but was associated with lower lung ultrasound scores on days 2 and 3.

Trust comment: Randomized double-blind placebo-controlled trial in humans but small sample (n=34); delayed effect observed on secondary days 2–3.

Study Details

PMID:33453456
Participants:34
Impact:No significant difference (median 23 vs 18; p=0.31)
Trust score:4/5

Echo Comet Score day 2

1 evidences

In severe preeclampsia postpartum patients, repeated IV vitamin C did not reduce pulmonary oedema on day 1 but was associated with lower lung ultrasound scores on days 2 and 3.

Trust comment: Randomized double-blind placebo-controlled trial in humans but small sample (n=34); delayed effect observed on secondary days 2–3.

Study Details

PMID:33453456
Participants:34
Impact:↓ (vitamin C median 8 vs placebo 35; p=0.03)
Trust score:4/5

Echo Comet Score day 3

1 evidences

In severe preeclampsia postpartum patients, repeated IV vitamin C did not reduce pulmonary oedema on day 1 but was associated with lower lung ultrasound scores on days 2 and 3.

Trust comment: Randomized double-blind placebo-controlled trial in humans but small sample (n=34); delayed effect observed on secondary days 2–3.

Study Details

PMID:33453456
Participants:34
Impact:↓ (vitamin C median 5 vs placebo 18; p=0.04)
Trust score:4/5

Skin roughness (Rgh)

1 evidences

In 149 women undergoing laser-assisted delivery, topical vitamin C applied after resurfacing significantly reduced periorbital skin roughness and wrinkle depth at 3 months; adding growth factors produced larger improvements.

Trust comment: Large randomized double-blind trial with objective 3D measurements; topical vitamin C effect evident though both groups received vitamin C (comparison tests additive GFs).

Study Details

PMID:33326047
Participants:149
Impact:Median reduction ~18.8% with vitamin C alone (group R-C)
Trust score:4/5

Wrinkle average depth (AD)

1 evidences

In 149 women undergoing laser-assisted delivery, topical vitamin C applied after resurfacing significantly reduced periorbital skin roughness and wrinkle depth at 3 months; adding growth factors produced larger improvements.

Trust comment: Large randomized double-blind trial with objective 3D measurements; topical vitamin C effect evident though both groups received vitamin C (comparison tests additive GFs).

Study Details

PMID:33326047
Participants:149
Impact:Median reduction ~33.3% with vitamin C alone (group R-C)
Trust score:4/5

Combined Rgh+AD improvement

1 evidences

In 149 women undergoing laser-assisted delivery, topical vitamin C applied after resurfacing significantly reduced periorbital skin roughness and wrinkle depth at 3 months; adding growth factors produced larger improvements.

Trust comment: Large randomized double-blind trial with objective 3D measurements; topical vitamin C effect evident though both groups received vitamin C (comparison tests additive GFs).

Study Details

PMID:33326047
Participants:149
Impact:Median combined ∂ reduction ~50.1% with vitamin C alone
Trust score:4/5

Post-reperfusion syndrome (PRS) incidence

1 evidences

In this pilot RCT of IV 1500 mg vitamin C given before reperfusion, PRS incidence was lower in the vitamin C group (10.5% vs 30%) but not statistically significant; vitamin C raised plasma levels and was associated with higher acute kidney injury and higher re-transplantation in this small sample.

Trust comment: Single-center double-blind RCT but small pilot sample (n=39) and underpowered for primary endpoint; unexpected adverse signals require cautious interpretation.

Study Details

PMID:40719561
Participants:39
Impact:Control 30.0% (6/20) vs Vitamin C 10.5% (2/19); p=0.24 (not significant)
Trust score:3/5

Post-transplant plasma vitamin C

1 evidences

In this pilot RCT of IV 1500 mg vitamin C given before reperfusion, PRS incidence was lower in the vitamin C group (10.5% vs 30%) but not statistically significant; vitamin C raised plasma levels and was associated with higher acute kidney injury and higher re-transplantation in this small sample.

Trust comment: Single-center double-blind RCT but small pilot sample (n=39) and underpowered for primary endpoint; unexpected adverse signals require cautious interpretation.

Study Details

PMID:40719561
Participants:39
Impact:↑ to 15.0 mg/L in treated group vs 6.9 mg/L control at 12 h; p=0.046 (increase +4.8 mg/L; p=0.001)
Trust score:3/5

Acute kidney injury (AKI) incidence

1 evidences

In this pilot RCT of IV 1500 mg vitamin C given before reperfusion, PRS incidence was lower in the vitamin C group (10.5% vs 30%) but not statistically significant; vitamin C raised plasma levels and was associated with higher acute kidney injury and higher re-transplantation in this small sample.

Trust comment: Single-center double-blind RCT but small pilot sample (n=39) and underpowered for primary endpoint; unexpected adverse signals require cautious interpretation.

Study Details

PMID:40719561
Participants:39
Impact:↑ in vitamin C group 68.4% vs control 35.0%; p=0.037
Trust score:3/5

plasma ascorbic acid

12 evidences

Adding oral vitamin C to atypical antipsychotics for 8 weeks reduced oxidative stress markers and improved psychiatric rating scores in schizophrenia patients.

Trust comment: Prospective double-blind placebo-controlled trial with objective biomarkers and clinical scale but small sample (n=40).

Study Details

PMID:16133138
Participants:40
Impact:increase (levels reversed toward normal)
Trust score:4/5

Vitamin C raised blood vitamin C levels but did not prevent oxidative or immune changes during/after an ultramarathon.

Trust comment: Randomized double-blind trial in runners with clear biochemical measures but small sample (n=28) limits generalizability.

Study Details

PMID:11960947
Participants:28
Impact:+151% (3.21 vs 1.28 µg/100 µL postrace, P < 0.001)
Trust score:4/5

In hepatitis C patients receiving interferon and ribavirin, vitamins E+C kept a fatty acid (EPA) level stable and raised blood vitamin levels.

Trust comment: Randomized clinical study but small sample (n=30) and combined vitamin E+C makes isolating vitamin C effects less certain.

Study Details

PMID:16459223
Participants:30
Impact:increased (plasma ascorbic acid rose after supplementation)
Trust score:3/5

Four-week antioxidant regimens including ascorbic acid increased plasma ascorbic acid but did not change measures of mononuclear leukocyte DNA damage in smokers or nonsmokers.

Trust comment: Randomized double-blind placebo-controlled design but very small groups (n=9 smokers, n=12 nonsmokers) limit power to detect effects.

Study Details

PMID:10578484
Participants:21
Impact:increased with supplementation
Trust score:3/5

A 4-week blueberry/apple juice (providing 16 mg ascorbic acid/day) raised plasma antioxidants and reduced some oxidative DNA damage but increased another DNA adduct type; effects varied by genotype.

Trust comment: Intervention in 168 volunteers with biomarker endpoints and reported p-values; moderate quality though not clearly randomized in excerpt.

Study Details

PMID:17602170
Participants:168
Impact:increased (significant)
Trust score:4/5

An antioxidant-rich (vitamin C–containing) diet after acute MI increased plasma vitamin C and reduced lipid peroxidation and cardiac enzyme rise versus control diet.

Trust comment: Large randomized controlled diet intervention in MI patients with clear biochemical endpoints and adequate sample size, increasing confidence.

Study Details

PMID:7797808
Participants:406
Impact:intervention ↑23.38 μmol/L vs control ↑7.95 μmol/L (difference ≈+15.43 μmol/L)
Trust score:4/5

Giving 25 mg vitamin C twice daily as limeade raised plasma vitamin C but did not improve hemoglobin or other iron status markers in iron‑deficient women consuming high‑phytate diets.

Trust comment: Randomized community trial with prolonged follow‑up and objective measures but small sample size and high‑phytate diets that limit vitamin C efficacy for iron absorption.

Study Details

PMID:12885707
Participants:36
Impact:significantly increased (P < 0.01) in the AA group
Trust score:3/5

Three-month moderate-dose vitamin supplementation (including 272 mg vitamin C) repleted plasma ascorbic acid in smokers and raised plasma vitamin E markers.

Trust comment: Double-blind placebo-controlled design with matched dietary data and adequate sample size supports credibility.

Study Details

PMID:10648268
Participants:75
Impact:repleted with supplementation in smokers (P<0.001); smokers had lower baseline levels
Trust score:4/5

Individualized nutrition support in malnourished hospital patients improved energy/protein intake, maintained weight, raised vitamin C levels, and reduced complications and readmissions.

Trust comment: Randomized controlled trial measuring biochemical vitamin C and clinical outcomes with moderate sample size.

Study Details

PMID:20937544
Participants:132
Impact:46.7 μmol/l (intervention) vs 34.1 μmol/l (control); difference +12.6 μmol/l
Trust score:4/5

Vitamin C (with vitamin E) doubled plasma ascorbic acid and increased mucosal ascorbic acid but did not reduce mucosal reactive oxygen species or malondialdehyde associated with H. pylori infection.

Trust comment: Randomized human trial with objective biochemical endpoints; short-term follow-up limits longer-term inference.

Study Details

PMID:11898768
Participants:117
Impact:+100% (doubled)
Trust score:4/5

In a double‑blind crossover study, vitamin C supplementation raised plasma ascorbic acid and increased lipid‑standardized alpha‑tocopherol and antioxidant capacity (FRAP), indicating in vivo interactions between vitamins C and E.

Trust comment: Double‑blind crossover in 30 healthy adults with clear biochemical changes and appropriate design, supporting credibility.

Study Details

PMID:10967604
Participants:30
Impact:increased (from 62.8 to 101.3 μmol/L with 500 mg AA; P<0.005)
Trust score:4/5

Six months of combined high-dose vitamins C and E raised plasma antioxidant levels but did not improve coronary or brachial endothelial function in CAD patients.

Trust comment: Double-blind RCT in CAD patients but small sample and some endpoints measured in subsets (coronary n=18, brachial n=25).

Study Details

PMID:14975474
Participants:30
Impact:increased (p < 0.02)
Trust score:4/5

oxidative stress markers (lipid hydroperoxide, F2-isoprostane)

1 evidences

Vitamin C raised blood vitamin C levels but did not prevent oxidative or immune changes during/after an ultramarathon.

Trust comment: Randomized double-blind trial in runners with clear biochemical measures but small sample (n=28) limits generalizability.

Study Details

PMID:11960947
Participants:28
Impact:no significant change
Trust score:4/5

immune markers and function (IL-6, IL-10, IL-1ra, IL-8, immune cell counts, lymphocyte proliferation, IL-2, IFN-γ)

1 evidences

Vitamin C raised blood vitamin C levels but did not prevent oxidative or immune changes during/after an ultramarathon.

Trust comment: Randomized double-blind trial in runners with clear biochemical measures but small sample (n=28) limits generalizability.

Study Details

PMID:11960947
Participants:28
Impact:no significant change
Trust score:4/5

incidence of coughing

1 evidences

Six months of a probiotic plus 50 mg vitamin C reduced coughing, school absenteeism and antibiotic use in children.

Trust comment: Well-conducted randomized double-blind RCT but intervention combined probiotics and vitamin C, so effects cannot be attributed to vitamin C alone.

Study Details

PMID:34511049
Participants:171
Impact:-16% (significant, P=0.03)
Trust score:4/5

school absenteeism

1 evidences

Six months of a probiotic plus 50 mg vitamin C reduced coughing, school absenteeism and antibiotic use in children.

Trust comment: Well-conducted randomized double-blind RCT but intervention combined probiotics and vitamin C, so effects cannot be attributed to vitamin C alone.

Study Details

PMID:34511049
Participants:171
Impact:-16% (P=0.006)
Trust score:4/5

antibiotic use

1 evidences

Six months of a probiotic plus 50 mg vitamin C reduced coughing, school absenteeism and antibiotic use in children.

Trust comment: Well-conducted randomized double-blind RCT but intervention combined probiotics and vitamin C, so effects cannot be attributed to vitamin C alone.

Study Details

PMID:34511049
Participants:171
Impact:-27% (P=0.0203)
Trust score:4/5

hemorrhage volume

1 evidences

Perioperative IV vitamin C (2 g total) reduced intraoperative hemorrhage volume during abdominal hysterectomy.

Trust comment: Randomized double-blind placebo-controlled surgical trial with 80 patients showing a significant hemorrhage reduction, though single-procedure context limits wider applicability.

Study Details

PMID:35623878
Participants:80
Impact:−42.9 mL (≈11% reduction; ~388.1 → 345.2 mL, P < 0.001)
Trust score:4/5

plasma ascorbate

6 evidences

Oral vitamin C increased plasma and urinary ascorbate in a dose-dependent manner; nasal lavage (RTLF) ascorbate showed an acute rise after a high (1000 mg) dose peaking at 2–4 h but returned to baseline by 24 h.

Trust comment: Double-blind crossover switching study in 24 healthy subjects with direct biochemical measures; modest sample but solid design.

Study Details

PMID:19009458
Participants:24
Impact:+dose-dependent increase with supplementation
Trust score:4/5

In a 4-week crossover trial of 500 mg/day vitamin C in healthy smokers, plasma ascorbate rose but markers of oxidation and endothelial activation did not change.

Trust comment: Randomized, double-blind, placebo-controlled crossover with measured biomarkers but small sample of healthy smokers limits generalizability.

Study Details

PMID:15127090
Participants:34
Impact:+~50% (46.6 → 70.1 μmol/L after 4 weeks)
Trust score:4/5

In 40 gout patients, 500 mg/day vitamin C for 8 weeks raised plasma ascorbate but produced only a very small and clinically insignificant decrease in serum urate compared with allopurinol.

Trust comment: Pilot randomized trial (n=40) with clear numerical outcomes showing minimal urate-lowering effect of 500 mg/day vitamin C.

Study Details

PMID:23681955
Participants:40
Impact:Significant increase between day 0 and week 8 in vitamin C recipients
Trust score:4/5

Randomized dietary intervention (0.5 vs 2 kiwifruit/day) in healthy young men showing plasma and skeletal muscle ascorbate increase after 6 weeks; muscle ascorbate rose ≈3.5‑fold and correlated with plasma levels.

Trust comment: Randomized parallel dietary intervention with objective biochemical endpoints and clear pre/post measurements but small, all-male sample limits generalizability.

Study Details

PMID:23446899
Participants:35
Impact:0.5 kiwifruit: 22.7 → 45.5 μmol/L (+22.8 μmol/L); 2 kiwifruit: 25.4 → 62.6 μmol/L (+37.2 μmol/L)
Trust score:4/5

Half a kiwifruit or a 50 mg vitamin C tablet daily similarly increased plasma, leukocyte and muscle vitamin C with no difference between sources.

Trust comment: Randomized human study with rigorous sampling and appropriate measures but small, all-male healthy sample limits generalizability.

Study Details

PMID:24067392
Participants:36
Impact:+~28 µmol/L (23.5 → 51.3 µmol/L post-intervention, P < 0.001)
Trust score:4/5

Daily moderate antioxidant supplementation (including 272 mg vitamin C) raised plasma ascorbate but did not change measured markers of lipid or protein oxidative damage in healthy men.

Trust comment: Placebo-controlled supplementation in 77 men with objective biochemical endpoints; negative results are plausible and well measured.

Study Details

PMID:12612146
Participants:77
Impact:increased after supplementation
Trust score:4/5

leukocyte ascorbate (mononuclear cells and neutrophils)

1 evidences

Half a kiwifruit or a 50 mg vitamin C tablet daily similarly increased plasma, leukocyte and muscle vitamin C with no difference between sources.

Trust comment: Randomized human study with rigorous sampling and appropriate measures but small, all-male healthy sample limits generalizability.

Study Details

PMID:24067392
Participants:36
Impact:mononuclear cells +~45.8 nmol/10^8 cells (38.7 → 84.5, P < 0.001); neutrophils +~17.7 nmol/10^8 cells (21.9 → 39.6, P < 0.01)
Trust score:4/5

skeletal muscle ascorbate

2 evidences

Half a kiwifruit or a 50 mg vitamin C tablet daily similarly increased plasma, leukocyte and muscle vitamin C with no difference between sources.

Trust comment: Randomized human study with rigorous sampling and appropriate measures but small, all-male healthy sample limits generalizability.

Study Details

PMID:24067392
Participants:36
Impact:~3.5–4-fold increase (14.5 → 61.3 nmol/g, P < 0.001)
Trust score:4/5

Randomized dietary intervention (0.5 vs 2 kiwifruit/day) in healthy young men showing plasma and skeletal muscle ascorbate increase after 6 weeks; muscle ascorbate rose ≈3.5‑fold and correlated with plasma levels.

Trust comment: Randomized parallel dietary intervention with objective biochemical endpoints and clear pre/post measurements but small, all-male sample limits generalizability.

Study Details

PMID:23446899
Participants:35
Impact:0.5 kiwifruit: 15.1 → 52.8 nmol/g (+37.7 nmol/g, ~3.5-fold); 2 kiwifruit: 17.1 → 60.8 nmol/g (+43.7 nmol/g, ~3.6-fold)
Trust score:4/5

F2-isoprostanes (oxidative stress)

1 evidences

In vitamin C–deficient individuals, 1 g/day vitamin C for 30 days lowered oxidative stress and improved VO2max and muscle peak torque in most participants.

Trust comment: Randomized double-blind crossover in deficient subjects with objective physiological outcomes, but small sample reduces precision and some individual non-responders noted.

Study Details

PMID:37401190
Participants:22
Impact:−13.7 pg/mL (95% CI −18.9, −8.4, significant)
Trust score:4/5

VO2max

1 evidences

In vitamin C–deficient individuals, 1 g/day vitamin C for 30 days lowered oxidative stress and improved VO2max and muscle peak torque in most participants.

Trust comment: Randomized double-blind crossover in deficient subjects with objective physiological outcomes, but small sample reduces precision and some individual non-responders noted.

Study Details

PMID:37401190
Participants:22
Impact:+5.4 mL/kg/min (95% CI 2.7, 8.2, P = 0.001)
Trust score:4/5

isometric peak torque

1 evidences

In vitamin C–deficient individuals, 1 g/day vitamin C for 30 days lowered oxidative stress and improved VO2max and muscle peak torque in most participants.

Trust comment: Randomized double-blind crossover in deficient subjects with objective physiological outcomes, but small sample reduces precision and some individual non-responders noted.

Study Details

PMID:37401190
Participants:22
Impact:+18.7 Nm (95% CI 11.8, 25.7)
Trust score:4/5

interleukin-6 (IL-6)

4 evidences

A multi-component nutraceutical (includes vitamin D among other ingredients) reduced lymphocyte counts, IL-6, and CRP and improved self-reported wellness in hospitalized elderly compared with untreated elderly controls.

Trust comment: Adequately sized study with randomized elderly treatment groups but multi-ingredient supplement and hospitalized sample make isolating vitamin C effects and generalizability limited.

Study Details

PMID:36079732
Participants:120
Impact:decrease (statistically significant)
Trust score:3/5

One week of 2 g/day vitamin C in healthy young adults reduced inflammatory markers and modestly lowered blood pressure and improved antioxidant enzyme activity under high PM exposure.

Trust comment: Randomized double-blind crossover with biomarker and BP measures; short intervention (1 week) limits inference on long-term effects.

Study Details

PMID:35689890
Participants:58
Impact:−19.47% (significant)
Trust score:4/5

In 91 power-plant workers, 1000 mg/day vitamin C for 3 months reduced several proinflammatory cytokines compared with control.

Trust comment: Double-blind randomized controlled trial with reasonable sample size and clear biochemical outcomes, though groups were modest in size and exposure-specific population limits generalizability.

Study Details

PMID:32931612
Participants:91
Impact:decreased after vitamin C (effect size reported ~0.57)
Trust score:4/5

A 4-week polyphenol beverage that contained vitamin C did not improve vascular function but was associated with an increase in IL-6 compared with placebo.

Trust comment: Randomized pilot RCT (n=39) but small sample and intervention combined polyphenols with vitamin C, so vitamin C–specific effects cannot be isolated.

Study Details

PMID:26797134
Participants:39
Impact:active +0.32 pg/ml vs placebo -0.18 pg/ml (p=0.010)
Trust score:3/5

rate of BP variation (vitamin C alone)

1 evidences

In a 6-week RCT in treated hypertensive adults, vitamin C alone did not change BP variability versus placebo; the high-dose vitamin C + polyphenols combination increased some measures of BP variability.

Trust comment: Randomised, double-blind, placebo-controlled trials with clear outcomes but modest sample size for the vitamin C arm.

Study Details

PMID:25234339
Participants:69
Impact:no significant change vs placebo
Trust score:4/5

night-time systolic BP variation (vitamin C + polyphenols)

1 evidences

In a 6-week RCT in treated hypertensive adults, vitamin C alone did not change BP variability versus placebo; the high-dose vitamin C + polyphenols combination increased some measures of BP variability.

Trust comment: Randomised, double-blind, placebo-controlled trials with clear outcomes but modest sample size for the vitamin C arm.

Study Details

PMID:25234339
Participants:69
Impact:increased (P=0.022)
Trust score:4/5

pulse pressure variation (vitamin C + polyphenols)

1 evidences

In a 6-week RCT in treated hypertensive adults, vitamin C alone did not change BP variability versus placebo; the high-dose vitamin C + polyphenols combination increased some measures of BP variability.

Trust comment: Randomised, double-blind, placebo-controlled trials with clear outcomes but modest sample size for the vitamin C arm.

Study Details

PMID:25234339
Participants:69
Impact:increased (P=0.0036)
Trust score:4/5

plasmin-antiplasmin complex (PAP)

1 evidences

In a randomized, double-blind, crossover study of 25 hyperlipidaemic volunteers, a FoodState Vitamin C complex reduced markers of coagulation activation and increased fibrin network compaction versus placebo.

Trust comment: Randomized, double-blind crossover design supports internal validity but small sample limits generalizability.

Study Details

PMID:15613923
Participants:25
Impact:decreased by -4.05% (vs placebo 1.81%)
Trust score:4/5

thrombin-antithrombin complex (TAT)

1 evidences

In a randomized, double-blind, crossover study of 25 hyperlipidaemic volunteers, a FoodState Vitamin C complex reduced markers of coagulation activation and increased fibrin network compaction versus placebo.

Trust comment: Randomized, double-blind crossover design supports internal validity but small sample limits generalizability.

Study Details

PMID:15613923
Participants:25
Impact:decreased by -5.81% (vs placebo 0.12%)
Trust score:4/5

fibrin network compaction

1 evidences

In a randomized, double-blind, crossover study of 25 hyperlipidaemic volunteers, a FoodState Vitamin C complex reduced markers of coagulation activation and increased fibrin network compaction versus placebo.

Trust comment: Randomized, double-blind crossover design supports internal validity but small sample limits generalizability.

Study Details

PMID:15613923
Participants:25
Impact:increased from 49.95% to 51.85% (≈+1.9 percentage points)
Trust score:4/5

total mood disturbance (POMS)

1 evidences

A three‑arm randomized trial (kiwifruit, vitamin C tablet, placebo) in adults with low vitamin C showed that kiwifruit improved mood and well‑being early; vitamin C tablets raised plasma vitamin C to saturation and reduced fatigue in participants with low baseline vitamin C.

Trust comment: Well‑designed, preregistered RCT with objective vitamin C measures, adequate sample and subgroup analyses; high internal validity.

Study Details

PMID:32971991
Participants:159
Impact:reduced in kiwifruit group (significant at 2 and 4 weeks; returned to baseline at washout)
Trust score:5/5

fatigue (MFSI-SF)

1 evidences

A three‑arm randomized trial (kiwifruit, vitamin C tablet, placebo) in adults with low vitamin C showed that kiwifruit improved mood and well‑being early; vitamin C tablets raised plasma vitamin C to saturation and reduced fatigue in participants with low baseline vitamin C.

Trust comment: Well‑designed, preregistered RCT with objective vitamin C measures, adequate sample and subgroup analyses; high internal validity.

Study Details

PMID:32971991
Participants:159
Impact:reduced by vitamin C tablets in low baseline vitamin C subgroup (significant at 4 weeks, p=0.017; trend at 2 weeks)
Trust score:5/5

endothelial function (EndoPAT index / PAT ratio) overall

1 evidences

In a 4‑week randomized, double‑blind placebo‑controlled trial in Fontan patients, vitamin C did not change endothelial function or exercise capacity overall but normalized vascular function more often in those with baseline abnormal vascular function.

Trust comment: Randomized, double-blind design is strong, but small sample and subgroup findings are exploratory.

Study Details

PMID:22176653
Participants:44
Impact:no significant improvement overall
Trust score:4/5

normalization of abnormal vascular function (subgroup)

1 evidences

In a 4‑week randomized, double‑blind placebo‑controlled trial in Fontan patients, vitamin C did not change endothelial function or exercise capacity overall but normalized vascular function more often in those with baseline abnormal vascular function.

Trust comment: Randomized, double-blind design is strong, but small sample and subgroup findings are exploratory.

Study Details

PMID:22176653
Participants:44
Impact:greater normalization with vitamin C vs placebo (EndoPAT 45% vs 17%; PAT ratio 38% vs 13%)
Trust score:4/5

fasting malondialdehyde (MDA)

1 evidences

In a 6‑week randomized study of type 2 diabetic patients, 1000 mg/day vitamin C reduced fasting and postprandial oxidative stress (MDA) but did not change lipid profiles.

Trust comment: Randomized trial with small sample size; significant biochemical outcomes but limited clinical and generalisability data.

Study Details

PMID:22518934
Participants:30
Impact:decreased (p = 0.006)
Trust score:3/5

postprandial MDA

1 evidences

In a 6‑week randomized study of type 2 diabetic patients, 1000 mg/day vitamin C reduced fasting and postprandial oxidative stress (MDA) but did not change lipid profiles.

Trust comment: Randomized trial with small sample size; significant biochemical outcomes but limited clinical and generalisability data.

Study Details

PMID:22518934
Participants:30
Impact:decreased (p < 0.001)
Trust score:3/5

lipid profile

3 evidences

ESRD patients randomized to 1,000 mg/day vitamin C showed no significant differences versus placebo on lipid profile or lipoprotein oxidation after one year.

Trust comment: Randomized trial in clinical population but small sample and most comparisons were non-significant, limiting confidence in benefits.

Study Details

PMID:15912655
Participants:41
Impact:no significant change versus placebo (small decreases observed across groups but not attributed to vitamin C)
Trust score:3/5

Vitamin C 500 mg/day for 4 weeks increased brachial flow-mediated dilation but did not change lipids or inflammatory markers.

Trust comment: Randomized crossover in CAD patients with small sample and vitamin C used as active control; moderate confidence.

Study Details

PMID:16140428
Participants:31
Impact:no change
Trust score:3/5

In a 6‑week randomized study of type 2 diabetic patients, 1000 mg/day vitamin C reduced fasting and postprandial oxidative stress (MDA) but did not change lipid profiles.

Trust comment: Randomized trial with small sample size; significant biochemical outcomes but limited clinical and generalisability data.

Study Details

PMID:22518934
Participants:30
Impact:no significant change
Trust score:3/5

blood loss

1 evidences

Giving 2 g IV vitamin C during myomectomy reduced bleeding, shortened operations, and shortened hospital stay.

Trust comment: Prospective randomized clinical trial with clear, significant effects but likely single-center and not blinded.

Study Details

PMID:21448709
Participants:102
Impact:−411 ml (521.44 vs 932.9 ml; group A vs B)
Trust score:4/5

operation time

1 evidences

Giving 2 g IV vitamin C during myomectomy reduced bleeding, shortened operations, and shortened hospital stay.

Trust comment: Prospective randomized clinical trial with clear, significant effects but likely single-center and not blinded.

Study Details

PMID:21448709
Participants:102
Impact:−26 min (42 vs 68 min; group A vs B)
Trust score:4/5

hospitalization days

1 evidences

Giving 2 g IV vitamin C during myomectomy reduced bleeding, shortened operations, and shortened hospital stay.

Trust comment: Prospective randomized clinical trial with clear, significant effects but likely single-center and not blinded.

Study Details

PMID:21448709
Participants:102
Impact:−0.4 days (2.7 vs 3.1 days; group A vs B)
Trust score:4/5

plasma vitamin C

40 evidences

Ten-week zinc- and micronutrient-rich food or ayurvedic zinc supplements increased plasma zinc and reduced zinc deficiency prevalence in adolescent girls.

Trust comment: Randomized 10-week intervention with 180 participants and measured biochemical outcomes; moderate-high quality for nutritional status endpoints though effect attribution among multiple micronutrients is complex.

Study Details

PMID:22129855
Participants:180
Impact:increased ~28% in food-supplement group (10-week intervention)
Trust score:4/5

Giving low consumers ~480 g/day fruit/veg + up to 300 ml juice for 12 weeks raised blood vitamin C and other nutrients but did not change measures of plasma antioxidant capacity or vascular risk markers.

Trust comment: Randomised controlled trial with objective biomarkers and good compliance; not blinded and modest sample size limits generalizability.

Study Details

PMID:28560503
Participants:45
Impact:+35% (approx.)
Trust score:4/5

A perioperative antioxidant-containing drink raised plasma vitamin C and total antioxidant capacity shortly after surgery but did not reduce markers of systemic inflammation.

Trust comment: Double-blind RCT but small (n=36) and pilot in surgical patients, limiting power and generalizability.

Study Details

PMID:21890323
Participants:36
Impact:higher on postoperative day 1 in pONS group (P = 0.001)
Trust score:3/5

In 32 diabetic patients with low plasma vitamin C, high-dose oral vitamin C partially restored vitamin C levels but did not improve endothelial function or measures of insulin resistance.

Trust comment: Clinical intervention in Type 2 diabetes with objective vascular and metabolic measures but limited effect and incomplete repletion of vitamin C.

Study Details

PMID:16126809
Participants:32
Impact:Partially replenished but not fully restored (incomplete replenishment reported)
Trust score:3/5

In patients with type 2 diabetes, a calorie-restricted vegetarian diet (± exercise) improved insulin sensitivity, reduced visceral fat, and increased plasma vitamin C versus a conventional diet.

Trust comment: Randomized, parallel, metabolically controlled 24-week trial (n=74) with objective clamp and imaging outcomes; moderate sample size but robust measures.

Study Details

PMID:21480966
Participants:74
Impact:+16% after dietary intervention in vegetarian group (P = 0.002)
Trust score:4/5

Two-week vitamin C+E supplementation increased plasma vitamins and reduced exercise-induced protein oxidation in trained adults.

Trust comment: Randomized, controlled supplementation trial with repeated measures and objective biomarkers; moderate quality though group sizes modest.

Study Details

PMID:16775552
Participants:48
Impact:increased after 2 weeks with vitamin C+E treatment (V) (P ≤ 0.05)
Trust score:4/5

Children with chronic constipation had lower antioxidant enzyme activities and lower plasma vitamin C and E compared with matched healthy children.

Trust comment: Measured biochemical differences in matched groups show strong statistical signals, but study design and potential confounding make causal inference uncertain.

Study Details

PMID:15602823
Participants:120
Impact:significantly decreased in chronic constipation patients (P < 0.0001)
Trust score:3/5

Chlorella supplementation increased plasma vitamin C and other antioxidant markers and improved erythrocyte antioxidant enzymes in smokers, though DNA damage also decreased with placebo.

Trust comment: Randomized double-blind placebo-controlled trial (n=52) showing clear increases in plasma antioxidant nutrients, but primary intervention was Chlorella (contains vitamin C) and DNA damage findings were not specific to active treatment.

Study Details

PMID:19660910
Participants:52
Impact:+44.4% after 6 weeks of Chlorella supplementation
Trust score:3/5

IV vitamin C raised plasma levels and substantially reduced spontaneous pain in patients with postherpetic neuralgia but did not affect brush-evoked pain.

Trust comment: Double-blind, placebo-controlled RCT with objective pain scales but modest sample size.

Study Details

PMID:19692796
Participants:41
Impact:lower in PHN vs healthy; restored by IV ascorbate
Trust score:4/5

In low-income adults, fruit-and-vegetable vouchers increased short-term consumption but did not change blood vitamin C levels at 3 months.

Trust comment: Randomized 12-month trial with objective vitamin measurements, but high loss-to-follow-up limited long-term analysis.

Study Details

PMID:21989324
Participants:302
Impact:no change at 3 months
Trust score:3/5

In surgical patients on TPN, plasma vitamin C and other non-supplemented antioxidants fell during TPN despite alpha-tocopherol supplementation normalizing tocopherol levels in one group.

Trust comment: Randomized clinical setting but small sample and short duration; vitamin C was measured but not manipulated as the primary intervention.

Study Details

PMID:10895108
Participants:33
Impact:decreased during 5-day TPN (both groups)
Trust score:3/5

A 12-week water-soluble vitamin supplement improved some vitamin biomarkers, increased weight, and lowered homocysteine in elderly female residents; plasma vitamin C rose in both groups.

Trust comment: Single-blind randomized placebo-controlled trial with clear endpoints but modest sample size.

Study Details

PMID:7498103
Participants:42
Impact:increased (both supplement and control groups)
Trust score:4/5

In adolescent girls with metabolic syndrome, 6 weeks of DASH recommendations increased vitamin C levels, lowered insulin and prevented rise in diastolic blood pressure versus usual advice.

Trust comment: Randomised crossover trial with objective biochemical measures but moderate sample size and short intervention period.

Study Details

PMID:23773316
Participants:60
Impact:+197 ng/l (+30%) (860 vs 663 ng/l), P=0.06
Trust score:4/5

In septic shock patients, IV antioxidant therapy including vitamin C raised vitamin C levels and improved some hemodynamic measures.

Trust comment: Small randomized clinical study but used combination antioxidant therapy (ascorbate + others), so vitamin C–specific effects are confounded.

Study Details

PMID:9296454
Participants:30
Impact:increase (significant, p=0.0002)
Trust score:3/5

An 8-week double-blind RCT of a multivitamin/multimineral/phytonutrient product increased vitamin C and folate status and reduced homocysteine in adults with low fruit/veg intake.

Trust comment: Well-designed double-blind, placebo-controlled RCT with 120 completers and measured biomarkers; short duration limits clinical outcome inference.

Study Details

PMID:29370120
Participants:120
Impact:+8.21 mg/dL (VMP) vs +2.97 mg/dL (PLA) at Day 56
Trust score:4/5

Grapefruit intake for 2 weeks increased blood vitamin C and reduced gum bleeding in periodontitis patients.

Trust comment: Checklist: 1) Confirm Vitamin C relevance; 2) Identify top outcomes; 3) Determine participants; 4) Rate quality; 5) Document changes; 6) Summarize; Study rated 4/5—reasonable sample and clear pre/post measures but short duration and limited longer-term data.

Study Details

PMID:16127404
Participants:80
Impact:non-smokers +0.31 mg/dL (0.56 → 0.87 mg/dL); smokers +0.35 mg/dL (0.39 → 0.74 mg/dL)
Trust score:4/5

In 122 premenopausal women, a high fruit-and-vegetable dietary intervention significantly increased plasma vitamin C and other carotenoids over one year.

Trust comment: Randomized dietary intervention (n=122) with serial biomarker measurements; dietary adherence and generalizability may limit inference.

Study Details

PMID:16766775
Participants:122
Impact:significantly increased with high fruit-vegetable intervention (magnitude not specified)
Trust score:3/5

Cross‑sectional study found vegetarians had higher plasma antioxidant status and higher plasma vitamin C (statistically significant) and lower LDL TBARS compared with nonvegetarians.

Trust comment: Small cross‑sectional human study (n=38) with clear biochemical measures; associations are plausible but limited by sample size and observational design.

Study Details

PMID:9895420
Participants:38
Impact:Higher in vegetarians (statistically significant increase vs nonvegetarians)
Trust score:3/5

One tablet daily containing iron plus vitamin C for four weeks raised hemoglobin, hematocrit, serum iron, and vitamin C without increasing plasma oxalate in dialysis patients.

Trust comment: Open-label, short (4-week) study with small sample (n=24) but objective laboratory endpoints; limited by lack of blinding and short duration.

Study Details

PMID:12563623
Participants:24
Impact:increased (prevented deficiency; levels rose)
Trust score:3/5

Combined vitamin C (1000 mg) and vitamin E supplementation for 4 weeks raised plasma antioxidant levels and reduced multiple oxidative stress markers in Crohn's disease patients.

Trust comment: Randomized controlled trial with objective biochemical endpoints but short duration (4 weeks) and modest sample size.

Study Details

PMID:12591053
Participants:57
Impact:increased (after supplementation)
Trust score:4/5

12-week double-blind RCT of an MVM (including vitamin D) increased vitamin C and zinc levels and reduced reported illness duration/severity, but did not change 25(OH) vitamin D or measured neutrophil functional assays.

Trust comment: Well-designed double-blind RCT with objective nutrient measures but small sample (n=42); multinutrient formulation prevents attribution to vitamin C alone.

Study Details

PMID:32823974
Participants:42
Impact:+126% (+59.7 ± 6.4 µmol/L; P<0.0001)
Trust score:4/5

Smokers had smaller, more superficial punch wounds and lower vitamin C and PINP (a collagen synthesis marker); smoking cessation increased wound depth, vitamin C, and PINP; nicotine patch had no detectable effect.

Trust comment: Well-characterized randomized/controlled wound study with biomarker measures and sufficient sample size to show significant vitamin C differences by smoking status.

Study Details

PMID:20347467
Participants:78
Impact:lower in smokers (50.5 ±9.0 μmol/L) vs never smokers (68.8 ±14.5 μmol/L); difference ≈ -18.3 μmol/L (P<.001)
Trust score:4/5

A fruit/vegetable purée drink acutely raised plasma vitamin C and plasma antioxidant capacity and showed a trend toward improved endothelium-dependent vasodilation.

Trust comment: Randomized, single-blind crossover but small sample (n=24) and short-term (acute) outcomes.

Study Details

PMID:23017441
Participants:24
Impact:significant increase (P = 0.002)
Trust score:3/5

Patients with IgA nephropathy had more oxidative damage and lower antioxidant levels including vitamin C than healthy volunteers.

Trust comment: Moderate-quality comparative study with clear measurements but observational design limits causal inference about vitamin C effects.

Study Details

PMID:15593395
Participants:144
Impact:decreased (significantly vs controls, P<0.0001)
Trust score:3/5

Isoflavone supplementation reduced homocysteine and some resting oxidative markers but did not change plasma vitamin C or prevent exercise-induced oxidative stress.

Trust comment: Randomized trial with clear biochemical endpoints but small N and the intervention was isoflavones, not vitamin C.

Study Details

PMID:15735366
Participants:30
Impact:no change with isoflavone supplementation
Trust score:3/5

Double-blind RCT of a multivitamin/mineral vs placebo in older adults on certain medications; MVMS increased folate and vitamin C status but did not significantly change serum calcium.

Trust comment: Double-blind, placebo-controlled RCT with direct biochemical measurement showing a small but significant increase in plasma vitamin C; small sample size limits precision.

Study Details

PMID:33078646
Participants:54
Impact:+0.2 mg/dL change in MVMS group vs 0.0 mg/dL in placebo (p=0.004)
Trust score:4/5

A mobile intervention or providing fruits/vegetables increased daily intake (~+0.9 servings/day) and raised plasma vitamin C compared to control in young adults.

Trust comment: Randomized trial with objective biomarker confirmation and moderate sample size; effect is dietary (increases vitamin C intake) rather than supplementation.

Study Details

PMID:27642037
Participants:171
Impact:increased (objective biomarker rose post-intervention)
Trust score:4/5

Adding guava to a supplemental meal increased vitamin C and improved iron status in preschoolers; the study measured B12 but did not report a B12 effect.

Trust comment: Cluster-RCT (n=399) with objective biomarker outcomes and clear statistically significant effects on iron status.

Study Details

PMID:33385184
Participants:399
Impact:increased (P = 0.047)
Trust score:4/5

In institutionalized elderly, daily vitamin supplementation (including 120 mg vitamin C) raised plasma vitamin levels (including vitamin C) and some antioxidant enzyme activity over 6–12 months, with limited effects on most immune markers.

Trust comment: Large randomized double-blind trial in institutionalized elderly with biochemical endpoints and long follow-up, supporting reliable changes in vitamin status though clinical benefits limited.

Study Details

PMID:9433680
Participants:756
Impact:significant increase after 6 months in groups receiving vitamins
Trust score:4/5

In very elderly institutionalized participants, a multivitamin beverage plus exercise raised some antioxidant carotenoids but vitamin C levels were not reported to increase.

Trust comment: Small controlled study in elderly subjects; multinutrient beverage was used so vitamin C-specific effects are not isolated.

Study Details

PMID:18382077
Participants:39
Impact:no reported increase (unchanged)
Trust score:3/5

In a long-term randomized trial subset, daily multivitamin/mineral (Centrum) increased plasma vitamin B12, folate, vitamin E and improved some other nutrient statuses versus placebo.

Trust comment: Large randomized trial with long follow-up; vitamin C effect was small compared with other measured nutrients.

Study Details

PMID:19636163
Participants:407
Impact:minimal or statistically less relevant change with multivitamin vs placebo
Trust score:4/5

In a 4-week randomized study, adding mandarin juice (rich in vitamin C and other antioxidants) to a low-calorie diet in obese children reduced oxidative stress markers and greatly increased plasma vitamin C.

Trust comment: Randomized controlled dietary intervention in children with consistent biomarker changes but short duration and small sample limit long-term inference.

Study Details

PMID:20528796
Participants:40
Impact:+94.6% (P<0.0001)
Trust score:3/5

In RA patients, shifting to a Mediterranean diet increased reported vitamin C intake but plasma vitamin C levels were unchanged at 12 weeks; baseline vitamin C correlated inversely with inflammation markers.

Trust comment: Randomized dietary intervention in RA with objective biochemical measures but modest sample size and potential dietary-report limitations.

Study Details

PMID:12952549
Participants:51
Impact:no sustained change by week 12 (plasma vitamin C relatively unchanged at end of study)
Trust score:3/5

A randomized dietary trial showed the Mediterranean-type diet group had fewer deaths and cancers over 4 years; plasma vitamin C levels increased in the diet group, but the effect cannot be attributed solely to vitamin C.

Trust comment: Randomized trial with clinically important outcomes, but diet changes were multifactorial so vitamin C-specific attribution is limited.

Study Details

PMID:9625397
Participants:605
Impact:increased in diet group (P < .05)
Trust score:3/5

Crossover RCT increasing potassium intake from fruit/veg or supplements in early hypertensives; plasma vitamin C was measured and remained unchanged and blood pressure did not improve.

Trust comment: Well-designed crossover RCT with biochemical verification and reasonable completion (48 completers), but modest sample size.

Study Details

PMID:20673378
Participants:48
Impact:no significant change versus control
Trust score:4/5

Randomized cross-over trial in hemodialysis patients with low vitamin C showed that 200 mg/day oral vitamin C raised plasma vitamin C and reduced hs-CRP; some nutritional markers trended upward.

Trust comment: Randomized controlled cross-over with selected deficient patients and measurable biomarker changes; modest sample (100) and some dropouts/no placebo limit certainty.

Study Details

PMID:24228847
Participants:100
Impact:increase: group1 mean 1.5 → 10.4 μg/mL (p<0.01); group2 baseline 2.0 → 9.1 μg/mL when treated (p<0.01)
Trust score:4/5

Combined antioxidant therapy including vitamin C (1,000 mg/day) given after suspected MI was associated with smaller mean infarct size and reduced oxidative markers and cardiac events versus placebo, but vitamins were given as a combination so effects cannot be attributed to vitamin C alone.

Trust comment: Randomized double-blind trial with positive clinical signals, but vitamins were administered as a multi-nutrient combination so individual contribution of vitamin C is uncertain.

Study Details

PMID:8607399
Participants:125
Impact:Increased by +12.6 μmol/L in antioxidant group vs +4.2 μmol/L in placebo (p<0.01)
Trust score:3/5

Patients with chronic bacterial prostatitis had lower plasma vitamin C and antioxidant enzymes and higher oxidative-damage markers than healthy controls.

Trust comment: Case-control biochemical study with adequate sample size but observational design limits causal inference.

Study Details

PMID:16625281
Participants:140
Impact:↓ in chronic bacterial prostatitis patients vs healthy volunteers
Trust score:3/5

In healthy middle-aged adults, 7-week supplementation with fruit/vegetable concentrates raised blood levels of several antioxidants including vitamin C.

Trust comment: Double-blind randomized crossover human study with moderate sample size but supplement contained many nutrients, so isolated vitamin C effect is indirect.

Study Details

PMID:15190044
Participants:59
Impact:increased (significant) after active supplementation
Trust score:3/5

Two-week antioxidant supplementation (vitamin C + E or fruit/veg powder) reduced some exercise-induced oxidative stress markers in men and women.

Trust comment: Randomized human study with pre/post measures and exercise challenge, moderate sample size (48); outcomes are biochemical markers.

Study Details

PMID:18059586
Participants:48
Impact:+39% (A) and +21% (FV) vs placebo
Trust score:4/5

leukocyte vitamin C

1 evidences

Obese participants on a 3-month low-calorie, DRI-covering formula diet showed declines in cellular and serum vitamin C but an increase in leukocyte vitamin C; some vitamin C deficiency cases increased after the diet.

Trust comment: Human pilot study with well-described methods and intracellular measures but small subgroup sample sizes (serum n=14) limit precision.

Study Details

PMID:22657586
Participants:32
Impact:+36% (81.64 → 111.2 ng/10^8 cells; p<0.05)
Trust score:3/5

oxidative stress markers

3 evidences

In hypertensive men, 8 weeks of vitamins C (1 g/day) + E increased erythrocyte (Na,K)-ATPase activity, improved oxidative stress markers and reduced blood pressure versus placebo.

Trust comment: Double-blind randomized placebo-controlled trial in 120 men with direct biochemical and clinical measures; moderate-high quality but supplements were combined (C+E).

Study Details

PMID:23659494
Participants:120
Impact:decrease (improved GSH/GSSG, lower F2-isoprostanes)
Trust score:4/5

Combined vitamin C (1000 mg) and vitamin E supplementation for 4 weeks raised plasma antioxidant levels and reduced multiple oxidative stress markers in Crohn's disease patients.

Trust comment: Randomized controlled trial with objective biochemical endpoints but short duration (4 weeks) and modest sample size.

Study Details

PMID:12591053
Participants:57
Impact:decreased (breath pentane/ethane, plasma lipid peroxides, F2-isoprostane; significant)
Trust score:4/5

Intravenous antioxidant therapy (including vitamin C) raised antioxidant levels and lowered oxidative stress markers but did not reduce organ dysfunction at 7 days in severe acute pancreatitis.

Trust comment: Randomized double-blind placebo-controlled trial but small sample and no benefit on primary clinical endpoint despite biomarker changes.

Study Details

PMID:17356040
Participants:43
Impact:decreased in treatment group (no numeric effect size provided)
Trust score:3/5

plasma vitamin C level

4 evidences

Oral vitamin C (250 mg thrice weekly for 2 months) restored plasma vitamin C but did not change markers of oxidative stress or inflammation in haemodialysis patients.

Trust comment: Randomized prospective open-label trial with objective biochemical endpoints but small sample size limits precision.

Study Details

PMID:15972322
Participants:33
Impact:normalized
Trust score:3/5

Vitamin C 50 mg/day in premature infants increased plasma vitamin C but did not increase hemolysis markers, bilirubin, or other morbidities versus placebo.

Trust comment: Multicenter double-blind randomized trial in neonates with appropriate design; sample size modest.

Study Details

PMID:9003858
Participants:56
Impact:increased (supplemented vs control)
Trust score:4/5

A twice-daily enriched drink increased plasma antioxidant levels including vitamin C in frail elderly people over six months.

Trust comment: Six‑month randomized double‑blind placebo‑controlled trial in frail elderly with clear biochemical outcomes, moderate sample size.

Study Details

PMID:12805250
Participants:55
Impact:increased (change reported ≈+37 ±5 vs +1 ±5 mmol/L between groups)
Trust score:4/5

In older adults undertaking regular exercise, a multi-ingredient antioxidant beverage (containing vitamin C among others) prevented exercise-induced increases in markers of lipid, protein and DNA oxidation and normalized glutathione and vitamin C levels.

Trust comment: Large, long-term intervention but used a multi-ingredient product (not isolated vitamin C), so effects cannot be attributed solely to vitamin C.

Study Details

PMID:19857542
Participants:400
Impact:Exercise ↓ plasma vitamin C −22%; supplementation restored/normalized levels
Trust score:3/5

oxidative stress markers (protein carbonyls, glutathione)

1 evidences

Oral vitamin C (250 mg thrice weekly for 2 months) restored plasma vitamin C but did not change markers of oxidative stress or inflammation in haemodialysis patients.

Trust comment: Randomized prospective open-label trial with objective biochemical endpoints but small sample size limits precision.

Study Details

PMID:15972322
Participants:33
Impact:no change
Trust score:3/5

daytime systolic blood pressure

1 evidences

Vitamin C 500 mg/day modestly lowered daytime systolic blood pressure and increased HDL in women, with no change in clinic BP or LDL.

Trust comment: Well-designed double-blind randomized placebo-controlled crossover trial but modest sample size.

Study Details

PMID:10779091
Participants:40
Impact:-2.0 mmHg
Trust score:4/5

clinic blood pressure

1 evidences

Vitamin C 500 mg/day modestly lowered daytime systolic blood pressure and increased HDL in women, with no change in clinic BP or LDL.

Trust comment: Well-designed double-blind randomized placebo-controlled crossover trial but modest sample size.

Study Details

PMID:10779091
Participants:40
Impact:no change
Trust score:4/5

HDL cholesterol (women)

1 evidences

Vitamin C 500 mg/day modestly lowered daytime systolic blood pressure and increased HDL in women, with no change in clinic BP or LDL.

Trust comment: Well-designed double-blind randomized placebo-controlled crossover trial but modest sample size.

Study Details

PMID:10779091
Participants:40
Impact:+0.08 mmol/L (women)
Trust score:4/5

hemoglobin

11 evidences

Iron-containing micronutrient supplements that included vitamin C improved hemoglobin and increased ferritin (iron stores); weekly 60 mg iron regimen was effective and better tolerated.

Trust comment: Randomized double-blind trial with objective hematologic outcomes; vitamin C was part of combination supplements, so effects cannot be isolated to vitamin C alone.

Study Details

PMID:9209187
Participants:273
Impact:significant increase after 2 months in both daily and weekly supplemented groups (P<0.001)
Trust score:4/5

Adding iron plus ascorbic acid to household water increased hemoglobin and ferritin in children and adults over 4 months.

Trust comment: Small community intervention (88 people) with clear pre/post biochemical changes, but iron+ascorbic combination makes isolated vitamin C effect indirect.

Study Details

PMID:12362799
Participants:88
Impact:Children: 10.9±1.1 to 11.7±1.1 g/dL (p<0.01); Adults: 12.9±1.7 to 13.7±1.7 g/dL (p<0.01)
Trust score:3/5

Six months of providing drinking-water with ascorbic acid (with or without iron) in daycare centers reduced anemia prevalence and increased mean hemoglobin and height gain in preschool children.

Trust comment: Clustered day-care center intervention with adequate sample and clear outcomes, but allocation by center and lack of individual-level randomization and detailed effect sizes reduce internal validity.

Study Details

PMID:16222916
Participants:150
Impact:mean hemoglobin increased (both groups)
Trust score:3/5

In 606 schoolchildren with group A strep infection, adding antioxidant vitamins to penicillin was associated with an increase in hemoglobin compared with penicillin alone.

Trust comment: Large randomized trial in children, but 'antioxidant vitamins' composition not specified and blinding/details unclear, limiting attribution specifically to vitamin C.

Study Details

PMID:12894046
Participants:606
Impact:antioxidant-vitamin group: increased from 10.8 to 11.6 mg/dL (+0.8 mg/dL) vs penicillin-alone: 11.0 to 10.5 mg/dL (−0.5 mg/dL)
Trust score:3/5

Daily guava juice (≈200 mg ascorbic acid) given with a meal modestly increased hemoglobin and had a smaller, non-significant increase in ferritin in mildly anemic children.

Trust comment: Randomized placebo-controlled trial with adequate sample size and clear ascorbic acid exposure, though ferritin change was not statistically significant.

Study Details

PMID:21896877
Participants:95
Impact:mean +0.64 g/dL vs placebo (95% CI 0.18–1.11; p=0.01)
Trust score:4/5

Higher intake of vitamin C–rich fruits and vegetables was associated with slightly higher hemoglobin in the whole sample and higher ferritin in premenopausal women.

Trust comment: Large observational cohort with repeated dietary records supports associations but cannot prove causality.

Study Details

PMID:18469253
Participants:4358
Impact:Up to +1.5 g/L higher in the highest vs lowest intake tertile
Trust score:3/5

In 62 CKD patients randomized to three oral iron therapies, the group receiving ferric sodium EDTA combined with vitamin C and other micronutrients showed larger improvements in hemoglobin and iron parameters and reductions in inflammatory markers.

Trust comment: Randomized multicenter study with objective labs, but open-label design and multi-nutrient combination prevent attributing effects to vitamin C alone.

Study Details

PMID:35631257
Participants:62
Impact:+1.21 g/dL (Group 2, 6 months)
Trust score:3/5

Intravenous vitamin C (500 mg thrice weekly) increased hemoglobin, raised transferrin saturation, and lowered the EPO/hemoglobin ratio in hemodialysis patients.

Trust comment: Randomized double-blind crossover with reasonable sample and clinically relevant hematologic endpoints.

Study Details

PMID:12776276
Participants:58
Impact:increased (P<0.0001)
Trust score:4/5

Adding guava to a supplemental meal increased vitamin C and improved iron status in preschoolers; the study measured B12 but did not report a B12 effect.

Trust comment: Cluster-RCT (n=399) with objective biomarker outcomes and clear statistically significant effects on iron status.

Study Details

PMID:33385184
Participants:399
Impact:increase versus controls (P = 0.002)
Trust score:4/5

Preschool children consumed milk fortified with multiple micronutrients (including vitamin C) for 1 year; fortified milk improved growth and iron status and reduced anemia.

Trust comment: Large double-masked RCT with high adherence and clinically meaningful, statistically robust outcomes.

Study Details

PMID:20730057
Participants:633
Impact:+13.6 g/L vs control (95% CI 11.1–16.0; p<0.001)
Trust score:5/5

Two months of multi-micronutrient Sprinkles (including vitamin C) reduced anemia and increased hemoglobin in 9–24 month old children.

Trust comment: Cluster-randomized programmatic trial with good sample size but uses multi-micronutrient product so vitamin C-specific effects cannot be isolated.

Study Details

PMID:17374671
Participants:415
Impact:+5.5 g/L at 1st follow-up and +10.9 g/L at 7-month follow-up in Sprinkles group
Trust score:3/5

EPO/hemoglobin ratio (EPO need)

1 evidences

Intravenous vitamin C (500 mg thrice weekly) increased hemoglobin, raised transferrin saturation, and lowered the EPO/hemoglobin ratio in hemodialysis patients.

Trust comment: Randomized double-blind crossover with reasonable sample and clinically relevant hematologic endpoints.

Study Details

PMID:12776276
Participants:58
Impact:decreased (P<0.0001 and P=0.019)
Trust score:4/5

transferrin saturation

4 evidences

Intravenous vitamin C (500 mg thrice weekly) increased hemoglobin, raised transferrin saturation, and lowered the EPO/hemoglobin ratio in hemodialysis patients.

Trust comment: Randomized double-blind crossover with reasonable sample and clinically relevant hematologic endpoints.

Study Details

PMID:12776276
Participants:58
Impact:increased (P≤0.009)
Trust score:4/5

Hemodialysis patients receiving 300 mg IV vitamin C each session for 3 months showed improved hemoglobin and transferrin saturation and reduced reticulocyte hemoglobin content and serum ferritin compared with standard care.

Trust comment: Small clinical intervention in hemodialysis patients with measurable improvements, but randomization and full trial details are unclear from the summary.

Study Details

PMID:18974579
Participants:46
Impact:significant increase after 3 months in vitamin C group (p<0.05)
Trust score:3/5

IV vitamin C given to iron-overloaded hemodialysis patients improved hematologic markers and reduced erythropoietin requirements.

Trust comment: Small clinical cohort with before/after and maintenance phases showing consistent objective hematologic changes, but not a large randomized trial.

Study Details

PMID:11952508
Participants:36
Impact:increase (significant)
Trust score:3/5

IV ascorbic acid improved haematocrit and iron availability and reduced erythropoietin dose in iron‑overloaded hemodialysis patients.

Trust comment: Randomized parallel comparative trial in humans (n=50) with objective laboratory endpoints; sample modest but findings are internally consistent.

Study Details

PMID:9829492
Participants:50
Impact:+21 percentage points (from 27% to 48%)
Trust score:4/5

osmotic fragility (erythrocytes)

1 evidences

In zinc-deficient hemodialysis patients, three months of zinc supplementation increased serum zinc, improved red blood cell osmotic fragility and reduced lipid peroxidation (MDA), but some side effects occurred with zinc.

Trust comment: Randomized study with clear biochemical outcomes but small, specific (zinc-deficient) population limits generalizability.

Study Details

PMID:11979503
Participants:34
Impact:improved (decreased fragility)
Trust score:3/5

neuron-specific enolase (NSE)

1 evidences

Intravenous vitamin C (1.5 g every 12 h, 8 doses) in post-cardiac arrest patients did not significantly lower NSE (primary outcome) but was associated with some improved inflammatory and clinical parameters (e.g., lower max PCT, shorter ventilation and ICU stay).

Trust comment: Randomized double-blind single-center trial but very small sample with some baseline imbalances and limited power.

Study Details

PMID:38256364
Participants:30
Impact:no significant change (higher in vitamin C group but not significant)
Trust score:3/5

maximum procalcitonin (PCT)

1 evidences

Intravenous vitamin C (1.5 g every 12 h, 8 doses) in post-cardiac arrest patients did not significantly lower NSE (primary outcome) but was associated with some improved inflammatory and clinical parameters (e.g., lower max PCT, shorter ventilation and ICU stay).

Trust comment: Randomized double-blind single-center trial but very small sample with some baseline imbalances and limited power.

Study Details

PMID:38256364
Participants:30
Impact:decreased (statistically significant)
Trust score:3/5

mechanical ventilation duration

1 evidences

Intravenous vitamin C (1.5 g every 12 h, 8 doses) in post-cardiac arrest patients did not significantly lower NSE (primary outcome) but was associated with some improved inflammatory and clinical parameters (e.g., lower max PCT, shorter ventilation and ICU stay).

Trust comment: Randomized double-blind single-center trial but very small sample with some baseline imbalances and limited power.

Study Details

PMID:38256364
Participants:30
Impact:decreased
Trust score:3/5

total cholesterol

6 evidences

An 8-month randomized double-blind placebo-controlled trial (n=138 completers) found no overall effect of 1 g/day vitamin C on HDL, LDL, total cholesterol or triglycerides; a small subgroup (n=43, low baseline AA) showed HDL +0.10 mmol/L.

Trust comment: Large randomized double-blind placebo-controlled trial with 138 completers; overall null primary results and subgroup findings are exploratory.

Study Details

PMID:7728285
Participants:138
Impact:no overall change
Trust score:4/5

Hemodialysis patients received vitamins; vitamin D3 group had reductions in triglycerides and TG/HDL ratio over 3 months.

Trust comment: Randomized allocation with measurable lipid outcomes (n=84) but small group sizes and short follow-up limit confidence.

Study Details

PMID:10757273
Participants:84
Impact:decreased after vitamin C therapy
Trust score:3/5

In a 75-day randomized double-blind trial, vitamin C (and vitamin E) reduced total and LDL cholesterol and raised HDL in healthy adults aged 50+; vitamin C group showed no significant triglyceride change.

Trust comment: Well-designed randomized double-blind placebo-controlled trial (n=120) showing favorable lipid changes with vitamin C, though duration was 75 days and full data detail is limited in abstract.

Study Details

PMID:12841306
Participants:120
Impact:significant decrease with vitamin C (vs placebo)
Trust score:4/5

In this large randomized trial of combined atorvastatin plus vitamin C and E vs placebo, treatment did not alter progression of coronary calcification; possible non-significant reduction in ASCVD events was observed.

Trust comment: Large, double-blind randomized trial (n=1,005); multicomponent intervention (statin + vitamins) limits attribution of effects specifically to vitamin C.

Study Details

PMID:15992652
Participants:1005
Impact:-reduced by ~26.5%–30.4% (attributed to atorvastatin component)
Trust score:4/5

Adding vitamin C to simvastatin did not provide lipid-profile benefits beyond simvastatin alone in patients with low HDL-C.

Trust comment: Randomized study but combined interventions and limited reporting on magnitude for vitamin C-specific effects.

Study Details

PMID:15590360
Participants:108
Impact:decreased with simvastatin (significant)
Trust score:3/5

Long-term micronutrient supplementation (capsules including 250 mg vitamin C plus vitamin E and selenium) was associated with small increases in total and LDL cholesterol after ~7.3 years.

Trust comment: Large randomized, placebo-controlled factorial trial but the exposure was a combined micronutrient supplement (vitamin C among others), so effects cannot be attributed to vitamin C alone.

Study Details

PMID:17023720
Participants:3411
Impact:+0.22 mmol/L (increase at 7.3 y; P = 0.01)
Trust score:4/5

von Willebrand factor

1 evidences

In a subset of PAD patients, antioxidant vitamin therapy was associated with a small increase in von Willebrand factor.

Trust comment: Subset analysis (n=80) from a randomized trial; antioxidant cocktail tested but component-specific effects (e.g., vitamin C alone) are unclear.

Study Details

PMID:11011338
Participants:80
Impact:Increased after antioxidant vitamin treatment (P = 0.04)
Trust score:3/5

pre-eclampsia incidence

5 evidences

Secondary analysis of an RCT in type-1 diabetic pregnant women; vitamins C+E did not prevent pre-eclampsia across haptoglobin phenotypes.

Trust comment: Large randomized controlled trial dataset; secondary analysis underpowered for interaction but overall robust for main null finding.

Study Details

PMID:23718253
Participants:685
Impact:no significant reduction with vitamins C+E (no preventive effect)
Trust score:4/5

Daily 1000 mg vitamin C from mid-pregnancy until delivery did not significantly reduce pre-eclampsia or major neonatal adverse outcomes.

Trust comment: Large, well-conducted randomized double-blind trial with intention-to-treat analysis, though lower-than-expected event rate may reduce power.

Study Details

PMID:25142305
Participants:833
Impact:3.1% (vitC) vs 4.1% (placebo); RR 0.77, p=0.4 (no significant change)
Trust score:4/5

Large randomized trial in pregnant women with type 1 diabetes: vitamins C+E increased blood vitamin levels but did not reduce pre-eclampsia or gestational hypertension overall.

Trust comment: Large, multicentre randomized placebo-controlled trial with predefined outcomes and high methodological quality.

Study Details

PMID:20580423
Participants:761
Impact:no change (no reduction vs placebo)
Trust score:5/5

Combined vitamin C (1000 mg) and vitamin E did not prevent pre-eclampsia and was associated with a higher rate of low birthweight infants.

Trust comment: Large multicenter randomized placebo-controlled trial with high participant number and intention-to-treat analysis.

Study Details

PMID:16616557
Participants:2395
Impact:no change (15% vs 16%)
Trust score:5/5

Daily vitamins C and E in high-risk pregnant women did not reduce pre-eclampsia or improve maternal/perinatal outcomes.

Trust comment: Large multicentre randomized double-blind trial with good compliance and follow-up showing no benefit for primary or key secondary outcomes.

Study Details

PMID:19432566
Participants:1365
Impact:no reduction (RR 1.0; 95% CI 0.9–1.3)
Trust score:5/5

low birthweight (<2.5 kg)

1 evidences

Combined vitamin C (1000 mg) and vitamin E did not prevent pre-eclampsia and was associated with a higher rate of low birthweight infants.

Trust comment: Large multicenter randomized placebo-controlled trial with high participant number and intention-to-treat analysis.

Study Details

PMID:16616557
Participants:2395
Impact:increased (28% vs 24%; RR 1.15)
Trust score:5/5

lipid peroxidation (MDA)

1 evidences

Patients given n‑3 PUFA plus antioxidant vitamins (including 1 g/day vitamin C) before and around cardiac surgery showed reduced oxidative stress and inflammation markers in atrial tissue and blood.

Trust comment: Clinical intervention in surgical patients with clear biochemical endpoints; reasonably powered (n=95) though trial design details (blinding/randomization) are not fully described.

Study Details

PMID:21138533
Participants:95
Impact:-27.5%
Trust score:4/5

urine vitamin C detection

1 evidences

A fully remote randomized trial where all participants received vitamin C; no clear benefit of added probiotic over vitamin C alone and good detectability of vitamin C in urine tests.

Trust comment: Randomized but open-label, small sample, and both arms received vitamin C so isolation of vitamin C effect is limited.

Study Details

PMID:37632169
Participants:30
Impact:no undetectable results after treatment; tests correctly performed ~76.7% of the time
Trust score:3/5

constipation symptom improvement

1 evidences

A fully remote randomized trial where all participants received vitamin C; no clear benefit of added probiotic over vitamin C alone and good detectability of vitamin C in urine tests.

Trust comment: Randomized but open-label, small sample, and both arms received vitamin C so isolation of vitamin C effect is limited.

Study Details

PMID:37632169
Participants:30
Impact:no remarkable difference between Lactobacillus+vitamin C and vitamin C alone
Trust score:3/5

latency period before delivery

2 evidences

Giving vitamins C and E after PPROM was associated with a longer time from membrane rupture to delivery.

Trust comment: Double-blind randomized controlled trial but small sample (n=60); outcome was statistically significant for latency.

Study Details

PMID:15907848
Participants:60
Impact:+7.0 days (mean 10.5 vs 3.5 days; P=0.03)
Trust score:4/5

Maternal vitamins C+E after PPROM were associated with a longer time to delivery and slightly later gestational age at birth without increased maternal or neonatal harms.

Trust comment: Prospective randomized trial with a moderate sample size and clear clinically relevant outcomes.

Study Details

PMID:23592317
Participants:229
Impact:+5.0 days (11.2 ± 6.3 vs 6.2 ± 4.0 days; p < 0.001)
Trust score:4/5

gestational age at delivery

1 evidences

Maternal vitamins C+E after PPROM were associated with a longer time to delivery and slightly later gestational age at birth without increased maternal or neonatal harms.

Trust comment: Prospective randomized trial with a moderate sample size and clear clinically relevant outcomes.

Study Details

PMID:23592317
Participants:229
Impact:+0.9 weeks (31.9 ± 2.6 vs 31.0 ± 2.6 weeks; p = 0.01)
Trust score:4/5

asthma diagnosis (infants)

1 evidences

High‑dose antenatal vitamins C+E did not improve infant respiratory outcomes and were associated with increased healthcare visits and costs.

Trust comment: Large randomized study with follow-up and healthcare utilization data, though subgroup sample for utilization was smaller.

Study Details

PMID:20889523
Participants:643
Impact:no significant difference
Trust score:4/5

healthcare utilization

1 evidences

High‑dose antenatal vitamins C+E did not improve infant respiratory outcomes and were associated with increased healthcare visits and costs.

Trust comment: Large randomized study with follow-up and healthcare utilization data, though subgroup sample for utilization was smaller.

Study Details

PMID:20889523
Participants:643
Impact:increased (A&E/outpatient visits 2.6×; GP visits 3.2×) and higher outpatient/GP/medication costs
Trust score:4/5

pulse wave velocity (PWV)

2 evidences

A 4-week polyphenol beverage that contained vitamin C did not improve vascular function but was associated with an increase in IL-6 compared with placebo.

Trust comment: Randomized pilot RCT (n=39) but small sample and intervention combined polyphenols with vitamin C, so vitamin C–specific effects cannot be isolated.

Study Details

PMID:26797134
Participants:39
Impact:no change (mean group difference 0.029 m/s)
Trust score:3/5

In healthy young adults a single antioxidant cocktail (including vitamin C) taken before a high-sodium meal did not change endothelial function or arterial stiffness compared with placebo.

Trust comment: Randomized, crossover design in humans but small, acute study using a combined antioxidant cocktail so isolating vitamin C effects is not possible.

Study Details

PMID:32610254
Participants:41
Impact:no treatment effect (treatment × time interaction P = 0.91)
Trust score:4/5

vitamin C deficiency prevalence

2 evidences

A fortified drink given 6 days/week for 8 weeks reduced vitamin B12 deficiency prevalence and increased vitamin B12 concentration and hemoglobin in schoolchildren.

Trust comment: Checklist: confirmed Vitamin C included in the fortified drink; primary outcomes (vitamin C status, Hb, ferritin) identified; participant count confirmed—randomized double-blind placebo-controlled trial with strong internal validity.

Study Details

PMID:23232585
Participants:246
Impact:-21% (prevalence reduction, P<0.01)
Trust score:4/5

More frequent hemodialysis did not significantly change predialysis plasma vitamin C concentrations or prevalence of deficiency in this small ancillary cohort.

Trust comment: Ancillary quasi-randomized analysis with small sample and some loss to follow-up, limiting power to detect differences.

Study Details

PMID:31101018
Participants:30
Impact:no significant difference between 6×/week and 3×/week groups
Trust score:3/5

catalase (CAT) activity

1 evidences

Radioiodine therapy increased oxidative stress markers; vitamin C given before therapy reduced some oxidative enzyme responses versus control.

Trust comment: Small randomized patient groups (n=58) with biomarker endpoints; human but moderate sample and limited detail on randomization/blinding.

Study Details

PMID:29860661
Participants:58
Impact:RAIT-induced increase attenuated in vitamin C groups (groups 3 and 4 showed significantly lower increase vs control)
Trust score:3/5

acute adverse symptom severity score

1 evidences

Spraying 2% vitamin C after Lugol iodine reduced acute and late mucosal irritation and sped fading of the iodine stain compared with saline; effects were similar or better than sodium thiosulfate for several symptoms.

Trust comment: Multicenter, randomized, double-blind trial with adequate sample (n=240) and clear, significant clinical endpoints.

Study Details

PMID:31783028
Participants:240
Impact:reduced (NS 2.58 vs VCS 1.61; P=0.040)
Trust score:5/5

late adverse symptom severity score

1 evidences

Spraying 2% vitamin C after Lugol iodine reduced acute and late mucosal irritation and sped fading of the iodine stain compared with saline; effects were similar or better than sodium thiosulfate for several symptoms.

Trust comment: Multicenter, randomized, double-blind trial with adequate sample (n=240) and clear, significant clinical endpoints.

Study Details

PMID:31783028
Participants:240
Impact:reduced (NS 1.70 vs VCS 0.91; P=0.002)
Trust score:5/5

acid regurgitation/heartburn and retrosternal pain (specific symptoms)

1 evidences

Spraying 2% vitamin C after Lugol iodine reduced acute and late mucosal irritation and sped fading of the iodine stain compared with saline; effects were similar or better than sodium thiosulfate for several symptoms.

Trust comment: Multicenter, randomized, double-blind trial with adequate sample (n=240) and clear, significant clinical endpoints.

Study Details

PMID:31783028
Participants:240
Impact:reduced vs STS (acid regurgitation 33% vs 15%, P=0.017; retrosternal pain 21% vs 9%, P=0.027)
Trust score:5/5

iodine-stained mucosa decolorization

1 evidences

Spraying 2% vitamin C after Lugol iodine reduced acute and late mucosal irritation and sped fading of the iodine stain compared with saline; effects were similar or better than sodium thiosulfate for several symptoms.

Trust comment: Multicenter, randomized, double-blind trial with adequate sample (n=240) and clear, significant clinical endpoints.

Study Details

PMID:31783028
Participants:240
Impact:faster/better decolorization (decolorization score VCS 2.26 vs NS 3.56; P<0.001)
Trust score:5/5

serum amyloid A (SAA)

1 evidences

In people with atrophic gastritis, a higher vitamin C dose raised serum ascorbic acid but did not change CRP or SAA over 5 years.

Trust comment: Population-based, double-blind RCT with long follow-up and adequate completion (120 and 124), but limited to biomarker outcomes.

Study Details

PMID:23167953
Participants:244
Impact:no significant difference between groups (P=0.61)
Trust score:4/5

forced expiratory flow at 50% (FEF50)

1 evidences

Pregnant smokers given 500 mg/day vitamin C had infants with improved certain measures of airway function at 3 months (two secondary FEF measures), though the primary FEF75 was not significantly changed.

Trust comment: Randomized, double-blind, placebo-controlled multicenter trial with clear physiologic endpoints and good sample size of infants (n≈222).

Study Details

PMID:30522343
Participants:222
Impact:increased in vitamin C group (436.7 vs 408.5 ml/s; adjusted difference ~+28.2 ml/s; P=0.02)
Trust score:5/5

forced expiratory flow 25-75% (FEF25-75)

1 evidences

Pregnant smokers given 500 mg/day vitamin C had infants with improved certain measures of airway function at 3 months (two secondary FEF measures), though the primary FEF75 was not significantly changed.

Trust comment: Randomized, double-blind, placebo-controlled multicenter trial with clear physiologic endpoints and good sample size of infants (n≈222).

Study Details

PMID:30522343
Participants:222
Impact:increased in vitamin C group (387.4 vs 365.8 ml/s; adjusted difference ~+21.6 ml/s; P=0.04)
Trust score:5/5

forced expiratory flow at 75% (FEF75)

1 evidences

Pregnant smokers given 500 mg/day vitamin C had infants with improved certain measures of airway function at 3 months (two secondary FEF measures), though the primary FEF75 was not significantly changed.

Trust comment: Randomized, double-blind, placebo-controlled multicenter trial with clear physiologic endpoints and good sample size of infants (n≈222).

Study Details

PMID:30522343
Participants:222
Impact:no significant improvement (200.7 vs 188.7 ml/s; P=0.10)
Trust score:5/5

placental vitamin C and E levels

1 evidences

In pregnant women with type 1 diabetes, maternal vitamin C/E supplementation did not increase placental or cord vitamin levels nor change placental antioxidant enzyme activity or lipid peroxidation versus placebo.

Trust comment: Moderate-size clinical study (n=57) nested in DAPIT with negative findings; appropriate measures but limited by sample size and lack of placental vitamin increase.

Study Details

PMID:26597598
Participants:57
Impact:no significant increase with maternal supplementation vs placebo
Trust score:3/5

placental antioxidant enzyme activity (Gpx, Gred, SOD, catalase)

1 evidences

In pregnant women with type 1 diabetes, maternal vitamin C/E supplementation did not increase placental or cord vitamin levels nor change placental antioxidant enzyme activity or lipid peroxidation versus placebo.

Trust comment: Moderate-size clinical study (n=57) nested in DAPIT with negative findings; appropriate measures but limited by sample size and lack of placental vitamin increase.

Study Details

PMID:26597598
Participants:57
Impact:no significant change with supplementation vs placebo
Trust score:3/5

lipid peroxidation markers (aqueous hydroperoxides, 8-iso-PGF2α)

1 evidences

In pregnant women with type 1 diabetes, maternal vitamin C/E supplementation did not increase placental or cord vitamin levels nor change placental antioxidant enzyme activity or lipid peroxidation versus placebo.

Trust comment: Moderate-size clinical study (n=57) nested in DAPIT with negative findings; appropriate measures but limited by sample size and lack of placental vitamin increase.

Study Details

PMID:26597598
Participants:57
Impact:no significant change with supplementation vs placebo
Trust score:3/5

net endothelial tissue plasminogen activator (t-PA) release — acute

1 evidences

In overweight/obese adults, acute intra-arterial vitamin C greatly increased endothelial t-PA release, and 3 months of oral vitamin C (500 mg/day) also increased t-PA release compared with before supplementation.

Trust comment: Human mechanistic study with both acute and 3-month supplementation data; moderate sample with clear physiological effects in at-risk (overweight/obese) group.

Study Details

PMID:18499730
Participants:33
Impact:potentiated ≈95% higher after intra-arterial vitamin C (from ~50 to ~95 ng (100 ml tissue)^-1 min^-1)
Trust score:4/5

net endothelial t-PA release — chronic oral (500 mg/day)

1 evidences

In overweight/obese adults, acute intra-arterial vitamin C greatly increased endothelial t-PA release, and 3 months of oral vitamin C (500 mg/day) also increased t-PA release compared with before supplementation.

Trust comment: Human mechanistic study with both acute and 3-month supplementation data; moderate sample with clear physiological effects in at-risk (overweight/obese) group.

Study Details

PMID:18499730
Participants:33
Impact:increased after 3 months (net values increased from ~48.2 to ~66.3 ng (100 ml tissue)^-1 min^-1; absolute increase ~18.1 ng/100 ml tissue/min)
Trust score:4/5

serum uric acid

5 evidences

500 mg/day vitamin C for 12 weeks did not significantly lower serum uric acid overall; subgroup with higher baseline uric acid showed a significant reduction.

Trust comment: Double-blind randomized placebo-controlled trial with 71 completers but limited power; subgroup signal noted but small sample.

Study Details

PMID:27941730
Participants:71
Impact:Vitamin C mean change -0.32 mg/dL; placebo mean change +0.12 mg/dL (overall not statistically significant)
Trust score:4/5

Smokers who drank milk supplemented with fruit/vegetable extracts and vitamin C twice daily for 6 weeks had higher plasma vitamin C and antioxidant potential and lower uric acid than non‑supplemented milk.

Trust comment: Controlled intervention in smokers with measurable biochemical outcomes but modest sample size and complex multi-component beverages limit attribution to vitamin C alone.

Study Details

PMID:21770863
Participants:42
Impact:decreased (vs non-supplemented milk)
Trust score:3/5

In hemodialysis patients, giving 250 mg vitamin C three times weekly for 8 weeks lowered serum uric acid but did not change creatinine.

Trust comment: Randomized placebo-controlled trial with a substantial sample (n=172) and reported statistical significance for the primary outcome.

Study Details

PMID:25194408
Participants:172
Impact:median -0.4 mg/dL (from 6.2 to 5.8 mg/dL in vitamin C group; P=0.02)
Trust score:4/5

In a double-blind RCT, 500 mg/day vitamin C for 2 months lowered serum uric acid by about 0.5 mg/dl and increased estimated GFR.

Trust comment: Double-blind, placebo-controlled randomized trial with a moderate sample size and clear outcome measures.

Study Details

PMID:15934094
Participants:184
Impact:-0.5 mg/dl mean change in vitamin C group over 2 months (placebo +0.09 mg/dl); P < 0.0001
Trust score:4/5

In women with severe early pre-eclampsia, combined antioxidant therapy (including vitamin C) did not clearly improve biochemical markers or clinical prolongation of pregnancy.

Trust comment: Randomized placebo-controlled trial but small sample and multi-agent intervention limit attribution to vitamin C alone.

Study Details

PMID:9197872
Participants:56
Impact:decreased in antioxidant group
Trust score:3/5

skin hydration

2 evidences

Daily oral collagen tripeptide (3 g) improved skin hydration and elasticity and tended to reduce transepidermal water loss over 12 weeks compared with no supplement.

Trust comment: Randomized controlled trial but very small groups (n≈8 per arm) limiting confidence in vitamin C-specific conclusions.

Study Details

PMID:24131075
Participants:32
Impact:improved with collagen peptide; addition of vitamin C did not further enhance effect (no additional benefit reported)
Trust score:3/5

Randomized placebo‑controlled 12‑week trial in 72 women: daily drinkable collagen peptides + dermonutrients improved objective measures of skin appearance versus placebo.

Trust comment: Randomized, placebo-controlled trial with objective measurements and complete follow-up (n=72); single-blind and combination supplement limits attribution solely to vitamin C.

Study Details

PMID:31627309
Participants:72
Impact:+28.0% (verum T12 vs baseline); placebo +9.0%; between-group p<0.0004
Trust score:4/5

erythrocyte and plasma lipid peroxidation

1 evidences

Perioperative vitamin C+E reduced markers of lipid peroxidation and increased antioxidant enzyme activity and plasma antioxidant vitamin levels versus control.

Trust comment: Randomized perioperative trial with objective biochemical endpoints but modest sample size (n=40).

Study Details

PMID:20464539
Participants:40
Impact:Lower in VCE group than control at 1, 24, and 72 hours postoperatively
Trust score:4/5

erythrocyte glutathione peroxidase activity

2 evidences

Perioperative vitamin C+E reduced markers of lipid peroxidation and increased antioxidant enzyme activity and plasma antioxidant vitamin levels versus control.

Trust comment: Randomized perioperative trial with objective biochemical endpoints but modest sample size (n=40).

Study Details

PMID:20464539
Participants:40
Impact:Higher in VCE group than control at 1, 24, and 72 hours postoperatively
Trust score:4/5

A 6-month antioxidant regimen including vitamin C raised blood antioxidant levels but did not change liver enzymes or hepatitis C viral load.

Trust comment: Randomized, placebo-controlled double-blind trial but small sample (n=23) limits power to detect clinical effects.

Study Details

PMID:16894312
Participants:23
Impact:increased from baseline to month 6 (significant)
Trust score:3/5

plasma vitamins A, C, and E levels

1 evidences

Perioperative vitamin C+E reduced markers of lipid peroxidation and increased antioxidant enzyme activity and plasma antioxidant vitamin levels versus control.

Trust comment: Randomized perioperative trial with objective biochemical endpoints but modest sample size (n=40).

Study Details

PMID:20464539
Participants:40
Impact:Higher in VCE group than control at 1, 24, and 72 hours postoperatively
Trust score:4/5

serum urate

1 evidences

In 40 gout patients, 500 mg/day vitamin C for 8 weeks raised plasma ascorbate but produced only a very small and clinically insignificant decrease in serum urate compared with allopurinol.

Trust comment: Pilot randomized trial (n=40) with clear numerical outcomes showing minimal urate-lowering effect of 500 mg/day vitamin C.

Study Details

PMID:23681955
Participants:40
Impact:Mean reduction 0.014 mmol/L (0.23 mg/dL) over 8 weeks with vitamin C versus 0.118 mmol/L (1.9 mg/dL) with allopurinol
Trust score:4/5

parotid gland uptake index

1 evidences

Randomized study in 89 patients receiving 131I comparing vitamin E, vitamin C, and supragingival scaling with vitamin C; vitamin E protected parotid excretion function, and supragingival scaling with vitamin C improved uptake indices and excretion rates and attenuated serum amylase reduction.

Trust comment: Randomized groups (n=89 total) with some significant endpoints for scaling+vitamin C, but reporting for vitamin C alone is unclear and details limited.

Study Details

PMID:35950355
Participants:89
Impact:Significantly higher in supragingival scaling with vitamin C group (group C) after 131I (P < 0.05)
Trust score:3/5

parotid excretion rate (left)

1 evidences

Randomized study in 89 patients receiving 131I comparing vitamin E, vitamin C, and supragingival scaling with vitamin C; vitamin E protected parotid excretion function, and supragingival scaling with vitamin C improved uptake indices and excretion rates and attenuated serum amylase reduction.

Trust comment: Randomized groups (n=89 total) with some significant endpoints for scaling+vitamin C, but reporting for vitamin C alone is unclear and details limited.

Study Details

PMID:35950355
Participants:89
Impact:Significantly higher in supragingival scaling with vitamin C group (P < 0.05)
Trust score:3/5

serum amylase reduction

1 evidences

Randomized study in 89 patients receiving 131I comparing vitamin E, vitamin C, and supragingival scaling with vitamin C; vitamin E protected parotid excretion function, and supragingival scaling with vitamin C improved uptake indices and excretion rates and attenuated serum amylase reduction.

Trust comment: Randomized groups (n=89 total) with some significant endpoints for scaling+vitamin C, but reporting for vitamin C alone is unclear and details limited.

Study Details

PMID:35950355
Participants:89
Impact:Degree of serum amylase level reduction decreased significantly in supragingival scaling with vitamin C group (P < 0.05)
Trust score:3/5

postoperative pulmonary complication score

1 evidences

Intraoperative IV vitamin C (3 g total given in three 1 g doses) reduced postoperative pulmonary complication (PPC) scores and lowered the incidence of PPCs versus saline in low-risk cardiac surgery patients.

Trust comment: Prospective double-blind randomized trial with 70 analyzed patients showing statistically significant reductions in PPC measures, though single-center and moderate size.

Study Details

PMID:32848365
Participants:70
Impact:Median PPC score lower in vitamin C group: 2 (1–2) vs 2 (2–3); P = 0.009
Trust score:4/5

incidence of postoperative pulmonary complications

1 evidences

Intraoperative IV vitamin C (3 g total given in three 1 g doses) reduced postoperative pulmonary complication (PPC) scores and lowered the incidence of PPCs versus saline in low-risk cardiac surgery patients.

Trust comment: Prospective double-blind randomized trial with 70 analyzed patients showing statistically significant reductions in PPC measures, though single-center and moderate size.

Study Details

PMID:32848365
Participants:70
Impact:Lower in vitamin C group: 12.12% vs 32.43%; P = 0.043
Trust score:4/5

lipid peroxidation (malondialdehyde)

1 evidences

In burned children, combined vitamin C+E+zinc lowered lipid peroxidation and sped wound healing compared with placebo.

Trust comment: Small double-blind RCT in children showing improvements in oxidative stress and wound healing, but vitamin C was given as part of a multinutrient mix so attribution to vitamin C alone is uncertain.

Study Details

PMID:19692922
Participants:32
Impact:decrease in malondialdehyde level (P = 0.006)
Trust score:3/5

time to wound healing

1 evidences

In burned children, combined vitamin C+E+zinc lowered lipid peroxidation and sped wound healing compared with placebo.

Trust comment: Small double-blind RCT in children showing improvements in oxidative stress and wound healing, but vitamin C was given as part of a multinutrient mix so attribution to vitamin C alone is uncertain.

Study Details

PMID:19692922
Participants:32
Impact:shorter wound healing time in supplemented group (P < 0.001)
Trust score:3/5

serum vitamin concentrations

1 evidences

In burned children, combined vitamin C+E+zinc lowered lipid peroxidation and sped wound healing compared with placebo.

Trust comment: Small double-blind RCT in children showing improvements in oxidative stress and wound healing, but vitamin C was given as part of a multinutrient mix so attribution to vitamin C alone is uncertain.

Study Details

PMID:19692922
Participants:32
Impact:serum vitamin C and E concentrations increased in supplemented group (serum changes confirmed; zinc not significantly changed)
Trust score:3/5

antioxidant enzymes (SOD, GPx)

1 evidences

In healthy elderly adults, 6 months of 500–1000 mg ascorbic acid plus 400 IU vitamin E did not significantly change oxidative stress markers, antioxidant enzymes, or DNA damage versus placebo.

Trust comment: Checklist: 1) Confirm Vitamin C relevance; 2) extract N and main outcomes; 3) rate trustworthiness; Justification: double-blind controlled human trial (N=66) with null results, limiting support for high-dose vitamin C+E in healthy elderly.

Study Details

PMID:18446021
Participants:66
Impact:no significant change (non-significant increases reported)
Trust score:4/5

estimated glomerular filtration rate (eGFR)

3 evidences

In a double-blind RCT, 500 mg/day vitamin C for 2 months lowered serum uric acid by about 0.5 mg/dl and increased estimated GFR.

Trust comment: Double-blind, placebo-controlled randomized trial with a moderate sample size and clear outcome measures.

Study Details

PMID:15934094
Participants:184
Impact:increased (estimated; reported improvement vs placebo)
Trust score:4/5

Perioperative IV vitamin C did not reduce postoperative AKI or improve eGFR after on-pump cardiac surgery; MDA (oxidative stress marker) was not reduced and was higher on POD1 in a subgroup.

Trust comment: Large randomized prospective multicenter trial with predefined primary endpoint and appropriate analyses; MDA subgroup small and some secondary outcomes underpowered.

Study Details

PMID:35643076
Participants:332
Impact:No significant difference across postoperative time points (no improvement with AA)
Trust score:4/5

Statin plus ascorbic acid reduced the incidence of post-contrast acute kidney injury compared to placebo, though serum creatinine and eGFR changes were not improved between groups.

Trust comment: Randomized clinical trial with adequate sample but ascorbic acid was given together with high‑dose atorvastatin, so effect of vitamin C alone is not separable.

Study Details

PMID:37742328
Participants:213
Impact:placebo 100.45→92.85 mL/min; treatment 102.27→96.17 mL/min (both decreased; between-group NS)
Trust score:3/5

periorbital melanosis improvement (>50%)

1 evidences

Topical 20% vitamin C daily produced >50% improvement in under-eye pigmentation in about 27% of patients over 12 weeks and was less effective than chemical peels.

Trust comment: Moderate-quality comparative clinical study with moderate sample size but likely non-blinded and not clearly randomized.

Study Details

PMID:27380862
Participants:90
Impact:26.67% of patients in the topical 20% vitamin C group achieved >50% improvement at 12 weeks
Trust score:3/5

tolerability / adverse effects

1 evidences

Topical 20% vitamin C daily produced >50% improvement in under-eye pigmentation in about 27% of patients over 12 weeks and was less effective than chemical peels.

Trust comment: Moderate-quality comparative clinical study with moderate sample size but likely non-blinded and not clearly randomized.

Study Details

PMID:27380862
Participants:90
Impact:lower incidence of adverse effects than glycolic and lactic peels (qualitative)
Trust score:3/5

plasma vitamin C levels

1 evidences

Double-blind RCT in post-menopausal women (159 completers) testing an oral multi-ingredient supplement (not collagen); reported reduced wrinkle depth and increased skin collagen deposition in biopsies.

Trust comment: Well-conducted double-blind RCT with good sample and objective measures, but multi-ingredient product prevents attribution of effects to vitamin C alone.

Study Details

PMID:23927381
Participants:159
Impact:plasma vitamin C increased from ~55 µM baseline to ~72 µM in active groups at T15
Trust score:3/5

lipid peroxides

1 evidences

Daily supplementation (vitamin C + E + zinc + selenium) for 17 weeks improved quadriceps maximal voluntary contraction and endurance and altered antioxidant markers, but did not improve 2-minute walk distance.

Trust comment: Randomized double-blind placebo-controlled clinical trial with clear between-group biochemical and functional differences though modest sample size (pilot).

Study Details

PMID:25246239
Participants:53
Impact:variation significantly different between groups (P<0.001), indicating reduced oxidative stress with supplementation
Trust score:4/5

neonatal total bilirubin

1 evidences

In a double-blind RCT, maternal 500 mg/day vitamin C in the last month of pregnancy significantly reduced neonatal total bilirubin measured on day 5.

Trust comment: Double-blind randomized trial with adequate sample size and a clear clinically relevant outcome.

Study Details

PMID:32444041
Participants:128
Impact:decreased (statistically significant, P = 0.02)
Trust score:4/5

ACh-stimulated forearm blood flow (endothelium-dependent vasodilation)

1 evidences

Vitamin C acutely increased endothelium-dependent vasodilation (ACh-mediated forearm blood flow) in hypercholesterolemic patients.

Trust comment: Small non-blinded physiological study with objective vascular measures but limited sample size (30) and potential confounders.

Study Details

PMID:10998481
Participants:30
Impact:increase (improved ACh-vasodilation)
Trust score:3/5

Basal nitric oxide availability (L-NMMA response)

1 evidences

Vitamin C acutely increased endothelium-dependent vasodilation (ACh-mediated forearm blood flow) in hypercholesterolemic patients.

Trust comment: Small non-blinded physiological study with objective vascular measures but limited sample size (30) and potential confounders.

Study Details

PMID:10998481
Participants:30
Impact:enhanced (improved endothelial effect)
Trust score:3/5

Endothelium-independent vasodilation (SNP)

1 evidences

Vitamin C acutely increased endothelium-dependent vasodilation (ACh-mediated forearm blood flow) in hypercholesterolemic patients.

Trust comment: Small non-blinded physiological study with objective vascular measures but limited sample size (30) and potential confounders.

Study Details

PMID:10998481
Participants:30
Impact:no significant change
Trust score:3/5

Radial artery flow volume

1 evidences

A single 2 g oral dose of vitamin C (with or without vitamin E) acutely increased radial artery flow, lumen diameter and area in patients awaiting CABG.

Trust comment: Randomized allocation with blinded ultrasound assessment and adequate sample (n=93); acute physiological endpoints measured reliably.

Study Details

PMID:24217301
Participants:93
Impact:increase (mean FV4–FV1 ≈ +1.322) (statistically significant)
Trust score:4/5

Radial artery lumen area

1 evidences

A single 2 g oral dose of vitamin C (with or without vitamin E) acutely increased radial artery flow, lumen diameter and area in patients awaiting CABG.

Trust comment: Randomized allocation with blinded ultrasound assessment and adequate sample (n=93); acute physiological endpoints measured reliably.

Study Details

PMID:24217301
Participants:93
Impact:increase (mean A4–A1 ≈ +8.096) (statistically significant)
Trust score:4/5

Radial artery lumen diameter

1 evidences

A single 2 g oral dose of vitamin C (with or without vitamin E) acutely increased radial artery flow, lumen diameter and area in patients awaiting CABG.

Trust comment: Randomized allocation with blinded ultrasound assessment and adequate sample (n=93); acute physiological endpoints measured reliably.

Study Details

PMID:24217301
Participants:93
Impact:increase (mean D4–D1 ≈ +2.225) (statistically significant)
Trust score:4/5

Restless legs symptom severity (IRLS score)

1 evidences

Vitamin C (200 mg) and/or vitamin E (400 mg) taken for 8 weeks reduced restless legs symptom scores (~10-point drop) versus placebo (~3-point drop) in hemodialysis patients.

Trust comment: Randomized, double-blind, placebo-controlled trial with clear clinical outcome measures but moderate sample size (n=60).

Study Details

PMID:22317944
Participants:60
Impact:~−10 points in treatment groups vs −3.1 points in placebo (greater symptom reduction)
Trust score:4/5

Serum malondialdehyde (MDA) - oxidative stress marker

1 evidences

Adding oral vitamin C to atypical antipsychotics for 8 weeks reduced oxidative stress markers and improved psychiatric rating scores in schizophrenia patients.

Trust comment: Prospective double-blind placebo-controlled trial with objective biomarkers and clinical scale but small sample (n=40).

Study Details

PMID:16133138
Participants:40
Impact:decrease (reduced MDA vs placebo)
Trust score:4/5

Psychiatric symptoms (BPRS score)

1 evidences

Adding oral vitamin C to atypical antipsychotics for 8 weeks reduced oxidative stress markers and improved psychiatric rating scores in schizophrenia patients.

Trust comment: Prospective double-blind placebo-controlled trial with objective biomarkers and clinical scale but small sample (n=40).

Study Details

PMID:16133138
Participants:40
Impact:improvement (greater reduction in BPRS change scores vs placebo)
Trust score:4/5

Serum PGI/II ratio (marker of gastric mucosal atrophy)

1 evidences

Over 5 years, higher-dose vitamin C (500 mg/day) attenuated the decline in PGI/II ratio versus 50 mg/day, suggesting reduced progression of gastric mucosal atrophy.

Trust comment: Population-based double-blind randomized trial with long follow-up and objective serological outcome, though subgroup completers used (n=244).

Study Details

PMID:12824908
Participants:244
Impact:less decline with 500 mg/d (change −0.13) vs 50 mg/d (change −0.25); P=0.046
Trust score:4/5

malondialdehyde (lipid peroxidation)

1 evidences

In a 4-week randomized study, adding mandarin juice (rich in vitamin C and other antioxidants) to a low-calorie diet in obese children reduced oxidative stress markers and greatly increased plasma vitamin C.

Trust comment: Randomized controlled dietary intervention in children with consistent biomarker changes but short duration and small sample limit long-term inference.

Study Details

PMID:20528796
Participants:40
Impact:−9.6% (P=0.014)
Trust score:3/5

spontaneous pain (NRS)

1 evidences

IV vitamin C raised plasma levels and substantially reduced spontaneous pain in patients with postherpetic neuralgia but did not affect brush-evoked pain.

Trust comment: Double-blind, placebo-controlled RCT with objective pain scales but modest sample size.

Study Details

PMID:19692796
Participants:41
Impact:−3.1 (vitamin C) vs −0.85 (placebo) from baseline to day 7
Trust score:4/5

brush-evoked pain

1 evidences

IV vitamin C raised plasma levels and substantially reduced spontaneous pain in patients with postherpetic neuralgia but did not affect brush-evoked pain.

Trust comment: Double-blind, placebo-controlled RCT with objective pain scales but modest sample size.

Study Details

PMID:19692796
Participants:41
Impact:no significant change vs placebo
Trust score:4/5

minimal erythema dose (MED)

1 evidences

One-week oral antioxidant regimens showed that vitamin E alone and vitamin E plus vitamin C increased minimal erythema dose (photoprotection), whereas vitamin C alone did not.

Trust comment: Controlled human trial but single-blind, short duration, and small groups limit strength of evidence for vitamin C alone.

Study Details

PMID:12013192
Participants:45
Impact:Group1 (vitamin E): 60→65 mJ/cm² (+5); Group2 (ascorbic acid alone): no change; Group3 (vitamin E + ascorbic acid): 50→70 mJ/cm² (+20)
Trust score:3/5

BV cure rate (ITT)

1 evidences

Six daily 250 mg vitamin C vaginal tablets significantly increased cure rates of bacterial vaginosis versus placebo and were well tolerated.

Trust comment: Large randomized double-blind placebo-controlled trial with clear, clinically relevant endpoints and robust effect size.

Study Details

PMID:21650086
Participants:277
Impact:55.3% with Vit C vs 25.7% placebo; between-group difference 29.6% (p<0.001)
Trust score:4/5

BV cure rate (PP)

1 evidences

Six daily 250 mg vitamin C vaginal tablets significantly increased cure rates of bacterial vaginosis versus placebo and were well tolerated.

Trust comment: Large randomized double-blind placebo-controlled trial with clear, clinically relevant endpoints and robust effect size.

Study Details

PMID:21650086
Participants:277
Impact:66.4% with Vit C vs 27.1% placebo (p<0.001)
Trust score:4/5

penile-vaginal intercourse frequency (FSI)

1 evidences

14-day high-dose vitamin C (3000 mg/day) increased penile-vaginal intercourse frequency and reduced depression scores versus placebo.

Trust comment: Randomized double-blind placebo-controlled trial with moderate sample size and subjective diary outcomes; short duration limits long-term inference.

Study Details

PMID:12208645
Participants:81
Impact:increased (significant vs placebo)
Trust score:4/5

depressive symptoms (Beck Depression Inventory)

1 evidences

14-day high-dose vitamin C (3000 mg/day) increased penile-vaginal intercourse frequency and reduced depression scores versus placebo.

Trust comment: Randomized double-blind placebo-controlled trial with moderate sample size and subjective diary outcomes; short duration limits long-term inference.

Study Details

PMID:12208645
Participants:81
Impact:decreased (significant vs placebo)
Trust score:4/5

ascorbic acid (serum level)

1 evidences

4-month antioxidant supplement (vitamin C as part of a combination) increased antioxidant status, reduced oxidative stress marker and modestly lowered ALT but did not change inflammatory markers.

Trust comment: Randomized trial in humans but used a multinutrient antioxidant mix so effects cannot be attributed to vitamin C alone; small sample.

Study Details

PMID:24353344
Participants:44
Impact:increased (β = 70.6)
Trust score:3/5

oxidative stress (8-iso-prostaglandin F2α)

1 evidences

4-month antioxidant supplement (vitamin C as part of a combination) increased antioxidant status, reduced oxidative stress marker and modestly lowered ALT but did not change inflammatory markers.

Trust comment: Randomized trial in humans but used a multinutrient antioxidant mix so effects cannot be attributed to vitamin C alone; small sample.

Study Details

PMID:24353344
Participants:44
Impact:decreased (β = -0.11)
Trust score:3/5

alanine aminotransferase (ALT)

3 evidences

In hepatitis C patients receiving interferon and ribavirin, vitamins E+C kept a fatty acid (EPA) level stable and raised blood vitamin levels.

Trust comment: Randomized clinical study but small sample (n=30) and combined vitamin E+C makes isolating vitamin C effects less certain.

Study Details

PMID:16459223
Participants:30
Impact:decreased in both groups (therapy effect; not specific to vitamins)
Trust score:3/5

4-month antioxidant supplement (vitamin C as part of a combination) increased antioxidant status, reduced oxidative stress marker and modestly lowered ALT but did not change inflammatory markers.

Trust comment: Randomized trial in humans but used a multinutrient antioxidant mix so effects cannot be attributed to vitamin C alone; small sample.

Study Details

PMID:24353344
Participants:44
Impact:decreased (β = -0.13)
Trust score:3/5

In children with NAFLD, adding vitamin E plus vitamin C to diet/exercise did not improve liver enzymes, insulin resistance, or weight loss compared with placebo.

Trust comment: Double-blind RCT in 90 pediatric NAFLD patients; well-conducted but vitamin C was given with vitamin E so individual C effect is not isolated.

Study Details

PMID:17206944
Participants:90
Impact:no significant difference between antioxidant and placebo at 12 months (P = NS)
Trust score:4/5

serum and follicular fluid vitamin C levels

1 evidences

Vitamin C 1000 mg/day for 2 months raised serum and follicular-fluid vitamin C but did not change measured oxidative stress markers or IVF implantation and clinical pregnancy rates.

Trust comment: Large randomized study with relevant clinical endpoints; no placebo control and some attrition but methods and sample size are generally robust.

Study Details

PMID:30058418
Participants:377
Impact:increased (post-treatment vs baseline/non-treatment)
Trust score:4/5

oxidative stress markers (ROS, TAC, SOD, MDA)

1 evidences

Vitamin C 1000 mg/day for 2 months raised serum and follicular-fluid vitamin C but did not change measured oxidative stress markers or IVF implantation and clinical pregnancy rates.

Trust comment: Large randomized study with relevant clinical endpoints; no placebo control and some attrition but methods and sample size are generally robust.

Study Details

PMID:30058418
Participants:377
Impact:no significant change
Trust score:4/5

IVF outcomes (fertilization, implantation, clinical pregnancy rates)

1 evidences

Vitamin C 1000 mg/day for 2 months raised serum and follicular-fluid vitamin C but did not change measured oxidative stress markers or IVF implantation and clinical pregnancy rates.

Trust comment: Large randomized study with relevant clinical endpoints; no placebo control and some attrition but methods and sample size are generally robust.

Study Details

PMID:30058418
Participants:377
Impact:no significant change
Trust score:4/5

markers of hemolysis (corrected carboxyhemoglobin and others)

1 evidences

Vitamin C 50 mg/day in premature infants increased plasma vitamin C but did not increase hemolysis markers, bilirubin, or other morbidities versus placebo.

Trust comment: Multicenter double-blind randomized trial in neonates with appropriate design; sample size modest.

Study Details

PMID:9003858
Participants:56
Impact:no significant difference
Trust score:4/5

bilirubin (day 14)

1 evidences

Vitamin C 50 mg/day in premature infants increased plasma vitamin C but did not increase hemolysis markers, bilirubin, or other morbidities versus placebo.

Trust comment: Multicenter double-blind randomized trial in neonates with appropriate design; sample size modest.

Study Details

PMID:9003858
Participants:56
Impact:no consistent increase (difference lost after outlier removal)
Trust score:4/5

plasma F2-isoprostanes (lipid peroxidation)

1 evidences

Over 12 months, vitamin C 500 mg/day did not reduce plasma F2-isoprostanes (a lipid peroxidation marker), whereas vitamin E did.

Trust comment: Subset analysis from a randomized placebo-controlled trial with adequate follow-up; population restricted to hypercholesterolemic men.

Study Details

PMID:11811547
Participants:100
Impact:no significant change vs placebo
Trust score:4/5

salivary gland absorbed radiation dose (parotid and submandibular)

1 evidences

In thyroid cancer patients given therapeutic 131I, sucking vitamin C at various times had only a limited effect on salivary radioiodine dose.

Trust comment: Prospective randomized single-blind study with appropriate dosimetry endpoints and reasonable sample size.

Study Details

PMID:20237029
Participants:72
Impact:no significant difference among timing groups
Trust score:4/5

soft-tissue healing (Landry index)

1 evidences

Vitamin C supplementation improved soft‑tissue healing after dental implant surgery in several patient subgroups but did not reduce pain.

Trust comment: Randomized controlled clinical trial with a substantial sample size and objective healing indices, though subgroup effects and blinding details are unclear.

Study Details

PMID:30039526
Participants:128
Impact:improved — significant increase at day 7 (group B) and day 14 (groups A, B, C)
Trust score:4/5

CDRS (children's depression rating scale)

1 evidences

In this small pediatric RCT, adding 1000 mg/day vitamin C to fluoxetine produced greater reductions in depressive symptom scores (CDRS, CDI) versus placebo; no effect on CGI.

Trust comment: Double‑blind, placebo‑controlled RCT but small sample size (pilot), limiting generalizability.

Study Details

PMID:23510529
Participants:24
Impact:−8.3 points at 6 months (vit C 9.0 vs placebo 17.3); significant improvement vs placebo
Trust score:3/5

CDI (children's depression inventory)

1 evidences

In this small pediatric RCT, adding 1000 mg/day vitamin C to fluoxetine produced greater reductions in depressive symptom scores (CDRS, CDI) versus placebo; no effect on CGI.

Trust comment: Double‑blind, placebo‑controlled RCT but small sample size (pilot), limiting generalizability.

Study Details

PMID:23510529
Participants:24
Impact:−6.5 points at 6 months (vit C 9.0 vs placebo 15.5); significant improvement vs placebo
Trust score:3/5

CGI (clinical global impression)

1 evidences

In this small pediatric RCT, adding 1000 mg/day vitamin C to fluoxetine produced greater reductions in depressive symptom scores (CDRS, CDI) versus placebo; no effect on CGI.

Trust comment: Double‑blind, placebo‑controlled RCT but small sample size (pilot), limiting generalizability.

Study Details

PMID:23510529
Participants:24
Impact:no significant change
Trust score:3/5

LDL oxidizability (lag time / oxidation rate)

1 evidences

In young smokers, vitamin C alone did not change LDL oxidizability or neutrophil respiratory burst; vitamin E increased LDL oxidation lag time and combined E+C reduced oxidation rate.

Trust comment: Randomized, double‑blind trial in humans with clear biochemical endpoints, but modest sample size.

Study Details

PMID:10872898
Participants:30
Impact:vitamin C alone: no change; vitamin E: increased lag time; combined E+C: reduced oxidation rate
Trust score:4/5

neutrophil (PMN) superoxide production / PMN LDL oxidation

1 evidences

In young smokers, vitamin C alone did not change LDL oxidizability or neutrophil respiratory burst; vitamin E increased LDL oxidation lag time and combined E+C reduced oxidation rate.

Trust comment: Randomized, double‑blind trial in humans with clear biochemical endpoints, but modest sample size.

Study Details

PMID:10872898
Participants:30
Impact:no significant change with vitamin C, vitamin E, or combined treatment
Trust score:4/5

endothelium-dependent dilation (RH%)

1 evidences

High‑dose vitamin C alone (2 g/day) did not improve endothelial function or most thrombosis/fibrinolysis markers in smokers, but combined high‑dose C+E improved endothelial-dependent dilation and reduced some thrombosis markers at higher E dose.

Trust comment: Randomized study in smokers with physiological and biochemical endpoints; moderate sample size and dose‑response information supports findings.

Study Details

PMID:12783111
Participants:41
Impact:improved in combined C+E groups (groups B and C) but not with C alone
Trust score:4/5

PAI-1 and von Willebrand factor (vWF)

1 evidences

High‑dose vitamin C alone (2 g/day) did not improve endothelial function or most thrombosis/fibrinolysis markers in smokers, but combined high‑dose C+E improved endothelial-dependent dilation and reduced some thrombosis markers at higher E dose.

Trust comment: Randomized study in smokers with physiological and biochemical endpoints; moderate sample size and dose‑response information supports findings.

Study Details

PMID:12783111
Participants:41
Impact:decreased in high‑dose combined group (group C); no change with C alone
Trust score:4/5

PAI-1/tPA ratio

1 evidences

High‑dose vitamin C alone (2 g/day) did not improve endothelial function or most thrombosis/fibrinolysis markers in smokers, but combined high‑dose C+E improved endothelial-dependent dilation and reduced some thrombosis markers at higher E dose.

Trust comment: Randomized study in smokers with physiological and biochemical endpoints; moderate sample size and dose‑response information supports findings.

Study Details

PMID:12783111
Participants:41
Impact:decreased in combined C+E groups (B and C)
Trust score:4/5

serum phosphorus

1 evidences

Intravenous vitamin C given during dialysis for 8 weeks lowered blood phosphorus and inflammation markers.

Trust comment: Double-blind randomized trial in hemodialysis patients with clear significant findings though sample size is modest (n=60).

Study Details

PMID:22634906
Participants:60
Impact:decrease (statistically significant, p=0.01)
Trust score:4/5

CRP (inflammation)

1 evidences

Intravenous vitamin C given during dialysis for 8 weeks lowered blood phosphorus and inflammation markers.

Trust comment: Double-blind randomized trial in hemodialysis patients with clear significant findings though sample size is modest (n=60).

Study Details

PMID:22634906
Participants:60
Impact:decrease (statistically significant, p=0.01)
Trust score:4/5

Ca×P product

1 evidences

Intravenous vitamin C given during dialysis for 8 weeks lowered blood phosphorus and inflammation markers.

Trust comment: Double-blind randomized trial in hemodialysis patients with clear significant findings though sample size is modest (n=60).

Study Details

PMID:22634906
Participants:60
Impact:decrease (statistically significant, p=0.03)
Trust score:4/5

GAS +3 (much improved) rate

1 evidences

Adding the multi-ingredient supplement (contains vitamin C) to standard drug treatment increased the proportion of patients with marked hair improvement at 6 months.

Trust comment: Large multicenter randomized assessor-blinded trial with full completion, but not double-blind and supplement is multi-ingredient so attribution to vitamin C alone is limited.

Study Details

PMID:40853071
Participants:225
Impact:increase 36.5% vs 24% (absolute +12.5 percentage points), p=0.0428
Trust score:4/5

patient-reported great improvement

1 evidences

Adding the multi-ingredient supplement (contains vitamin C) to standard drug treatment increased the proportion of patients with marked hair improvement at 6 months.

Trust comment: Large multicenter randomized assessor-blinded trial with full completion, but not double-blind and supplement is multi-ingredient so attribution to vitamin C alone is limited.

Study Details

PMID:40853071
Participants:225
Impact:increase 46% vs 30%, p=0.0136
Trust score:4/5

clinical global average score

1 evidences

Adding the multi-ingredient supplement (contains vitamin C) to standard drug treatment increased the proportion of patients with marked hair improvement at 6 months.

Trust comment: Large multicenter randomized assessor-blinded trial with full completion, but not double-blind and supplement is multi-ingredient so attribution to vitamin C alone is limited.

Study Details

PMID:40853071
Participants:225
Impact:2.0±0.9 vs 1.7±1.0 (trend, p=0.07)
Trust score:4/5

common carotid artery intima-media thickness (CCA-IMT) progression rate

1 evidences

Six years of combined slow-release vitamin C and vitamin E slowed carotid atherosclerosis progression, with larger effects in men.

Trust comment: Long randomized trial with substantial follow-up and completers, but intervention combined vitamin C with vitamin E so effects cannot be attributed to vitamin C alone.

Study Details

PMID:12600905
Participants:440
Impact:decrease ~25% (annual increase 0.014→0.010 mm; 25% treatment effect, p=0.034)
Trust score:4/5

effect in men

1 evidences

Six years of combined slow-release vitamin C and vitamin E slowed carotid atherosclerosis progression, with larger effects in men.

Trust comment: Long randomized trial with substantial follow-up and completers, but intervention combined vitamin C with vitamin E so effects cannot be attributed to vitamin C alone.

Study Details

PMID:12600905
Participants:440
Impact:larger treatment effect (reported ~33–37% greater reduction; p≈0.02)
Trust score:4/5

pure tone audiometry (PTA) improvement

1 evidences

High-dose IV vitamin C added to steroids improved hearing recovery in sudden sensorineural hearing loss compared with steroids alone.

Trust comment: Randomized single-blind trial with statistically significant results but modest sample size and single-blind design.

Study Details

PMID:23208525
Participants:67
Impact:greater improvement: HDVC −30.5 dB (67.6→37.1) vs control −22.7 dB (70.3→47.6); between-group p=0.030
Trust score:3/5

complete recovery rate

1 evidences

High-dose IV vitamin C added to steroids improved hearing recovery in sudden sensorineural hearing loss compared with steroids alone.

Trust comment: Randomized single-blind trial with statistically significant results but modest sample size and single-blind design.

Study Details

PMID:23208525
Participants:67
Impact:>2× higher in HDVC vs control (p=0.031)
Trust score:3/5

MDA (lipid peroxidation marker)

1 evidences

Hemodialysis patients given 250 mg vitamin C every other day for 12 weeks had higher blood vitamin C, lower oxidative stress marker, and improved cholesterol/LDL measures.

Trust comment: Randomized double-blind RCT in a relevant patient group with clear biochemical endpoints but small sample (n=42).

Study Details

PMID:20533214
Participants:42
Impact:decrease (marginal within-group p=0.057; significant between-group change p=0.002)
Trust score:4/5

LDL-C / total cholesterol

1 evidences

Hemodialysis patients given 250 mg vitamin C every other day for 12 weeks had higher blood vitamin C, lower oxidative stress marker, and improved cholesterol/LDL measures.

Trust comment: Randomized double-blind RCT in a relevant patient group with clear biochemical endpoints but small sample (n=42).

Study Details

PMID:20533214
Participants:42
Impact:decrease (significant between-group differences: total cholesterol p=0.005; LDL-C p=0.012; LDL-C/HDL-C ratio p=0.018)
Trust score:4/5

presence of non-specific vaginitis (symptom cluster)

1 evidences

Daily 250 mg vitamin C vaginal tablets for 6 days reduced signs and recurrence of non-specific vaginitis versus placebo.

Trust comment: Well-designed randomized double-blind placebo-controlled trial with good sample size and objective microscopy outcomes, minor losses to follow-up.

Study Details

PMID:15474248
Participants:93
Impact:reduced (14.0% on Vitamin C vs 35.7% on placebo remaining affected at follow-up)
Trust score:4/5

clue cells on vaginal smear

1 evidences

Daily 250 mg vitamin C vaginal tablets for 6 days reduced signs and recurrence of non-specific vaginitis versus placebo.

Trust comment: Well-designed randomized double-blind placebo-controlled trial with good sample size and objective microscopy outcomes, minor losses to follow-up.

Study Details

PMID:15474248
Participants:93
Impact:disappearance increased (79% with Vitamin C vs 53% with placebo)
Trust score:4/5

vaginal pH ≥4.7 frequency

1 evidences

Daily 250 mg vitamin C vaginal tablets for 6 days reduced signs and recurrence of non-specific vaginitis versus placebo.

Trust comment: Well-designed randomized double-blind placebo-controlled trial with good sample size and objective microscopy outcomes, minor losses to follow-up.

Study Details

PMID:15474248
Participants:93
Impact:reduced (16.3% with Vitamin C vs 38.6% with placebo at 1 week post-treatment)
Trust score:4/5

incidence of common cold

1 evidences

Daily vitamin C supplement over 60 days reduced the number of colds and shortened severe symptom duration compared with placebo.

Trust comment: Double-blind randomized design but limited detail on randomization/analysis and moderate sample size; results reported as a survey-style RCT.

Study Details

PMID:12201356
Participants:168
Impact:reduced (37 colds in active group vs 50 in placebo; P<0.05)
Trust score:3/5

days challenged/illness days

1 evidences

Daily vitamin C supplement over 60 days reduced the number of colds and shortened severe symptom duration compared with placebo.

Trust comment: Double-blind randomized design but limited detail on randomization/analysis and moderate sample size; results reported as a survey-style RCT.

Study Details

PMID:12201356
Participants:168
Impact:reduced (85 days in active group vs 178 in placebo)
Trust score:3/5

duration of severe symptoms

1 evidences

Daily vitamin C supplement over 60 days reduced the number of colds and shortened severe symptom duration compared with placebo.

Trust comment: Double-blind randomized design but limited detail on randomization/analysis and moderate sample size; results reported as a survey-style RCT.

Study Details

PMID:12201356
Participants:168
Impact:shortened (1.8 days vs 3.1 days; P<0.03)
Trust score:3/5

prevalence of complex regional pain syndrome (CRPS)

1 evidences

Vitamin C given daily after wrist fracture significantly reduced the risk of complex regional pain syndrome; 500 mg/day for 50 days recommended.

Trust comment: Large randomized multicenter, double-blind dose-response trial with clear clinical endpoint and statistically significant results.

Study Details

PMID:17606778
Participants:416
Impact:reduced (2.4% with vitamin C vs 10.1% with placebo; absolute difference ≈ -7.7 percentage points; p=0.002)
Trust score:5/5

dose response (CRPS by dose)

1 evidences

Vitamin C given daily after wrist fracture significantly reduced the risk of complex regional pain syndrome; 500 mg/day for 50 days recommended.

Trust comment: Large randomized multicenter, double-blind dose-response trial with clear clinical endpoint and statistically significant results.

Study Details

PMID:17606778
Participants:416
Impact:lower rates at 500 mg (1.8%) and 1500 mg (1.7%) than at 200 mg (4.2%) and placebo
Trust score:5/5

relationship: plasma vitamin C vs adiposity (BMI/waist/% body fat)

1 evidences

In adults, plasma vitamin C correlated inversely with adiposity measures; in a small weight-loss trial both vitamin C and placebo groups lost weight and showed similar increases in adiponectin.

Trust comment: Combined cross-sectional and small randomized intervention with limited intervention sample size and some attrition, limiting inference on supplementation effects.

Study Details

PMID:17585027
Participants:118
Impact:inverse correlation (r = -0.383 to -0.497, P < 0.025)
Trust score:3/5

plasma adiponectin (response to supplementation)

1 evidences

In adults, plasma vitamin C correlated inversely with adiposity measures; in a small weight-loss trial both vitamin C and placebo groups lost weight and showed similar increases in adiponectin.

Trust comment: Combined cross-sectional and small randomized intervention with limited intervention sample size and some attrition, limiting inference on supplementation effects.

Study Details

PMID:17585027
Participants:118
Impact:no differential effect of vitamin C supplementation (both groups increased ~13% by week 8)
Trust score:3/5

body mass change during intervention

1 evidences

In adults, plasma vitamin C correlated inversely with adiposity measures; in a small weight-loss trial both vitamin C and placebo groups lost weight and showed similar increases in adiponectin.

Trust comment: Combined cross-sectional and small randomized intervention with limited intervention sample size and some attrition, limiting inference on supplementation effects.

Study Details

PMID:17585027
Participants:118
Impact:decreased similarly in both groups (vitamin C group -5.9 ± 0.9 kg [n=6]; placebo -6.5 ± 0.7 kg [n=8])
Trust score:3/5

leukocyte ascorbate

2 evidences

A 4-month high-antioxidant diet (designed to raise vitamins A, C and E) increased plasma and leukocyte vitamin C, boosted antioxidant enzyme activities, and lowered lipid oxidative markers in women with endometriosis.

Trust comment: Randomized diet intervention with objective biochemical endpoints and moderate completion rates, but unblinded and with some dropouts.

Study Details

PMID:19476631
Participants:72
Impact:+28% (from third month)
Trust score:3/5

Randomized dietary intervention (0.5 vs 2 kiwifruit/day) in healthy young men showing plasma and skeletal muscle ascorbate increase after 6 weeks; muscle ascorbate rose ≈3.5‑fold and correlated with plasma levels.

Trust comment: Randomized parallel dietary intervention with objective biochemical endpoints and clear pre/post measurements but small, all-male sample limits generalizability.

Study Details

PMID:23446899
Participants:35
Impact:Mononuclear cells ~60.5 → 90.9 nmol/10^8 cells (+~1.5-fold); neutrophils ~13.7 → 30.4 nmol/10^8 cells (>2-fold increase)
Trust score:4/5

fibrosis score

1 evidences

In NASH patients, combined vitamin E and vitamin C for 6 months improved liver fibrosis scores but did not change inflammation or ALT.

Trust comment: Double‑blind, randomized, placebo‑controlled trial with moderate sample and blinded histologic assessment; credible result though sample relatively small.

Study Details

PMID:14638353
Participants:45
Impact:statistically significant improvement with vitamin E + C (p=0.002)
Trust score:4/5

reflex sympathetic dystrophy incidence

1 evidences

Daily 500 mg vitamin C for 50 days after wrist fracture reduced the 1-year occurrence of reflex sympathetic dystrophy compared with placebo.

Trust comment: Double-blind randomized trial with a clear primary outcome and reported effect sizes, moderate sample size; applicable to adult wrist fractures.

Study Details

PMID:10636366
Participants:115
Impact:Vitamin C: 4/54 wrists (7%) vs placebo: 14/65 (22%); absolute reduction 15% (95% CI 2–26)
Trust score:4/5

exhaled nitric oxide (eNO)

1 evidences

Four-week multi-antioxidant supplementation (including 1500 mg/day vitamin C) raised serum vitamin levels but did not change markers of oxidative stress, airway inflammation, or allergen-specific immune responses.

Trust comment: Randomized controlled trial with measured biochemical and functional endpoints; modest sample size and multi-nutrient supplement complicates attribution to vitamin C alone.

Study Details

PMID:17250690
Participants:54
Impact:no change vs placebo
Trust score:4/5

plasma F2-isoprostanes

3 evidences

Four-week multi-antioxidant supplementation (including 1500 mg/day vitamin C) raised serum vitamin levels but did not change markers of oxidative stress, airway inflammation, or allergen-specific immune responses.

Trust comment: Randomized controlled trial with measured biochemical and functional endpoints; modest sample size and multi-nutrient supplement complicates attribution to vitamin C alone.

Study Details

PMID:17250690
Participants:54
Impact:no change vs placebo
Trust score:4/5

In 67 nonsmokers exposed to environmental tobacco smoke, daily vitamin C reduced a plasma oxidative stress biomarker (F2-isoprostanes) over two months.

Trust comment: Randomized intervention with 67 participants and controlled measurements; moderate sample and appropriate biomarkers.

Study Details

PMID:12881011
Participants:67
Impact:-17.2 pmol/L (~-11.4%) vs placebo
Trust score:4/5

In smokers with higher BMI, 500 mg/day vitamin C for 2 months lowered a blood marker of lipid oxidation; no effect in low-BMI smokers.

Trust comment: Randomized double-blind placebo-controlled trial with clear biomarker outcome and adequate sample size, though effect limited to a BMI-defined subgroup.

Study Details

PMID:11815395
Participants:126
Impact:-28.8 pmol/L (high-BMI smokers vs placebo, 2 months)
Trust score:4/5

liver iron concentration (LIC)

2 evidences

In vitamin C–deficient young β-thalassemia major patients, adding 100 mg/day vitamin C to chelation therapy (especially with deferoxamine) improved iron-related measures over 1 year without adverse events.

Trust comment: Randomized prospective trial with 180 patients and objective iron measures; subgroup analyses reported but some conclusions phrased cautiously in source.

Study Details

PMID:26018112
Participants:180
Impact:decreased with vitamin C adjunct to chelation
Trust score:4/5

Children with β-thalassemia and low vitamins received combined vitamin therapy for 12 months and showed improved antioxidant markers and reduced liver iron.

Trust comment: Prospective clinical study with clear before/after measures in humans, but multi-vitamin intervention and non-randomized comparison limit attribution to vitamin C alone.

Study Details

PMID:23565660
Participants:60
Impact:↓ LIC (significant, p<0.001)
Trust score:3/5

serum ferritin and transferrin saturation

1 evidences

In vitamin C–deficient young β-thalassemia major patients, adding 100 mg/day vitamin C to chelation therapy (especially with deferoxamine) improved iron-related measures over 1 year without adverse events.

Trust comment: Randomized prospective trial with 180 patients and objective iron measures; subgroup analyses reported but some conclusions phrased cautiously in source.

Study Details

PMID:26018112
Participants:180
Impact:decreased with vitamin C adjunct
Trust score:4/5

hemoglobin and cardiac MRI T2*

1 evidences

In vitamin C–deficient young β-thalassemia major patients, adding 100 mg/day vitamin C to chelation therapy (especially with deferoxamine) improved iron-related measures over 1 year without adverse events.

Trust comment: Randomized prospective trial with 180 patients and objective iron measures; subgroup analyses reported but some conclusions phrased cautiously in source.

Study Details

PMID:26018112
Participants:180
Impact:increased with vitamin C adjunct (improved cardiac iron signal)
Trust score:4/5

gastric juice ascorbic acid

1 evidences

Twelve weeks of vitamin C (500 mg twice daily) plus vitamin E raised plasma and gastric-juice vitamin C but did not change gastric mucosal oxidative markers or DNA damage versus placebo.

Trust comment: Randomized controlled study with objective biochemical and DNA-damage measures; moderate completion rate (72/100) and short follow-up limit conclusions about long-term cancer risk.

Study Details

PMID:12207836
Participants:72
Impact:significant increase with supplementation (P=0.01)
Trust score:4/5

mucosal DNA damage (comet assay)

1 evidences

Twelve weeks of vitamin C (500 mg twice daily) plus vitamin E raised plasma and gastric-juice vitamin C but did not change gastric mucosal oxidative markers or DNA damage versus placebo.

Trust comment: Randomized controlled study with objective biochemical and DNA-damage measures; moderate completion rate (72/100) and short follow-up limit conclusions about long-term cancer risk.

Study Details

PMID:12207836
Participants:72
Impact:no change with supplementation
Trust score:4/5

mucosal malondialdehyde / chemiluminescence

1 evidences

Twelve weeks of vitamin C (500 mg twice daily) plus vitamin E raised plasma and gastric-juice vitamin C but did not change gastric mucosal oxidative markers or DNA damage versus placebo.

Trust comment: Randomized controlled study with objective biochemical and DNA-damage measures; moderate completion rate (72/100) and short follow-up limit conclusions about long-term cancer risk.

Study Details

PMID:12207836
Participants:72
Impact:no change with supplementation
Trust score:4/5

number of illness episodes

1 evidences

A 12-week randomized trial in young children found the herbal product containing echinacea, propolis and vitamin C reduced respiratory infections and fever days versus placebo.

Trust comment: Large randomized double-blind multicenter trial in children, but vitamin C was part of a multi-component product so effects cannot be attributed to vitamin C alone.

Study Details

PMID:14993078
Participants:430
Impact:-55% (138 vs 308 total episodes)
Trust score:4/5

episodes per child

1 evidences

A 12-week randomized trial in young children found the herbal product containing echinacea, propolis and vitamin C reduced respiratory infections and fever days versus placebo.

Trust comment: Large randomized double-blind multicenter trial in children, but vitamin C was part of a multi-component product so effects cannot be attributed to vitamin C alone.

Study Details

PMID:14993078
Participants:430
Impact:-50% (0.9 ± 1.1 vs 1.8 ± 1.3 episodes/child)
Trust score:4/5

days with fever per child

1 evidences

A 12-week randomized trial in young children found the herbal product containing echinacea, propolis and vitamin C reduced respiratory infections and fever days versus placebo.

Trust comment: Large randomized double-blind multicenter trial in children, but vitamin C was part of a multi-component product so effects cannot be attributed to vitamin C alone.

Study Details

PMID:14993078
Participants:430
Impact:-62% (2.1 ± 2.9 vs 5.4 ± 4.4 days/child)
Trust score:4/5

oxidized LDL (OxLDL)

1 evidences

In a 4-week crossover trial of 500 mg/day vitamin C in healthy smokers, plasma ascorbate rose but markers of oxidation and endothelial activation did not change.

Trust comment: Randomized, double-blind, placebo-controlled crossover with measured biomarkers but small sample of healthy smokers limits generalizability.

Study Details

PMID:15127090
Participants:34
Impact:no significant change (0.73 ± 0.25 vs 0.72 ± 0.21 mg/dL)
Trust score:4/5

endothelial activation markers (sICAM-1, sVCAM-1, vWF)

1 evidences

In a 4-week crossover trial of 500 mg/day vitamin C in healthy smokers, plasma ascorbate rose but markers of oxidation and endothelial activation did not change.

Trust comment: Randomized, double-blind, placebo-controlled crossover with measured biomarkers but small sample of healthy smokers limits generalizability.

Study Details

PMID:15127090
Participants:34
Impact:no significant change
Trust score:4/5

general mental health (GHQ-12)

1 evidences

Thirty-three days of a high-dose B‑vitamin/mineral product (including 500 mg vitamin C) improved some mood scores, reduced perceived stress and increased some cognitive task correct responses in healthy men.

Trust comment: Well-powered randomized double-blind trial with robust cognitive and mood measures, but vitamin C was given in a multi-nutrient formula so individual contribution of vitamin C is unclear.

Study Details

PMID:20454891
Participants:210
Impact:-1.69 points (9.99 → 8.30; significant)
Trust score:4/5

perceived stress (PSS)

1 evidences

Thirty-three days of a high-dose B‑vitamin/mineral product (including 500 mg vitamin C) improved some mood scores, reduced perceived stress and increased some cognitive task correct responses in healthy men.

Trust comment: Well-powered randomized double-blind trial with robust cognitive and mood measures, but vitamin C was given in a multi-nutrient formula so individual contribution of vitamin C is unclear.

Study Details

PMID:20454891
Participants:210
Impact:-1.8 points (14.2 → 12.4; significant)
Trust score:4/5

Serial 3s correct responses (cognitive performance)

1 evidences

Thirty-three days of a high-dose B‑vitamin/mineral product (including 500 mg vitamin C) improved some mood scores, reduced perceived stress and increased some cognitive task correct responses in healthy men.

Trust comment: Well-powered randomized double-blind trial with robust cognitive and mood measures, but vitamin C was given in a multi-nutrient formula so individual contribution of vitamin C is unclear.

Study Details

PMID:20454891
Participants:210
Impact:significant increase in correct responses across repetitions (treatment > placebo)
Trust score:4/5

flow-mediated dilation (FMD)

7 evidences

In healthy young adults a single antioxidant cocktail (including vitamin C) taken before a high-sodium meal did not change endothelial function or arterial stiffness compared with placebo.

Trust comment: Randomized, crossover design in humans but small, acute study using a combined antioxidant cocktail so isolating vitamin C effects is not possible.

Study Details

PMID:32610254
Participants:41
Impact:no treatment effect (treatment × time interaction P = 0.65)
Trust score:4/5

Double-blind RCT of blackcurrant juice rich in vitamin C and polyphenols for 6 weeks: raised plasma vitamin C, lowered oxidative stress and improved endothelial function.

Trust comment: Well-conducted double-blind RCT with objective vascular and biochemical outcomes, but intervention combined vitamin C with polyphenols so effects of vitamin C alone are uncertain.

Study Details

PMID:24742818
Participants:66
Impact:increased in high-dose blackcurrant group (5.8±3.1% to 6.9±3.1%, P=0.022)
Trust score:4/5

Antioxidant vitamins including vitamin C (500 mg twice daily) did not improve flow-mediated dilation or nitroglycerin-induced dilation in postmenopausal women with coronary artery disease.

Trust comment: Substudy of an RCT with objective vascular measures, but small sample size and limited power.

Study Details

PMID:15721027
Participants:61
Impact:no significant change (vitamin group: 3.0% → 3.1% at 34 months; NS)
Trust score:3/5

In patients with intermittent claudication, vitamin C administration prevented exercise-induced impairment of endothelial function and rises in oxidative stress markers.

Trust comment: Small human trial with physiological and biochemical endpoints and randomized subset assignment, but limited sample size.

Study Details

PMID:12417278
Participants:31
Impact:exercise-induced fall (8.5%→3.7%) was abolished by vitamin C in randomized patients
Trust score:3/5

In CAD patients, folic acid supplementation markedly raised plasma folate and produced a modest homocysteine fall and a significant improvement in flow-mediated dilation versus placebo; adding antioxidants did not produce significant additional benefit.

Trust comment: Double-blind, placebo-controlled randomized trial with clear outcomes; high internal validity showing no added benefit from vitamins C+E.

Study Details

PMID:10987596
Participants:75
Impact:folic acid alone: increased from 3.2% to 5.2% (+2.0 percentage points, p=0.04); folic acid+vitamins C+E: 2.6% to 4.0% (insignificant)
Trust score:4/5

Children conceived by ART given vitamins C (1 g) and E (400 IU) for 4 weeks showed improved NO levels, better brachial FMD and lower pulmonary artery pressure versus placebo (effects seen in ART children only).

Trust comment: Randomized double‑blind placebo‑controlled RCT in 42 children with significant, physiologically relevant endpoints—moderate sample size but solid design.

Study Details

PMID:24817695
Participants:42
Impact:7.0 ± 2.1% → 8.7 ± 2.0% in ART children (p = 0.004) (+1.7 percentage points)
Trust score:4/5

In postmenopausal women, estrogen treatment enabled exercise to improve endothelial function; intravenous ascorbic acid infusion increased endothelial function in certain groups.

Trust comment: Randomized, controlled design with clear measurements (FMD) and a direct ascorbic acid infusion substudy; moderate sample size for subgroup analyses.

Study Details

PMID:24092827
Participants:36
Impact:increased with estrogen treatment (after 12 wk) and further increased with estrogen + endurance exercise
Trust score:4/5

malondialdehyde (oxidative stress marker)

1 evidences

In patients undergoing bilateral knee replacement, intraoperative high‑dose IV vitamin C was associated with lower oxidative stress markers and lower postoperative troponin I compared with controls.

Trust comment: Interventional surgical study with measurable clinical biomarkers but small sample and unclear randomization/blinding limit strength.

Study Details

PMID:20926027
Participants:32
Impact:decreased in vitamin C group versus control
Trust score:3/5

arterial oxygen tension and mean blood pressure

1 evidences

In patients undergoing bilateral knee replacement, intraoperative high‑dose IV vitamin C was associated with lower oxidative stress markers and lower postoperative troponin I compared with controls.

Trust comment: Interventional surgical study with measurable clinical biomarkers but small sample and unclear randomization/blinding limit strength.

Study Details

PMID:20926027
Participants:32
Impact:higher in vitamin C group after tourniquet release
Trust score:3/5

troponin I (myocardial enzyme)

1 evidences

In patients undergoing bilateral knee replacement, intraoperative high‑dose IV vitamin C was associated with lower oxidative stress markers and lower postoperative troponin I compared with controls.

Trust comment: Interventional surgical study with measurable clinical biomarkers but small sample and unclear randomization/blinding limit strength.

Study Details

PMID:20926027
Participants:32
Impact:lower at 8 h post-operation in vitamin C group
Trust score:3/5

IL-10 (anti-inflammatory)

1 evidences

In critically ill patients with TRALI, high-dose IV vitamin C (2.5 g every 6 h for 96 h) reduced pro-inflammatory and oxidative stress markers and increased anti-inflammatory and antioxidant markers versus placebo.

Trust comment: Randomized trial in a clinical ICU population with clear biomarker improvements and reasonable sample size, though results are disease-specific.

Study Details

PMID:34866234
Participants:80
Impact:+ (31.6 ± 25.8 vs 17.7 ± 12.0 pg/mL at T96, P < .0001)
Trust score:4/5

pro-inflammatory markers (IL-8, CRP)

1 evidences

In critically ill patients with TRALI, high-dose IV vitamin C (2.5 g every 6 h for 96 h) reduced pro-inflammatory and oxidative stress markers and increased anti-inflammatory and antioxidant markers versus placebo.

Trust comment: Randomized trial in a clinical ICU population with clear biomarker improvements and reasonable sample size, though results are disease-specific.

Study Details

PMID:34866234
Participants:80
Impact:IL-8 decreased (11.8 ± 7.3 vs 35.5 ± 19.8 pg/mL, P < .0001); CRP decreased (76 ± 50 vs 89 ± 56 mg/L, P = .033)
Trust score:4/5

oxidative stress markers (SOD activity, malondialdehyde)

1 evidences

In critically ill patients with TRALI, high-dose IV vitamin C (2.5 g every 6 h for 96 h) reduced pro-inflammatory and oxidative stress markers and increased anti-inflammatory and antioxidant markers versus placebo.

Trust comment: Randomized trial in a clinical ICU population with clear biomarker improvements and reasonable sample size, though results are disease-specific.

Study Details

PMID:34866234
Participants:80
Impact:SOD activity increased (12,876 ± 4,627 vs 5,895 ± 6,632 U/L, P < .0001); malondialdehyde decreased (0.197 ± 0.034 vs 0.234 ± 0.074 μM/L, P = .002)
Trust score:4/5

plasma DHA (500 mg)

1 evidences

Compared calcium ascorbate (CA) vs ascorbic acid (AA) in crossover trials: 250 mg showed no differences; 500 mg CA altered vitamin C kinetics and increased neutrophil phagocytosis and certain NK cells.

Trust comment: Well-powered, randomized, double-blind, counterbalanced crossover study with detailed PK and immune assays in healthy adults.

Study Details

PMID:39408325
Participants:93
Impact:Higher DHA AUC with CA vs AA (500 mg); baseline difference −0.84 µg/mL (95% CI −1.3 to −0.5), p<0.001
Trust score:5/5

neutrophil phagocytosis

1 evidences

Compared calcium ascorbate (CA) vs ascorbic acid (AA) in crossover trials: 250 mg showed no differences; 500 mg CA altered vitamin C kinetics and increased neutrophil phagocytosis and certain NK cells.

Trust comment: Well-powered, randomized, double-blind, counterbalanced crossover study with detailed PK and immune assays in healthy adults.

Study Details

PMID:39408325
Participants:93
Impact:Increased from baseline in CA group +6.78 percentage points (95% CI 0.8 to 12.8), p=0.027
Trust score:5/5

natural killer cells (CD16+ & CD56+)

1 evidences

Compared calcium ascorbate (CA) vs ascorbic acid (AA) in crossover trials: 250 mg showed no differences; 500 mg CA altered vitamin C kinetics and increased neutrophil phagocytosis and certain NK cells.

Trust comment: Well-powered, randomized, double-blind, counterbalanced crossover study with detailed PK and immune assays in healthy adults.

Study Details

PMID:39408325
Participants:93
Impact:Increased at 24 h after CA +12.2 percentage points (95% CI 2.7 to 21.7), p=0.012
Trust score:5/5

oxidative stress

2 evidences

In corticosteroid‑dependent asthma patients, adding antioxidants including CoQ10, vitamin E and 250 mg vitamin C/day was associated with reduced corticosteroid requirements.

Trust comment: Open, randomized crossover clinical study with small sample and limited blinding; outcome reported but magnitude not quantified.

Study Details

PMID:16873952
Participants:41
Impact:decreased (reported qualitatively)
Trust score:3/5

In acute amitriptyline intoxication cases, supplementation with antioxidants (alpha lipoic acid with or without vitamin C) reduced oxidative stress markers more than routine treatment, greatest with combination.

Trust comment: Human clinical groups with 132 subjects and statistically significant results, but limited methodological detail and vitamin C not tested alone reduce confidence.

Study Details

PMID:34699040
Participants:132
Impact:decrease with antioxidants; greatest reduction with combined alpha-lipoic acid + vitamin C (statistically significant, P<0.001)
Trust score:3/5

melasma severity (MASI score)

1 evidences

In 50 female patients with mixed melasma, salicylic acid peel plus intradermal vitamin C mesotherapy and peel alone both reduced pigmentation severity and improved quality-of-life; combination was safe and well tolerated.

Trust comment: Small comparative clinical study (50 patients) with objective MASI scoring but limited detail on randomization and follow-up.

Study Details

PMID:28388246
Participants:50
Impact:MASI scores significantly decreased after treatment in both groups (no numeric % reported)
Trust score:3/5

patient quality of life (MelasQoL)

1 evidences

In 50 female patients with mixed melasma, salicylic acid peel plus intradermal vitamin C mesotherapy and peel alone both reduced pigmentation severity and improved quality-of-life; combination was safe and well tolerated.

Trust comment: Small comparative clinical study (50 patients) with objective MASI scoring but limited detail on randomization and follow-up.

Study Details

PMID:28388246
Participants:50
Impact:MelasQoL scores significantly improved after treatment in both groups (no numeric % reported)
Trust score:3/5

adverse effects / tolerability

1 evidences

In 50 female patients with mixed melasma, salicylic acid peel plus intradermal vitamin C mesotherapy and peel alone both reduced pigmentation severity and improved quality-of-life; combination was safe and well tolerated.

Trust comment: Small comparative clinical study (50 patients) with objective MASI scoring but limited detail on randomization and follow-up.

Study Details

PMID:28388246
Participants:50
Impact:No significant adverse events reported apart from transient burning
Trust score:3/5

endothelial function (forearm blood flow to ACh/SNP/insulin)

1 evidences

In 32 diabetic patients with low plasma vitamin C, high-dose oral vitamin C partially restored vitamin C levels but did not improve endothelial function or measures of insulin resistance.

Trust comment: Clinical intervention in Type 2 diabetes with objective vascular and metabolic measures but limited effect and incomplete repletion of vitamin C.

Study Details

PMID:16126809
Participants:32
Impact:No significant change after treatment
Trust score:3/5

insulin resistance (SI by clamp, fasting glucose/insulin)

1 evidences

In 32 diabetic patients with low plasma vitamin C, high-dose oral vitamin C partially restored vitamin C levels but did not improve endothelial function or measures of insulin resistance.

Trust comment: Clinical intervention in Type 2 diabetes with objective vascular and metabolic measures but limited effect and incomplete repletion of vitamin C.

Study Details

PMID:16126809
Participants:32
Impact:No significant changes observed
Trust score:3/5

All-cause mortality (interaction with dietary vitamin C)

1 evidences

In a large trial of male smokers, dietary vitamin C intake modified the effect of vitamin E on mortality, with opposite effects in some age subgroups.

Trust comment: Very large randomized trial for vitamin E with robust subgroup analyses, but dietary vitamin C was observational (not randomized), limiting causal inference for vitamin C.

Study Details

PMID:19218294
Participants:29133
Impact:No overall effect; in high dietary vitamin C (≥90 mg/day): ages 50–62 RR=1.19 (+19% mortality with vitamin E); ages 66–69 RR=0.59 (-41% mortality with vitamin E)
Trust score:4/5

Effect modification by dietary vitamin C

1 evidences

In a large trial of male smokers, dietary vitamin C intake modified the effect of vitamin E on mortality, with opposite effects in some age subgroups.

Trust comment: Very large randomized trial for vitamin E with robust subgroup analyses, but dietary vitamin C was observational (not randomized), limiting causal inference for vitamin C.

Study Details

PMID:19218294
Participants:29133
Impact:Statistically significant interaction (heterogeneity) between vitamin E effect, age, and dietary vitamin C intake
Trust score:4/5

Respiratory infection-related subgroup signals

1 evidences

In a large trial of male smokers, dietary vitamin C intake modified the effect of vitamin E on mortality, with opposite effects in some age subgroups.

Trust comment: Very large randomized trial for vitamin E with robust subgroup analyses, but dietary vitamin C was observational (not randomized), limiting causal inference for vitamin C.

Study Details

PMID:19218294
Participants:29133
Impact:Prior subgroup signals motivated analysis; dietary vitamin C used as modifier (observational intake data)
Trust score:4/5

Carotid intima-media thickness (IMT) progression (men)

1 evidences

Three-year RCT found combined vitamin E + slow‑release vitamin C slowed carotid IMT progression in men versus placebo.

Trust comment: Randomized, double-masked factorial trial of moderate size with objective ultrasound outcomes; effects mainly in men.

Study Details

PMID:11123502
Participants:520
Impact:Mean IMT increase: placebo 0.020 mm/yr vs combo (E+C) 0.011 mm/yr (P=0.008 for E+C vs placebo)
Trust score:4/5

Proportion of men with progression

1 evidences

Three-year RCT found combined vitamin E + slow‑release vitamin C slowed carotid IMT progression in men versus placebo.

Trust comment: Randomized, double-masked factorial trial of moderate size with objective ultrasound outcomes; effects mainly in men.

Study Details

PMID:11123502
Participants:520
Impact:Reduced by 74% with combined supplementation (95% CI 36–89%, P=0.003)
Trust score:4/5

Endothelial function (flow-mediated dilation, FMD)

2 evidences

In chronic smokers, vitamin C alone improved endothelial function; adding Enzogenol gave additional reductions in protein oxidation and fibrinogen but no extra macrovascular benefit.

Trust comment: Randomized study in smokers with objective vascular and biochemical outcomes but small sample and both groups received vitamin C, limiting isolation of vitamin C effect.

Study Details

PMID:16298763
Participants:44
Impact:Improved in both groups (p<0.001) with no difference between Enzogenol+vitamin C and vitamin C alone
Trust score:3/5

In a crossover human experiment, vitamin C infusion during recovery from hypoglycemia with hyperglycemia attenuated the worsening of endothelial function and increases in oxidative stress and inflammation.

Trust comment: Randomized crossover experiments in humans with direct vascular and biochemical measures and moderate sample size (n=42 total).

Study Details

PMID:22891214
Participants:42
Impact:hyperglycemia after hypoglycemia decreased FMD; vitamin C significantly attenuated the decrease
Trust score:4/5

Protein carbonyls (protein oxidative damage)

1 evidences

In chronic smokers, vitamin C alone improved endothelial function; adding Enzogenol gave additional reductions in protein oxidation and fibrinogen but no extra macrovascular benefit.

Trust comment: Randomized study in smokers with objective vascular and biochemical outcomes but small sample and both groups received vitamin C, limiting isolation of vitamin C effect.

Study Details

PMID:16298763
Participants:44
Impact:Greater reduction with Enzogenol+vitamin C vs vitamin C alone (p=0.03)
Trust score:3/5

Fibrinogen (inflammation marker) in heavy smokers

1 evidences

In chronic smokers, vitamin C alone improved endothelial function; adding Enzogenol gave additional reductions in protein oxidation and fibrinogen but no extra macrovascular benefit.

Trust comment: Randomized study in smokers with objective vascular and biochemical outcomes but small sample and both groups received vitamin C, limiting isolation of vitamin C effect.

Study Details

PMID:16298763
Participants:44
Impact:Significant reduction with Enzogenol+vitamin C vs vitamin C alone (p<0.009)
Trust score:3/5

Proportion of perfused small vessels (PPV)

1 evidences

In a small RCT of sepsis patients, high‑dose IV vitamin C transiently improved early microvascular perfusion (PPV) and reduced a glycocalyx metric in the smallest capillaries, with no change in mortality.

Trust comment: Double-blind randomized pilot in critically ill patients with objective microcirculation measures but very small sample and heterogeneous sepsis sources.

Study Details

PMID:37700249
Participants:23
Impact:At 6 h: 89.7% (vitamin C) vs 79.9% (placebo), p=0.041 (~+9.8 percentage points)
Trust score:3/5

Perfused boundary region (PBR) in 5–9 μm capillaries

1 evidences

In a small RCT of sepsis patients, high‑dose IV vitamin C transiently improved early microvascular perfusion (PPV) and reduced a glycocalyx metric in the smallest capillaries, with no change in mortality.

Trust comment: Double-blind randomized pilot in critically ill patients with objective microcirculation measures but very small sample and heterogeneous sepsis sources.

Study Details

PMID:37700249
Participants:23
Impact:Immediate decrease: 1.07 μm (vitamin C) vs 1.18 μm (placebo), p=0.015 (≈ -0.11 μm)
Trust score:3/5

mononuclear cell eicosapentaenoic acid (EPA)

1 evidences

In hepatitis C patients receiving interferon and ribavirin, vitamins E+C kept a fatty acid (EPA) level stable and raised blood vitamin levels.

Trust comment: Randomized clinical study but small sample (n=30) and combined vitamin E+C makes isolating vitamin C effects less certain.

Study Details

PMID:16459223
Participants:30
Impact:prevented decrease (maintained EPA vs significant decrease in control at 4 and 8 wk)
Trust score:3/5

endothelium-dependent vasodilation

4 evidences

In hypercholesterolemic patients, vitamin C coinfusion acutely improved endothelium-dependent vasodilation before statin therapy but not after short-term statin treatment.

Trust comment: Well-controlled physiologic measures in humans but small sample and vitamin C used as an acute probe rather than as a primary intervention.

Study Details

PMID:15864218
Participants:41
Impact:vitamin C coinfusion improved ACh-induced vasodilation before statin therapy but had no additional effect after 3 or 14 days of statin therapy
Trust score:3/5

In healthy older people, oral vitamin C raised blood vitamin levels but did not improve vascular dilation; a Mediterranean-type diet did improve vascular function.

Trust comment: Randomized, physiologic measurement study with moderate sample size (n=54) and objective vascular endpoints; clear negative result for vitamin C.

Study Details

PMID:12237172
Participants:54
Impact:no improvement with oral vitamin C (diet improved dependent dilation; vitamin C had no effect)
Trust score:4/5

A fruit/vegetable purée drink acutely raised plasma vitamin C and plasma antioxidant capacity and showed a trend toward improved endothelium-dependent vasodilation.

Trust comment: Randomized, single-blind crossover but small sample (n=24) and short-term (acute) outcomes.

Study Details

PMID:23017441
Participants:24
Impact:trend toward increase (P = 0.061)
Trust score:3/5

Daily fruit-and-vegetable puree drinks raised dietary vitamin C and plasma carotenoids and produced a trend toward improved endothelium-dependent vasodilation.

Trust comment: Randomized crossover with 39 completers and objective biochemical and vascular measures; reasonably reliable though vasodilation effect was borderline.

Study Details

PMID:22831286
Participants:39
Impact:near-significant increase (P=0.060)
Trust score:4/5

endothelium-independent vasodilation

2 evidences

In healthy older people, oral vitamin C raised blood vitamin levels but did not improve vascular dilation; a Mediterranean-type diet did improve vascular function.

Trust comment: Randomized, physiologic measurement study with moderate sample size (n=54) and objective vascular endpoints; clear negative result for vitamin C.

Study Details

PMID:12237172
Participants:54
Impact:no improvement with oral vitamin C (diet improved independent dilation; vitamin C had no effect)
Trust score:4/5

Oral antioxidant combination including vitamin C (1,000 mg) improved endothelium-dependent vasodilation in type 1 but not type 2 diabetic patients after 6 months.

Trust comment: Randomized placebo-controlled study but small sample and intervention combined vitamin C with vitamin E, limiting attribution specifically to vitamin C.

Study Details

PMID:12881209
Participants:94
Impact:No significant effect reported
Trust score:3/5

median nerve motor conduction velocity

1 evidences

High-dose oral vitamin C for 12 months in children with CMT1A was safe but did not meaningfully improve nerve conduction, strength, function, or quality of life.

Trust comment: Large (for this condition), double-blind, randomized placebo-controlled pediatric trial with intention-to-treat analysis; high internal validity and clear null result.

Study Details

PMID:19427269
Participants:80
Impact:small non-significant increase (+1.7 m/s adjusted mean difference; p=0.06)
Trust score:5/5

muscle strength and motor function

1 evidences

High-dose oral vitamin C for 12 months in children with CMT1A was safe but did not meaningfully improve nerve conduction, strength, function, or quality of life.

Trust comment: Large (for this condition), double-blind, randomized placebo-controlled pediatric trial with intention-to-treat analysis; high internal validity and clear null result.

Study Details

PMID:19427269
Participants:80
Impact:no measurable effect (no improvement)
Trust score:5/5

acne severity (Investigator's Global Assessment)

1 evidences

Topical stable vitamin C derivative (5%) significantly improved acne severity and lesion counts versus vehicle over 12 weeks with similar tolerability.

Trust comment: Randomized, double-blind controlled trial with objective lesion counts but modest sample size (n=50).

Study Details

PMID:20367669
Participants:50
Impact:statistically significant improvement vs vehicle
Trust score:4/5

lesion counts

1 evidences

Topical stable vitamin C derivative (5%) significantly improved acne severity and lesion counts versus vehicle over 12 weeks with similar tolerability.

Trust comment: Randomized, double-blind controlled trial with objective lesion counts but modest sample size (n=50).

Study Details

PMID:20367669
Participants:50
Impact:statistically significant reduction vs vehicle
Trust score:4/5

cutaneous tolerability / adverse events

1 evidences

Topical stable vitamin C derivative (5%) significantly improved acne severity and lesion counts versus vehicle over 12 weeks with similar tolerability.

Trust comment: Randomized, double-blind controlled trial with objective lesion counts but modest sample size (n=50).

Study Details

PMID:20367669
Participants:50
Impact:no increase in adverse events (similar to vehicle)
Trust score:4/5

hematocrit and hemoglobin

1 evidences

One tablet daily containing iron plus vitamin C for four weeks raised hemoglobin, hematocrit, serum iron, and vitamin C without increasing plasma oxalate in dialysis patients.

Trust comment: Open-label, short (4-week) study with small sample (n=24) but objective laboratory endpoints; limited by lack of blinding and short duration.

Study Details

PMID:12563623
Participants:24
Impact:increased (significant increase after 4 weeks)
Trust score:3/5

serum iron

1 evidences

One tablet daily containing iron plus vitamin C for four weeks raised hemoglobin, hematocrit, serum iron, and vitamin C without increasing plasma oxalate in dialysis patients.

Trust comment: Open-label, short (4-week) study with small sample (n=24) but objective laboratory endpoints; limited by lack of blinding and short duration.

Study Details

PMID:12563623
Participants:24
Impact:increased (significant increase after 4 weeks)
Trust score:3/5

incidence of preeclampsia

1 evidences

In nulliparous pregnant women, combined vitamins C and E (with iron) from mid-pregnancy reduced the rate of preeclampsia compared with iron alone.

Trust comment: Moderate-sized clinical trial (n=160) with a large absolute reduction in preeclampsia but methods (randomization/blinding) and some reported BP data are unclear in text excerpt.

Study Details

PMID:32755100
Participants:160
Impact:reduced (control 17.5% vs intervention 5%)
Trust score:3/5

urinary ATNC (total nitroso compounds)

1 evidences

Drinking concentrated beetroot juice (high nitrate) raised urinary nitrate, nitrite and N‑nitroso compounds; 1000 mg vitamin C blocked the immediate (one-dose) rise in N‑nitroso compounds but not after seven days.

Trust comment: Randomized human dietary intervention with per-protocol analysis but small sample (n=29); measurements and statistics clearly reported.

Study Details

PMID:31072023
Participants:29
Impact:~20-fold increase by day 8 (5 → 104 nmol/mmol); vitamin C reduced ATNC on day 2 (BRJ+VitC 16 vs BRJ 72 nmol/mmol, ≈−78%) but not significantly different by day 8 (BRJ 123 vs BRJ+VitC 81 nmol/mmol)
Trust score:4/5

urinary nitrate excretion

1 evidences

Drinking concentrated beetroot juice (high nitrate) raised urinary nitrate, nitrite and N‑nitroso compounds; 1000 mg vitamin C blocked the immediate (one-dose) rise in N‑nitroso compounds but not after seven days.

Trust comment: Randomized human dietary intervention with per-protocol analysis but small sample (n=29); measurements and statistics clearly reported.

Study Details

PMID:31072023
Participants:29
Impact:increased from 0.708 → 17.88 µmol/mmol (day 1 → day 2) and remained ~18.9 µmol/mmol at day 8
Trust score:4/5

urinary nitrite excretion

1 evidences

Drinking concentrated beetroot juice (high nitrate) raised urinary nitrate, nitrite and N‑nitroso compounds; 1000 mg vitamin C blocked the immediate (one-dose) rise in N‑nitroso compounds but not after seven days.

Trust comment: Randomized human dietary intervention with per-protocol analysis but small sample (n=29); measurements and statistics clearly reported.

Study Details

PMID:31072023
Participants:29
Impact:increased from 4 → 21 nmol/mmol (day 1 → day 8)
Trust score:4/5

duration of mechanical ventilation

2 evidences

High-dose IV ascorbic acid during the first 24 hours after major burns reduced fluid needs, edema/weight gain, and duration of mechanical ventilation.

Trust comment: Prospective randomized trial in a critical care setting with objective clinical endpoints, though single-center and modest sample.

Study Details

PMID:10722036
Participants:37
Impact:reduced: 12.1±8.8 vs 21.3±15.6 days (P<.05)
Trust score:4/5

In 80 ICU patients with severe pneumonia, high‑dose IV vitamin C (60 mg/kg/day for 96 h) was safe and associated with shorter mechanical ventilation and vasopressor durations and improved organ‑failure markers, but mortality difference was not statistically significant.

Trust comment: Randomized, double‑blind clinical trial with adequate sample for secondary outcomes but single center and limited power for mortality.

Study Details

PMID:34187382
Participants:80
Impact:reduced from 8.92 ± 2.96 (control) to 4.05 ± 2.29 days (intervention), p<0.001 (≈−4.9 days)
Trust score:4/5

vasopressor use duration

1 evidences

In 80 ICU patients with severe pneumonia, high‑dose IV vitamin C (60 mg/kg/day for 96 h) was safe and associated with shorter mechanical ventilation and vasopressor durations and improved organ‑failure markers, but mortality difference was not statistically significant.

Trust comment: Randomized, double‑blind clinical trial with adequate sample for secondary outcomes but single center and limited power for mortality.

Study Details

PMID:34187382
Participants:80
Impact:reduced from 3.39 ± 1.23 to 2.28 ± 1.24 days, p=0.003 (≈−1.11 days)
Trust score:4/5

mortality (28-day)

2 evidences

In 80 ICU patients with severe pneumonia, high‑dose IV vitamin C (60 mg/kg/day for 96 h) was safe and associated with shorter mechanical ventilation and vasopressor durations and improved organ‑failure markers, but mortality difference was not statistically significant.

Trust comment: Randomized, double‑blind clinical trial with adequate sample for secondary outcomes but single center and limited power for mortality.

Study Details

PMID:34187382
Participants:80
Impact:non-significant lower mortality in intervention (6/40) vs control (11/40), p=0.17
Trust score:4/5

In 111 septic shock patients, IV vitamin C plus thiamine for 48 h raised blood vitamin levels but did not improve organ dysfunction (ΔSOFA) or mortality compared with placebo.

Trust comment: Multi-centre, double‑blind RCT with pre-specified primary outcome and clear reporting; moderate sample size for septic shock limits power for some secondary endpoints.

Study Details

PMID:32780166
Participants:111
Impact:no significant difference (20.8% vs 15.5%; p = 0.47)
Trust score:4/5

plasma ascorbic acid concentration

5 evidences

Dietary vitamin C enrichment (500 mg/day) in young men increased plasma ascorbic acid and reduced the susceptibility of lipoproteins to oxidation.

Trust comment: Randomized dietary intervention with clear biochemical measures but small, homogeneous sample (young male students).

Study Details

PMID:9459371
Participants:36
Impact:+38.2 μmol/L (13.5 → 51.7 μmol/L)
Trust score:3/5

Phase I randomized placebo-controlled trial (severe sepsis) showed IV ascorbic acid rapidly restored plasma levels, was well tolerated, reduced inflammatory biomarkers and was associated with faster declines in SOFA scores versus placebo.

Trust comment: Randomized, placebo‑controlled phase I safety trial with clear biomarker and SOFA changes but small sample limiting generalizability.

Study Details

PMID:24484547
Participants:24
Impact:rose from ~17–20 µM baseline to ~331 µM (low dose) and ~3,082 µM (high dose) by day 4 (≈+18× and +172× respectively)
Trust score:3/5

Oral ascorbic acid markedly raised plasma ascorbate levels but did not improve brachial artery flow‑mediated (endothelium-dependent) dilation in hypertensive patients; chronic treatment previously reported to lower blood pressure.

Trust comment: Randomized, double-blind, placebo-controlled trial in hypertensive patients with objective vascular measures, but modest sample size.

Study Details

PMID:11158948
Participants:39
Impact:acute increase from 50 ± 12 to 149 ± 51 µmol/L; maintained at 99 ± 33 µmol/L with chronic dosing (both P < 0.001)
Trust score:4/5

Postoperative ICU patients given an intravenous ascorbic acid substitution overnight reached normal/high-normal plasma ascorbic acid concentrations.

Trust comment: Randomized postoperative ICU trial with objective plasma measurements and clear numeric outcome; moderate sample size (n=57) supports reasonable confidence.

Study Details

PMID:15681169
Participants:57
Impact:increased to normal/high-normal overnight (≥45.5 µmol/L in 26/28 patients; 92.9%)
Trust score:4/5

Vitamin C quickly and sustainably improved blood-vessel dilation in patients with coronary artery disease.

Trust comment: Randomized, double-blind, placebo-controlled human trial but relatively small sample (n=46).

Study Details

PMID:10385496
Participants:46
Impact:+74.5 μmol/L (single-dose to 115.9 μmol/L from 41.4); +53.6 μmol/L after 30 days (95.0 μmol/L)
Trust score:4/5

SOFA score (organ failure)

1 evidences

Phase I randomized placebo-controlled trial (severe sepsis) showed IV ascorbic acid rapidly restored plasma levels, was well tolerated, reduced inflammatory biomarkers and was associated with faster declines in SOFA scores versus placebo.

Trust comment: Randomized, placebo‑controlled phase I safety trial with clear biomarker and SOFA changes but small sample limiting generalizability.

Study Details

PMID:24484547
Participants:24
Impact:faster decline in SOFA with high-dose vs placebo (regression slope difference significant; Hi-AscA slope −0.043 vs placebo 0.003, p<0.01)
Trust score:3/5

inflammatory biomarkers (CRP, PCT)

1 evidences

Phase I randomized placebo-controlled trial (severe sepsis) showed IV ascorbic acid rapidly restored plasma levels, was well tolerated, reduced inflammatory biomarkers and was associated with faster declines in SOFA scores versus placebo.

Trust comment: Randomized, placebo‑controlled phase I safety trial with clear biomarker and SOFA changes but small sample limiting generalizability.

Study Details

PMID:24484547
Participants:24
Impact:CRP significantly lower by 24 h vs baseline/placebo; PCT significantly lower by 48 h in high-dose group
Trust score:3/5

baseline correlation serum vitamin C vs BP

1 evidences

In a long-term (5 year) randomized trial among participants taking vitamin C (50 mg or 500 mg daily), systolic blood pressure increased over time in all groups and high‑dose vitamin C did not reduce blood pressure.

Trust comment: Large randomized double‑blind long‑term trial with many completers in vitamin C arms, suitable for BP outcomes though cohort had atrophic gastritis limiting generalizability.

Study Details

PMID:12468560
Participants:244
Impact:no significant relationship before or after adjustment for confounders
Trust score:4/5

depression symptom scores

1 evidences

Among 322 acutely ill older inpatients, biochemical vitamin C depletion was common and associated with higher depression symptom scores at baseline and at 6 weeks.

Trust comment: Well‑conducted cohort analysis within an RCT sample showing consistent associations, but observational nature limits causal inference.

Study Details

PMID:25835231
Participants:322
Impact:patients with vitamin C biochemical depletion had significantly increased depression symptoms at baseline (p=0.035) and at 6 weeks (p=0.028)
Trust score:3/5

prevalence of vitamin C deficiency

1 evidences

Among 322 acutely ill older inpatients, biochemical vitamin C depletion was common and associated with higher depression symptom scores at baseline and at 6 weeks.

Trust comment: Well‑conducted cohort analysis within an RCT sample showing consistent associations, but observational nature limits causal inference.

Study Details

PMID:25835231
Participants:322
Impact:116/322 (36%) had <11 µmol/L at baseline; at 6 weeks and 6 months deficiency was 22% and 28% respectively
Trust score:3/5

associations with low vitamin C

1 evidences

Among 322 acutely ill older inpatients, biochemical vitamin C depletion was common and associated with higher depression symptom scores at baseline and at 6 weeks.

Trust comment: Well‑conducted cohort analysis within an RCT sample showing consistent associations, but observational nature limits causal inference.

Study Details

PMID:25835231
Participants:322
Impact:older age, male sex, smoking, dependency and inflammation associated with lower vitamin C concentrations
Trust score:3/5

lipid peroxidation (breath pentane, plasma MDA)

1 evidences

In 56 healthy smokers randomized to 500 mg vitamin C daily or placebo for 4 weeks, plasma vitamin C increased but markers of lipid peroxidation and pulmonary function tests did not change.

Trust comment: Randomized double‑blind trial with complete follow‑up but small sample and short duration for clinical pulmonary endpoints.

Study Details

PMID:10052021
Participants:56
Impact:no significant change after 4 weeks with 500 mg vitamin C
Trust score:3/5

urinary albumin excretion rate (AER)

1 evidences

In a 4-week double-blind crossover trial, combined high-dose vitamin C and E lowered urinary albumin excretion in Type 2 diabetic patients.

Trust comment: Randomised, double-blind crossover RCT with clear endpoints but small N and short duration limits generalizability.

Study Details

PMID:11606175
Participants:30
Impact:-19% (geometric mean 197 vs 243 mg/24 h)
Trust score:4/5

haemoglobin A1C / blood pressure / serum creatinine

1 evidences

In a 4-week double-blind crossover trial, combined high-dose vitamin C and E lowered urinary albumin excretion in Type 2 diabetic patients.

Trust comment: Randomised, double-blind crossover RCT with clear endpoints but small N and short duration limits generalizability.

Study Details

PMID:11606175
Participants:30
Impact:no change
Trust score:4/5

periorbital wrinkle severity

1 evidences

Topical oil‑soluble vitamin C derivative applied twice daily for 8 weeks improved periorbital wrinkles versus placebo on the contralateral side.

Trust comment: Well-designed double-blind randomized split-face trial with moderate sample size; outcome assessment includes objective topography.

Study Details

PMID:34910367
Participants:69
Impact:improved (marked/moderate by visual grading and confirmed by topography)
Trust score:4/5

fasting plasma vitamin C

1 evidences

Smokers who drank milk supplemented with fruit/vegetable extracts and vitamin C twice daily for 6 weeks had higher plasma vitamin C and antioxidant potential and lower uric acid than non‑supplemented milk.

Trust comment: Controlled intervention in smokers with measurable biochemical outcomes but modest sample size and complex multi-component beverages limit attribution to vitamin C alone.

Study Details

PMID:21770863
Participants:42
Impact:increased
Trust score:3/5

antioxidant potential (plasma)

1 evidences

Smokers who drank milk supplemented with fruit/vegetable extracts and vitamin C twice daily for 6 weeks had higher plasma vitamin C and antioxidant potential and lower uric acid than non‑supplemented milk.

Trust comment: Controlled intervention in smokers with measurable biochemical outcomes but modest sample size and complex multi-component beverages limit attribution to vitamin C alone.

Study Details

PMID:21770863
Participants:42
Impact:increased
Trust score:3/5

self-rated physical stamina

1 evidences

In a 28-day randomized trial, a multivitamin/mineral supplement (including minerals) produced small self-reported improvements in physical stamina, concentration/mental stamina, and alertness in working men.

Trust comment: Large, randomized double-blind trial but intervention was a multivitamin/mineral so effects cannot be attributed to vitamin C alone.

Study Details

PMID:21751253
Participants:198
Impact:increased across assessments/weeks
Trust score:3/5

concentration and mental stamina (during work)

1 evidences

In a 28-day randomized trial, a multivitamin/mineral supplement (including minerals) produced small self-reported improvements in physical stamina, concentration/mental stamina, and alertness in working men.

Trust comment: Large, randomized double-blind trial but intervention was a multivitamin/mineral so effects cannot be attributed to vitamin C alone.

Study Details

PMID:21751253
Participants:198
Impact:increased at post-work assessments
Trust score:3/5

subjective alertness

1 evidences

In a 28-day randomized trial, a multivitamin/mineral supplement (including minerals) produced small self-reported improvements in physical stamina, concentration/mental stamina, and alertness in working men.

Trust comment: Large, randomized double-blind trial but intervention was a multivitamin/mineral so effects cannot be attributed to vitamin C alone.

Study Details

PMID:21751253
Participants:198
Impact:increased at selected timepoints (day 14 and 28)
Trust score:3/5

plasma ascorbate concentration on fixed intake

1 evidences

In a controlled-diet depletion–repletion study, plasma ascorbate achieved on identical intake varied widely and was inversely associated with body weight and influenced by prior depletion.

Trust comment: Well-controlled dietary study with adequate sample size and objective biochemical outcomes supporting robust conclusions.

Study Details

PMID:10613415
Participants:68
Impact:wide range after 4 weeks at 117 mg/day: 26.8–85.8 μmol/L
Trust score:4/5

effect of body weight on plasma ascorbate

1 evidences

In a controlled-diet depletion–repletion study, plasma ascorbate achieved on identical intake varied widely and was inversely associated with body weight and influenced by prior depletion.

Trust comment: Well-controlled dietary study with adequate sample size and objective biochemical outcomes supporting robust conclusions.

Study Details

PMID:10613415
Participants:68
Impact:higher body weight associated with lower plasma AA (e.g., 200-lb man ~10 μmol/L lower after first repletion, ~18 μmol/L lower after second)
Trust score:4/5

effect of prior depletion

1 evidences

In a controlled-diet depletion–repletion study, plasma ascorbate achieved on identical intake varied widely and was inversely associated with body weight and influenced by prior depletion.

Trust comment: Well-controlled dietary study with adequate sample size and objective biochemical outcomes supporting robust conclusions.

Study Details

PMID:10613415
Participants:68
Impact:prior depletion/repletion altered attainable plasma AA (only 10% reached same plasma AA on second repletion)
Trust score:4/5

operating time

1 evidences

IV 2 g ascorbic acid given perioperatively did not reduce intraoperative blood loss or change operative outcomes in women undergoing laparoscopic myomectomy.

Trust comment: Randomized, double-blind placebo-controlled RCT but small sample (46 completers) limiting power to detect modest effects.

Study Details

PMID:26946313
Participants:46
Impact:no significant change (95±29 min vs 110±52 min; P=0.50)
Trust score:4/5

postoperative hemoglobin decrease

1 evidences

IV 2 g ascorbic acid given perioperatively did not reduce intraoperative blood loss or change operative outcomes in women undergoing laparoscopic myomectomy.

Trust comment: Randomized, double-blind placebo-controlled RCT but small sample (46 completers) limiting power to detect modest effects.

Study Details

PMID:26946313
Participants:46
Impact:no significant change (ΔHb 1.9±1.31 g/dL vs 1.4±1.4 g/dL; P=0.24)
Trust score:4/5

serum vitamin C level

3 evidences

A revised parenteral nutrition formula restored vitamin C and other vitamin levels to normal ranges after gastrointestinal surgery.

Trust comment: Randomized multicenter phase III trial with objective biochemical outcomes; open-label design reduces blinding.

Study Details

PMID:30799392
Participants:110
Impact:Restored to within normal range on POD5 and POD8 versus previous formula
Trust score:4/5

In iron-deficient non-anemic girls, iron therapy with or without added vitamin C improved oxidative stress markers; adding vitamin C did not further change TAC or MDA but raised serum vitamin C levels more.

Trust comment: Double-blind randomized controlled trial with 60 participants; biochemical endpoints well measured though modest sample size.

Study Details

PMID:23686563
Participants:60
Impact:greater increase with iron+vitamin C vs iron alone (P group <0.01)
Trust score:4/5

Low-dose vitamin supplementation (including 120 mg vitamin C) for 2 years increased nutrient levels and improved a red blood cell antioxidant resistance assay in elderly participants.

Trust comment: Double-blind, placebo-controlled trial with 57 completers showing increased serum vitamin C and improved an in vitro antioxidant defense test; hospitalized elderly population limits generalizability.

Study Details

PMID:9263186
Participants:57
Impact:increased (nutrient increases ranged ~1.1–4.0-fold)
Trust score:4/5

composite adverse cardiac events

1 evidences

In patients with acute MI, adjunctive antioxidant vitamins C+E for 30 days modestly reduced a composite in-hospital adverse cardiac endpoint versus placebo.

Trust comment: Large multicenter randomized double-blind pilot trial showing a small statistically significant benefit, but being a pilot warrants confirmation in larger trials.

Study Details

PMID:16059992
Participants:800
Impact:+5% absolute reduction (14% vs 19%; OR 0.82; p=0.048)
Trust score:4/5

not hospitalized during pregnancy

1 evidences

Daily 400 mg vitamin C added to routine antenatal vitamins was associated with fewer hospitalizations and fewer low-birth-weight infants in this Ugandan cohort.

Trust comment: Randomized open-label cohort study with adequate size but limited blinding, diagnostic limitations, and potential contextual confounders reduce certainty.

Study Details

PMID:21293742
Participants:384
Impact:higher in vitamin C group 42.2% vs 27.9% (P=0.003)
Trust score:3/5

low birth weight (<2500 g)

1 evidences

Daily 400 mg vitamin C added to routine antenatal vitamins was associated with fewer hospitalizations and fewer low-birth-weight infants in this Ugandan cohort.

Trust comment: Randomized open-label cohort study with adequate size but limited blinding, diagnostic limitations, and potential contextual confounders reduce certainty.

Study Details

PMID:21293742
Participants:384
Impact:reduced in vitamin C group 15.5% vs 23.8% (P=0.041; OR 0.58)
Trust score:3/5

systolic blood pressure increase

1 evidences

Daily 400 mg vitamin C added to routine antenatal vitamins was associated with fewer hospitalizations and fewer low-birth-weight infants in this Ugandan cohort.

Trust comment: Randomized open-label cohort study with adequate size but limited blinding, diagnostic limitations, and potential contextual confounders reduce certainty.

Study Details

PMID:21293742
Participants:384
Impact:greater mean rise with vitamin C (8.04 mmHg vs 4.5 mmHg; between-group trend p=0.059)
Trust score:3/5

antioxidant enzyme activity

1 evidences

In acute amitriptyline intoxication cases, supplementation with antioxidants (alpha lipoic acid with or without vitamin C) reduced oxidative stress markers more than routine treatment, greatest with combination.

Trust comment: Human clinical groups with 132 subjects and statistically significant results, but limited methodological detail and vitamin C not tested alone reduce confidence.

Study Details

PMID:34699040
Participants:132
Impact:decrease (improved towards normal) in antioxidant-treated groups versus routine standard treatment (P<0.001)
Trust score:3/5

malondialdehyde (MDA) / lipid peroxidation

2 evidences

In SLE patients, 12 weeks of combined vitamins C and E increased plasma vitamin levels and reduced MDA but did not change endothelial function measures.

Trust comment: Double-blind randomized pilot with objective biochemical endpoints but small sample and combined-vitamin intervention limit attribution to vitamin C alone.

Study Details

PMID:15693087
Participants:39
Impact:decrease (statistically significant)
Trust score:3/5

In critically ill patients, supplementation with vitamins A, C and E reduced lipid peroxidation (MDA) and altered antioxidant vitamin levels but did not change clinical outcomes (ventilation, mortality, length of stay).

Trust comment: Small non-blinded dietary supplementation study with limited sample (n=34) and no demonstrated clinical benefit, limiting confidence in clinical relevance.

Study Details

PMID:24160231
Participants:34
Impact:significant decrease in supplemented group after intervention
Trust score:3/5

clinical outcomes (mortality, ventilation, LOS, infection)

1 evidences

In critically ill patients, supplementation with vitamins A, C and E reduced lipid peroxidation (MDA) and altered antioxidant vitamin levels but did not change clinical outcomes (ventilation, mortality, length of stay).

Trust comment: Small non-blinded dietary supplementation study with limited sample (n=34) and no demonstrated clinical benefit, limiting confidence in clinical relevance.

Study Details

PMID:24160231
Participants:34
Impact:no significant differences between groups
Trust score:3/5

immune-associated serum proteins correlation

1 evidences

In people at risk for type 2 diabetes, blood vitamin C levels were positively associated with immune-related serum proteins and a 21-feature signature (including proteins and clinical variables) predicted vitamin C levels.

Trust comment: Small human crossover study using proteomics and machine learning; findings are associative and limited by small sample size.

Study Details

PMID:38030046
Participants:25
Impact:positive correlation with serum ascorbic acid (association reported; no effect size provided)
Trust score:3/5

fractional iron absorption

1 evidences

Randomized, double-blind crossover in 25 mildly anemic children found adding equimolar ascorbic acid to iron-fortified milk (both drinks contained calcium) nearly doubled fractional iron absorption versus iron alone.

Trust comment: Randomized double-blind two-way crossover in children with direct stable-isotope absorption measures; small sample but rigorous methodology.

Study Details

PMID:30045423
Participants:25
Impact:+98% (0.80% → 1.58%; ~2-fold increase)
Trust score:4/5

organ dysfunction at 7 days

1 evidences

Intravenous antioxidant therapy (including vitamin C) raised antioxidant levels and lowered oxidative stress markers but did not reduce organ dysfunction at 7 days in severe acute pancreatitis.

Trust comment: Randomized double-blind placebo-controlled trial but small sample and no benefit on primary clinical endpoint despite biomarker changes.

Study Details

PMID:17356040
Participants:43
Impact:32% (antioxidant) vs 17% (placebo), p=0.33 (no significant difference)
Trust score:3/5

H. pylori eradication rate (ITT)

1 evidences

Adding vitamins C and E to standard triple therapy substantially increased H. pylori eradication rates compared with standard therapy alone.

Trust comment: Randomized open-label trial with objective breath-test outcome and a large, clinically meaningful effect, though not double-blind.

Study Details

PMID:21740452
Participants:195
Impact:increased from 45% → 82.5% (absolute +37.5 percentage points); Per-protocol 47.4% → 84%
Trust score:4/5

other maternal/perinatal outcomes

1 evidences

Daily vitamins C and E in high-risk pregnant women did not reduce pre-eclampsia or improve maternal/perinatal outcomes.

Trust comment: Large multicentre randomized double-blind trial with good compliance and follow-up showing no benefit for primary or key secondary outcomes.

Study Details

PMID:19432566
Participants:1365
Impact:no significant effect on gestational hypertension, low birthweight, small for gestational age, or perinatal death
Trust score:5/5

forced expiratory flows (FEF25–75)

1 evidences

Follow-up of an RCT where pregnant smokers received 500 mg/day vitamin C or placebo; at age 5 offspring of vitamin C mothers had better small-airway function, less wheeze, and persistent buccal DNA methylation differences.

Trust comment: Multi-center, double-blind randomized controlled trial with objective spirometry and epigenome-wide analysis, moderate sample for epigenetics (n=158) and robust statistical analyses.

Study Details

PMID:38413986
Participants:158
Impact:+0.19 L/sec (1.28 → 1.47 L/sec; ≈+15%)
Trust score:4/5

current wheeze (4–6 yrs)

1 evidences

Follow-up of an RCT where pregnant smokers received 500 mg/day vitamin C or placebo; at age 5 offspring of vitamin C mothers had better small-airway function, less wheeze, and persistent buccal DNA methylation differences.

Trust comment: Multi-center, double-blind randomized controlled trial with objective spirometry and epigenome-wide analysis, moderate sample for epigenetics (n=158) and robust statistical analyses.

Study Details

PMID:38413986
Participants:158
Impact:-~20 percentage points (48.8% → 28.2%)
Trust score:4/5

buccal DNA methylation (DMCs)

1 evidences

Follow-up of an RCT where pregnant smokers received 500 mg/day vitamin C or placebo; at age 5 offspring of vitamin C mothers had better small-airway function, less wheeze, and persistent buccal DNA methylation differences.

Trust comment: Multi-center, double-blind randomized controlled trial with objective spirometry and epigenome-wide analysis, moderate sample for epigenetics (n=158) and robust statistical analyses.

Study Details

PMID:38413986
Participants:158
Impact:457 FDR-significant DMCs associated with prenatal vitamin C
Trust score:4/5

parotid gland excretion fraction (EF)

1 evidences

In 69 postoperative thyroid cancer patients receiving 131I, antioxidant regimens (vitamin E+C, selenium, selenium+C) were associated with improved salivary gland function parameters one month after treatment.

Trust comment: Randomized groups and objective imaging endpoints, but interventions were combination regimens so vitamin C–specific contribution is not isolated and sample sizes per arm are small.

Study Details

PMID:38312062
Participants:69
Impact:improved with vitamin E + vitamin C (left parotid EF increased vs baseline)
Trust score:3/5

multiple salivary gland functional parameters (ER, UR20, EF)

1 evidences

In 69 postoperative thyroid cancer patients receiving 131I, antioxidant regimens (vitamin E+C, selenium, selenium+C) were associated with improved salivary gland function parameters one month after treatment.

Trust comment: Randomized groups and objective imaging endpoints, but interventions were combination regimens so vitamin C–specific contribution is not isolated and sample sizes per arm are small.

Study Details

PMID:38312062
Participants:69
Impact:improved with selenium + vitamin C combination (greater effect reported)
Trust score:3/5

plasma ascorbic acid level

3 evidences

In patients with cirrhosis, IV ascorbic acid reduced oxidative marker MDA and markedly blunted the postprandial rise in portal pressure.

Trust comment: Randomized human study with objective hemodynamic endpoints and significant effects, though sample size is modest.

Study Details

PMID:16496307
Participants:37
Impact:lower at baseline in cirrhosis and increased after administration
Trust score:4/5

120 subjects (4 groups) showed lower plasma vitamin C in gingivitis/periodontitis; short-term dietary vitamin C (450 mg/day) plus scaling reduced bleeding in gingivitis and diabetic periodontitis subgroups.

Trust comment: Moderate-sized clinical study with objective biochemical and clinical periodontal measures; short follow-up (2 weeks) and combination with SRP limits attribution to vitamin C alone.

Study Details

PMID:23725523
Participants:120
Impact:lower in gingivitis and diabetics with periodontitis vs healthy controls
Trust score:3/5

In 51 high‑risk premature infants, daily ascorbic acid (100 mg/kg) during the first week prevented the normal postnatal drop in levels and was not associated with increased hemolysis or short‑term adverse outcomes.

Trust comment: Double‑blind randomized trial in premature infants but small sample limits power to detect differences in clinical outcomes.

Study Details

PMID:9514139
Participants:51
Impact:prevented immediate postnatal drop
Trust score:4/5

sulcus bleeding index (SBI)

2 evidences

Grapefruit intake for 2 weeks increased blood vitamin C and reduced gum bleeding in periodontitis patients.

Trust comment: Checklist: 1) Confirm Vitamin C relevance; 2) Identify top outcomes; 3) Determine participants; 4) Rate quality; 5) Document changes; 6) Summarize; Study rated 4/5—reasonable sample and clear pre/post measures but short duration and limited longer-term data.

Study Details

PMID:16127404
Participants:80
Impact:decreased −0.63 points (1.68 → 1.05) in test group (non-smokers), p<0.001
Trust score:4/5

120 subjects (4 groups) showed lower plasma vitamin C in gingivitis/periodontitis; short-term dietary vitamin C (450 mg/day) plus scaling reduced bleeding in gingivitis and diabetic periodontitis subgroups.

Trust comment: Moderate-sized clinical study with objective biochemical and clinical periodontal measures; short follow-up (2 weeks) and combination with SRP limits attribution to vitamin C alone.

Study Details

PMID:23725523
Participants:120
Impact:reduced with SRP + 450 mg vitamin C for 2 weeks (significant; p≤0.036)
Trust score:3/5

plasma malondialdehyde (MDA, lipid peroxidation)

1 evidences

A 3-month trial of a polyphenol-rich antioxidant supplement (pomegranate, green tea extracts, plus ascorbic acid) in type 2 diabetics lowered LDL and MDA and increased antioxidant markers compared with placebo.

Trust comment: Placebo-controlled human trial with 114 participants, but multi-ingredient supplement (includes ascorbic acid) prevents attributing effects solely to Vitamin C.

Study Details

PMID:19834314
Participants:114
Impact:decrease (p<0.001)
Trust score:3/5

mild dementia (odds)

1 evidences

Higher blood vitamin C was associated with lower odds of mild dementia in this cross-sectional case-control study of older adults.

Trust comment: Population-based case-control (cross-sectional) association with multiple adjustments but cannot establish causality.

Study Details

PMID:22710913
Participants:232
Impact:Higher vitamin C tertile associated with lower odds: OR 0.29 (3rd vs 1st tertile; 95% CI 0.09–0.96)
Trust score:3/5

total cholesterol (TC)

1 evidences

In hyperlipidemic patients, 500 mg vitamin C daily for 10 weeks increased blood vitamin C and was associated with reductions in total cholesterol, apo-B, and MDA versus baseline.

Trust comment: Randomized placebo-controlled trial but small total sample and short duration and multiple arms reduce per-group power.

Study Details

PMID:12847992
Participants:68
Impact:decrease vs baseline (P=0.004)
Trust score:3/5

apo-B

1 evidences

In hyperlipidemic patients, 500 mg vitamin C daily for 10 weeks increased blood vitamin C and was associated with reductions in total cholesterol, apo-B, and MDA versus baseline.

Trust comment: Randomized placebo-controlled trial but small total sample and short duration and multiple arms reduce per-group power.

Study Details

PMID:12847992
Participants:68
Impact:decrease vs baseline (P=0.005)
Trust score:3/5

ACh-dependent forearm blood flow (endothelium-dependent vasodilation)

1 evidences

In healthy men given endotoxin, high‑dose IV vitamin C restored endothelial-dependent forearm vasodilation that was suppressed by endotoxin.

Trust comment: Well-controlled, placebo crossover in healthy humans with objective vascular measures, but modest sample size (n=36).

Study Details

PMID:24512733
Participants:36
Impact:restored to baseline (reversed up to 76% LPS-induced reduction)
Trust score:4/5

FEF25-75 (mid-expiratory flow)

1 evidences

Children whose mothers (smokers) received vitamin C in pregnancy had higher expiratory flow measures at age 5, but forced oscillation measures largely did not detect the effect.

Trust comment: Double-blind RCT with objective lung-function endpoints and multicenter follow-up to age 5, providing robust evidence for spirometric improvements.

Study Details

PMID:39565207
Participants:178
Impact:+15.5% (vitamin C vs placebo at 5 years; p=0.0002)
Trust score:5/5

FEF75 (forced expiratory flow at 75%)

1 evidences

Children whose mothers (smokers) received vitamin C in pregnancy had higher expiratory flow measures at age 5, but forced oscillation measures largely did not detect the effect.

Trust comment: Double-blind RCT with objective lung-function endpoints and multicenter follow-up to age 5, providing robust evidence for spirometric improvements.

Study Details

PMID:39565207
Participants:178
Impact:+23.9% (vitamin C vs placebo at 5 years; p<0.0001)
Trust score:5/5

FEF50 (forced expiratory flow at 50%)

1 evidences

Children whose mothers (smokers) received vitamin C in pregnancy had higher expiratory flow measures at age 5, but forced oscillation measures largely did not detect the effect.

Trust comment: Double-blind RCT with objective lung-function endpoints and multicenter follow-up to age 5, providing robust evidence for spirometric improvements.

Study Details

PMID:39565207
Participants:178
Impact:+13.5% (vitamin C vs placebo at 5 years; p=0.0007)
Trust score:5/5

Brachial systolic blood pressure

1 evidences

Oral 500 mg/day vitamin C for 4 weeks lowered blood pressure and improved arterial stiffness measures in patients with type 2 diabetes.

Trust comment: Randomized double-blind trial with clear hemodynamic endpoints but small sample (n=30) and short duration (4 weeks).

Study Details

PMID:12468561
Participants:30
Impact:-9.9 mmHg (142.1 → 132.3 mmHg; 95% CI 4.7 to 15.0; P<0.01)
Trust score:4/5

Brachial diastolic blood pressure

1 evidences

Oral 500 mg/day vitamin C for 4 weeks lowered blood pressure and improved arterial stiffness measures in patients with type 2 diabetes.

Trust comment: Randomized double-blind trial with clear hemodynamic endpoints but small sample (n=30) and short duration (4 weeks).

Study Details

PMID:12468561
Participants:30
Impact:-4.4 mmHg (83.9 → 79.5 mmHg; 95% CI 1.8 to 7.0; P<0.01)
Trust score:4/5

Augmentation index (AgIx, arterial stiffness)

1 evidences

Oral 500 mg/day vitamin C for 4 weeks lowered blood pressure and improved arterial stiffness measures in patients with type 2 diabetes.

Trust comment: Randomized double-blind trial with clear hemodynamic endpoints but small sample (n=30) and short duration (4 weeks).

Study Details

PMID:12468561
Participants:30
Impact:-4.3 percentage points (26.8% → 22.5%; P<0.01)
Trust score:4/5

Plasma F2-isoprostanes (lipid peroxidation biomarker) - overall

1 evidences

In overweight/obese nonsmokers, 1000 mg/day vitamin C for 2 months reduced plasma F2-isoprostanes, especially in participants with high baseline levels.

Trust comment: Large randomized trial with intention-to-treat analysis and significant biomarker changes, though outcome is a surrogate marker and effect depended on baseline levels.

Study Details

PMID:18455517
Participants:396
Impact:-10.6% (vitamin C vs placebo; P=0.001)
Trust score:4/5

Plasma F2-isoprostanes (baseline >50 µg/mL subgroup)

1 evidences

In overweight/obese nonsmokers, 1000 mg/day vitamin C for 2 months reduced plasma F2-isoprostanes, especially in participants with high baseline levels.

Trust comment: Large randomized trial with intention-to-treat analysis and significant biomarker changes, though outcome is a surrogate marker and effect depended on baseline levels.

Study Details

PMID:18455517
Participants:396
Impact:-22% in high-baseline subgroup (P=0.01)
Trust score:4/5

Normalization to normal vaginal flora (ITT)

1 evidences

Vaginal vitamin C insertion improved normalization of vaginal flora and pH versus no treatment but caused irritation in some women.

Trust comment: Randomized study with clear clinical outcome but control was no treatment (likely unblinded) and tolerability issues noted.

Study Details

PMID:23677418
Participants:140
Impact:+27.1 percentage points (51.4% vs 24.3%; difference 27.1%; 95% CI 11.7–42.6)
Trust score:3/5

Treatment discontinuation due to side effects

1 evidences

Vaginal vitamin C insertion improved normalization of vaginal flora and pH versus no treatment but caused irritation in some women.

Trust comment: Randomized study with clear clinical outcome but control was no treatment (likely unblinded) and tolerability issues noted.

Study Details

PMID:23677418
Participants:140
Impact:10% stopped treatment
Trust score:3/5

Urinary 8-epi-PGF2α (oxidative stress marker) increase after PTCA

1 evidences

Urinary 8-epi-PGF2α (a free-radical marker) rose transiently after primary PTCA; pre-treatment with vitamin C did not suppress this rise.

Trust comment: Human clinical study with direct biomarker measurement but small group sizes (n=11,10,6) limiting power.

Study Details

PMID:10614835
Participants:27
Impact:Transient increase at 60–90 min post-PTCA; vitamin C did not reduce the percent increase versus no vitamin C
Trust score:3/5

Total hip areal bone mineral density (aBMD) response to training

1 evidences

In elderly men undergoing 12 weeks of resistance training, high-dose vitamin C+E supplementation blunted exercise-induced gains in bone mineral density and altered some bone-related serum markers.

Trust comment: Randomized, double-blind placebo-controlled trial with objective DXA outcomes but small sample size (n=33).

Study Details

PMID:28382551
Participants:33
Impact:Placebo group increased total hip aBMD by +1.0% (CI 0.3–1.7); antioxidant group showed smaller/no comparable increase
Trust score:4/5

Lumbar spine aBMD response to training

1 evidences

In elderly men undergoing 12 weeks of resistance training, high-dose vitamin C+E supplementation blunted exercise-induced gains in bone mineral density and altered some bone-related serum markers.

Trust comment: Randomized, double-blind placebo-controlled trial with objective DXA outcomes but small sample size (n=33).

Study Details

PMID:28382551
Participants:33
Impact:Placebo group increase +0.9% versus antioxidant group (antioxidants attenuated the training effect)
Trust score:4/5

leukocyte count

1 evidences

A multicomponent supplement (containing vitamin C among others) lowered leukocyte counts in smokers and increased plasma vitamin E and Q10; effects cannot be attributed solely to vitamin C.

Trust comment: Double-blind randomized placebo-controlled design but multiple active ingredients prevent isolating vitamin C effects.

Study Details

PMID:12622238
Participants:48
Impact:decreased (significant in smoker verum group)
Trust score:3/5

plasma vitamin E

3 evidences

In healthy middle-aged adults, 7-week supplementation with fruit/vegetable concentrates raised blood levels of several antioxidants including vitamin C.

Trust comment: Double-blind randomized crossover human study with moderate sample size but supplement contained many nutrients, so isolated vitamin C effect is indirect.

Study Details

PMID:15190044
Participants:59
Impact:increased (significant) after active supplementation
Trust score:3/5

A multicomponent supplement (containing vitamin C among others) lowered leukocyte counts in smokers and increased plasma vitamin E and Q10; effects cannot be attributed solely to vitamin C.

Trust comment: Double-blind randomized placebo-controlled design but multiple active ingredients prevent isolating vitamin C effects.

Study Details

PMID:12622238
Participants:48
Impact:increased after intervention
Trust score:3/5

Children with chronic constipation had lower antioxidant enzyme activities and lower plasma vitamin C and E compared with matched healthy children.

Trust comment: Measured biochemical differences in matched groups show strong statistical signals, but study design and potential confounding make causal inference uncertain.

Study Details

PMID:15602823
Participants:120
Impact:significantly decreased in chronic constipation patients (P < 0.0001)
Trust score:3/5

water-soluble antioxidant capacity

1 evidences

A multicomponent supplement (containing vitamin C among others) lowered leukocyte counts in smokers and increased plasma vitamin E and Q10; effects cannot be attributed solely to vitamin C.

Trust comment: Double-blind randomized placebo-controlled design but multiple active ingredients prevent isolating vitamin C effects.

Study Details

PMID:12622238
Participants:48
Impact:attenuated/increased towards normal in smokers
Trust score:3/5

gingival redness

1 evidences

A dentifrice containing an ascorbic acid derivative showed reduced gingival redness and higher salivary antioxidant activity; primary GI outcome was not significant in ITT but improved in per-protocol analysis.

Trust comment: Large multicenter randomized controlled trial with objective endpoints, but primary outcome not significant in ITT which reduces certainty.

Study Details

PMID:25277459
Participants:300
Impact:decreased (P=0.04)
Trust score:4/5

salivary total antioxidant activity

1 evidences

A dentifrice containing an ascorbic acid derivative showed reduced gingival redness and higher salivary antioxidant activity; primary GI outcome was not significant in ITT but improved in per-protocol analysis.

Trust comment: Large multicenter randomized controlled trial with objective endpoints, but primary outcome not significant in ITT which reduces certainty.

Study Details

PMID:25277459
Participants:300
Impact:increased (P=0.03)
Trust score:4/5

collagen-induced platelet aggregation

1 evidences

Intravenous vitamin C reduced collagen-induced platelet aggregation in both smokers and nonsmokers at early time points.

Trust comment: Randomized placebo-controlled infusion study with objective platelet aggregation measures, but small sample size.

Study Details

PMID:12078386
Participants:40
Impact:decreased at 3 and 6 hours after IV 3 g vitamin C (significant vs placebo)
Trust score:4/5

sperm motility

2 evidences

After varicocele surgery, men given vitamin C had improved sperm movement and shape but not higher sperm counts.

Trust comment: Randomized double-blind placebo-controlled RCT with 115 men and clear semen outcomes though seminal/serum vitamin C levels were not measured.

Study Details

PMID:26005963
Participants:115
Impact:+8.2 percentage points (mean change +20.8% vs +12.6% in placebo)
Trust score:4/5

In obese men, alternate-day 1,000 mg vitamin C improved sperm concentration and motility but did not change semen volume or normal morphology.

Trust comment: Randomized with a control group and reasonable sample size but effect sizes not reported and methodology/details limited in abstract.

Study Details

PMID:27085565
Participants:250
Impact:significant improvement (all BMI groups)
Trust score:3/5

flow-mediated dilatation (FMD)

1 evidences

In patients with metabolic syndrome, intravenous vitamin C quickly improved artery dilation and prevented an exercise/ischemia-related rise in an oxidative stress marker.

Trust comment: Randomized double-blind crossover mechanistic study but small sample (18 MS patients; 30 controls), limiting external validity.

Study Details

PMID:17664149
Participants:48
Impact:significantly increased after vitamin C infusion (P<0.001)
Trust score:3/5

fasting plasma free radicals

1 evidences

In 40 older type II diabetic patients, chronic oral vitamin C (1 g/day) improved oxidative markers and reduced insulin and lipid concentrations.

Trust comment: Double-blind randomized cross-over in 40 elderly diabetics with multiple metabolic endpoints; moderate quality but older study and limited to one dose/population.

Study Details

PMID:8568117
Participants:40
Impact:decreased from 0.49→0.26 (absolute −0.23, ~−47%, p<0.03)
Trust score:3/5

insulin (fasting)

1 evidences

In 40 older type II diabetic patients, chronic oral vitamin C (1 g/day) improved oxidative markers and reduced insulin and lipid concentrations.

Trust comment: Double-blind randomized cross-over in 40 elderly diabetics with multiple metabolic endpoints; moderate quality but older study and limited to one dose/population.

Study Details

PMID:8568117
Participants:40
Impact:decreased from 90→73 pmol/L (−17 pmol/L, p<0.04)
Trust score:3/5

KDQOL symptom score

1 evidences

In 99 patients with severe renal failure, thrice-weekly low-dose ascorbate did not improve uraemic symptoms or cardiovascular stability and showed a trend to slightly worse nausea.

Trust comment: Adequately powered (n=99), randomized double-blind trial in the target clinical population; outcomes clinically relevant though negative.

Study Details

PMID:20628180
Participants:99
Impact:no significant change (no improvement, P=0.19)
Trust score:4/5

nausea

1 evidences

In 99 patients with severe renal failure, thrice-weekly low-dose ascorbate did not improve uraemic symptoms or cardiovascular stability and showed a trend to slightly worse nausea.

Trust comment: Adequately powered (n=99), randomized double-blind trial in the target clinical population; outcomes clinically relevant though negative.

Study Details

PMID:20628180
Participants:99
Impact:trend to slightly worse after ascorbate (p=0.09 after adjustment)
Trust score:4/5

correction of ascorbate deficiency

1 evidences

In 99 patients with severe renal failure, thrice-weekly low-dose ascorbate did not improve uraemic symptoms or cardiovascular stability and showed a trend to slightly worse nausea.

Trust comment: Adequately powered (n=99), randomized double-blind trial in the target clinical population; outcomes clinically relevant though negative.

Study Details

PMID:20628180
Participants:99
Impact:corrected in ~85% of treated subjects
Trust score:4/5

ischemic electrocardiographic events

1 evidences

Giving vitamin C and E plus allopurinol around bypass surgery reduced some electrocardiographic ischemic events, perioperative infarctions and enzyme release in certain patient groups.

Trust comment: Randomized perioperative trial (n=81) showing clinical and biomarker improvements, but combined interventions (vitamin C + vitamin E + allopurinol) and small subgroup sizes limit attribution to Vitamin C alone.

Study Details

PMID:7771834
Participants:81
Impact:reduced (fewer events in treated groups vs controls)
Trust score:3/5

perioperative myocardial infarction

1 evidences

Giving vitamin C and E plus allopurinol around bypass surgery reduced some electrocardiographic ischemic events, perioperative infarctions and enzyme release in certain patient groups.

Trust comment: Randomized perioperative trial (n=81) showing clinical and biomarker improvements, but combined interventions (vitamin C + vitamin E + allopurinol) and small subgroup sizes limit attribution to Vitamin C alone.

Study Details

PMID:7771834
Participants:81
Impact:reduced (especially in unstable patients receiving treatment vs controls)
Trust score:3/5

creatine kinase-MB release

1 evidences

Giving vitamin C and E plus allopurinol around bypass surgery reduced some electrocardiographic ischemic events, perioperative infarctions and enzyme release in certain patient groups.

Trust comment: Randomized perioperative trial (n=81) showing clinical and biomarker improvements, but combined interventions (vitamin C + vitamin E + allopurinol) and small subgroup sizes limit attribution to Vitamin C alone.

Study Details

PMID:7771834
Participants:81
Impact:decreased (less release in treated unstable group vs control)
Trust score:3/5

lesion complete resolution (8 weeks)

1 evidences

Topical 30% ascorbic acid cleared more basal cell carcinoma lesions at 8 weeks and caused fewer side effects than imiquimod.

Trust comment: Small randomized comparative trial with significant short-term clearance benefit and fewer adverse effects, but limited sample size.

Study Details

PMID:35217280
Participants:25
Impact:increased (86.7% with ascorbic acid vs 57.1% with imiquimod; p<0.05)
Trust score:3/5

adverse effects (including long-term hypopigmentation)

1 evidences

Topical 30% ascorbic acid cleared more basal cell carcinoma lesions at 8 weeks and caused fewer side effects than imiquimod.

Trust comment: Small randomized comparative trial with significant short-term clearance benefit and fewer adverse effects, but limited sample size.

Study Details

PMID:35217280
Participants:25
Impact:decreased (0% hypopigmentation with ascorbate vs 70% with imiquimod at 30 months)
Trust score:3/5

skin iron (day 8)

1 evidences

Supplementation with vitamin C and pantothenic acid showed no major improvement in wound healing; tissue trace-element (including Zn) content correlated with scar mechanical properties in the supplemented group.

Trust comment: Double-blind randomized trial (n=49) but small sample and combined supplementation (vitamin C + pantothenic acid) limit isolation of Vitamin C effects; no major clinical wound-healing improvement documented.

Study Details

PMID:7781653
Participants:49
Impact:increased (p<0.05)
Trust score:3/5

scar manganese (day 21)

1 evidences

Supplementation with vitamin C and pantothenic acid showed no major improvement in wound healing; tissue trace-element (including Zn) content correlated with scar mechanical properties in the supplemented group.

Trust comment: Double-blind randomized trial (n=49) but small sample and combined supplementation (vitamin C + pantothenic acid) limit isolation of Vitamin C effects; no major clinical wound-healing improvement documented.

Study Details

PMID:7781653
Participants:49
Impact:decreased (p<0.01)
Trust score:3/5

blood ascorbic acid levels post-surgery

1 evidences

Supplementation with vitamin C and pantothenic acid showed no major improvement in wound healing; tissue trace-element (including Zn) content correlated with scar mechanical properties in the supplemented group.

Trust comment: Double-blind randomized trial (n=49) but small sample and combined supplementation (vitamin C + pantothenic acid) limit isolation of Vitamin C effects; no major clinical wound-healing improvement documented.

Study Details

PMID:7781653
Participants:49
Impact:increased with supplementation (while decreased in controls)
Trust score:3/5

total, HDL-, LDL-cholesterol and triacylglycerol (overall)

1 evidences

Five years of vitamin C (500 mg vs 50 mg/day) did not improve overall serum lipid profiles, though high-dose vitamin C may have reduced triglycerides in some women with high baseline levels.

Trust comment: Five-year double-blind population trial with >300 completers; well-designed though subgroup effects are exploratory and not definitive.

Study Details

PMID:14748940
Participants:305
Impact:no marked change (no favourable effect overall)
Trust score:4/5

serum triacylglycerol in women (overall)

1 evidences

Five years of vitamin C (500 mg vs 50 mg/day) did not improve overall serum lipid profiles, though high-dose vitamin C may have reduced triglycerides in some women with high baseline levels.

Trust comment: Five-year double-blind population trial with >300 completers; well-designed though subgroup effects are exploratory and not definitive.

Study Details

PMID:14748940
Participants:305
Impact:decreased in high-dose vs increased in low-dose (mean change -0.12 mmol/L vs +0.12 mmol/L)
Trust score:4/5

triacylglycerol in hypertriacylglycerolaemic women

1 evidences

Five years of vitamin C (500 mg vs 50 mg/day) did not improve overall serum lipid profiles, though high-dose vitamin C may have reduced triglycerides in some women with high baseline levels.

Trust comment: Five-year double-blind population trial with >300 completers; well-designed though subgroup effects are exploratory and not definitive.

Study Details

PMID:14748940
Participants:305
Impact:significant decrease (-1.21; 95% CI -2.38, -0.05) with high-dose vitamin C)
Trust score:4/5

plasma total ascorbate

1 evidences

In 48 men, 500 mg/day slow-release vitamin C raised blood vitamin C but did not reduce markers of lipid peroxidation or DNA oxidation over 36 months.

Trust comment: Double-masked randomized trial with measured biochemical endpoints and 36-month follow-up, but effect mostly seen for vitamin E not vitamin C.

Study Details

PMID:10978253
Participants:48
Impact:+30.1% (12 mo); +91.1% (36 mo)
Trust score:4/5

urinary 7-hydro-8-oxo-2'-deoxyguanosine

1 evidences

In 48 men, 500 mg/day slow-release vitamin C raised blood vitamin C but did not reduce markers of lipid peroxidation or DNA oxidation over 36 months.

Trust comment: Double-masked randomized trial with measured biochemical endpoints and 36-month follow-up, but effect mostly seen for vitamin E not vitamin C.

Study Details

PMID:10978253
Participants:48
Impact:no change
Trust score:4/5

oxidation resistance of lipids/lipoproteins

1 evidences

In 48 men, 500 mg/day slow-release vitamin C raised blood vitamin C but did not reduce markers of lipid peroxidation or DNA oxidation over 36 months.

Trust comment: Double-masked randomized trial with measured biochemical endpoints and 36-month follow-up, but effect mostly seen for vitamin E not vitamin C.

Study Details

PMID:10978253
Participants:48
Impact:no improvement with vitamin C alone
Trust score:4/5

half-life (pharmacokinetics)

1 evidences

In 21 septic shock patients, 1.5 g IV vitamin C every 6 hours corrected deficiency and produced high plasma concentrations with a short half-life.

Trust comment: Prospective pharmacokinetic study in critically ill patients with clear measurements but small sample size.

Study Details

PMID:31778629
Participants:21
Impact:median ~4.3 h (pre-first-dose group) and ~6.9 h (after doses)
Trust score:4/5

PBMC 8-oxoguanine (oxidative DNA damage)

1 evidences

In 160 healthy volunteers, 80–400 mg/day vitamin C for 15 weeks did not increase PBMC vitamin C or reduce oxidative DNA damage.

Trust comment: Randomized double-blind placebo-controlled trial with adequate sample size in healthy, likely replete subjects yielding null results.

Study Details

PMID:16021530
Participants:160
Impact:no change
Trust score:4/5

PBMC vitamin C levels

1 evidences

In 160 healthy volunteers, 80–400 mg/day vitamin C for 15 weeks did not increase PBMC vitamin C or reduce oxidative DNA damage.

Trust comment: Randomized double-blind placebo-controlled trial with adequate sample size in healthy, likely replete subjects yielding null results.

Study Details

PMID:16021530
Participants:160
Impact:no increase with supplementation
Trust score:4/5

8-epi-PGF2α (oxidative stress)

1 evidences

In 35 people with type II diabetes, 1.5 g/day oral vitamin C raised plasma levels but did not change oxidative stress marker, blood pressure, or endothelial function after 3 weeks.

Trust comment: Randomized double-blind trial but small sample and short duration limit generalizability of negative findings.

Study Details

PMID:12241530
Participants:35
Impact:no significant change
Trust score:3/5

blood pressure

2 evidences

In 35 people with type II diabetes, 1.5 g/day oral vitamin C raised plasma levels but did not change oxidative stress marker, blood pressure, or endothelial function after 3 weeks.

Trust comment: Randomized double-blind trial but small sample and short duration limit generalizability of negative findings.

Study Details

PMID:12241530
Participants:35
Impact:no significant change
Trust score:3/5

In hypertensive men, 8 weeks of vitamins C (1 g/day) + E increased erythrocyte (Na,K)-ATPase activity, improved oxidative stress markers and reduced blood pressure versus placebo.

Trust comment: Double-blind randomized placebo-controlled trial in 120 men with direct biochemical and clinical measures; moderate-high quality but supplements were combined (C+E).

Study Details

PMID:23659494
Participants:120
Impact:decrease versus placebo
Trust score:4/5

H. pylori eradication

1 evidences

High‑dose oral vitamin C for 4 weeks eradicated H. pylori in some patients and raised gastric juice vitamin C levels.

Trust comment: Randomized controlled trial with objective outcomes but modest sample size and some dropouts.

Study Details

PMID:9926292
Participants:51
Impact:+30% (8/27) eradication in vitamin C group vs 0/24 in controls (P=0.01)
Trust score:4/5

gastric juice total vitamin C concentration

1 evidences

High‑dose oral vitamin C for 4 weeks eradicated H. pylori in some patients and raised gastric juice vitamin C levels.

Trust comment: Randomized controlled trial with objective outcomes but modest sample size and some dropouts.

Study Details

PMID:9926292
Participants:51
Impact:increase to 7.2±1.6 µg/ml after 4 weeks and 19.8 µg/ml 4 weeks after stopping in eradicated patients
Trust score:4/5

gastric juice total vitamin C concentration (persistent infection)

1 evidences

High‑dose oral vitamin C for 4 weeks eradicated H. pylori in some patients and raised gastric juice vitamin C levels.

Trust comment: Randomized controlled trial with objective outcomes but modest sample size and some dropouts.

Study Details

PMID:9926292
Participants:51
Impact:6.3±1.7 → 10.8±1.5 µg/ml after 4 weeks, returned to ~7.1 µg/ml after cessation
Trust score:4/5

plasma urate measurement difference between assays

1 evidences

In patients given 500 mg/day vitamin C, two urate assays yielded similar plasma urate concentrations with only a small non‑significant difference.

Trust comment: Small randomized study comparing assays; measurements appropriate but sample size limited for small differences.

Study Details

PMID:24798153
Participants:40
Impact:mean PU 0.525 mmol/L (ascorbate‑oxidase assay) vs 0.510 mmol/L (non‑ascorbate assay) in vitamin C recipients (p=0.079; not significant)
Trust score:3/5

platelet count over time

1 evidences

Post hoc analysis of a large randomized trial found vitamin C did not alter platelet counts and platelet count changes did not mediate vitamin C–related mortality.

Trust comment: Large randomized trial dataset and robust statistical modeling; post hoc analysis but high sample size and reliable measurements.

Study Details

PMID:40927646
Participants:859
Impact:no effect of vitamin C allocation on longitudinal platelet counts (no interaction)
Trust score:5/5

association of platelet count with 28‑day mortality

1 evidences

Post hoc analysis of a large randomized trial found vitamin C did not alter platelet counts and platelet count changes did not mediate vitamin C–related mortality.

Trust comment: Large randomized trial dataset and robust statistical modeling; post hoc analysis but high sample size and reliable measurements.

Study Details

PMID:40927646
Participants:859
Impact:lower platelet count associated with higher mortality (HR 0.98 per 10×10^9/L increase; 95% CI 0.97–0.99)
Trust score:5/5

carotid intima‑media thickness (IMT) progression

1 evidences

A 3‑year dietary intervention that increased vitamin C intake was associated with slightly less progression of carotid intima‑media thickness in elderly men.

Trust comment: Well‑powered randomized factorial trial with objective imaging outcomes, though dietary intervention is multifactorial and effects modest.

Study Details

PMID:18472409
Participants:563
Impact:diet group IMT progression 0.044±0.091 mm vs control 0.062±0.105 mm (difference ≈ −0.018 mm; P=0.047)
Trust score:4/5

vitamin C intake vs IMT progression

1 evidences

A 3‑year dietary intervention that increased vitamin C intake was associated with slightly less progression of carotid intima‑media thickness in elderly men.

Trust comment: Well‑powered randomized factorial trial with objective imaging outcomes, though dietary intervention is multifactorial and effects modest.

Study Details

PMID:18472409
Participants:563
Impact:increased vitamin C intake inversely correlated with IMT progression (r=−0.181; P=0.006)
Trust score:4/5

plasma ascorbic acid fluctuation

1 evidences

Slow‑release ascorbic acid produced smaller plasma concentration fluctuations than plain release after 4 weeks in smokers, but clinical significance was small.

Trust comment: Randomized placebo‑controlled trial with reasonable sample size and pharmacokinetic endpoints, though clinical relevance is limited.

Study Details

PMID:15380894
Participants:48
Impact:fluctuation decreased significantly in slow‑release vs plain after 4 weeks (P=0.003)
Trust score:4/5

mucosal ascorbic acid

1 evidences

Vitamin C (with vitamin E) doubled plasma ascorbic acid and increased mucosal ascorbic acid but did not reduce mucosal reactive oxygen species or malondialdehyde associated with H. pylori infection.

Trust comment: Randomized human trial with objective biochemical endpoints; short-term follow-up limits longer-term inference.

Study Details

PMID:11898768
Participants:117
Impact:increased (qualitative)
Trust score:4/5

mucosal reactive oxygen species / malondialdehyde

1 evidences

Vitamin C (with vitamin E) doubled plasma ascorbic acid and increased mucosal ascorbic acid but did not reduce mucosal reactive oxygen species or malondialdehyde associated with H. pylori infection.

Trust comment: Randomized human trial with objective biochemical endpoints; short-term follow-up limits longer-term inference.

Study Details

PMID:11898768
Participants:117
Impact:no significant reduction (no effect of vitamins)
Trust score:4/5

radial artery lumen surface (vasodilation)

1 evidences

Oral single-dose vitamin C (2 g) acutely increased radial artery lumen area (vasodilation), with larger effects in smokers and greater increase than diltiazem in preoperative patients.

Trust comment: Small, well-controlled studies including a randomized double-blind comparison; sample sizes modest but ultrasound endpoints objective.

Study Details

PMID:12579102
Participants:60
Impact:study1: smokers +37.5%, nonsmokers +14.3%; study2: vitamin C +33.3% (vs diltiazem +18.2%); multivariate vitamin C vs diltiazem +21.2%
Trust score:4/5

flow-mediated vasodilation (brachial artery)

1 evidences

An oral antioxidant cocktail (including 1000 mg vitamin C) acutely improved flow-mediated brachial artery vasodilation in older adults but reduced it in young adults; reactive hyperemia was unchanged.

Trust comment: Double-blind crossover with objective vascular measures; effect cannot be attributed solely to vitamin C because a multi-antioxidant cocktail was used.

Study Details

PMID:22353612
Participants:87
Impact:older: placebo 5.2% → antioxidant 8.2% (+3.0 percentage points); young: placebo 7.4% → antioxidant 5.8% (−1.6 percentage points)
Trust score:4/5

reactive hyperemia

1 evidences

An oral antioxidant cocktail (including 1000 mg vitamin C) acutely improved flow-mediated brachial artery vasodilation in older adults but reduced it in young adults; reactive hyperemia was unchanged.

Trust comment: Double-blind crossover with objective vascular measures; effect cannot be attributed solely to vitamin C because a multi-antioxidant cocktail was used.

Study Details

PMID:22353612
Participants:87
Impact:no change
Trust score:4/5

femoral neck BMD

2 evidences

Higher dietary vitamin C was associated with small increases in hip and femoral neck bone density, especially when calcium intake was adequate.

Trust comment: Large cross-sectional analysis with statistical adjustment but observational design prevents causal inference.

Study Details

PMID:9701620
Participants:775
Impact:+0.017 g/cm2 per 100 mg dietary vitamin C (overall); +0.019 g/cm2 per 100 mg in higher calcium stratum
Trust score:3/5

In postmenopausal women, daily antioxidant supplementation including 1000 mg vitamin C prevented the small lumbar spine bone loss seen in the placebo group over 6 months.

Trust comment: Small randomized pilot trial with limited sample sizes per arm; results are suggestive but underpowered for definitive conclusions.

Study Details

PMID:19020919
Participants:34
Impact:No significant changes observed in any group over 6 months
Trust score:3/5

total hip BMD

1 evidences

Higher dietary vitamin C was associated with small increases in hip and femoral neck bone density, especially when calcium intake was adequate.

Trust comment: Large cross-sectional analysis with statistical adjustment but observational design prevents causal inference.

Study Details

PMID:9701620
Participants:775
Impact:+0.017 g/cm2 per 100 mg dietary vitamin C (overall); similar association in higher calcium stratum
Trust score:3/5

lumbar spine BMD

1 evidences

Higher dietary vitamin C was associated with small increases in hip and femoral neck bone density, especially when calcium intake was adequate.

Trust comment: Large cross-sectional analysis with statistical adjustment but observational design prevents causal inference.

Study Details

PMID:9701620
Participants:775
Impact:association not statistically significant in total sample (P=0.08); significant in higher calcium subgroup (beta≈+0.0199 g/cm2)
Trust score:3/5

epigastric adverse effects

1 evidences

In healthy volunteers sensitive to acidic foods, Ester-C caused fewer stomach (epigastric) side effects and was better tolerated than regular ascorbic acid.

Trust comment: Randomized double‑blind crossover in 50 humans with clear statistically significant tolerability outcome (P<0.05).

Study Details

PMID:16644619
Participants:50
Impact:−25 percentage points of events (37.5% Ester‑C vs 62.5% AA; 33 vs 55 of 88 events)
Trust score:4/5

tolerability rated very good

1 evidences

In healthy volunteers sensitive to acidic foods, Ester-C caused fewer stomach (epigastric) side effects and was better tolerated than regular ascorbic acid.

Trust comment: Randomized double‑blind crossover in 50 humans with clear statistically significant tolerability outcome (P<0.05).

Study Details

PMID:16644619
Participants:50
Impact:Ester‑C 72% vs AA 54% (P<0.05)
Trust score:4/5

length of hospital stay

2 evidences

In this small RCT of severe acute pancreatitis, daily antioxidant vitamins including 1 g vitamin C did not significantly change organ dysfunction or oxidative stress markers versus standard care.

Trust comment: Randomized trial with blinded endpoint assessment and independent analysis, but small single-center sample and open-label treatment introduce limitations.

Study Details

PMID:21546719
Participants:39
Impact:Mean 12.8 vs 15.1 days (antioxidant vs control); difference not statistically significant
Trust score:4/5

In patients with early acute pancreatitis, adding antioxidants including vitamin C lowered oxidative stress markers and raised vitamin C, with a non‑significant trend to shorter hospital stay.

Trust comment: Small randomized open‑label pilot (n=53) with biochemical endpoints significant but clinical outcomes not statistically significant; pilot study design limits strength.

Study Details

PMID:20426279
Participants:53
Impact:−3.1 days (10.3±7 vs 7.2±5 days; p=0.07, NS)
Trust score:3/5

TBARS (oxidative stress)

3 evidences

In patients with early acute pancreatitis, adding antioxidants including vitamin C lowered oxidative stress markers and raised vitamin C, with a non‑significant trend to shorter hospital stay.

Trust comment: Small randomized open‑label pilot (n=53) with biochemical endpoints significant but clinical outcomes not statistically significant; pilot study design limits strength.

Study Details

PMID:20426279
Participants:53
Impact:decreased (p=0.05)
Trust score:3/5

Intravenous vitamin C reduced oxidative stress and, in enalapril-treated moderate CHF patients, augmented the natriuretic effect of furosemide.

Trust comment: Small study with multiple small protocols and crossover elements showing physiologic effects, but limited power and group sizes reduce confidence.

Study Details

PMID:12514674
Participants:35
Impact:TBARS decreased after vitamin C (reported reduction; no numeric value in excerpt)
Trust score:3/5

In patients with intermittent claudication, vitamin C administration prevented exercise-induced impairment of endothelial function and rises in oxidative stress markers.

Trust comment: Small human trial with physiological and biochemical endpoints and randomized subset assignment, but limited sample size.

Study Details

PMID:12417278
Participants:31
Impact:exercise-induced increase (1.93→2.22 nmol/ml) was abolished by vitamin C in treated patients
Trust score:3/5

plasma vitamin C / FRAP

1 evidences

In patients with early acute pancreatitis, adding antioxidants including vitamin C lowered oxidative stress markers and raised vitamin C, with a non‑significant trend to shorter hospital stay.

Trust comment: Small randomized open‑label pilot (n=53) with biochemical endpoints significant but clinical outcomes not statistically significant; pilot study design limits strength.

Study Details

PMID:20426279
Participants:53
Impact:increased (vitamin C and FRAP, p=0.01)
Trust score:3/5

plasma total vitamin C

1 evidences

In people with precancerous stomach lesions, short antioxidant regimens raised plasma vitamin C and other plasma antioxidant vitamins but did not increase gastric‑juice vitamin C.

Trust comment: Randomized pilot in 43 subjects with biochemical endpoints measured; short duration (7 days) and small sample limit generalizability.

Study Details

PMID:8664811
Participants:43
Impact:increased after both treatments (measured on day 8)
Trust score:3/5

gastric juice ascorbic acid / total vitamin C

1 evidences

In people with precancerous stomach lesions, short antioxidant regimens raised plasma vitamin C and other plasma antioxidant vitamins but did not increase gastric‑juice vitamin C.

Trust comment: Randomized pilot in 43 subjects with biochemical endpoints measured; short duration (7 days) and small sample limit generalizability.

Study Details

PMID:8664811
Participants:43
Impact:no change after treatment
Trust score:3/5

plasma beta‑carotene / alpha‑tocopherol

1 evidences

In people with precancerous stomach lesions, short antioxidant regimens raised plasma vitamin C and other plasma antioxidant vitamins but did not increase gastric‑juice vitamin C.

Trust comment: Randomized pilot in 43 subjects with biochemical endpoints measured; short duration (7 days) and small sample limit generalizability.

Study Details

PMID:8664811
Participants:43
Impact:increased (treatment 1 produced greater increases)
Trust score:3/5

lipid‑standardised alpha‑tocopherol

1 evidences

In a double‑blind crossover study, vitamin C supplementation raised plasma ascorbic acid and increased lipid‑standardized alpha‑tocopherol and antioxidant capacity (FRAP), indicating in vivo interactions between vitamins C and E.

Trust comment: Double‑blind crossover in 30 healthy adults with clear biochemical changes and appropriate design, supporting credibility.

Study Details

PMID:10967604
Participants:30
Impact:increased (from 4.09 to 4.53 μmol/mmol cholesterol+TAG with AA; P<0.05)
Trust score:4/5

FRAP (antioxidant power)

1 evidences

In a double‑blind crossover study, vitamin C supplementation raised plasma ascorbic acid and increased lipid‑standardized alpha‑tocopherol and antioxidant capacity (FRAP), indicating in vivo interactions between vitamins C and E.

Trust comment: Double‑blind crossover in 30 healthy adults with clear biochemical changes and appropriate design, supporting credibility.

Study Details

PMID:10967604
Participants:30
Impact:increased (P<0.05)
Trust score:4/5

plaque index (PI) and probing pocket depth (PPD)

1 evidences

Grapefruit intake for 2 weeks increased blood vitamin C and reduced gum bleeding in periodontitis patients.

Trust comment: Checklist: 1) Confirm Vitamin C relevance; 2) Identify top outcomes; 3) Determine participants; 4) Rate quality; 5) Document changes; 6) Summarize; Study rated 4/5—reasonable sample and clear pre/post measures but short duration and limited longer-term data.

Study Details

PMID:16127404
Participants:80
Impact:no change
Trust score:4/5

protein carbonyls (PC)

1 evidences

Two-week vitamin C+E supplementation increased plasma vitamins and reduced exercise-induced protein oxidation in trained adults.

Trust comment: Randomized, controlled supplementation trial with repeated measures and objective biomarkers; moderate quality though group sizes modest.

Study Details

PMID:16775552
Participants:48
Impact:exercise-induced PC increase attenuated: V −21%, FV −17% after 2 weeks vs placebo; after 1-wk washout V −13%, FV −6%
Trust score:4/5

hematocrit

1 evidences

IV vitamin C given to iron-overloaded hemodialysis patients improved hematologic markers and reduced erythropoietin requirements.

Trust comment: Small clinical cohort with before/after and maintenance phases showing consistent objective hematologic changes, but not a large randomized trial.

Study Details

PMID:11952508
Participants:36
Impact:increase (significant)
Trust score:3/5

weekly rHuEPO dose requirement

1 evidences

IV vitamin C given to iron-overloaded hemodialysis patients improved hematologic markers and reduced erythropoietin requirements.

Trust comment: Small clinical cohort with before/after and maintenance phases showing consistent objective hematologic changes, but not a large randomized trial.

Study Details

PMID:11952508
Participants:36
Impact:decrease (significant)
Trust score:3/5

mutagen sensitivity (bleomycin assay)

1 evidences

A multicenter randomized trial in smokers found no dose-response effect of oral vitamin C on in vitro mutagen sensitivity.

Trust comment: Large randomized multicenter trial with objective endpoints; negative result is likely reliable.

Study Details

PMID:9232342
Participants:228
Impact:no significant change / no dose-response across 0–4 g/day
Trust score:4/5

catheter patency

1 evidences

Randomized study of catheter sealing solutions found vitamin C solution did not prolong central venous catheter patency compared with saline; heparin did prolong patency.

Trust comment: Prospective randomized study with clear outcome measures though limited to catheter placements; conclusion about vitamin C (no effect) is direct and well reported.

Study Details

PMID:12185445
Participants:99
Impact:no prolongation with vitamin C versus sodium chloride (no significant difference)
Trust score:4/5

H. pylori eradication rate

2 evidences

High-dose oral vitamin C (5 g/day for 28 days) did not eradicate H. pylori nor reduce bacterial load in treated patients.

Trust comment: Randomized, double-blind placebo-controlled component present but small sample sizes and negative result; outcome measurement (urea breath test) is objective.

Study Details

PMID:16200253
Participants:46
Impact:0% eradication with vitamin C (Protocol I: 21 patients on vitamin C; Protocol II: 8 patients)
Trust score:3/5

Adding 500 mg daily vitamin C to standard eradication therapy significantly increased H. pylori eradication rates.

Trust comment: Large randomized controlled trial (n=312 randomized; 281 completed) showing a clear, significant effect, though single-center.

Study Details

PMID:19493713
Participants:281
Impact:+29.2 percentage points (78% vs 48.8%; p<0.0001)
Trust score:4/5

adequate bowel cleansing success

1 evidences

Multicenter randomized trial found 1 L PEG with ascorbic acid was non-inferior to sodium picosulfate with magnesium citrate for adequate bowel cleansing and superior for high-quality cleansing, but had slightly lower patient satisfaction.

Trust comment: Well-powered, multicenter randomized controlled trial with registered protocol and objective primary endpoints; high trustworthiness.

Study Details

PMID:36584216
Participants:228
Impact:97.4% (1L PEG+ascorbic) vs. 97.3% (PICO) — non-inferior
Trust score:5/5

high-quality bowel cleansing

1 evidences

Multicenter randomized trial found 1 L PEG with ascorbic acid was non-inferior to sodium picosulfate with magnesium citrate for adequate bowel cleansing and superior for high-quality cleansing, but had slightly lower patient satisfaction.

Trust comment: Well-powered, multicenter randomized controlled trial with registered protocol and objective primary endpoints; high trustworthiness.

Study Details

PMID:36584216
Participants:228
Impact:87% vs. 77% (1L PEG+ascorbic vs PICO), ~+10%, p=0.05
Trust score:5/5

patient satisfaction (taste/overall)

1 evidences

Multicenter randomized trial found 1 L PEG with ascorbic acid was non-inferior to sodium picosulfate with magnesium citrate for adequate bowel cleansing and superior for high-quality cleansing, but had slightly lower patient satisfaction.

Trust comment: Well-powered, multicenter randomized controlled trial with registered protocol and objective primary endpoints; high trustworthiness.

Study Details

PMID:36584216
Participants:228
Impact:lower with 1L PEG+ascorbic (taste 7.05 vs 7.74; overall satisfaction 7.60 vs 8.12)
Trust score:5/5

wrinkle severity

2 evidences

Topical THDA combined with acetyl zingerone reduced wrinkles, pigment intensity, and redness more than THDA alone over 8 weeks.

Trust comment: Double-blind randomized controlled trial with objective measures and reported p-values, moderate sample size (n=44).

Study Details

PMID:38525606
Participants:44
Impact:THDA+AZ: -0.75% (W4) and -3.72% (W8) vs THDA which showed +7.88% (W4) and +4.48% (W8)
Trust score:4/5

Applying a topical serum containing vitamin C (with vitamin E and ferulic acid) after microneedle RF produced greater wrinkle reduction, higher global improvement ratings, and increased elastin on histology versus placebo.

Trust comment: Prospective double-blind split-neck RCT with objective and histologic endpoints but small sample (n=31).

Study Details

PMID:40464749
Participants:31
Impact:29.9% vs 18.0% reduction (antioxidant side vs placebo; significant)
Trust score:4/5

facial pigment intensity

1 evidences

Topical THDA combined with acetyl zingerone reduced wrinkles, pigment intensity, and redness more than THDA alone over 8 weeks.

Trust comment: Double-blind randomized controlled trial with objective measures and reported p-values, moderate sample size (n=44).

Study Details

PMID:38525606
Participants:44
Impact:THDA+AZ: -4.10% (W8) vs THDA: -0.69% (W8)
Trust score:4/5

facial redness/erythema

1 evidences

Topical THDA combined with acetyl zingerone reduced wrinkles, pigment intensity, and redness more than THDA alone over 8 weeks.

Trust comment: Double-blind randomized controlled trial with objective measures and reported p-values, moderate sample size (n=44).

Study Details

PMID:38525606
Participants:44
Impact:THDA+AZ: -3.73% (W4) and -14.25% (W8) vs THDA: +27.5% (W4) and +8.34% (W8)
Trust score:4/5

LDL oxidation susceptibility

1 evidences

Combined vitamin E and C supplementation reduced LDL oxidation susceptibility in smokers and non-smokers.

Trust comment: Double-blind randomized study in humans showing large antioxidant effects, but effect is from combined E+C supplementation and sample size is small.

Study Details

PMID:15916166
Participants:30
Impact:decreased by 41.3% in smokers and by 54.4% in non-smokers versus placebo after 30 days of vitamins E+C
Trust score:3/5

antioxidant capacity (FRAP)

1 evidences

Dietary changes (and mate tea) increased vitamin C intake and were associated with higher antioxidant capacity and glutathione in dyslipidemic subjects.

Trust comment: Randomized clinical trial with dietary interventions showing associations between increased vitamin C intake and antioxidant markers, but effects are from diet/tea interventions rather than isolated vitamin C supplementation.

Study Details

PMID:22578980
Participants:74
Impact:significant increase in all groups; increase correlated with higher vitamin C intake
Trust score:3/5

lipid hydroperoxide (LOOH)

1 evidences

Dietary changes (and mate tea) increased vitamin C intake and were associated with higher antioxidant capacity and glutathione in dyslipidemic subjects.

Trust comment: Randomized clinical trial with dietary interventions showing associations between increased vitamin C intake and antioxidant markers, but effects are from diet/tea interventions rather than isolated vitamin C supplementation.

Study Details

PMID:22578980
Participants:74
Impact:LOOH inversely correlated with vitamin C intake (higher vitamin C associated with lower LOOH)
Trust score:3/5

TNF-alpha production by PBMCs

1 evidences

Combined vitamin C and E increased certain immune cell cytokine outputs more than either vitamin alone in healthy adults.

Trust comment: Controlled supplementation study with clear outcomes but small group sizes (n=10 per arm) and single-blind design.

Study Details

PMID:8942423
Participants:30
Impact:increased (significantly higher with vitamins C+E vs vitamin C or E alone, P<0.05)
Trust score:3/5

IL-1 beta production by PBMCs

1 evidences

Combined vitamin C and E increased certain immune cell cytokine outputs more than either vitamin alone in healthy adults.

Trust comment: Controlled supplementation study with clear outcomes but small group sizes (n=10 per arm) and single-blind design.

Study Details

PMID:8942423
Participants:30
Impact:increased (significantly higher with vitamins C+E vs vitamin C or E alone, P<0.05)
Trust score:3/5

baroreceptor sensitivity (BRS)

1 evidences

In CHF patients, an acute IV dose of vitamin C improved baroreceptor sensitivity, but chronic oral vitamin C did not.

Trust comment: Well-powered clinical study with randomized acute and chronic arms; clear physiological outcome but some subgrouping complexity.

Study Details

PMID:12549975
Participants:144
Impact:acute IV vitamin C: +24% improvement (~+1.8 mmHg/ms, P<0.05); chronic oral vitamin C: no improvement
Trust score:4/5

24 h urinary oxalate excretion

1 evidences

High-dose vitamin C (1000 mg twice daily) increased urinary oxalate and stone-risk markers in a subset of participants.

Trust comment: Randomized crossover, controlled metabolic-unit study with measured dietary control and objective urinary endpoints.

Study Details

PMID:15987848
Participants:48
Impact:increase in 40% of participants (responders defined as >10% increase)
Trust score:4/5

blood-lead level

1 evidences

In smokers, daily 1000 mg vitamin C raised blood vitamin C and produced a large (81%) drop in blood lead after one week; 200 mg had no effect on lead.

Trust comment: Randomized 3-arm trial with clear, large effect for 1000 mg group though limited to healthy young male smokers and short follow-up.

Study Details

PMID:10204833
Participants:75
Impact:-81% (1000 mg/day after 1 week); no change with 200 mg/day
Trust score:4/5

palatability of halogen-disinfected water

1 evidences

Blinded randomized tasting study: iodine-based disinfectant (TGHP) worsened water taste, but adding ascorbic acid restored palatability to near plain water.

Trust comment: Blinded randomized sensory study with adequate sample size and clear effects on taste/preference.

Study Details

PMID:22137863
Participants:60
Impact:improved to similar preference as distilled water (TGHP+ascorbic and CD+ascorbic rated best); TGHP alone ranked least pleasant by 58%
Trust score:4/5

plasma antioxidant capacity (ACP)

1 evidences

In young adults, 500 mg vitamin C daily increased plasma antioxidant capacity (ACP) by ~25% at 4 h, ~32% at 24 h, and ~36% after 7 days.

Trust comment: Randomized multi-arm trial with repeated measures showing dose/time effects on ACP, though short duration and young healthy cohort.

Study Details

PMID:17526461
Participants:79
Impact:+25% (4 h), +32% (24 h), +36% (7 d) with 500 mg/day vitamin C
Trust score:4/5

plasma malondialdehyde

3 evidences

Daily 250 mg vitamin C for six weeks reduced monocyte adhesion in subjects with low baseline vitamin C to levels seen in those with normal levels.

Trust comment: Randomized double-blind crossover with objective ex vivo assay and adequate sample for the endpoints reported.

Study Details

PMID:12074599
Participants:40
Impact:no change
Trust score:4/5

Perioperative supplementation with n-3 PUFAs plus vitamins C and E reduced postoperative atrial fibrillation more in older patients and increased atrial glutathione peroxidase activity in those >60 years.

Trust comment: Randomized double-blind design and moderate size, but vitamin C was combined with other agents (n-3 PUFAs and vitamin E), so isolated vitamin C effects cannot be determined.

Study Details

PMID:22561296
Participants:152
Impact:no clear decrease reported
Trust score:3/5

In young adults, 500 mg vitamin C daily increased plasma antioxidant capacity (ACP) by ~25% at 4 h, ~32% at 24 h, and ~36% after 7 days.

Trust comment: Randomized multi-arm trial with repeated measures showing dose/time effects on ACP, though short duration and young healthy cohort.

Study Details

PMID:17526461
Participants:79
Impact:measured but specific change vs baseline not specified in excerpt; overall ACP increase reported
Trust score:4/5

visual acuity (VA)

1 evidences

In a double-masked RCT of vitamins C (500 mg) plus E, visual acuity was better at 56 days in the vitamin group, but laser flare (inflammation marker) showed no significant difference over time.

Trust comment: Well-conducted double-masked RCT (n=145) but vitamins C and E were given together, so effects cannot be attributed to vitamin C alone.

Study Details

PMID:10535857
Participants:145
Impact:significantly better in vitamin group at 56 days (p=0.01)
Trust score:4/5

laser flare (cell/flare measurement)

1 evidences

In a double-masked RCT of vitamins C (500 mg) plus E, visual acuity was better at 56 days in the vitamin group, but laser flare (inflammation marker) showed no significant difference over time.

Trust comment: Well-conducted double-masked RCT (n=145) but vitamins C and E were given together, so effects cannot be attributed to vitamin C alone.

Study Details

PMID:10535857
Participants:145
Impact:no significant effect over time (p=0.53)
Trust score:4/5

self-reported adherence

1 evidences

Adults asked to take one vitamin C pill daily for a month showed large self-reported adherence increases in both groups; text reminders correlated with fewer missed pills but between-group difference was not significant.

Trust comment: Small unblinded RCT relying on self-reported adherence with limited power, so results are suggestive but inconclusive.

Study Details

PMID:18778967
Participants:102
Impact:increased by 246% (intervention) vs 131% (control); between-group difference non-significant
Trust score:3/5

pills missed (last week)

1 evidences

Adults asked to take one vitamin C pill daily for a month showed large self-reported adherence increases in both groups; text reminders correlated with fewer missed pills but between-group difference was not significant.

Trust comment: Small unblinded RCT relying on self-reported adherence with limited power, so results are suggestive but inconclusive.

Study Details

PMID:18778967
Participants:102
Impact:intervention 2.5/7 vs control 3.3/7 (difference 0.8, non-significant); acknowledgements correlated with fewer missed pills (r=-0.352, p=0.01)
Trust score:3/5

LDL oxidation lag phase (susceptibility to oxidation)

1 evidences

In a 12-week double-blind RCT of combined antioxidant doses including vitamin C, high-dose antioxidants markedly increased LDL oxidation lag phase (reduced LDL susceptibility to oxidation) with a dose-response effect.

Trust comment: Double-blind placebo-controlled RCT measuring a biochemical surrogate (n=45); combined antioxidant intervention means vitamin C's isolated effect is unclear.

Study Details

PMID:9247510
Participants:45
Impact:increased from 190.1 to 391.1 min in high-dose group (p<0.01); dose-response trend across groups (p=0.004)
Trust score:4/5

hemoglobin (Hb)

4 evidences

Randomized blind clinical study in preschool children testing water fortification with iron+ascorbic acid, ascorbic acid alone, or plain water over 3 months; hemoglobin rose in all groups, MCV improved with iron+ascorbic and with ascorbic alone, ferritin increased only with iron+ascorbic.

Trust comment: Randomized blinded clinical trial in children with clear hematologic outcomes and moderate sample size, although duration was short (3 months).

Study Details

PMID:23963460
Participants:153
Impact:increased within all three groups; difference between timepoints significant between A (iron+ascorbic) and B (ascorbic) for Hb
Trust score:4/5

Hemodialysis patients receiving 300 mg IV vitamin C each session for 3 months showed improved hemoglobin and transferrin saturation and reduced reticulocyte hemoglobin content and serum ferritin compared with standard care.

Trust comment: Small clinical intervention in hemodialysis patients with measurable improvements, but randomization and full trial details are unclear from the summary.

Study Details

PMID:18974579
Participants:46
Impact:significant increase after 3 months in vitamin C group (p<0.05)
Trust score:3/5

Daily baobab fruit pulp (rich in vitamin C) given with a school meal for 83 days produced a small increase in hemoglobin and smaller declines in ferritin versus control, but differences were not statistically significant.

Trust comment: Randomized, single-blind trial with appropriate biochemical outcomes but small, underpowered sample and variable vitamin C content limit confidence.

Study Details

PMID:33355689
Participants:58
Impact:+2.2% (intervention mean change baseline→endline); control -1.2% (no significant between-group difference)
Trust score:3/5

In hemodialysis patients with refractory anemia, intravenous vitamin C (300 mg each dialysis) improved hemoglobin and iron availability and reduced inflammation markers over 6 months.

Trust comment: Randomized but open-label and moderate sample size; objective lab endpoints supportive but potential bias from unblinded design.

Study Details

PMID:16564942
Participants:41
Impact:+1.2 g/dL (9.3 → 10.5 g/dL) in vitamin C group at 6 months
Trust score:3/5

brachial artery flow-mediated dilation

1 evidences

Vitamin C 500 mg/day for 4 weeks increased brachial flow-mediated dilation but did not change lipids or inflammatory markers.

Trust comment: Randomized crossover in CAD patients with small sample and vitamin C used as active control; moderate confidence.

Study Details

PMID:16140428
Participants:31
Impact:+3.17% (P=0.0003)
Trust score:3/5

circulating inflammatory markers

1 evidences

Vitamin C 500 mg/day for 4 weeks increased brachial flow-mediated dilation but did not change lipids or inflammatory markers.

Trust comment: Randomized crossover in CAD patients with small sample and vitamin C used as active control; moderate confidence.

Study Details

PMID:16140428
Participants:31
Impact:no change
Trust score:3/5

sperm DNA fragmentation (%)

1 evidences

Daily 1 g vitamin C + 1 g vitamin E for 2 months markedly reduced sperm DNA fragmentation in men with elevated baseline levels.

Trust comment: Randomized placebo-controlled trial in target population with clear, statistically significant primary endpoint.

Study Details

PMID:15867002
Participants:64
Impact:-13 percentage points (22.1% → 9.1%, P<0.001; ≈-59% relative)
Trust score:4/5

basic sperm parameters

1 evidences

Daily 1 g vitamin C + 1 g vitamin E for 2 months markedly reduced sperm DNA fragmentation in men with elevated baseline levels.

Trust comment: Randomized placebo-controlled trial in target population with clear, statistically significant primary endpoint.

Study Details

PMID:15867002
Participants:64
Impact:no change
Trust score:4/5

peak expiratory flow (PEF)

1 evidences

Ascorbic acid 250 mg/day for 6 weeks improved peak expiratory flow in adults ≥35 years, while most other lung measures were unchanged.

Trust comment: Randomized pilot RCT with small arms (n=15 per arm); findings preliminary but plausible.

Study Details

PMID:34914338
Participants:45
Impact:increase (P=0.049) in AA250 arm vs baseline
Trust score:3/5

% predicted PEF

1 evidences

Ascorbic acid 250 mg/day for 6 weeks improved peak expiratory flow in adults ≥35 years, while most other lung measures were unchanged.

Trust comment: Randomized pilot RCT with small arms (n=15 per arm); findings preliminary but plausible.

Study Details

PMID:34914338
Participants:45
Impact:increase (P=0.026) in AA250 arm vs baseline
Trust score:3/5

FEV1, FVC and most pulmonary functions

1 evidences

Ascorbic acid 250 mg/day for 6 weeks improved peak expiratory flow in adults ≥35 years, while most other lung measures were unchanged.

Trust comment: Randomized pilot RCT with small arms (n=15 per arm); findings preliminary but plausible.

Study Details

PMID:34914338
Participants:45
Impact:no significant change
Trust score:3/5

plasma alpha-tocopherol and alpha/gamma-tocopherol ratio

1 evidences

Three-month moderate-dose vitamin supplementation (including 272 mg vitamin C) repleted plasma ascorbic acid in smokers and raised plasma vitamin E markers.

Trust comment: Double-blind placebo-controlled design with matched dietary data and adequate sample size supports credibility.

Study Details

PMID:10648268
Participants:75
Impact:increase with supplementation (P<0.05)
Trust score:4/5

plasma carotenoids

1 evidences

Three-month moderate-dose vitamin supplementation (including 272 mg vitamin C) repleted plasma ascorbic acid in smokers and raised plasma vitamin E markers.

Trust comment: Double-blind placebo-controlled design with matched dietary data and adequate sample size supports credibility.

Study Details

PMID:10648268
Participants:75
Impact:no significant change attributed to smoking after dietary matching
Trust score:4/5

cardiac index (hemodynamics)

1 evidences

In septic shock patients, IV antioxidant therapy including vitamin C raised vitamin C levels and improved some hemodynamic measures.

Trust comment: Small randomized clinical study but used combination antioxidant therapy (ascorbate + others), so vitamin C–specific effects are confounded.

Study Details

PMID:9296454
Participants:30
Impact:increase at 60 and 120 min (significant)
Trust score:3/5

plasma total nitrite

1 evidences

In septic shock patients, IV antioxidant therapy including vitamin C raised vitamin C levels and improved some hemodynamic measures.

Trust comment: Small randomized clinical study but used combination antioxidant therapy (ascorbate + others), so vitamin C–specific effects are confounded.

Study Details

PMID:9296454
Participants:30
Impact:increase (significant, p=0.007)
Trust score:3/5

monocyte–endothelial adhesion

1 evidences

Daily 250 mg vitamin C for six weeks reduced monocyte adhesion in subjects with low baseline vitamin C to levels seen in those with normal levels.

Trust comment: Randomized double-blind crossover with objective ex vivo assay and adequate sample for the endpoints reported.

Study Details

PMID:12074599
Participants:40
Impact:decrease 37% in low-baseline group (significant, P<0.02)
Trust score:4/5

vaginal pH

1 evidences

Local vaginal application of 250 mg vitamin C devices lowered and maintained vaginal pH in women with high baseline pH.

Trust comment: Randomized, double-blind, controlled study with clear primary outcome, though sample size is modest.

Study Details

PMID:16723311
Participants:39
Impact:decrease to normal range after first application and maintained over 6 days
Trust score:4/5

acceptability/tolerability

1 evidences

Local vaginal application of 250 mg vitamin C devices lowered and maintained vaginal pH in women with high baseline pH.

Trust comment: Randomized, double-blind, controlled study with clear primary outcome, though sample size is modest.

Study Details

PMID:16723311
Participants:39
Impact:rated very good/good in most participants
Trust score:4/5

24-hour fluid infusion volume

1 evidences

High-dose IV ascorbic acid during the first 24 hours after major burns reduced fluid needs, edema/weight gain, and duration of mechanical ventilation.

Trust comment: Prospective randomized trial in a critical care setting with objective clinical endpoints, though single-center and modest sample.

Study Details

PMID:10722036
Participants:37
Impact:reduced from 5.5±3.1 to 3.0±1.7 mL/kg per %burn (P<.01)
Trust score:4/5

percent weight gain (edema)

1 evidences

High-dose IV ascorbic acid during the first 24 hours after major burns reduced fluid needs, edema/weight gain, and duration of mechanical ventilation.

Trust comment: Prospective randomized trial in a critical care setting with objective clinical endpoints, though single-center and modest sample.

Study Details

PMID:10722036
Participants:37
Impact:reduced: 9.2%±8.2 vs 17.8%±6.9 (ascorbic acid vs control)
Trust score:4/5

age-related maculopathy incidence

1 evidences

In male physicians, vitamin C supplement use was not associated with a reduced risk of age-related maculopathy.

Trust comment: Large prospective cohort with long follow-up but observational design limits causal inference.

Study Details

PMID:10067908
Participants:21120
Impact:no significant effect (RR=1.03, 95% CI 0.71–1.50)
Trust score:3/5

urinary nicotine metabolites (cotinine equivalents)

1 evidences

Oral vitamin C increased blood levels and dose-dependently reduced urinary nicotine metabolite excretion in smokers.

Trust comment: Randomized group allocation and clear biomarker changes, but moderate sample size and short duration limit generalizability.

Study Details

PMID:10600424
Participants:75
Impact:decreased ~5% weekly with 200 mg/day and ~33% weekly with 1000 mg/day; strong negative correlation with serum AA (r=-0.798)
Trust score:3/5

plasma lipoprotein(a) (Lp[a])

1 evidences

High-dose vitamin C (4.5 g/day) did not significantly lower plasma Lp(a) in patients with premature coronary heart disease.

Trust comment: Randomized double-blind trial but modest sample size and short duration for lipid outcomes.

Study Details

PMID:7479198
Participants:44
Impact:no significant change (no clinically important lowering; p=0.39)
Trust score:3/5

nasal lavage ascorbate (RTLF)

1 evidences

Oral vitamin C increased plasma and urinary ascorbate in a dose-dependent manner; nasal lavage (RTLF) ascorbate showed an acute rise after a high (1000 mg) dose peaking at 2–4 h but returned to baseline by 24 h.

Trust comment: Double-blind crossover switching study in 24 healthy subjects with direct biochemical measures; modest sample but solid design.

Study Details

PMID:19009458
Participants:24
Impact:transient increase 2–4 h after 1000 mg; returned to baseline by 24 h
Trust score:4/5

urinary ascorbate excretion

1 evidences

Oral vitamin C increased plasma and urinary ascorbate in a dose-dependent manner; nasal lavage (RTLF) ascorbate showed an acute rise after a high (1000 mg) dose peaking at 2–4 h but returned to baseline by 24 h.

Trust comment: Double-blind crossover switching study in 24 healthy subjects with direct biochemical measures; modest sample but solid design.

Study Details

PMID:19009458
Participants:24
Impact:+increased with dose
Trust score:4/5

erythrocyte malondialdehyde (MDA)

1 evidences

Patients with chronic bacterial prostatitis had lower plasma vitamin C and antioxidant enzymes and higher oxidative-damage markers than healthy controls.

Trust comment: Case-control biochemical study with adequate sample size but observational design limits causal inference.

Study Details

PMID:16625281
Participants:140
Impact:↑ in chronic bacterial prostatitis patients vs healthy volunteers
Trust score:3/5

postoperative atrial fibrillation incidence

6 evidences

Perioperative supplementation with n-3 PUFAs plus vitamins C and E reduced postoperative atrial fibrillation more in older patients and increased atrial glutathione peroxidase activity in those >60 years.

Trust comment: Randomized double-blind design and moderate size, but vitamin C was combined with other agents (n-3 PUFAs and vitamin E), so isolated vitamin C effects cannot be determined.

Study Details

PMID:22561296
Participants:152
Impact:decreased (effect more marked in patients >60 years)
Trust score:3/5

Supplementation with n‑3 PUFAs plus vitamins C (1 g/day) and E reduced post‑operative atrial fibrillation and increased cardiac antioxidant enzyme activity.

Trust comment: Large randomized trial with a clear clinical endpoint, but intervention combined n‑3 PUFA with vitamins C and E so effects cannot be ascribed to vitamin C alone.

Study Details

PMID:23916928
Participants:203
Impact:Reduced from 32% (placebo) to 9.7% (supplemented); absolute −22.3 percentage points (p<0.001)
Trust score:4/5

Adding oral vitamin C around surgery greatly reduced postoperative atrial fibrillation compared with controls on beta-blockers alone.

Trust comment: Prospective randomized trial (50 vs 50) with a large, clinically meaningful reduction in atrial fibrillation incidence.

Study Details

PMID:17948074
Participants:100
Impact:-22 percentage points (4% vs 26%; P = 0.002)
Trust score:4/5

Perioperative oral ascorbic acid did not significantly reduce the incidence or timing of postoperative atrial fibrillation after on-pump CABG.

Trust comment: Prospective randomized single-center trial with adequate sample size for a surgical population; negative result reported with appropriate statistics.

Study Details

PMID:26917198
Participants:105
Impact:no significant difference (13.5% vs 18.9%, p=0.314)
Trust score:4/5

Randomized, triple‑blind trial of perioperative ascorbic acid vs placebo in CABG patients; monitored postoperative atrial fibrillation and complications.

Trust comment: Randomized, triple‑blind trial with adequate sample and clear clinical endpoints; well‑reported negative finding.

Study Details

PMID:23022248
Participants:185
Impact:no difference (30.3% treatment vs 30.2% control)
Trust score:4/5

Perioperative vitamin C supplementation reduced incidence of postoperative atrial fibrillation and shortened hospital and ICU stays compared with control.

Trust comment: Randomized single-center pilot with adequate sample but limited by single-center design and being a pilot study.

Study Details

PMID:21098510
Participants:170
Impact:44.7% vs 61.2% (vitamin C vs control), absolute reduction 16.5 percentage points, P=0.041
Trust score:3/5

time to atrial fibrillation occurrence

1 evidences

Perioperative oral ascorbic acid did not significantly reduce the incidence or timing of postoperative atrial fibrillation after on-pump CABG.

Trust comment: Prospective randomized single-center trial with adequate sample size for a surgical population; negative result reported with appropriate statistics.

Study Details

PMID:26917198
Participants:105
Impact:no significant difference
Trust score:4/5

plasma malondialdehyde (MDA)

5 evidences

Isoflavone supplementation reduced homocysteine and some resting oxidative markers but did not change plasma vitamin C or prevent exercise-induced oxidative stress.

Trust comment: Randomized trial with clear biochemical endpoints but small N and the intervention was isoflavones, not vitamin C.

Study Details

PMID:15735366
Participants:30
Impact:decreased pre-exercise (p < 0.05) but exercise-induced rise not prevented
Trust score:3/5

In smoking men, 2-month ascorbic acid (500 mg/day) raised plasma vitamin C but did not improve lipoprotein oxidation resistance and plain ascorbate was associated with increased MDA.

Trust comment: Randomized, placebo-controlled trial with 59 completers in relevant human population (smokers), though single-blind and limited to biochemical endpoints.

Study Details

PMID:9076405
Participants:59
Impact:increased in plain ascorbate vs placebo (P<0.05)
Trust score:4/5

Women with endometriosis taking combined vitamins C and E had lower oxidative stress markers over months, but pregnancy rates did not improve.

Trust comment: Small clinical study in humans showing biomarker changes but co-supplementation with vitamin E and low sample size limit attribution to vitamin C alone.

Study Details

PMID:18005966
Participants:34
Impact:decreased (significant by month 4)
Trust score:3/5

Daily antioxidant supplement (included ascorbic acid) given to children, young and elderly improved oxidative markers and erythrocyte membrane fluidity in young/elderly but not children.

Trust comment: Randomized human groups and clear biomarker changes, but Vitamin C was given as part of a multi-nutrient mix so effects cannot be attributed to Vitamin C alone.

Study Details

PMID:21736780
Participants:255
Impact:decreased (young & elderly; significant); no change in children
Trust score:3/5

In women using oral contraceptives, combined low-dose vitamin C and E supplementation decreased lipid peroxidation (MDA) and increased GPx and GR activities.

Trust comment: Reasonable sample and biochemical endpoints but combined vitamin intervention (C+E) prevents isolation of vitamin C-specific effects.

Study Details

PMID:22494786
Participants:120
Impact:significant decrease
Trust score:3/5

satisfactory bowel cleansing (Aronchick score 1+2)

1 evidences

Bowel prep containing ascorbic acid (PEGA) produced high satisfactory cleansing rates, especially with split-dose; tolerability was similar across groups.

Trust comment: Randomised multicentre study with large N and objective outcome measures; open-label design lowers blinding robustness.

Study Details

PMID:31398987
Participants:558
Impact:split-dose SIR 95.6%, split-dose PEGA 86.2% vs SPMC 72.5%
Trust score:4/5

preparation quality (single-dose)

1 evidences

Bowel prep containing ascorbic acid (PEGA) produced high satisfactory cleansing rates, especially with split-dose; tolerability was similar across groups.

Trust comment: Randomised multicentre study with large N and objective outcome measures; open-label design lowers blinding robustness.

Study Details

PMID:31398987
Participants:558
Impact:comparable between groups
Trust score:4/5

tolerability/complaints

1 evidences

Bowel prep containing ascorbic acid (PEGA) produced high satisfactory cleansing rates, especially with split-dose; tolerability was similar across groups.

Trust comment: Randomised multicentre study with large N and objective outcome measures; open-label design lowers blinding robustness.

Study Details

PMID:31398987
Participants:558
Impact:no major differences reported on 5-point scale
Trust score:4/5

pigmentation index

1 evidences

Topical 10% L-ascorbic acid plus phytic acid serum lightened solar lentigines more than vehicle and was generally well tolerated.

Trust comment: Double-blind, vehicle-controlled randomized trial but small sample limits generalizability.

Study Details

PMID:22151934
Participants:30
Impact:maximum reduction 1.3 at 3 months (significant vs vehicle M1–M4, P≤0.003)
Trust score:4/5

brightness (L*)

1 evidences

Topical 10% L-ascorbic acid plus phytic acid serum lightened solar lentigines more than vehicle and was generally well tolerated.

Trust comment: Double-blind, vehicle-controlled randomized trial but small sample limits generalizability.

Study Details

PMID:22151934
Participants:30
Impact:statistically significant improvement at follow-up (M5) vs vehicle
Trust score:4/5

adverse events/tolerability

3 evidences

Non-hospitalized adults with COVID-19/covid-like illness received melatonin, zinc and multivitamins (including vitamin D) or placebo; the supplement arm had faster symptom resolution by days 5 and 10.

Trust comment: Well-conducted multicenter double-blind RCT with adequate sample size, but intervention is multi-component so effects cannot be attributed to vitamin C alone.

Study Details

PMID:37419768
Participants:163
Impact:treatment well tolerated; no severe adverse events reported
Trust score:3/5

Topical 10% L-ascorbic acid plus phytic acid serum lightened solar lentigines more than vehicle and was generally well tolerated.

Trust comment: Double-blind, vehicle-controlled randomized trial but small sample limits generalizability.

Study Details

PMID:22151934
Participants:30
Impact:15 subjects had 23 AEs; 6 possibly related; 6 mild–moderate intolerance in treatment group
Trust score:4/5

2-L PEG with ascorbic acid and sodium picosulfate/magnesium citrate had similar overall cleansing; the SP/MC regimen had better tolerability and fewer adverse events.

Trust comment: Randomized controlled trial but vitamin C functions as part of a bowel-prep formulation rather than as an isolated supplement.

Study Details

PMID:29497812
Participants:223
Impact:PEG/Asc had higher total adverse events (62.4%) vs SP/MC (47.4%); SP/MC better tolerated
Trust score:3/5

plasma MDA (lipid peroxidation)

1 evidences

Pre-exercise oral ascorbic acid acutely reduced postexercise MDA but over 3 months supplementation produced no consistent changes in oxidative stress markers or metabolic profile.

Trust comment: Moderate-sized randomized assignment with objective markers but limited power and mixed acute vs long-term results.

Study Details

PMID:26789096
Participants:46
Impact:postexercise MDA increased overall; AA pre-exercise decreased MDA significantly (P<0.05); after 3 months no group differences
Trust score:3/5

total antioxidant status (TAS)

2 evidences

Pre-exercise oral ascorbic acid acutely reduced postexercise MDA but over 3 months supplementation produced no consistent changes in oxidative stress markers or metabolic profile.

Trust comment: Moderate-sized randomized assignment with objective markers but limited power and mixed acute vs long-term results.

Study Details

PMID:26789096
Participants:46
Impact:no significant change
Trust score:3/5

Cross‑sectional study found vegetarians had higher plasma antioxidant status and higher plasma vitamin C (statistically significant) and lower LDL TBARS compared with nonvegetarians.

Trust comment: Small cross‑sectional human study (n=38) with clear biochemical measures; associations are plausible but limited by sample size and observational design.

Study Details

PMID:9895420
Participants:38
Impact:Increased plasma TAS in vegetarians (statistically significant)
Trust score:3/5

antioxidant enzyme activities (SOD, GPx, catalase)

1 evidences

Pre-exercise oral ascorbic acid acutely reduced postexercise MDA but over 3 months supplementation produced no consistent changes in oxidative stress markers or metabolic profile.

Trust comment: Moderate-sized randomized assignment with objective markers but limited power and mixed acute vs long-term results.

Study Details

PMID:26789096
Participants:46
Impact:minor, inconsistent reductions associated with AA (P<0.05)
Trust score:3/5

clinical pregnancy rate

1 evidences

High-dose oral vitamin C during the luteal phase did not improve clinical pregnancy or implantation rates in women undergoing IVF.

Trust comment: Large randomized, double-blind, placebo-controlled trial with adequate sample size and consistent null results for primary outcomes.

Study Details

PMID:12036083
Participants:620
Impact:no difference between ascorbic acid (1, 5, 10 g/day) and placebo
Trust score:5/5

implantation rate

1 evidences

High-dose oral vitamin C during the luteal phase did not improve clinical pregnancy or implantation rates in women undergoing IVF.

Trust comment: Large randomized, double-blind, placebo-controlled trial with adequate sample size and consistent null results for primary outcomes.

Study Details

PMID:12036083
Participants:620
Impact:no difference between groups
Trust score:5/5

safety/adverse events

2 evidences

High-dose oral vitamin C during the luteal phase did not improve clinical pregnancy or implantation rates in women undergoing IVF.

Trust comment: Large randomized, double-blind, placebo-controlled trial with adequate sample size and consistent null results for primary outcomes.

Study Details

PMID:12036083
Participants:620
Impact:no clinical evidence of benefit or major adverse effects reported
Trust score:5/5

Large randomized trial testing simvastatin and antioxidant vitamin supplementation (including vitamin C) in high-risk patients; early results showed good tolerability and biochemical changes but no specific vitamin C outcomes reported in this early report.

Trust comment: This large RCT directly tested an antioxidant-vitamin regimen that included vitamin C, but the early report did not present vitamin C-specific effects; overall study design is high quality.

Study Details

PMID:10329064
Participants:20536
Impact:no significant differences between vitamin supplement and placebo in early side-effects or elevated liver/muscle enzymes
Trust score:3/5

glomerular filtration rate (GFR)

1 evidences

High-dose vitamin C for 4 weeks did not change kidney filtration measures in male type 1 diabetes patients.

Trust comment: Double-blind randomized placebo-controlled trial but small, all-male sample and short (4-week) duration.

Study Details

PMID:7624737
Participants:24
Impact:-7 ml·min⁻¹·1.73 m⁻² (141 → 134), not significant
Trust score:4/5

effective renal plasma flow (ERPF)

1 evidences

High-dose vitamin C for 4 weeks did not change kidney filtration measures in male type 1 diabetes patients.

Trust comment: Double-blind randomized placebo-controlled trial but small, all-male sample and short (4-week) duration.

Study Details

PMID:7624737
Participants:24
Impact:-39 ml·min⁻¹·1.73 m⁻² (584 → 545), trend to decline (p≈0.06)
Trust score:4/5

filtration fraction (FF)

1 evidences

High-dose vitamin C for 4 weeks did not change kidney filtration measures in male type 1 diabetes patients.

Trust comment: Double-blind randomized placebo-controlled trial but small, all-male sample and short (4-week) duration.

Study Details

PMID:7624737
Participants:24
Impact:unchanged (0.244 → 0.246), not significant
Trust score:4/5

gingival pigmentation (L* value)

1 evidences

Topical ascorbic acid (AS-G gel) lightened gingival melanin pigmentation versus placebo over 12 weeks.

Trust comment: Double-masked split-mouth clinical trial with a reasonable sample (n=73) and objective spectrophotometry outcome.

Study Details

PMID:19186973
Participants:73
Impact:increased lightness (relative change vs placebo) significant after 4 weeks
Trust score:4/5

soluble transferrin receptor (TfR)

1 evidences

Ascorbic acid status/IV treatment was associated with lower soluble transferrin receptor levels and higher transferrin saturation in hemodialysis patients.

Trust comment: Moderate-sized study but design and intervention details unclear in the excerpt (observational vs interventional not fully specified).

Study Details

PMID:15339999
Participants:138
Impact:decreased (significant)
Trust score:3/5

transferrin saturation (TSAT)

3 evidences

Ascorbic acid status/IV treatment was associated with lower soluble transferrin receptor levels and higher transferrin saturation in hemodialysis patients.

Trust comment: Moderate-sized study but design and intervention details unclear in the excerpt (observational vs interventional not fully specified).

Study Details

PMID:15339999
Participants:138
Impact:increased (significant)
Trust score:3/5

In hemodialysis patients with refractory anemia, intravenous vitamin C (300 mg each dialysis) improved hemoglobin and iron availability and reduced inflammation markers over 6 months.

Trust comment: Randomized but open-label and moderate sample size; objective lab endpoints supportive but potential bias from unblinded design.

Study Details

PMID:16564942
Participants:41
Impact:+8.4 percentage points (28.9% → 37.3%)
Trust score:3/5

In 62 CKD patients randomized to three oral iron therapies, the group receiving ferric sodium EDTA combined with vitamin C and other micronutrients showed larger improvements in hemoglobin and iron parameters and reductions in inflammatory markers.

Trust comment: Randomized multicenter study with objective labs, but open-label design and multi-nutrient combination prevent attributing effects to vitamin C alone.

Study Details

PMID:35631257
Participants:62
Impact:+16.77% (Group 2, 6 months)
Trust score:3/5

cisplatin nephrotoxicity

1 evidences

Daily supplementation with vitamin C, vitamin E and selenium did not reduce cisplatin-induced nephrotoxicity or ototoxicity overall, though higher plasma antioxidant levels correlated with less high-tone hearing loss.

Trust comment: Randomized double-blind trial but small sample and possible compliance/inadequate dosing issues reduce confidence in null result.

Study Details

PMID:15251161
Participants:48
Impact:no significant difference with supplementation
Trust score:3/5

cisplatin ototoxicity (high-tone hearing loss)

1 evidences

Daily supplementation with vitamin C, vitamin E and selenium did not reduce cisplatin-induced nephrotoxicity or ototoxicity overall, though higher plasma antioxidant levels correlated with less high-tone hearing loss.

Trust comment: Randomized double-blind trial but small sample and possible compliance/inadequate dosing issues reduce confidence in null result.

Study Details

PMID:15251161
Participants:48
Impact:no overall difference; less loss in subgroup with highest plasma antioxidant levels
Trust score:3/5

Heart rate

1 evidences

In children undergoing outpatient pin removal, acetaminophen or ibuprofen did not reduce pain compared with placebo (vitamin C used as placebo).

Trust comment: Large randomized controlled trial (n=240) with clear outcomes and no effect of the vitamin C placebo on pain or heart rate.

Study Details

PMID:24695927
Participants:240
Impact:no significant difference vs vitamin C placebo
Trust score:4/5

Acetylcholine-mediated endothelial response

1 evidences

In healthy volunteers, single short GTN protected endothelium from I/R injury but protection was lost with prolonged GTN; intra-arterial vitamin C restored acetylcholine-mediated endothelial responses and prevented loss of preconditioning.

Trust comment: Randomized human study with direct vitamin C infusion in a subset showing restoration of endothelial function after nitrate tolerance; moderate sample and clear physiological endpoints.

Study Details

PMID:19933412
Participants:29
Impact:normalized by vitamin C after prolonged GTN (restored endothelial function)
Trust score:4/5

Endothelial preconditioning (protection against I/R)

1 evidences

In healthy volunteers, single short GTN protected endothelium from I/R injury but protection was lost with prolonged GTN; intra-arterial vitamin C restored acetylcholine-mediated endothelial responses and prevented loss of preconditioning.

Trust comment: Randomized human study with direct vitamin C infusion in a subset showing restoration of endothelial function after nitrate tolerance; moderate sample and clear physiological endpoints.

Study Details

PMID:19933412
Participants:29
Impact:single GTN prevented I/R dysfunction; protection lost after 1 week of GTN but restored by vitamin C infusion
Trust score:4/5

HDL cholesterol

5 evidences

Long-term micronutrient supplementation (capsules including 250 mg vitamin C plus vitamin E and selenium) was associated with small increases in total and LDL cholesterol after ~7.3 years.

Trust comment: Large randomized, placebo-controlled factorial trial but the exposure was a combined micronutrient supplement (vitamin C among others), so effects cannot be attributed to vitamin C alone.

Study Details

PMID:17023720
Participants:3411
Impact:no significant effect reported
Trust score:4/5

In a 75-day randomized double-blind trial, vitamin C (and vitamin E) reduced total and LDL cholesterol and raised HDL in healthy adults aged 50+; vitamin C group showed no significant triglyceride change.

Trust comment: Well-designed randomized double-blind placebo-controlled trial (n=120) showing favorable lipid changes with vitamin C, though duration was 75 days and full data detail is limited in abstract.

Study Details

PMID:12841306
Participants:120
Impact:significant increase with vitamin C (vs placebo)
Trust score:4/5

In type 2 diabetic patients, combined mineral (Mg+Zn) plus vitamins C+E increased HDL cholesterol and apolipoprotein A1 over 3 months; Mg+Zn alone showed no significant changes.

Trust comment: Randomized double-blind placebo-controlled human RCT with clear biochemical outcomes but small total sample (n=69) and short duration (3 months).

Study Details

PMID:15163474
Participants:69
Impact:+24% (MV group vs baseline; 50.4 vs 40.6 mg/dl; significant)
Trust score:4/5

An 8-month randomized double-blind placebo-controlled trial (n=138 completers) found no overall effect of 1 g/day vitamin C on HDL, LDL, total cholesterol or triglycerides; a small subgroup (n=43, low baseline AA) showed HDL +0.10 mmol/L.

Trust comment: Large randomized double-blind placebo-controlled trial with 138 completers; overall null primary results and subgroup findings are exploratory.

Study Details

PMID:7728285
Participants:138
Impact:no overall change; subgroup (n=43, baseline AA <55 μmol/L) +0.10 mmol/L (3.8 mg/dL)
Trust score:4/5

A 3-month trial of a polyphenol-rich antioxidant supplement (pomegranate, green tea extracts, plus ascorbic acid) in type 2 diabetics lowered LDL and MDA and increased antioxidant markers compared with placebo.

Trust comment: Placebo-controlled human trial with 114 participants, but multi-ingredient supplement (includes ascorbic acid) prevents attributing effects solely to Vitamin C.

Study Details

PMID:19834314
Participants:114
Impact:increase (statistically significant vs placebo, p<0.001)
Trust score:3/5

cigarette consumption

1 evidences

Smokers who believed they took a dietary supplement smoked more and felt more invulnerable; positive attitudes toward supplements increased this effect.

Trust comment: Randomized between-subjects design with both student and community samples, but behavioral/deception study and effects are reported qualitatively without numeric effect sizes.

Study Details

PMID:21806694
Participants:154
Impact:increased (participants who believed they took a supplement smoked more than controls)
Trust score:3/5

perceived invulnerability

1 evidences

Smokers who believed they took a dietary supplement smoked more and felt more invulnerable; positive attitudes toward supplements increased this effect.

Trust comment: Randomized between-subjects design with both student and community samples, but behavioral/deception study and effects are reported qualitatively without numeric effect sizes.

Study Details

PMID:21806694
Participants:154
Impact:increased (greater perceived invulnerability after supplement cue)
Trust score:3/5

attitudes toward supplements (moderator)

1 evidences

Smokers who believed they took a dietary supplement smoked more and felt more invulnerable; positive attitudes toward supplements increased this effect.

Trust comment: Randomized between-subjects design with both student and community samples, but behavioral/deception study and effects are reported qualitatively without numeric effect sizes.

Study Details

PMID:21806694
Participants:154
Impact:positive attitudes amplified the increase in smoking
Trust score:3/5

LDL/HDL oxidation susceptibility

1 evidences

ESRD patients randomized to 1,000 mg/day vitamin C showed no significant differences versus placebo on lipid profile or lipoprotein oxidation after one year.

Trust comment: Randomized trial in clinical population but small sample and most comparisons were non-significant, limiting confidence in benefits.

Study Details

PMID:15912655
Participants:41
Impact:no significant difference (trend toward decreased oxidation products with vitamin C, not statistically significant)
Trust score:3/5

Global Photodamage Score

1 evidences

A vitamin C (ascorbic acid) microneedle patch reduced crow's-feet wrinkle measures versus control without causing irritation or sensitization.

Trust comment: Double-blind within-subject design showed significant cosmetic effects but sample size was small (n=23 for efficacy).

Study Details

PMID:26648582
Participants:23
Impact:improved (statistically significant improvement vs control)
Trust score:3/5

skin roughness (visiometer R and R2 values)

1 evidences

A vitamin C (ascorbic acid) microneedle patch reduced crow's-feet wrinkle measures versus control without causing irritation or sensitization.

Trust comment: Double-blind within-subject design showed significant cosmetic effects but sample size was small (n=23 for efficacy).

Study Details

PMID:26648582
Participants:23
Impact:reduced roughness; R and R2 values significantly improved (R2 highly significant)
Trust score:3/5

ascorbic acid concentration in gastric mucosa

1 evidences

Oral ascorbic acid increased ASC concentrations in gastric mucosa, plasma and urine; acetylsalicylic acid (ASA) alone decreased ASC, reducing gastric mucosa ASC by ~10% in 6 days.

Trust comment: Prospective randomized double-blind parallel and switch design with clear compartmental measurements, but modest sample size (15 per group).

Study Details

PMID:15487806
Participants:45
Impact:ASA reduced gastric mucosa ASC by ~10%; ASC administration increased mucosal ASC
Trust score:4/5

plasma and urine ASC concentrations

1 evidences

Oral ascorbic acid increased ASC concentrations in gastric mucosa, plasma and urine; acetylsalicylic acid (ASA) alone decreased ASC, reducing gastric mucosa ASC by ~10% in 6 days.

Trust comment: Prospective randomized double-blind parallel and switch design with clear compartmental measurements, but modest sample size (15 per group).

Study Details

PMID:15487806
Participants:45
Impact:increased with ASC administration (no ASC: decreased with ASA alone)
Trust score:4/5

exercise-induced QT dispersion

1 evidences

In patients with acute MI, 14-day treatment with vitamins C and E reduced exercise-induced QT dispersion compared with placebo.

Trust comment: Randomized double-blind placebo-controlled trial but small sample (n=37).

Study Details

PMID:14523485
Participants:37
Impact:-15 msec (59 ± 20 ms vs 74 ± 24 ms; p<0.05)
Trust score:4/5

plasma ascorbic acid concentration (>23 μmol/L)

1 evidences

A short controlled intervention with vitamin C–rich nectar in men with low baseline levels substantially increased the proportion exceeding a threshold plasma ascorbic acid concentration.

Trust comment: Population survey with a small randomized intervention subgroup (n=60); reasonable design but limited intervention size.

Study Details

PMID:8641247
Participants:60
Impact:+41 percentage points (46% in treated vs 5% in control had >23 μmol/L after intervention)
Trust score:3/5

prevalence of severe vitamin C deficiency

1 evidences

A short controlled intervention with vitamin C–rich nectar in men with low baseline levels substantially increased the proportion exceeding a threshold plasma ascorbic acid concentration.

Trust comment: Population survey with a small randomized intervention subgroup (n=60); reasonable design but limited intervention size.

Study Details

PMID:8641247
Participants:60
Impact:Pitkäranta 93% vs North Karelia 2% (baseline cross-sectional difference)
Trust score:3/5

incidence of contrast-induced nephropathy (CIN)

2 evidences

In patients with chronic renal impairment undergoing coronary angiography, ascorbic acid did not reduce the incidence of contrast-induced nephropathy versus placebo.

Trust comment: Randomized double-blind prospective trial with adequate sample size for the question, negative result.

Study Details

PMID:18044259
Participants:143
Impact:no significant difference (Vitamin C 6.8% [5/74] vs placebo 4.3% [3/69])
Trust score:4/5

Adding oral vitamin C to bicarbonate hydration did not significantly reduce contrast-induced kidney injury compared with bicarbonate alone.

Trust comment: Prospective randomized multicenter study with moderate sample size and negative (non-significant) result for the primary endpoint.

Study Details

PMID:28551197
Participants:160
Impact:6.3% (vitamin C) vs 10% (control); P=0.38 — no significant difference
Trust score:3/5

LDL susceptibility to oxidation (lag period)

1 evidences

Dietary vitamin C enrichment (500 mg/day) in young men increased plasma ascorbic acid and reduced the susceptibility of lipoproteins to oxidation.

Trust comment: Randomized dietary intervention with clear biochemical measures but small, homogeneous sample (young male students).

Study Details

PMID:9459371
Participants:36
Impact:increase in lag period (reduced in vitro LDL oxidation susceptibility; correlated with plasma ascorbic acid)
Trust score:3/5

health-related quality of life at 7 days

1 evidences

In adults with acute bronchitis, low‑dose vitamin C was as effective as azithromycin—no meaningful difference in quality of life or return to activities at day 7.

Trust comment: Randomized, double-blind controlled trial with a planned sample and intention-to-treat analysis; stopped after 220 recruited and primary outcome reported with CIs.

Study Details

PMID:12020525
Participants:220
Impact:no significant change vs azithromycin (difference 0.03, 95% CI −0.20 to 0.26; p=0.8)
Trust score:4/5

return to usual activities by day 7

1 evidences

In adults with acute bronchitis, low‑dose vitamin C was as effective as azithromycin—no meaningful difference in quality of life or return to activities at day 7.

Trust comment: Randomized, double-blind controlled trial with a planned sample and intention-to-treat analysis; stopped after 220 recruited and primary outcome reported with CIs.

Study Details

PMID:12020525
Participants:220
Impact:89% returned to usual activities (vitamin C group)
Trust score:4/5

study discontinuation/adverse effects

1 evidences

In adults with acute bronchitis, low‑dose vitamin C was as effective as azithromycin—no meaningful difference in quality of life or return to activities at day 7.

Trust comment: Randomized, double-blind controlled trial with a planned sample and intention-to-treat analysis; stopped after 220 recruited and primary outcome reported with CIs.

Study Details

PMID:12020525
Participants:220
Impact:3 participants in vitamin C group discontinued due to perceived adverse effects
Trust score:4/5

SOFA score (organ dysfunction)

3 evidences

In 131 patients with septic shock randomized to antioxidant arms, vitamin C treatment (oral 1 g q6h for 5 days) was associated with marked SOFA score improvement and reductions in some oxidative stress markers and inflammatory cytokines.

Trust comment: Prospective randomized, blinded trial with 131 septic shock patients showing clinically meaningful SOFA improvement with vitamin C; multiple antioxidant arms and short follow-up are limitations.

Study Details

PMID:38068931
Participants:131
Impact:decrease from 8 to 3.5 between day 0 and day 5 with Vit C (p=0.001)
Trust score:4/5

In septic shock patients, oral vitamin C (small group) restored vitamin C levels and improved organ dysfunction and some inflammation/oxidative markers.

Trust comment: Randomized, triple-masked clinical trial but small arm sizes (vitamin C n=18) limit power for clinical endpoints despite statistically significant biomarker/score changes.

Study Details

PMID:33213070
Participants:97
Impact:decreased by −1.94 points (95% CI −2.95 to −0.93; p<0.001) in vitamin C group
Trust score:4/5

In septic shock patients, vitamin C (1 g q6h) as part of antioxidant therapy reduced organ dysfunction (SOFA) and lowered inflammatory/oxidative markers.

Trust comment: Randomized blinded trial in ICU patients with detailed biomarker and clinical data; multiple antioxidant arms mean vitamin C effects are within combination context.

Study Details

PMID:37174730
Participants:131
Impact:decreased from 8 to 3 over 5 days (≈63% reduction)
Trust score:4/5

NO3−/NO2− ratio (nitric oxide markers)

1 evidences

In septic shock patients, oral vitamin C (small group) restored vitamin C levels and improved organ dysfunction and some inflammation/oxidative markers.

Trust comment: Randomized, triple-masked clinical trial but small arm sizes (vitamin C n=18) limit power for clinical endpoints despite statistically significant biomarker/score changes.

Study Details

PMID:33213070
Participants:97
Impact:decreased in patients with pulmonary infection treated with vitamin C (p<0.01)
Trust score:4/5

major cardiovascular events (MI, stroke, CVD death)

1 evidences

Long-term daily vitamin C (500 mg) did not reduce major cardiovascular events or mortality in middle-aged and older men.

Trust comment: Large, long-term randomized double-blind placebo-controlled trial with high participant number and long follow-up, providing high-quality evidence.

Study Details

PMID:18997197
Participants:14641
Impact:no significant effect (HR 0.99; P=0.91)
Trust score:5/5

myocardial infarction

1 evidences

Long-term daily vitamin C (500 mg) did not reduce major cardiovascular events or mortality in middle-aged and older men.

Trust comment: Large, long-term randomized double-blind placebo-controlled trial with high participant number and long follow-up, providing high-quality evidence.

Study Details

PMID:18997197
Participants:14641
Impact:no significant effect (HR 1.04; P=0.65)
Trust score:5/5

total mortality

2 evidences

Long-term daily vitamin C (500 mg) did not reduce major cardiovascular events or mortality in middle-aged and older men.

Trust comment: Large, long-term randomized double-blind placebo-controlled trial with high participant number and long follow-up, providing high-quality evidence.

Study Details

PMID:18997197
Participants:14641
Impact:no significant effect (HR 1.07; P=0.16)
Trust score:5/5

A randomized dietary trial showed the Mediterranean-type diet group had fewer deaths and cancers over 4 years; plasma vitamin C levels increased in the diet group, but the effect cannot be attributed solely to vitamin C.

Trust comment: Randomized trial with clinically important outcomes, but diet changes were multifactorial so vitamin C-specific attribution is limited.

Study Details

PMID:9625397
Participants:605
Impact:−56% (reduction in experimental vs control after adjustment)
Trust score:3/5

Skeletal muscle mass index (SMI) / appendicular lean mass

1 evidences

Older women with sarcopenia did 12 weeks of resistance training with either vitamins C+E or placebo; supplementation improved some muscle mass and strength gains and improved antioxidant markers versus placebo.

Trust comment: Randomized, double-blind, placebo-controlled trial with objective measures, full adherence and intention-to-treat analysis supports high trustworthiness.

Study Details

PMID:40859523
Participants:60
Impact:+0.71 kg/m² SMI (AS group); +0.42 kg/m² (PLA); AS > PLA post-test (P=0.004); arm lean mass +0.96 kg (AS) vs +0.59 kg (PLA)
Trust score:5/5

Muscle strength (handgrip, knee extension)

1 evidences

Older women with sarcopenia did 12 weeks of resistance training with either vitamins C+E or placebo; supplementation improved some muscle mass and strength gains and improved antioxidant markers versus placebo.

Trust comment: Randomized, double-blind, placebo-controlled trial with objective measures, full adherence and intention-to-treat analysis supports high trustworthiness.

Study Details

PMID:40859523
Participants:60
Impact:Handgrip +3.66 kg (AS) vs +1.16 kg (PLA); Knee extension +2.28 kg (AS) vs +1.02 kg (PLA); AS > PLA (handgrip P=0.047, knee extension P<0.001)
Trust score:5/5

Oxidative stress biomarkers (GSH/GSSG ratio, MDA)

1 evidences

Older women with sarcopenia did 12 weeks of resistance training with either vitamins C+E or placebo; supplementation improved some muscle mass and strength gains and improved antioxidant markers versus placebo.

Trust comment: Randomized, double-blind, placebo-controlled trial with objective measures, full adherence and intention-to-treat analysis supports high trustworthiness.

Study Details

PMID:40859523
Participants:60
Impact:GSH/GSSG ratio +1.48 (AS) vs -2.39 (PLA); MDA -1.63 µmol/L (AS) vs +0.66 µmol/L (PLA); AS better than PLA (P<0.001)
Trust score:5/5

Neuropathy severity (CMT neuropathy score, CMTNS)

1 evidences

Adults with CMT1A were randomized to 0, 1 g, or 3 g/day ascorbic acid for 12 months; no significant benefit on neuropathy score was observed and treatment was well tolerated.

Trust comment: Large multicenter randomized double-blind placebo-controlled trial with intention-to-treat analysis; high methodological quality.

Study Details

PMID:19818690
Participants:179
Impact:Median change at 12 months: placebo +0.5, 1 g +0.7, 3 g -0.4; no significant differences between groups (P=0.14)
Trust score:5/5

Lipid peroxidation (F2-isoprostanes)

1 evidences

Runners taking 1000 mg vitamin C + 300 mg vitamin E for 6 weeks showed prevention of exercise-induced lipid peroxidation but still exhibited marked inflammatory marker rises after a 50 km race.

Trust comment: Randomized supplementation with serial biomarker sampling in a real-world stressor (ultramarathon) but small sample limits generalizability.

Study Details

PMID:15110397
Participants:22
Impact:F2-IsoPs rose during the run in placebo (≈28→41 pg/ml) but did not increase in antioxidant group (AO)
Trust score:4/5

Inflammation markers (TNF-α, IL-6, CRP)

1 evidences

Runners taking 1000 mg vitamin C + 300 mg vitamin E for 6 weeks showed prevention of exercise-induced lipid peroxidation but still exhibited marked inflammatory marker rises after a 50 km race.

Trust comment: Randomized supplementation with serial biomarker sampling in a real-world stressor (ultramarathon) but small sample limits generalizability.

Study Details

PMID:15110397
Participants:22
Impact:Inflammatory markers increased dramatically after the run in both groups; AO had no effect on these increases
Trust score:4/5

Plasma ascorbic acid concentration postoperatively

1 evidences

Giving 1,000 mg oral vitamin C before surgery did not prevent the postoperative drop in plasma ascorbic acid on day 1.

Trust comment: Randomized study with clear outcome but single-dose preoperative intervention and small sample reduce applicability.

Study Details

PMID:12378045
Participants:54
Impact:Preoperative 1,000 mg oral vitamin C did not prevent the postoperative decrease in plasma ascorbic acid (both groups showed reduced levels on day 1)
Trust score:3/5

H. pylori eradication rate (clarithromycin-susceptible strains)

1 evidences

Adding 500 mg vitamin C to a one-week clarithromycin-based triple therapy increased H. pylori eradication rates for clarithromycin-susceptible strains compared with standard-dose clarithromycin.

Trust comment: Randomized clinical comparison with adequate sample and stratified analysis by resistance status, though single-center/duration limits broader inference.

Study Details

PMID:17419283
Participants:171
Impact:For susceptible infections: V‑C250 group eradication ITT 85% vs C250 68% (PP 90% vs 73%), difference significant (p=0.03); similar to higher-dose clarithromycin group
Trust score:4/5

total antioxidant capacity (TAOC)

2 evidences

Giving vitamin C with vitamin E soon after stroke increased antioxidant capacity and reduced markers of lipid oxidation and inflammation.

Trust comment: Randomized controlled trial in acute stroke patients with clear biochemical endpoints but modest sample size (n=48).

Study Details

PMID:16091766
Participants:48
Impact:increase (significant vs control, P<0.003)
Trust score:4/5

Antioxidant vitamins, with or without B-group vitamins (including B12), improved antioxidant capacity, lowered oxidative damage markers and reduced CRP after acute ischemic stroke; B vitamins reduced homocysteine.

Trust comment: Randomized controlled trial in 96 acute stroke patients with clear biomarker changes; sample modest and effects are biochemical/short-term.

Study Details

PMID:16517955
Participants:96
Impact:significant increase in antioxidant groups versus decline in control
Trust score:4/5

lipid peroxidation (plasma MDA)

1 evidences

Giving vitamin C with vitamin E soon after stroke increased antioxidant capacity and reduced markers of lipid oxidation and inflammation.

Trust comment: Randomized controlled trial in acute stroke patients with clear biochemical endpoints but modest sample size (n=48).

Study Details

PMID:16091766
Participants:48
Impact:decrease in treatment vs increase in control (significant, P<0.002)
Trust score:4/5

inflammation (CRP)

1 evidences

Giving vitamin C with vitamin E soon after stroke increased antioxidant capacity and reduced markers of lipid oxidation and inflammation.

Trust comment: Randomized controlled trial in acute stroke patients with clear biochemical endpoints but modest sample size (n=48).

Study Details

PMID:16091766
Participants:48
Impact:lower concentrations within 90 days in treatment group (significant after adjustment)
Trust score:4/5

PSA50 response rate

1 evidences

Adding high‑dose IV vitamin C to docetaxel did not improve PSA responses or progression outcomes and showed trends toward more toxicity.

Trust comment: Multi-site, randomized double-blind placebo-controlled phase II trial with robust design but limited by small final sample and early futility stopping.

Study Details

PMID:39076107
Participants:47
Impact:41% (HDIVC) vs 33% (placebo); no significant difference (P=0.44)
Trust score:4/5

toxicity (grade 3–4 AEs any type)

1 evidences

Adding high‑dose IV vitamin C to docetaxel did not improve PSA responses or progression outcomes and showed trends toward more toxicity.

Trust comment: Multi-site, randomized double-blind placebo-controlled phase II trial with robust design but limited by small final sample and early futility stopping.

Study Details

PMID:39076107
Participants:47
Impact:higher incidence in HDIVC group (64.7%) vs control (50%); non-significant trends in some AE types
Trust score:4/5

overall survival (OS)

1 evidences

Adding high‑dose IV vitamin C to docetaxel did not improve PSA responses or progression outcomes and showed trends toward more toxicity.

Trust comment: Multi-site, randomized double-blind placebo-controlled phase II trial with robust design but limited by small final sample and early futility stopping.

Study Details

PMID:39076107
Participants:47
Impact:median 15.2 months (HDIVC) vs 29.5 months (control); HR 1.98, P=0.11 (nonsignificant trend)
Trust score:4/5

serum cortisol (post-induction)

1 evidences

Preoperative oral vitamin C (500 mg twice daily for 7 days) prevented etomidate-induced cortisol suppression and reduced inotrope (adrenaline) requirement.

Trust comment: Randomized, double-blind RCT with clear, significant physiological effects and reasonable sample size (35 per arm analyzed).

Study Details

PMID:27397444
Participants:70
Impact:Group I (Vitamin C) 69.51 ± 7.65 vs Group II (placebo) 27.74 ± 4.72 at first postinduction hour (P=0.000); higher cortisol with vitamin C
Trust score:4/5

adrenaline requirement

1 evidences

Preoperative oral vitamin C (500 mg twice daily for 7 days) prevented etomidate-induced cortisol suppression and reduced inotrope (adrenaline) requirement.

Trust comment: Randomized, double-blind RCT with clear, significant physiological effects and reasonable sample size (35 per arm analyzed).

Study Details

PMID:27397444
Participants:70
Impact:lower in Vitamin C group (2.83 ± 1.27 units) vs control (3.40 ± 1.09 units); P=0.047
Trust score:4/5

cortisol over 24 h

1 evidences

Preoperative oral vitamin C (500 mg twice daily for 7 days) prevented etomidate-induced cortisol suppression and reduced inotrope (adrenaline) requirement.

Trust comment: Randomized, double-blind RCT with clear, significant physiological effects and reasonable sample size (35 per arm analyzed).

Study Details

PMID:27397444
Participants:70
Impact:higher throughout first 24 h in Vitamin C group (statistically significant)
Trust score:4/5

reactive oxygen species (ROS)

1 evidences

Daily vitamin C (1000 mg) plus vitamin E (800 IU) for 8 weeks reduced oxidative stress markers and improved pain scores in women with endometriosis versus placebo.

Trust comment: Triple-blind randomized placebo-controlled trial with moderate sample size (n=60); baseline imbalance in some markers was addressed by ANCOVA.

Study Details

PMID:34122682
Participants:60
Impact:decrease with vitamin C+E vs placebo (P<0.001)
Trust score:4/5

pelvic pain (VAS: dysmenorrhea, dyspareunia, chronic pelvic pain)

1 evidences

Daily vitamin C (1000 mg) plus vitamin E (800 IU) for 8 weeks reduced oxidative stress markers and improved pain scores in women with endometriosis versus placebo.

Trust comment: Triple-blind randomized placebo-controlled trial with moderate sample size (n=60); baseline imbalance in some markers was addressed by ANCOVA.

Study Details

PMID:34122682
Participants:60
Impact:significant reductions in VAS scores in vitamin group vs placebo after 8 weeks
Trust score:4/5

Sperm morphology

1 evidences

After varicocele surgery, men given vitamin C had improved sperm movement and shape but not higher sperm counts.

Trust comment: Randomized double-blind placebo-controlled RCT with 115 men and clear semen outcomes though seminal/serum vitamin C levels were not measured.

Study Details

PMID:26005963
Participants:115
Impact:+12.7 percentage points (mean change +23.2% vs +10.5% in placebo)
Trust score:4/5

Sperm count

1 evidences

After varicocele surgery, men given vitamin C had improved sperm movement and shape but not higher sperm counts.

Trust comment: Randomized double-blind placebo-controlled RCT with 115 men and clear semen outcomes though seminal/serum vitamin C levels were not measured.

Study Details

PMID:26005963
Participants:115
Impact:+4.8 million/mL (mean change +15.9 vs +11.1 million/mL; not statistically significant)
Trust score:4/5

Global cognitive change (composite score)

1 evidences

In older women at risk for cardiovascular disease, vitamin C did not slow cognitive decline over ~5 years though a small better score at the final assessment was observed.

Trust comment: Large randomized trial substudy (n=2824) with repeated cognitive assessments; randomized design supports credibility though effect on decline was null.

Study Details

PMID:19451353
Participants:2824
Impact:No significant effect on change over time (mean difference in change 0.02; P=0.39)
Trust score:4/5

Cognitive performance at last assessment

1 evidences

In older women at risk for cardiovascular disease, vitamin C did not slow cognitive decline over ~5 years though a small better score at the final assessment was observed.

Trust comment: Large randomized trial substudy (n=2824) with repeated cognitive assessments; randomized design supports credibility though effect on decline was null.

Study Details

PMID:19451353
Participants:2824
Impact:Small better score with vitamin C (mean difference 0.13; 95% CI 0.06–0.20; P=0.0005)
Trust score:4/5

Postoperative pain (VAS at 24 h and 48 h)

1 evidences

Perioperative IV vitamin C reduced reported postoperative pain and analgesic use after hip fracture surgery.

Trust comment: Prospective randomized, single-blind trial (n=60) showing reduced pain and analgesic use, but single-blind design and moderate sample size limit strength.

Study Details

PMID:39674960
Participants:60
Impact:Lower in vitamin C group (24 h: p=0.001; 48 h: p<0.0005)
Trust score:3/5

Analgesic consumption (metamizole)

2 evidences

Peri- and postoperative vitamin C reduced subjective pain and analgesic use after hip fracture surgery but did not change hip function scores.

Trust comment: Prospective randomized full-scale study with objective consumption and pain measures; blinding not clearly reported.

Study Details

PMID:40355782
Participants:74
Impact:decreased (control > vitamin C; p=0.003)
Trust score:4/5

Perioperative IV vitamin C reduced reported postoperative pain and analgesic use after hip fracture surgery.

Trust comment: Prospective randomized, single-blind trial (n=60) showing reduced pain and analgesic use, but single-blind design and moderate sample size limit strength.

Study Details

PMID:39674960
Participants:60
Impact:Lower in vitamin C group (p=0.003)
Trust score:3/5

Hemoglobin / blood loss

1 evidences

Perioperative IV vitamin C reduced reported postoperative pain and analgesic use after hip fracture surgery.

Trust comment: Prospective randomized, single-blind trial (n=60) showing reduced pain and analgesic use, but single-blind design and moderate sample size limit strength.

Study Details

PMID:39674960
Participants:60
Impact:No significant difference between groups
Trust score:3/5

blood reactive oxygen species (ROS)

1 evidences

In hemodialysis patients, intravenous vitamin C (with or without a vitamin E–coated dialyzer) reduced dialysis-related oxidative stress and preserved red blood cell reducing activity.

Trust comment: Randomized study in 80 human HD patients with objective biochemical measures, though co-intervention (VE membrane) complicates isolation of VC effect.

Study Details

PMID:16395251
Participants:80
Impact:reduced HD-induced ROS increase (attenuated)
Trust score:4/5

phosphatidylcholine hydroperoxide (PCOOH) / lipid peroxidation

1 evidences

In hemodialysis patients, intravenous vitamin C (with or without a vitamin E–coated dialyzer) reduced dialysis-related oxidative stress and preserved red blood cell reducing activity.

Trust comment: Randomized study in 80 human HD patients with objective biochemical measures, though co-intervention (VE membrane) complicates isolation of VC effect.

Study Details

PMID:16395251
Participants:80
Impact:decreased plasma and RBC PCOOH levels
Trust score:4/5

RBC methemoglobin/ferricyanide reductase (RBC-MFR) activity

1 evidences

In hemodialysis patients, intravenous vitamin C (with or without a vitamin E–coated dialyzer) reduced dialysis-related oxidative stress and preserved red blood cell reducing activity.

Trust comment: Randomized study in 80 human HD patients with objective biochemical measures, though co-intervention (VE membrane) complicates isolation of VC effect.

Study Details

PMID:16395251
Participants:80
Impact:preserved RBC-MFR activity (prevented decline)
Trust score:4/5

plasma reduced ascorbic acid

1 evidences

In smoking men, 2-month ascorbic acid (500 mg/day) raised plasma vitamin C but did not improve lipoprotein oxidation resistance and plain ascorbate was associated with increased MDA.

Trust comment: Randomized, placebo-controlled trial with 59 completers in relevant human population (smokers), though single-blind and limited to biochemical endpoints.

Study Details

PMID:9076405
Participants:59
Impact:increased (plain +32%; slow-release +54%)
Trust score:4/5

lipoprotein oxidation resistance (VLDL+LDL)

1 evidences

In smoking men, 2-month ascorbic acid (500 mg/day) raised plasma vitamin C but did not improve lipoprotein oxidation resistance and plain ascorbate was associated with increased MDA.

Trust comment: Randomized, placebo-controlled trial with 59 completers in relevant human population (smokers), though single-blind and limited to biochemical endpoints.

Study Details

PMID:9076405
Participants:59
Impact:no significant change vs placebo
Trust score:4/5

lipid hydroperoxides (LOOH)

1 evidences

Women with endometriosis taking combined vitamins C and E had lower oxidative stress markers over months, but pregnancy rates did not improve.

Trust comment: Small clinical study in humans showing biomarker changes but co-supplementation with vitamin E and low sample size limit attribution to vitamin C alone.

Study Details

PMID:18005966
Participants:34
Impact:decreased (significant by month 6)
Trust score:3/5

pregnancy rate

1 evidences

Women with endometriosis taking combined vitamins C and E had lower oxidative stress markers over months, but pregnancy rates did not improve.

Trust comment: Small clinical study in humans showing biomarker changes but co-supplementation with vitamin E and low sample size limit attribution to vitamin C alone.

Study Details

PMID:18005966
Participants:34
Impact:no significant improvement (19% vs 12%)
Trust score:3/5

forearm blood flow response to nitroglycerin (%FBF)

1 evidences

Oral vitamin C prevented development of nitrate tolerance: it preserved nitroglycerin-induced vasodilation and platelet cGMP after continuous nitrate exposure.

Trust comment: Well-controlled randomized double-blind human study with clear physiological endpoints, moderate sample size (48) across two cohorts.

Study Details

PMID:9581727
Participants:48
Impact:preserved after nitrate exposure (day6): normals ≈30% vs 19% placebo; IHD ≈29% vs 17% placebo)
Trust score:4/5

platelet cGMP (%cGMP)

1 evidences

Oral vitamin C prevented development of nitrate tolerance: it preserved nitroglycerin-induced vasodilation and platelet cGMP after continuous nitrate exposure.

Trust comment: Well-controlled randomized double-blind human study with clear physiological endpoints, moderate sample size (48) across two cohorts.

Study Details

PMID:9581727
Participants:48
Impact:preserved after nitrate exposure (day6): normals ≈36% vs 17% placebo; IHD ≈37% vs 15% placebo
Trust score:4/5

nitrate tolerance development (vasodilator response)

1 evidences

Oral vitamin C prevented development of nitrate tolerance: it preserved nitroglycerin-induced vasodilation and platelet cGMP after continuous nitrate exposure.

Trust comment: Well-controlled randomized double-blind human study with clear physiological endpoints, moderate sample size (48) across two cohorts.

Study Details

PMID:9581727
Participants:48
Impact:attenuated development of nitrate tolerance with vitamin C
Trust score:4/5

lesion regression rate

1 evidences

Daily 500 mg vitamin C did not increase lesion regression and was associated with a non-significant tendency toward higher progression; combined vitamin C + beta‑carotene showed a possible increased progression signal.

Trust comment: Well‑conducted randomized double‑blind factorial RCT with 141 analyzable participants but few progression events leading to wide confidence intervals and non-significant results.

Study Details

PMID:10188889
Participants:141
Impact:-35% hazard (HR 0.65 vs no Vit C; P=0.17; not significant)
Trust score:4/5

lesion progression rate

1 evidences

Daily 500 mg vitamin C did not increase lesion regression and was associated with a non-significant tendency toward higher progression; combined vitamin C + beta‑carotene showed a possible increased progression signal.

Trust comment: Well‑conducted randomized double‑blind factorial RCT with 141 analyzable participants but few progression events leading to wide confidence intervals and non-significant results.

Study Details

PMID:10188889
Participants:141
Impact:+140% hazard (HR 2.40 vs no Vit C; P=0.13; not significant)
Trust score:4/5

combined VitC+beta‑carotene progression

1 evidences

Daily 500 mg vitamin C did not increase lesion regression and was associated with a non-significant tendency toward higher progression; combined vitamin C + beta‑carotene showed a possible increased progression signal.

Trust comment: Well‑conducted randomized double‑blind factorial RCT with 141 analyzable participants but few progression events leading to wide confidence intervals and non-significant results.

Study Details

PMID:10188889
Participants:141
Impact:+157% hazard (HR 2.57 vs double placebo; interaction P=0.052; borderline)
Trust score:4/5

endothelium-dependent vasodilation (FMD)

1 evidences

Short‑term combined vitamins C (1 g) and E (400 IU) improved endothelial function and reduced arterial stiffness in untreated hypertensive men.

Trust comment: Randomized, double‑blind, placebo‑controlled crossover with objective vascular measures but small, male‑only sample and combined vitamins limit generalizability and attribution to vitamin C alone.

Study Details

PMID:17386345
Participants:30
Impact:significant improvement after supplementation (vs placebo)
Trust score:3/5

central pulse wave velocity (PWV)

1 evidences

Short‑term combined vitamins C (1 g) and E (400 IU) improved endothelial function and reduced arterial stiffness in untreated hypertensive men.

Trust comment: Randomized, double‑blind, placebo‑controlled crossover with objective vascular measures but small, male‑only sample and combined vitamins limit generalizability and attribution to vitamin C alone.

Study Details

PMID:17386345
Participants:30
Impact:significant reduction after supplementation
Trust score:3/5

oxidative stress markers / antioxidant capacity

1 evidences

Short‑term combined vitamins C (1 g) and E (400 IU) improved endothelial function and reduced arterial stiffness in untreated hypertensive men.

Trust comment: Randomized, double‑blind, placebo‑controlled crossover with objective vascular measures but small, male‑only sample and combined vitamins limit generalizability and attribution to vitamin C alone.

Study Details

PMID:17386345
Participants:30
Impact:decreased oxidative stress; increased antioxidant capacity (significant)
Trust score:3/5

iron status (hemoglobin, ferritin, transferrin receptor)

1 evidences

Giving 25 mg vitamin C twice daily as limeade raised plasma vitamin C but did not improve hemoglobin or other iron status markers in iron‑deficient women consuming high‑phytate diets.

Trust comment: Randomized community trial with prolonged follow‑up and objective measures but small sample size and high‑phytate diets that limit vitamin C efficacy for iron absorption.

Study Details

PMID:12885707
Participants:36
Impact:no improvement after 8 months (no between‑group differences)
Trust score:3/5

morphine (opioid) consumption — per‑protocol

1 evidences

Pilot RCT found feasibility for a larger trial; per‑protocol analysis suggested lower opioid use with vitamin C, but intention‑to‑treat results were inconsistent and the study was underpowered.

Trust comment: Well‑designed pilot RCT but modest sample (55 randomized, 41 completed), notable loss to follow‑up and baseline/treatment imbalances; underpowered for definitive clinical conclusions.

Study Details

PMID:39739762
Participants:41
Impact:decrease (median 6.5 vs 9.0 tablets; per‑protocol)
Trust score:3/5

morphine (opioid) consumption — intention‑to‑treat

1 evidences

Pilot RCT found feasibility for a larger trial; per‑protocol analysis suggested lower opioid use with vitamin C, but intention‑to‑treat results were inconsistent and the study was underpowered.

Trust comment: Well‑designed pilot RCT but modest sample (55 randomized, 41 completed), notable loss to follow‑up and baseline/treatment imbalances; underpowered for definitive clinical conclusions.

Study Details

PMID:39739762
Participants:41
Impact:no clear reduction (median 8.5 vs 6.0 tablets; ITT)
Trust score:3/5

pain intensity

2 evidences

Pilot RCT found feasibility for a larger trial; per‑protocol analysis suggested lower opioid use with vitamin C, but intention‑to‑treat results were inconsistent and the study was underpowered.

Trust comment: Well‑designed pilot RCT but modest sample (55 randomized, 41 completed), notable loss to follow‑up and baseline/treatment imbalances; underpowered for definitive clinical conclusions.

Study Details

PMID:39739762
Participants:41
Impact:no meaningful difference over 14 days (trends similar)
Trust score:3/5

Vitamin C given after distal radius fracture did not improve finger range of motion, arm function, or pain at 6 weeks or 6 months.

Trust comment: High-quality double-blind randomized placebo-controlled trial with pre-specified power and ITT analysis; modest loss to follow-up handled by imputation.

Study Details

PMID:32142501
Participants:119
Impact:no significant change (β -0.62; 95% CI -0.62 to 0.89; p=0.729)
Trust score:5/5

mean corpuscular volume (MCV)

2 evidences

Randomized blind clinical study in preschool children testing water fortification with iron+ascorbic acid, ascorbic acid alone, or plain water over 3 months; hemoglobin rose in all groups, MCV improved with iron+ascorbic and with ascorbic alone, ferritin increased only with iron+ascorbic.

Trust comment: Randomized blinded clinical trial in children with clear hematologic outcomes and moderate sample size, although duration was short (3 months).

Study Details

PMID:23963460
Participants:153
Impact:increased in A and B; A and B differed significantly vs control (C)
Trust score:4/5

In children with iron‑deficiency anemia, ferrous ascorbate produced larger and faster improvements in hemoglobin and other hematologic indices over 3 months compared with iron polymaltose complex.

Trust comment: Randomized controlled trial with a substantial sample (N=125) and consistent, statistically significant hematologic improvements favoring ferrous ascorbate.

Study Details

PMID:31520309
Participants:125
Impact:greater increases with FA (e.g., day7 +6.71 fL vs +2.91 fL; P=0.011)
Trust score:4/5

reticulocyte response

1 evidences

In children with iron‑deficiency anemia, ferrous ascorbate produced larger and faster improvements in hemoglobin and other hematologic indices over 3 months compared with iron polymaltose complex.

Trust comment: Randomized controlled trial with a substantial sample (N=125) and consistent, statistically significant hematologic improvements favoring ferrous ascorbate.

Study Details

PMID:31520309
Participants:125
Impact:larger rise in FA group at day3/day7 (e.g., day3 0.88 vs 0.43; P=0.017)
Trust score:4/5

mean arterial blood pressure

1 evidences

12‑week quercetin supplementation given with modest doses of vitamin C and niacin produced negligible effects on most disease risk factors in community adults.

Trust comment: Large randomized trial but vitamin C was given as part of a combination supplement, so effects cannot be attributed to vitamin C alone and observed changes were clinically small.

Study Details

PMID:21443986
Participants:1002
Impact:small decrease in Q‑500 and Q‑1000 groups versus placebo (clinically negligible)
Trust score:3/5

interleukin-6 (inflammation)

1 evidences

12‑week quercetin supplementation given with modest doses of vitamin C and niacin produced negligible effects on most disease risk factors in community adults.

Trust comment: Large randomized trial but vitamin C was given as part of a combination supplement, so effects cannot be attributed to vitamin C alone and observed changes were clinically small.

Study Details

PMID:21443986
Participants:1002
Impact:slight decrease in IL‑6 in Q‑1000 group
Trust score:3/5

blood lipids

1 evidences

12‑week quercetin supplementation given with modest doses of vitamin C and niacin produced negligible effects on most disease risk factors in community adults.

Trust comment: Large randomized trial but vitamin C was given as part of a combination supplement, so effects cannot be attributed to vitamin C alone and observed changes were clinically small.

Study Details

PMID:21443986
Participants:1002
Impact:minor changes (small total cholesterol decrease in Q‑500; small HDL decrease in Q‑1000)
Trust score:3/5

chorioamnionitis / early neonatal sepsis / RDS

1 evidences

Giving vitamins C and E after PPROM was associated with a longer time from membrane rupture to delivery.

Trust comment: Double-blind randomized controlled trial but small sample (n=60); outcome was statistically significant for latency.

Study Details

PMID:15907848
Participants:60
Impact:no significant difference reported between groups
Trust score:4/5

fingertip-to-palmar-crease distance (finger ROM)

1 evidences

Vitamin C given after distal radius fracture did not improve finger range of motion, arm function, or pain at 6 weeks or 6 months.

Trust comment: High-quality double-blind randomized placebo-controlled trial with pre-specified power and ITT analysis; modest loss to follow-up handled by imputation.

Study Details

PMID:32142501
Participants:119
Impact:no significant change (β -0.23; 95% CI -1.7 to 1.2; p=0.754)
Trust score:5/5

upper extremity function (PROMIS)

1 evidences

Vitamin C given after distal radius fracture did not improve finger range of motion, arm function, or pain at 6 weeks or 6 months.

Trust comment: High-quality double-blind randomized placebo-controlled trial with pre-specified power and ITT analysis; modest loss to follow-up handled by imputation.

Study Details

PMID:32142501
Participants:119
Impact:no significant change (β 0.32; 95% CI -2.6 to 3.2; p=0.828)
Trust score:5/5

CPT-induced myocardial blood flow (DeltaMBF) — hypertensive patients

1 evidences

Vitamin C altered cold-pressor–induced myocardial blood flow (MBF) responses heterogeneously: improved MBF in smokers (short- and long-term) and in hypertensives after long-term treatment, but not in hypercholesterolemic patients.

Trust comment: Well-controlled PET-based physiological study with subgroup analyses in a moderate-sized cohort (n=50); subgroup heterogeneity and sample size limit broad generalizability.

Study Details

PMID:12957426
Participants:50
Impact:increased to 0.58±0.27 ml/g/min at 3 months and 0.63±0.17 at 2 years vs 0.14±0.18 baseline (p≤0.001)
Trust score:4/5

CPT-induced myocardial blood flow (DeltaMBF) — smokers

1 evidences

Vitamin C altered cold-pressor–induced myocardial blood flow (MBF) responses heterogeneously: improved MBF in smokers (short- and long-term) and in hypertensives after long-term treatment, but not in hypercholesterolemic patients.

Trust comment: Well-controlled PET-based physiological study with subgroup analyses in a moderate-sized cohort (n=50); subgroup heterogeneity and sample size limit broad generalizability.

Study Details

PMID:12957426
Participants:50
Impact:increased (short-term infusion 0.52±0.10; long-term 0.54±0.13 and 0.50±0.07 vs -0.08±0.10 baseline; p≤0.001)
Trust score:4/5

CPT-induced myocardial blood flow (DeltaMBF) — hypercholesterolemia

1 evidences

Vitamin C altered cold-pressor–induced myocardial blood flow (MBF) responses heterogeneously: improved MBF in smokers (short- and long-term) and in hypertensives after long-term treatment, but not in hypercholesterolemic patients.

Trust comment: Well-controlled PET-based physiological study with subgroup analyses in a moderate-sized cohort (n=50); subgroup heterogeneity and sample size limit broad generalizability.

Study Details

PMID:12957426
Participants:50
Impact:no significant change with short- or long-term vitamin C (p=NS)
Trust score:4/5

patient-reported xerostomia

1 evidences

Short-term supplementation with vitamin C/E during radiotherapy reduced patient-reported dry mouth and improved oral indices at early follow-up compared with placebo.

Trust comment: Randomized double-blind trial but small sample (n=45) and combined vitamin C/E intervention; limits attribution to vitamin C alone.

Study Details

PMID:27048670
Participants:45
Impact:greater improvement at 6 months vs 1 month in supplement group (P=0.007)
Trust score:3/5

observer-rated oral indices (prestimulatory and poststimulatory)

1 evidences

Short-term supplementation with vitamin C/E during radiotherapy reduced patient-reported dry mouth and improved oral indices at early follow-up compared with placebo.

Trust comment: Randomized double-blind trial but small sample (n=45) and combined vitamin C/E intervention; limits attribution to vitamin C alone.

Study Details

PMID:27048670
Participants:45
Impact:maintained significantly better indices at 1 month post-RT (P=0.01 and P=0.009)
Trust score:3/5

salivary scintigraphy (accumulation/ejection)

1 evidences

Short-term supplementation with vitamin C/E during radiotherapy reduced patient-reported dry mouth and improved oral indices at early follow-up compared with placebo.

Trust comment: Randomized double-blind trial but small sample (n=45) and combined vitamin C/E intervention; limits attribution to vitamin C alone.

Study Details

PMID:27048670
Participants:45
Impact:no significant difference between groups
Trust score:3/5

in-hospital mortality

2 evidences

Randomized clinical trial in off-pump CABG patients found perioperative oral vitamin C (with other arms) did not reduce incidence or severity of acute kidney injury or related morbidity.

Trust comment: Prospective randomized clinical trial with reasonable sample and clear AKI definitions; oral dosing and low-risk population limit generalizability.

Study Details

PMID:29898141
Participants:272
Impact:no significant difference (vitamin C group 2 deaths; overall 4 deaths; P=0.548)
Trust score:4/5

In sepsis patients, adding vitamin C + thiamine + hydrocortisone did not change mortality but reduced vasopressor duration and increased lactate clearance.

Trust comment: Open-label randomized trial (100 patients) provides human data but uses a combination therapy so effects of vitamin C alone cannot be isolated.

Study Details

PMID:31990246
Participants:100
Impact:no change (28% control vs 24% treatment, p=0.82)
Trust score:3/5

30-day mortality

4 evidences

In sepsis patients, adding vitamin C + thiamine + hydrocortisone did not change mortality but reduced vasopressor duration and increased lactate clearance.

Trust comment: Open-label randomized trial (100 patients) provides human data but uses a combination therapy so effects of vitamin C alone cannot be isolated.

Study Details

PMID:31990246
Participants:100
Impact:no change (42% control vs 40% treatment, p=1.00)
Trust score:3/5

Large randomized, blinded trial gave IV antioxidants (3 g vitamin C + NAC) perioperatively and found no reduction in postoperative myocardial injury compared with placebo.

Trust comment: Large, multicenter, blinded randomized trial with low risk of bias demonstrating no cardiovascular benefit from perioperative IV vitamin C + NAC.

Study Details

PMID:35120193
Participants:576
Impact:no significant difference (9/576 overall; no significant difference between groups)
Trust score:4/5

In adults with septic shock, combination therapy including ascorbic acid did not significantly reduce organ failure (SOFA score), kidney failure, or 30-day mortality versus placebo.

Trust comment: Multicenter, randomized, blinded trial with adequate sample size and clear reporting showing no significant benefit of the combination including ascorbic acid.

Study Details

PMID:32809003
Participants:200
Impact:34.7% with intervention vs 29.3% with placebo (no significant difference; HR 1.3, 95% CI: 0.8–2.2)
Trust score:5/5

In 501 critically ill sepsis patients, IV vitamin C plus thiamine and hydrocortisone did not increase ventilator- and vasopressor-free days or reduce 30-day mortality compared with placebo.

Trust comment: Large multicenter randomized double-blind trial with rigorous design but stopped early for administrative reasons, which may reduce power.

Study Details

PMID:33620405
Participants:501
Impact:22% (intervention) vs 24% (placebo)
Trust score:4/5

duration of vasopressor use

1 evidences

In sepsis patients, adding vitamin C + thiamine + hydrocortisone did not change mortality but reduced vasopressor duration and increased lactate clearance.

Trust comment: Open-label randomized trial (100 patients) provides human data but uses a combination therapy so effects of vitamin C alone cannot be isolated.

Study Details

PMID:31990246
Participants:100
Impact:reduced by 20.41 h (96.13→75.72 h), p=0.010
Trust score:3/5

lactate clearance

1 evidences

In sepsis patients, adding vitamin C + thiamine + hydrocortisone did not change mortality but reduced vasopressor duration and increased lactate clearance.

Trust comment: Open-label randomized trial (100 patients) provides human data but uses a combination therapy so effects of vitamin C alone cannot be isolated.

Study Details

PMID:31990246
Participants:100
Impact:increased by 15.02% (41.81%→56.83%), p=0.031
Trust score:3/5

state-anxiety (STAI)

1 evidences

Single 1000 mg dose of ascorbic acid produced no overall anxiolytic effect, but reduced state-anxiety in a high trait‑anxiety subgroup.

Trust comment: Randomized double-blind trial with adequate size but limited generalizability (mostly young female grad students) and subgroup finding reduces confidence.

Study Details

PMID:29369301
Participants:142
Impact:no change overall; significant reduction in high trait‑anxiety subgroup
Trust score:3/5

VAMS anxiety subscale

1 evidences

Single 1000 mg dose of ascorbic acid produced no overall anxiolytic effect, but reduced state-anxiety in a high trait‑anxiety subgroup.

Trust comment: Randomized double-blind trial with adequate size but limited generalizability (mostly young female grad students) and subgroup finding reduces confidence.

Study Details

PMID:29369301
Participants:142
Impact:no change overall; significant reduction in high trait‑anxiety subgroup
Trust score:3/5

contrast-induced acute kidney injury (CI-AKI) incidence

2 evidences

Ascorbic acid given around coronary procedures reduced contrast-induced acute kidney injury (CI-AKI), significantly so with the iso-osmolar agent.

Trust comment: Randomized trial (n=222) with a clear clinical endpoint and reported between-group incidence data; adequate quality.

Study Details

PMID:19996728
Participants:222
Impact:reduced; iodixanol group 21.6% (placebo) → 7.4% (ascorbic acid), P=0.02; low-osmolar agents 20.6% → 9.1% (P=0.19)
Trust score:4/5

Intravenous ascorbic acid (500 mg twice before procedure) did not significantly prevent contrast-induced acute kidney injury compared with placebo.

Trust comment: Large randomized double-blind trial in high-risk patients provides reliable evidence but was single-center and used standard doses.

Study Details

PMID:23735352
Participants:520
Impact:no significant reduction (placebo 32.1% vs ascorbic acid 24.5%, P=0.11)
Trust score:4/5

serum creatinine/eGFR changes

1 evidences

Intravenous ascorbic acid (500 mg twice before procedure) did not significantly prevent contrast-induced acute kidney injury compared with placebo.

Trust comment: Large randomized double-blind trial in high-risk patients provides reliable evidence but was single-center and used standard doses.

Study Details

PMID:23735352
Participants:520
Impact:no clinically significant preventive effect reported
Trust score:4/5

FEV1 decline from ozone exposure

1 evidences

Supplementation with vitamin C (500 mg) + vitamin E (100 mg) attenuated ozone-induced acute declines in FEV1 and FVC in cyclists.

Trust comment: Double-blind randomized trial showing physiological benefit, but small sample and compliance exclusions limit robustness.

Study Details

PMID:10025472
Participants:38
Impact:placebo: −95 mL per 100 μg/m3 ozone vs vitamins: −1 mL (difference significant)
Trust score:3/5

FVC decline from ozone exposure

1 evidences

Supplementation with vitamin C (500 mg) + vitamin E (100 mg) attenuated ozone-induced acute declines in FEV1 and FVC in cyclists.

Trust comment: Double-blind randomized trial showing physiological benefit, but small sample and compliance exclusions limit robustness.

Study Details

PMID:10025472
Participants:38
Impact:placebo: −125 mL per 100 μg/m3 ozone vs vitamins: −42 mL (difference significant)
Trust score:3/5

procalcitonin (PCT)

1 evidences

In septic shock patients, vitamin C (1 g q6h) as part of antioxidant therapy reduced organ dysfunction (SOFA) and lowered inflammatory/oxidative markers.

Trust comment: Randomized blinded trial in ICU patients with detailed biomarker and clinical data; multiple antioxidant arms mean vitamin C effects are within combination context.

Study Details

PMID:37174730
Participants:131
Impact:decreased earlier in vitamin C group (early drop vs untreated)
Trust score:4/5

lipid peroxidation (LPO)

1 evidences

In septic shock patients, vitamin C (1 g q6h) as part of antioxidant therapy reduced organ dysfunction (SOFA) and lowered inflammatory/oxidative markers.

Trust comment: Randomized blinded trial in ICU patients with detailed biomarker and clinical data; multiple antioxidant arms mean vitamin C effects are within combination context.

Study Details

PMID:37174730
Participants:131
Impact:marked decrease (6–9-fold) in vitamin C and vitamin E groups
Trust score:4/5

serum creatinine

2 evidences

In hemodialysis patients, giving 250 mg vitamin C three times weekly for 8 weeks lowered serum uric acid but did not change creatinine.

Trust comment: Randomized placebo-controlled trial with a substantial sample (n=172) and reported statistical significance for the primary outcome.

Study Details

PMID:25194408
Participants:172
Impact:no significant change
Trust score:4/5

Statin plus ascorbic acid reduced the incidence of post-contrast acute kidney injury compared to placebo, though serum creatinine and eGFR changes were not improved between groups.

Trust comment: Randomized clinical trial with adequate sample but ascorbic acid was given together with high‑dose atorvastatin, so effect of vitamin C alone is not separable.

Study Details

PMID:37742328
Participants:213
Impact:placebo mean 0.80→0.82 mg/dL; treatment 0.80→0.81 mg/dL (no significant between-group difference)
Trust score:3/5

phosphocreatine utilization during exercise

1 evidences

In CHF patients, 4 g/day vitamin C for 4 weeks improved endothelial function but increased markers of skeletal muscle metabolic stress during exercise.

Trust comment: Double-blind randomized study with physiologic measurements in a defined clinical population (n=39), though sample is modest.

Study Details

PMID:17023203
Participants:39
Impact:increased
Trust score:4/5

glycolytic ATP synthesis

1 evidences

In CHF patients, 4 g/day vitamin C for 4 weeks improved endothelial function but increased markers of skeletal muscle metabolic stress during exercise.

Trust comment: Double-blind randomized study with physiologic measurements in a defined clinical population (n=39), though sample is modest.

Study Details

PMID:17023203
Participants:39
Impact:increased (change at 1 min: placebo -0.21±0.76 vs ascorbate 2.06±0.60; P<0.05)
Trust score:4/5

endothelial function (pulse wave velocity fall during reactive hyperaemia)

1 evidences

In CHF patients, 4 g/day vitamin C for 4 weeks improved endothelial function but increased markers of skeletal muscle metabolic stress during exercise.

Trust comment: Double-blind randomized study with physiologic measurements in a defined clinical population (n=39), though sample is modest.

Study Details

PMID:17023203
Participants:39
Impact:improved (from -6.3% to -12.1%; P<0.05)
Trust score:4/5

systolic blood pressure (vitamins+minerals group)

1 evidences

In type 2 diabetics, combined minerals + vitamins (including Mg+Zn) for 3 months lowered systolic, diastolic and mean blood pressure; Mg+Zn alone did not.

Trust comment: Randomized double-blind trial but small groups (total n=69) and primary BP changes were seen only in combined vitamin+mineral arm, not vitamin C+E alone.

Study Details

PMID:15190052
Participants:69
Impact:decreased by 8 mmHg (130 → 122 mmHg)
Trust score:3/5

diastolic blood pressure (vitamins+minerals group)

1 evidences

In type 2 diabetics, combined minerals + vitamins (including Mg+Zn) for 3 months lowered systolic, diastolic and mean blood pressure; Mg+Zn alone did not.

Trust comment: Randomized double-blind trial but small groups (total n=69) and primary BP changes were seen only in combined vitamin+mineral arm, not vitamin C+E alone.

Study Details

PMID:15190052
Participants:69
Impact:decreased by 6 mmHg (83 → 77 mmHg)
Trust score:3/5

mean blood pressure (vitamins+minerals group)

1 evidences

In type 2 diabetics, combined minerals + vitamins (including Mg+Zn) for 3 months lowered systolic, diastolic and mean blood pressure; Mg+Zn alone did not.

Trust comment: Randomized double-blind trial but small groups (total n=69) and primary BP changes were seen only in combined vitamin+mineral arm, not vitamin C+E alone.

Study Details

PMID:15190052
Participants:69
Impact:decreased by 7 mmHg (99 → 92 mmHg)
Trust score:3/5

blood pressure (vitamin C + E group)

1 evidences

In type 2 diabetics, combined minerals + vitamins (including Mg+Zn) for 3 months lowered systolic, diastolic and mean blood pressure; Mg+Zn alone did not.

Trust comment: Randomized double-blind trial but small groups (total n=69) and primary BP changes were seen only in combined vitamin+mineral arm, not vitamin C+E alone.

Study Details

PMID:15190052
Participants:69
Impact:no significant change
Trust score:3/5

soft tissue healing (socket depth)

1 evidences

Vitamin C taken orally or applied locally helped soft tissue healing (reduced socket depth) after tooth extraction by day 21 but did not change bone formation on x-rays.

Trust comment: Randomized split-mouth RCT but small sample (n=30) and single-blind, limiting generalizability.

Study Details

PMID:33597336
Participants:30
Impact:improved at 21 days vs control (P<0.05)
Trust score:3/5

radiographic density (new bone formation)

1 evidences

Vitamin C taken orally or applied locally helped soft tissue healing (reduced socket depth) after tooth extraction by day 21 but did not change bone formation on x-rays.

Trust comment: Randomized split-mouth RCT but small sample (n=30) and single-blind, limiting generalizability.

Study Details

PMID:33597336
Participants:30
Impact:no significant change
Trust score:3/5

skin roughness (R1)

1 evidences

Ascorbic acid-containing microneedle patches applied twice daily reduced crow's-feet wrinkle measures over 12 weeks with no reported side effects.

Trust comment: Within-subject clinical study with objective instrument measures but small sample (n=24).

Study Details

PMID:24910870
Participants:24
Impact:improved (P<0.001)
Trust score:3/5

arithmetic average roughness (R5)

1 evidences

Ascorbic acid-containing microneedle patches applied twice daily reduced crow's-feet wrinkle measures over 12 weeks with no reported side effects.

Trust comment: Within-subject clinical study with objective instrument measures but small sample (n=24).

Study Details

PMID:24910870
Participants:24
Impact:improved (P<0.001)
Trust score:3/5

other Visiometer R-values

1 evidences

Ascorbic acid-containing microneedle patches applied twice daily reduced crow's-feet wrinkle measures over 12 weeks with no reported side effects.

Trust comment: Within-subject clinical study with objective instrument measures but small sample (n=24).

Study Details

PMID:24910870
Participants:24
Impact:improved (P<0.05)
Trust score:3/5

LDL-C

2 evidences

Adding vitamin C to simvastatin did not provide lipid-profile benefits beyond simvastatin alone in patients with low HDL-C.

Trust comment: Randomized study but combined interventions and limited reporting on magnitude for vitamin C-specific effects.

Study Details

PMID:15590360
Participants:108
Impact:decreased with simvastatin (significant)
Trust score:3/5

Drinking 500 mL/day orange juice while doing aerobic training for 3 months was associated with better cholesterol and less muscle fatigue.

Trust comment: Controlled intervention in 26 women; orange juice raised vitamin C intake but contained multiple nutrients so attribution to vitamin C alone is uncertain (small sample).

Study Details

PMID:20729016
Participants:26
Impact:-15%
Trust score:3/5

preeclampsia incidence

1 evidences

High-dose vitamin C plus E did not reduce the rate of preeclampsia in women at increased risk in this large randomized trial.

Trust comment: Large, multicenter, double-blind randomized trial with adequate power planning; null result is reliable.

Study Details

PMID:18055726
Participants:707
Impact:no significant reduction (study 13.8% vs placebo 15.6%; adjusted RR 0.87, NS)
Trust score:4/5

mean gestational age / perinatal outcomes

1 evidences

High-dose vitamin C plus E did not reduce the rate of preeclampsia in women at increased risk in this large randomized trial.

Trust comment: Large, multicenter, double-blind randomized trial with adequate power planning; null result is reliable.

Study Details

PMID:18055726
Participants:707
Impact:no significant differences
Trust score:4/5

8-OHdG (oxidative stress marker)

1 evidences

In patients with metabolic syndrome, intravenous vitamin C quickly improved artery dilation and prevented an exercise/ischemia-related rise in an oxidative stress marker.

Trust comment: Randomized double-blind crossover mechanistic study but small sample (18 MS patients; 30 controls), limiting external validity.

Study Details

PMID:17664149
Participants:48
Impact:ischemia-induced increase counteracted by vitamin C (P<0.001)
Trust score:3/5

baseline oxidative stress vs controls

1 evidences

In patients with metabolic syndrome, intravenous vitamin C quickly improved artery dilation and prevented an exercise/ischemia-related rise in an oxidative stress marker.

Trust comment: Randomized double-blind crossover mechanistic study but small sample (18 MS patients; 30 controls), limiting external validity.

Study Details

PMID:17664149
Participants:48
Impact:MS patients had higher 8-OHdG and lower FMD vs controls (P<0.001)
Trust score:3/5

plasma ascorbic acid / alpha-tocopherol

1 evidences

A 6-month antioxidant regimen including vitamin C raised blood antioxidant levels but did not change liver enzymes or hepatitis C viral load.

Trust comment: Randomized, placebo-controlled double-blind trial but small sample (n=23) limits power to detect clinical effects.

Study Details

PMID:16894312
Participants:23
Impact:increased during supplementation (significant)
Trust score:3/5

alanine aminotransferase and HCV viral load

1 evidences

A 6-month antioxidant regimen including vitamin C raised blood antioxidant levels but did not change liver enzymes or hepatitis C viral load.

Trust comment: Randomized, placebo-controlled double-blind trial but small sample (n=23) limits power to detect clinical effects.

Study Details

PMID:16894312
Participants:23
Impact:no significant change vs placebo
Trust score:3/5

plasma antioxidant levels

1 evidences

Large randomized trial testing simvastatin and antioxidant vitamin supplementation (including vitamin C) in high-risk patients; early results showed good tolerability and biochemical changes but no specific vitamin C outcomes reported in this early report.

Trust comment: This large RCT directly tested an antioxidant-vitamin regimen that included vitamin C, but the early report did not present vitamin C-specific effects; overall study design is high quality.

Study Details

PMID:10329064
Participants:20536
Impact:allocation to vitamin supplement produced an average increase in plasma vitamin E (~24 μmol/L); no specific vitamin C effect reported in this early follow-up
Trust score:3/5

wrinkles

1 evidences

Topical serum containing a vitamin C derivative applied daily showed improved wrinkles, firmness and reduced redness over 12 weeks.

Trust comment: Multiple small clinical studies with instrument support but pooled, open-label design and mixed interventions limit strength of causal inference to vitamin C derivative.

Study Details

PMID:30924254
Participants:103
Impact:-11%
Trust score:3/5

skin firmness

1 evidences

Topical serum containing a vitamin C derivative applied daily showed improved wrinkles, firmness and reduced redness over 12 weeks.

Trust comment: Multiple small clinical studies with instrument support but pooled, open-label design and mixed interventions limit strength of causal inference to vitamin C derivative.

Study Details

PMID:30924254
Participants:103
Impact:+8%
Trust score:3/5

redness

1 evidences

Topical serum containing a vitamin C derivative applied daily showed improved wrinkles, firmness and reduced redness over 12 weeks.

Trust comment: Multiple small clinical studies with instrument support but pooled, open-label design and mixed interventions limit strength of causal inference to vitamin C derivative.

Study Details

PMID:30924254
Participants:103
Impact:-70%
Trust score:3/5

antioxidant enzyme activities (SOD, catalase, GST, GR)

1 evidences

Breast-cancer patients given vitamin C plus E during chemotherapy showed improved antioxidant markers and reduced lipid peroxidation and DNA damage compared with chemotherapy alone.

Trust comment: Randomized biomarker study with small sample size; biochemical effects measured robustly but clinical outcomes not assessed.

Study Details

PMID:21204889
Participants:40
Impact:significant increase (P < 0.01)
Trust score:3/5

reduced glutathione

1 evidences

Breast-cancer patients given vitamin C plus E during chemotherapy showed improved antioxidant markers and reduced lipid peroxidation and DNA damage compared with chemotherapy alone.

Trust comment: Randomized biomarker study with small sample size; biochemical effects measured robustly but clinical outcomes not assessed.

Study Details

PMID:21204889
Participants:40
Impact:significant increase (P < 0.01)
Trust score:3/5

malondialdehyde and DNA damage

1 evidences

Breast-cancer patients given vitamin C plus E during chemotherapy showed improved antioxidant markers and reduced lipid peroxidation and DNA damage compared with chemotherapy alone.

Trust comment: Randomized biomarker study with small sample size; biochemical effects measured robustly but clinical outcomes not assessed.

Study Details

PMID:21204889
Participants:40
Impact:significant decrease (P < 0.01)
Trust score:3/5

range of motion (ROM) at 1 year

1 evidences

Perioperative oral vitamin C prevented postoperative plasma vitamin C depletion and was associated with a lower (non-significant) rate of arthrofibrosis after knee replacement.

Trust comment: Double-blind randomized controlled trial with clear biochemical endpoints; modest sample size limits power for some clinical outcomes.

Study Details

PMID:29955932
Participants:95
Impact:no difference between groups
Trust score:4/5

arthrofibrosis prevalence

1 evidences

Perioperative oral vitamin C prevented postoperative plasma vitamin C depletion and was associated with a lower (non-significant) rate of arthrofibrosis after knee replacement.

Trust comment: Double-blind randomized controlled trial with clear biochemical endpoints; modest sample size limits power for some clinical outcomes.

Study Details

PMID:29955932
Participants:95
Impact:10.4% (vit C) vs 23.4% (placebo), p = 0.09
Trust score:4/5

plasma vitamin C concentration post-op

1 evidences

Perioperative oral vitamin C prevented postoperative plasma vitamin C depletion and was associated with a lower (non-significant) rate of arthrofibrosis after knee replacement.

Trust comment: Double-blind randomized controlled trial with clear biochemical endpoints; modest sample size limits power for some clinical outcomes.

Study Details

PMID:29955932
Participants:95
Impact:placebo: 49 → 12 µmol/L (drop); vitamin C: 53 → 57 µmol/L (maintained)
Trust score:4/5

anemia prevalence

6 evidences

Fortified porridge given for 6 months raised hemoglobin and ferritin and improved motor development in infants.

Trust comment: Large randomized trial with good completion (292); includes ascorbic acid as part of a multi-micronutrient fortification so effects are attributable to the combined formulation, not vitamin C alone.

Study Details

PMID:16280435
Participants:292
Impact:decreased from 45% to 17% in fortified group (control remained >40%)
Trust score:4/5

Two months of multi-micronutrient Sprinkles (including vitamin C) reduced anemia and increased hemoglobin in 9–24 month old children.

Trust comment: Cluster-randomized programmatic trial with good sample size but uses multi-micronutrient product so vitamin C-specific effects cannot be isolated.

Study Details

PMID:17374671
Participants:415
Impact:-30 percentage points (54% to 24%) in Sprinkles group at 2 months
Trust score:3/5

In this cohort, nonanemic children had higher vitamin C intake than anemic children, suggesting an association between vitamin C intake and lower anemia prevalence.

Trust comment: Large cohort with dietary assessment showing association, but observational (not randomized to vitamin C).

Study Details

PMID:17279280
Participants:369
Impact:63.7% overall in the studied cohort
Trust score:3/5

Six months of providing drinking-water with ascorbic acid (with or without iron) in daycare centers reduced anemia prevalence and increased mean hemoglobin and height gain in preschool children.

Trust comment: Clustered day-care center intervention with adequate sample and clear outcomes, but allocation by center and lack of individual-level randomization and detailed effect sizes reduce internal validity.

Study Details

PMID:16222916
Participants:150
Impact:decreased (both groups)
Trust score:3/5

A 6-month school feeding intervention with cowpea-based food plus a vitamin C-rich drink increased hemoglobin and reduced anemia prevalence in children.

Trust comment: Randomized school feeding intervention with 150 children in a malaria-endemic setting; reasonable size though infectious disease confounding present.

Study Details

PMID:26385950
Participants:150
Impact:reduction 19.5% (fish meal + vitamin C) vs 9.3% (vitamin C alone) and 12.2% (control)
Trust score:4/5

Daily mungbean meal with guava (high vitamin C) for 7 months increased hemoglobin and reduced anemia prevalence but did not increase body iron stores.

Trust comment: Large, randomized, registered trial in children with supervised feeding and clearly reported outcomes and CIs.

Study Details

PMID:39481541
Participants:200
Impact:-51% (95% CI: -74 to -10; P = 0.022)
Trust score:5/5

height gain

1 evidences

Six months of providing drinking-water with ascorbic acid (with or without iron) in daycare centers reduced anemia prevalence and increased mean hemoglobin and height gain in preschool children.

Trust comment: Clustered day-care center intervention with adequate sample and clear outcomes, but allocation by center and lack of individual-level randomization and detailed effect sizes reduce internal validity.

Study Details

PMID:16222916
Participants:150
Impact:associated increase observed
Trust score:3/5

plasma beta-carotene

3 evidences

Critically ill patients receiving enteral formula enriched with vitamins A, C, and E showed increased plasma antioxidant vitamins and improved LDL resistance to oxidation, with no change in clinical outcomes.

Trust comment: Prospective randomized double-blind placebo-controlled ICU study with demonstrated biochemical effects but small completed sample and no clinical outcome differences.

Study Details

PMID:11153621
Participants:37
Impact:increased from 0.2 to 0.6 μg/mL (+0.4 μg/mL; p<0.01)
Trust score:4/5

Brief behavioural counselling increased fruit and vegetable intake versus nutrition education; plasma beta-carotene and alpha-tocopherol rose but plasma ascorbic acid (vitamin C) did not change.

Trust comment: Adequately powered randomized trial with objective biomarkers; directly measured plasma ascorbic acid though no change observed.

Study Details

PMID:12702620
Participants:271
Impact:increased more in behavioural group (mean difference 0.16 μmol/l)
Trust score:4/5

After 2 years of daily antioxidant supplementation (including 120 mg vitamin C), plasma concentrations of vitamin C, vitamin E, beta-carotene, selenium and zinc were significantly higher than placebo in a 1000-person subsample.

Trust comment: Large randomized double-blind placebo-controlled trial with substantial sample and clear biomarker changes, though this report is preliminary on a subsample.

Study Details

PMID:11718454
Participants:1000
Impact:increased (men 0.86 µmol/L; women 1.25 µmol/L)
Trust score:4/5

CMT Neuropathy Score (CMTNS) change — ascorbic acid

1 evidences

High-dose vitamin C (4 g/day) did not produce clear clinical benefit vs placebo over 2 years for neuropathy in CMT1A patients.

Trust comment: Multicenter randomized double-masked trial with good sample size and follow-up, though futility design limits interpretation.

Study Details

PMID:23797954
Participants:85
Impact:-0.21 over 2 years
Trust score:4/5

CMT Neuropathy Score (CMTNS) change — placebo

1 evidences

High-dose vitamin C (4 g/day) did not produce clear clinical benefit vs placebo over 2 years for neuropathy in CMT1A patients.

Trust comment: Multicenter randomized double-masked trial with good sample size and follow-up, though futility design limits interpretation.

Study Details

PMID:23797954
Participants:85
Impact:-0.92 over 2 years
Trust score:4/5

comparison to natural history

1 evidences

High-dose vitamin C (4 g/day) did not produce clear clinical benefit vs placebo over 2 years for neuropathy in CMT1A patients.

Trust comment: Multicenter randomized double-masked trial with good sample size and follow-up, though futility design limits interpretation.

Study Details

PMID:23797954
Participants:85
Impact:both groups better than natural history (+1.33); no clear treatment benefit
Trust score:4/5

red blood cell folate (RCF)

1 evidences

In smoker blood-donors, vitamin C supplementation increased folate measures but unexpectedly increased homocysteine levels when given alone.

Trust comment: Randomized controlled design in 100 subjects but subgroup effects and short duration limit generalizability.

Study Details

PMID:12048127
Participants:100
Impact:significantly increased after 45 days (with supplementation)
Trust score:3/5

serum folate (SF)

1 evidences

In smoker blood-donors, vitamin C supplementation increased folate measures but unexpectedly increased homocysteine levels when given alone.

Trust comment: Randomized controlled design in 100 subjects but subgroup effects and short duration limit generalizability.

Study Details

PMID:12048127
Participants:100
Impact:significantly increased after 45 days (with supplementation)
Trust score:3/5

homocysteine (Hcy)

1 evidences

In smoker blood-donors, vitamin C supplementation increased folate measures but unexpectedly increased homocysteine levels when given alone.

Trust comment: Randomized controlled design in 100 subjects but subgroup effects and short duration limit generalizability.

Study Details

PMID:12048127
Participants:100
Impact:significantly increased with vitamin C alone (P=0.01)
Trust score:3/5

total lean mass gain

1 evidences

High-dose vitamins C+E during 12 weeks of strength training reduced gains in some muscle mass measures compared with placebo in elderly men.

Trust comment: Randomized trial with objective body-composition measures but small sample size.

Study Details

PMID:26129928
Participants:34
Impact:placebo +3.9% vs antioxidant +1.4% (antioxidants blunted gain; P=0.04)
Trust score:4/5

rectus femoris muscle thickness

1 evidences

High-dose vitamins C+E during 12 weeks of strength training reduced gains in some muscle mass measures compared with placebo in elderly men.

Trust comment: Randomized trial with objective body-composition measures but small sample size.

Study Details

PMID:26129928
Participants:34
Impact:placebo +16.2% vs antioxidant +10.9% (P=0.01)
Trust score:4/5

one-repetition maximum (1RM) strength

1 evidences

High-dose vitamins C+E during 12 weeks of strength training reduced gains in some muscle mass measures compared with placebo in elderly men.

Trust comment: Randomized trial with objective body-composition measures but small sample size.

Study Details

PMID:26129928
Participants:34
Impact:improved 15–21% in both groups (no difference)
Trust score:4/5

cognitive test performance

1 evidences

Long-term supplementation with antioxidants and zinc+copper had no detectable benefit or harm on cognition in older adults.

Trust comment: Large randomized controlled trial with long follow-up and standardized cognitive testing.

Study Details

PMID:15534261
Participants:2166
Impact:no difference between antioxidant (incl. vitamin C) and placebo after ~6.9 years
Trust score:4/5

neuropathic symptoms (numbness, jolting pain, irritation)

1 evidences

Small preliminary randomized, placebo-controlled trial of topical QR-333 (combination including vitamin D3) reported symptom improvements in diabetic neuropathy but attribution to vitamin D is unclear.

Trust comment: Small double-blind randomized safety/efficacy study; contains a vitamin C derivative but is a multi-component topical formulation.

Study Details

PMID:16112498
Participants:34
Impact:reduced severity from baseline with QR-333
Trust score:3/5

patient acceptance/compliance

1 evidences

A 2-L PEG solution with added vitamin C cleaned the bowel about as well as the standard 4-L solution, was better accepted by patients, and showed no unsafe lab values though one MI occurred.

Trust comment: Randomized, endoscopist-blinded RCT with robust sample size; limitation: no plasma vitamin C measurement and limited generalizability to inpatients.

Study Details

PMID:23838870
Participants:188
Impact:increased (significantly)
Trust score:4/5

bowel cleansing efficacy (overall)

1 evidences

A 2-L PEG solution with added vitamin C cleaned the bowel about as well as the standard 4-L solution, was better accepted by patients, and showed no unsafe lab values though one MI occurred.

Trust comment: Randomized, endoscopist-blinded RCT with robust sample size; limitation: no plasma vitamin C measurement and limited generalizability to inpatients.

Study Details

PMID:23838870
Participants:188
Impact:noninferior to 4-L PEG
Trust score:4/5

segmental cleansing (right/transverse colon)

1 evidences

A 2-L PEG solution with added vitamin C cleaned the bowel about as well as the standard 4-L solution, was better accepted by patients, and showed no unsafe lab values though one MI occurred.

Trust comment: Randomized, endoscopist-blinded RCT with robust sample size; limitation: no plasma vitamin C measurement and limited generalizability to inpatients.

Study Details

PMID:23838870
Participants:188
Impact:worse vs 4-L (reduced segmental rating, especially split-dose)
Trust score:4/5

urine lipid peroxidation products (TBARS)

1 evidences

In a 30-day supplementation trial, vitamin E reduced urine lipid peroxidation products, while the supplied text does not report a clear effect for the 1 g/day vitamin C arm.

Trust comment: Small randomized study including a vitamin C arm but the provided report emphasizes vitamin E effects and does not present clear vitamin C results.

Study Details

PMID:8936558
Participants:21
Impact:no clear reported effect for vitamin C (vitamin E: −27% over 30 days)
Trust score:3/5

hs-CRP

1 evidences

Daily 1 g vitamin C for 8 weeks reduced inflammatory markers (hs-CRP, IL-6) and fasting blood glucose in hypertensive and/or diabetic obese adults versus control.

Trust comment: Randomized controlled trial with objective inflammatory/metabolic biomarkers but open-label design and modest sample size limit confidence.

Study Details

PMID:26170625
Participants:64
Impact:significant reduction (between-group difference at 8 wk, P=0.01)
Trust score:4/5

fasting blood glucose (FBG)

1 evidences

Daily 1 g vitamin C for 8 weeks reduced inflammatory markers (hs-CRP, IL-6) and fasting blood glucose in hypertensive and/or diabetic obese adults versus control.

Trust comment: Randomized controlled trial with objective inflammatory/metabolic biomarkers but open-label design and modest sample size limit confidence.

Study Details

PMID:26170625
Participants:64
Impact:significant reduction (between-group difference at 8 wk, P<0.001)
Trust score:4/5

organ dysfunction (modified SOFA score)

1 evidences

In patients with sepsis and ARDS, a 96-hour IV vitamin C infusion did not significantly change organ dysfunction scores or biomarkers of inflammation/vascular injury compared with placebo.

Trust comment: Multicenter randomized double-blind placebo-controlled trial with 167 randomized and moderate attrition; primary endpoints were negative.

Study Details

PMID:31573637
Participants:103
Impact:no significant difference (change from baseline to 96 h similar between groups)
Trust score:4/5

C-reactive protein (inflammation biomarker)

1 evidences

In patients with sepsis and ARDS, a 96-hour IV vitamin C infusion did not significantly change organ dysfunction scores or biomarkers of inflammation/vascular injury compared with placebo.

Trust comment: Multicenter randomized double-blind placebo-controlled trial with 167 randomized and moderate attrition; primary endpoints were negative.

Study Details

PMID:31573637
Participants:103
Impact:no significant difference at 168 h
Trust score:4/5

thrombomodulin (vascular injury biomarker)

1 evidences

In patients with sepsis and ARDS, a 96-hour IV vitamin C infusion did not significantly change organ dysfunction scores or biomarkers of inflammation/vascular injury compared with placebo.

Trust comment: Multicenter randomized double-blind placebo-controlled trial with 167 randomized and moderate attrition; primary endpoints were negative.

Study Details

PMID:31573637
Participants:103
Impact:no significant difference at 168 h
Trust score:4/5

blood ferritin

1 evidences

In women with iron deficiency, the multi-nutrient supplement (contains vitamin C) increased blood iron markers after 60 days.

Trust comment: Small double-blind RCT but vitamin C was given as part of a multi-nutrient supplement, making attribution to vitamin C alone uncertain.

Study Details

PMID:17146419
Participants:49
Impact:increased (significant, P<0.05)
Trust score:3/5

blood iron

1 evidences

In women with iron deficiency, the multi-nutrient supplement (contains vitamin C) increased blood iron markers after 60 days.

Trust comment: Small double-blind RCT but vitamin C was given as part of a multi-nutrient supplement, making attribution to vitamin C alone uncertain.

Study Details

PMID:17146419
Participants:49
Impact:increased (significant in subgroup with low baseline iron)
Trust score:3/5

CRPS I incidence

1 evidences

Provision of 1 g/day vitamin C around foot/ankle surgery was associated with a large reduction in CRPS I incidence compared with the historical control period.

Trust comment: Large before–after quasi-experimental study with strong effect size, but non-randomized historical control limits causal certainty.

Study Details

PMID:19840748
Participants:392
Impact:decreased from 9.6% to 1.7% (absolute −7.9 percentage points; p<0.0001)
Trust score:3/5

gestational hypertension

2 evidences

Daily 1000 mg vitamin C from mid-pregnancy until delivery did not significantly reduce pre-eclampsia or major neonatal adverse outcomes.

Trust comment: Large, well-conducted randomized double-blind trial with intention-to-treat analysis, though lower-than-expected event rate may reduce power.

Study Details

PMID:25142305
Participants:833
Impact:7.7% (vitC) vs 11.5% (placebo); RR 0.67, p=0.06 (trend, not significant)
Trust score:4/5

Large randomized trial in pregnant women with type 1 diabetes: vitamins C+E increased blood vitamin levels but did not reduce pre-eclampsia or gestational hypertension overall.

Trust comment: Large, multicentre randomized placebo-controlled trial with predefined outcomes and high methodological quality.

Study Details

PMID:20580423
Participants:761
Impact:no change
Trust score:5/5

oxidative stress markers (breath pentane, plasma lipid peroxides, malondialdehyde)

1 evidences

Combined high-dose vitamin E and 1000 mg vitamin C for 3 months reduced markers of oxidative stress and showed a non-significant trend toward lower viral load.

Trust comment: Double-blind RCT shows clear biomarker changes but small sample and combination with vitamin E limit attribution to vitamin C alone.

Study Details

PMID:9764785
Participants:49
Impact:decreased (significant vs placebo: breath pentane P<0.025; lipid peroxides P<0.01; MDA P<0.0005)
Trust score:3/5

viral load

1 evidences

Combined high-dose vitamin E and 1000 mg vitamin C for 3 months reduced markers of oxidative stress and showed a non-significant trend toward lower viral load.

Trust comment: Double-blind RCT shows clear biomarker changes but small sample and combination with vitamin E limit attribution to vitamin C alone.

Study Details

PMID:9764785
Participants:49
Impact:trend to decrease (mean change −0.45 log10 vs +0.50 log10; P=0.1)
Trust score:3/5

mean blood pressure (MBP)

1 evidences

In obese children, 45-day 500 mg/day vitamin C supplementation lowered mean blood pressure and restored peripheral vasodilation during mental stress.

Trust comment: Small double-blind randomized study with clear physiological changes but limited sample size and short duration.

Study Details

PMID:21552645
Participants:21
Impact:decreased from 81±2 to 75±1 mmHg at rest (p=0.01)
Trust score:3/5

forearm vascular conductance (FVC)

1 evidences

In obese children, 45-day 500 mg/day vitamin C supplementation lowered mean blood pressure and restored peripheral vasodilation during mental stress.

Trust comment: Small double-blind randomized study with clear physiological changes but limited sample size and short duration.

Study Details

PMID:21552645
Participants:21
Impact:increased at rest 3.40±0.5 → 5.09±0.6 (p=0.04) and during stress 3.92±0.5 → 6.68±0.9 (p=0.03)
Trust score:3/5

8‑isoprostane (F2α) excretion

1 evidences

In septic shock patients, IV vitamin C raised blood vitamin C levels but did not reduce an oxidative stress biomarker (8‑isoprostane).

Trust comment: Randomized placebo-controlled trial (n=40) with objective biomarker endpoints; negative primary outcome but appropriate design.

Study Details

PMID:36401921
Participants:40
Impact:elevated in septic patients; not attenuated by parenteral vitamin C
Trust score:4/5

Vitamin C status

2 evidences

In 324 anemic adolescent girls, once- or twice-weekly multiple micronutrient supplements (including vitamin C) improved vitamin C status and several other micronutrients compared with iron+folic acid over 52 weeks; hemoglobin differences were minimal overall.

Trust comment: Checklist: Vitamin C measured as part of MMN vs IFA comparison; main outcomes (vitamin C status, Hb, ferritin) identified; participant count confirmed—large randomized double-blind trial with appropriate follow-up.

Study Details

PMID:20702745
Participants:324
Impact:improved vs IFA (significant)
Trust score:4/5

In septic shock patients, IV vitamin C raised blood vitamin C levels but did not reduce an oxidative stress biomarker (8‑isoprostane).

Trust comment: Randomized placebo-controlled trial (n=40) with objective biomarker endpoints; negative primary outcome but appropriate design.

Study Details

PMID:36401921
Participants:40
Impact:significantly increased within 24 hours after administration
Trust score:4/5

H2O2‑induced erythrocyte hemolysis

1 evidences

In elderly subjects, combined vitamin C+E (with varying beta‑carotene) improved red blood cell resistance to oxidative hemolysis and membrane function.

Trust comment: Large randomized trial (n=300) showing physiological improvements, but combined antioxidants and limited methodological detail reduce certainty.

Study Details

PMID:18646528
Participants:300
Impact:decreased significantly after supplementation
Trust score:3/5

Erythrocyte membrane ATPase activity

1 evidences

In elderly subjects, combined vitamin C+E (with varying beta‑carotene) improved red blood cell resistance to oxidative hemolysis and membrane function.

Trust comment: Large randomized trial (n=300) showing physiological improvements, but combined antioxidants and limited methodological detail reduce certainty.

Study Details

PMID:18646528
Participants:300
Impact:increased (higher in supplemented groups vs control)
Trust score:3/5

Erythrocyte membrane fluidity / microviscosity

1 evidences

In elderly subjects, combined vitamin C+E (with varying beta‑carotene) improved red blood cell resistance to oxidative hemolysis and membrane function.

Trust comment: Large randomized trial (n=300) showing physiological improvements, but combined antioxidants and limited methodological detail reduce certainty.

Study Details

PMID:18646528
Participants:300
Impact:improved (rho and eta decreased)
Trust score:3/5

recovery from very ill status

1 evidences

In hospitalized infants with severe ALRI, 5-day adjunctive vitamin C+E did not improve clinical recovery, oxidative stress, or immune skin-test responses.

Trust comment: Checklist: 1) Confirm Vitamin C relevance; 2) extract N and main outcomes; 3) rate trustworthiness; Justification: double-blind RCT in 174 infants with adequate design but short adjunct treatment and combined vitamin E confound interpretation; no clinical benefit observed.

Study Details

PMID:16391588
Participants:174
Impact:RR 0.89 (95% CI 0.64–1.25); no significant improvement
Trust score:4/5

oxidative stress (TBARS)

1 evidences

In hospitalized infants with severe ALRI, 5-day adjunctive vitamin C+E did not improve clinical recovery, oxidative stress, or immune skin-test responses.

Trust comment: Checklist: 1) Confirm Vitamin C relevance; 2) extract N and main outcomes; 3) rate trustworthiness; Justification: double-blind RCT in 174 infants with adequate design but short adjunct treatment and combined vitamin E confound interpretation; no clinical benefit observed.

Study Details

PMID:16391588
Participants:174
Impact:no change vs placebo at admission, discharge, 2-week follow-up
Trust score:4/5

cell-mediated immune response (skin antigens)

1 evidences

In hospitalized infants with severe ALRI, 5-day adjunctive vitamin C+E did not improve clinical recovery, oxidative stress, or immune skin-test responses.

Trust comment: Checklist: 1) Confirm Vitamin C relevance; 2) extract N and main outcomes; 3) rate trustworthiness; Justification: double-blind RCT in 174 infants with adequate design but short adjunct treatment and combined vitamin E confound interpretation; no clinical benefit observed.

Study Details

PMID:16391588
Participants:174
Impact:very poor in both groups; no improvement with supplementation
Trust score:4/5

colon epithelial cell proliferation (PCNA labeling index)

1 evidences

In patients post-colorectal cancer resection, 6 months of calcium plus vitamins A, C, E did not reduce colon epithelial proliferation more than placebo.

Trust comment: Checklist: 1) Confirm Vitamin C relevance; 2) extract N and main outcomes; 3) rate trustworthiness; Justification: randomized trial with 77 assessable patients but modest size and combined supplements limits isolation of vitamin C effect; no additional benefit found.

Study Details

PMID:10834024
Participants:77
Impact:Both groups decreased at 6 months (vitamins: 16.11→10.71; placebo: 17.30→12.53); between-group difference not significant (34% vs 28% reduction)
Trust score:4/5

gingival inflammation (GI)

1 evidences

In chronic periodontitis patients receiving SRP, 8-week adjunctive CELC (includes vitamin C) produced a small but statistically significant improvement in gingival inflammation (GI) versus control; other periodontal measures were similar.

Trust comment: Checklist: 1) Confirm Vitamin C relevance; 2) extract N and main outcomes; 3) rate trustworthiness; Justification: well-conducted multicenter randomized trial (93 completers) showing small GI benefit but interpretation limited because the product combined multiple agents and all patients received SRP.

Study Details

PMID:30845920
Participants:93
Impact:Mean Δ baseline–4wk −0.18 (test) vs +0.01 (control); intergroup p=0.015; GEE OR 2.46 (p=0.022)
Trust score:4/5

probing depth (PD)

1 evidences

In chronic periodontitis patients receiving SRP, 8-week adjunctive CELC (includes vitamin C) produced a small but statistically significant improvement in gingival inflammation (GI) versus control; other periodontal measures were similar.

Trust comment: Checklist: 1) Confirm Vitamin C relevance; 2) extract N and main outcomes; 3) rate trustworthiness; Justification: well-conducted multicenter randomized trial (93 completers) showing small GI benefit but interpretation limited because the product combined multiple agents and all patients received SRP.

Study Details

PMID:30845920
Participants:93
Impact:Small within-group decrease in test (−0.11 at 4 weeks) but no significant between-group difference
Trust score:4/5

patient-reported discomfort (VAS)

1 evidences

In chronic periodontitis patients receiving SRP, 8-week adjunctive CELC (includes vitamin C) produced a small but statistically significant improvement in gingival inflammation (GI) versus control; other periodontal measures were similar.

Trust comment: Checklist: 1) Confirm Vitamin C relevance; 2) extract N and main outcomes; 3) rate trustworthiness; Justification: well-conducted multicenter randomized trial (93 completers) showing small GI benefit but interpretation limited because the product combined multiple agents and all patients received SRP.

Study Details

PMID:30845920
Participants:93
Impact:Δ baseline–8wk −13.52 mm (test) vs −4.73 mm (control); intergroup difference at 8 weeks p=0.027 (not significant in adjusted GEE)
Trust score:4/5

hemoglobin recovery time

1 evidences

Among female regular blood donors, adding 500 mg/day ascorbic acid to ferrous fumarate accelerated hemoglobin and RBC index recovery to pre-donation levels (1 month vs 2–3 months).

Trust comment: Checklist: 1) Confirm Vitamin C relevance; 2) extract N and main outcomes; 3) rate trustworthiness; Justification: randomized comparison in 96 volunteers showing a clear, clinically relevant faster Hb recovery with high-dose ascorbic acid adjunct.

Study Details

PMID:23936981
Participants:96
Impact:Ferrous fumarate + ascorbic acid 500 mg: recovery in 1 month vs 2–3 months in other groups (N=96; p<0.001)
Trust score:4/5

oxidative stress markers (TBARS, TAS)

1 evidences

In healthy elderly adults, 6 months of 500–1000 mg ascorbic acid plus 400 IU vitamin E did not significantly change oxidative stress markers, antioxidant enzymes, or DNA damage versus placebo.

Trust comment: Checklist: 1) Confirm Vitamin C relevance; 2) extract N and main outcomes; 3) rate trustworthiness; Justification: double-blind controlled human trial (N=66) with null results, limiting support for high-dose vitamin C+E in healthy elderly.

Study Details

PMID:18446021
Participants:66
Impact:no significant change after 6 months with ascorbic acid + vitamin E
Trust score:4/5

DNA damage (comet assay)

1 evidences

In healthy elderly adults, 6 months of 500–1000 mg ascorbic acid plus 400 IU vitamin E did not significantly change oxidative stress markers, antioxidant enzymes, or DNA damage versus placebo.

Trust comment: Checklist: 1) Confirm Vitamin C relevance; 2) extract N and main outcomes; 3) rate trustworthiness; Justification: double-blind controlled human trial (N=66) with null results, limiting support for high-dose vitamin C+E in healthy elderly.

Study Details

PMID:18446021
Participants:66
Impact:no significant change after supplementation
Trust score:4/5

time to vasopressor requirement

1 evidences

In sepsis patients, IV ascorbic acid combined with thiamine and hydrocortisone shortened time on vasopressors but did not change organ-failure scores or mortality.

Trust comment: Randomized, double-blind, placebo-controlled ICU RCT with moderate sample size and clinically relevant endpoints.

Study Details

PMID:32194058
Participants:137
Impact:-26 hours (27 ± 22 vs 53 ± 38 h; P < .001)
Trust score:4/5

mortality (ICU/hospital/28-day)

1 evidences

In sepsis patients, IV ascorbic acid combined with thiamine and hydrocortisone shortened time on vasopressors but did not change organ-failure scores or mortality.

Trust comment: Randomized, double-blind, placebo-controlled ICU RCT with moderate sample size and clinically relevant endpoints.

Study Details

PMID:32194058
Participants:137
Impact:no significant difference
Trust score:4/5

iron absorption

2 evidences

In schoolchildren, added calcium (100–200 mg/meal) reduced iron absorption by ~18–27%, while ascorbic acid (vitamin C) increased absorption 2–4-fold and overcame the calcium inhibition.

Trust comment: Randomized crossover using stable isotopes in children; strong methodology though group sizes were modest.

Study Details

PMID:25332469
Participants:30
Impact:increased 2–4 fold with ascorbic acid (dose-dependent)
Trust score:4/5

In preschool children, iron absorption from a meal did not differ when served with orange juice versus apple juice.

Trust comment: Randomized crossover stable-isotope study in children with objective isotope-based measurement and 21 completers, giving moderate-high internal validity.

Study Details

PMID:14662581
Participants:21
Impact:median 7.17% (apple) vs 7.78% (orange); P = .44 (no significant difference)
Trust score:4/5

calcium-induced inhibition of iron absorption

1 evidences

In schoolchildren, added calcium (100–200 mg/meal) reduced iron absorption by ~18–27%, while ascorbic acid (vitamin C) increased absorption 2–4-fold and overcame the calcium inhibition.

Trust comment: Randomized crossover using stable isotopes in children; strong methodology though group sizes were modest.

Study Details

PMID:25332469
Participants:30
Impact:reduced absorption by 18–27% without ascorbic acid
Trust score:4/5

interaction by iron status

1 evidences

In schoolchildren, added calcium (100–200 mg/meal) reduced iron absorption by ~18–27%, while ascorbic acid (vitamin C) increased absorption 2–4-fold and overcame the calcium inhibition.

Trust comment: Randomized crossover using stable isotopes in children; strong methodology though group sizes were modest.

Study Details

PMID:25332469
Participants:30
Impact:ascorbic acid effect stronger in iron-deficient children (trend)
Trust score:4/5

palatability

2 evidences

For colonoscopy prep, 2 L ascorbic acid–supplemented PEG was less palatable and less often rated excellent than 4 L PEG+menthol but had similar overall cleansing rates.

Trust comment: Prospective randomized controlled trial with adequate sample size and blinded endoscopic assessment.

Study Details

PMID:25684963
Participants:200
Impact:-14 percentage points vs PEG+M (62% vs 76%; P = 0.03)
Trust score:4/5

Low-volume PEG with ascorbic acid cleans as well as standard PEG, tastes better, and split dosing gives the best cleansing.

Trust comment: Large randomized, single-blind multicenter trial with objective endpoints and good sample size, though not double-blind.

Study Details

PMID:20561621
Participants:868
Impact:Improved with low-volume PEG+ascorbic acid: acceptable/good 58% vs 51% (P < .005).
Trust score:4/5

willingness to retake

1 evidences

For colonoscopy prep, 2 L ascorbic acid–supplemented PEG was less palatable and less often rated excellent than 4 L PEG+menthol but had similar overall cleansing rates.

Trust comment: Prospective randomized controlled trial with adequate sample size and blinded endoscopic assessment.

Study Details

PMID:25684963
Participants:200
Impact:-14 percentage points vs PEG+M (40% vs 54%; P = 0.047)
Trust score:4/5

adequate bowel cleansing (modified Aronchick / Ottawa)

1 evidences

For colonoscopy prep, 2 L ascorbic acid–supplemented PEG was less palatable and less often rated excellent than 4 L PEG+menthol but had similar overall cleansing rates.

Trust comment: Prospective randomized controlled trial with adequate sample size and blinded endoscopic assessment.

Study Details

PMID:25684963
Participants:200
Impact:no significant difference overall (77% vs 82% Aronchick; P = 0.31)
Trust score:4/5

global aesthetic improvement (GAIS)

1 evidences

Applying a topical serum containing vitamin C (with vitamin E and ferulic acid) after microneedle RF produced greater wrinkle reduction, higher global improvement ratings, and increased elastin on histology versus placebo.

Trust comment: Prospective double-blind split-neck RCT with objective and histologic endpoints but small sample (n=31).

Study Details

PMID:40464749
Participants:31
Impact:87.5% vs 14.3% improved (antioxidant vs placebo)
Trust score:4/5

histologic markers (elastin, senescence)

1 evidences

Applying a topical serum containing vitamin C (with vitamin E and ferulic acid) after microneedle RF produced greater wrinkle reduction, higher global improvement ratings, and increased elastin on histology versus placebo.

Trust comment: Prospective double-blind split-neck RCT with objective and histologic endpoints but small sample (n=31).

Study Details

PMID:40464749
Participants:31
Impact:increased elastin and reduced senescence markers (p16, γ-H2A.X)
Trust score:4/5

total cancer incidence

3 evidences

Large double‑blind randomized trial of vitamin C (500 mg daily) ± other antioxidants assessing long‑term cancer incidence and mortality in women.

Trust comment: Large, long‑term, double‑blind randomized trial with hard clinical endpoints; high quality evidence showing no benefit for cancer prevention.

Study Details

PMID:19116389
Participants:7627
Impact:no significant effect (RR 1.11, 95% CI 0.95–1.30 for vitamin C) over ~9.4 years
Trust score:5/5

Daily 500 mg vitamin C did not change prostate or total cancer risk in this large trial of older male physicians.

Trust comment: Large randomized trial with long follow-up and clear outcome measures; high-quality evidence that vitamin C did not affect cancer risk.

Study Details

PMID:25008853
Participants:14641
Impact:HR 1.02 (no significant change)
Trust score:5/5

Long-term daily vitamin C (500 mg) supplementation did not reduce prostate cancer or total cancer incidence in middle-aged and older men over ~8 years.

Trust comment: Large, randomized, double-blind, placebo-controlled trial with long follow-up provides high-quality evidence of no cancer-preventive effect.

Study Details

PMID:19066368
Participants:14641
Impact:No effect of vitamin C: HR 1.01 (95% CI 0.92–1.10), P=0.86
Trust score:5/5

prostate cancer incidence

3 evidences

Long-term daily vitamin C (500 mg) supplementation did not reduce prostate cancer or total cancer incidence in middle-aged and older men over ~8 years.

Trust comment: Large, randomized, double-blind, placebo-controlled trial with long follow-up provides high-quality evidence of no cancer-preventive effect.

Study Details

PMID:19066368
Participants:14641
Impact:No effect of vitamin C: HR 1.02 (95% CI 0.90–1.15), P=0.80
Trust score:5/5

Daily 500 mg vitamin C did not change prostate or total cancer risk in this large trial of older male physicians.

Trust comment: Large randomized trial with long follow-up and clear outcome measures; high-quality evidence that vitamin C did not affect cancer risk.

Study Details

PMID:25008853
Participants:14641
Impact:HR 1.03 (no significant change)
Trust score:5/5

In this cohort of 1,985 men, higher intake of vitamin C‑rich vegetables (e.g., bell peppers, broccoli) was associated with lower prostate cancer risk.

Trust comment: Observational cohort evidence linking vitamin C‑rich vegetables (not isolated vitamin C) to lower prostate cancer risk; confounding possible.

Study Details

PMID:17519926
Participants:1985
Impact:decreased risk associated with increasing intake of vitamin C‑rich vegetables (effect size not provided)
Trust score:3/5

CK-MB release (myocardial injury marker)

1 evidences

Preoperative combined vitamin E and 1 g vitamin C given before bypass did not reduce markers or signs of myocardial injury.

Trust comment: Randomized double-blind trial but small sample and combined with vitamin E so vitamin C-specific effects cannot be isolated.

Study Details

PMID:9159629
Participants:76
Impact:no significant change
Trust score:3/5

myocardial perfusion defect

1 evidences

Preoperative combined vitamin E and 1 g vitamin C given before bypass did not reduce markers or signs of myocardial injury.

Trust comment: Randomized double-blind trial but small sample and combined with vitamin E so vitamin C-specific effects cannot be isolated.

Study Details

PMID:9159629
Participants:76
Impact:no significant change
Trust score:3/5

electrocardiographic evidence of ischemia

1 evidences

Preoperative combined vitamin E and 1 g vitamin C given before bypass did not reduce markers or signs of myocardial injury.

Trust comment: Randomized double-blind trial but small sample and combined with vitamin E so vitamin C-specific effects cannot be isolated.

Study Details

PMID:9159629
Participants:76
Impact:no significant change
Trust score:3/5

TPO antibody level

1 evidences

Three months of 500 mg/day vitamin C (and selenium arm) showed decreases in TPO antibodies within treated groups, but no significant differences compared with placebo.

Trust comment: Randomized clinical trial but small groups, short duration, and no between-group significance for primary antibody outcome.

Study Details

PMID:30182359
Participants:102
Impact:decrease within vitamin C group (not significant vs placebo)
Trust score:3/5

TSH

1 evidences

Three months of 500 mg/day vitamin C (and selenium arm) showed decreases in TPO antibodies within treated groups, but no significant differences compared with placebo.

Trust comment: Randomized clinical trial but small groups, short duration, and no between-group significance for primary antibody outcome.

Study Details

PMID:30182359
Participants:102
Impact:no significant change
Trust score:3/5

Tg antibody level

1 evidences

Three months of 500 mg/day vitamin C (and selenium arm) showed decreases in TPO antibodies within treated groups, but no significant differences compared with placebo.

Trust comment: Randomized clinical trial but small groups, short duration, and no between-group significance for primary antibody outcome.

Study Details

PMID:30182359
Participants:102
Impact:no significant change
Trust score:3/5

plasma lipoprotein(a) concentration

1 evidences

One gram/day vitamin C for 8 months did not lower plasma lipoprotein(a) compared with placebo.

Trust comment: Randomized, placebo-controlled, blinded trial of reasonable duration and sample size showing no effect on Lp(a).

Study Details

PMID:10924732
Participants:101
Impact:supplement: 0.033 → 0.038 g/L (+0.005 g/L, ~+15%, not significant); placebo: 0.026 → 0.027 g/L (no significant change)
Trust score:4/5

successful bowel cleansing (Harefield scale)

1 evidences

A 2-L PEG+ascorbate solution produced similar high-quality colon cleansing but better tolerability and fewer adverse events than standard 4-L PEG.

Trust comment: Large randomized clinical trial with clear endpoints showing improved acceptability for the ascorbate-containing low-volume prep.

Study Details

PMID:23769755
Participants:400
Impact:94.1% (2-L PEG+ascorbate) vs 90.9% (4-L PEG) — no superiority (non-significant)
Trust score:4/5

treatment-related adverse events

1 evidences

A 2-L PEG+ascorbate solution produced similar high-quality colon cleansing but better tolerability and fewer adverse events than standard 4-L PEG.

Trust comment: Large randomized clinical trial with clear endpoints showing improved acceptability for the ascorbate-containing low-volume prep.

Study Details

PMID:23769755
Participants:400
Impact:80.2% (2-L) vs 89.9% (4-L), fewer AEs with 2-L (p=0.011)
Trust score:4/5

willingness to repeat preparation

2 evidences

In 62 inpatients, low-volume PEG with ascorbic acid had comparable bowel-cleansing efficacy and tolerability to 2 L PEG plus bisacodyl when given split-dose.

Trust comment: Small randomized trial directly testing an ascorbic acid–containing bowel prep with clear endpoints but limited sample size.

Study Details

PMID:25862428
Participants:62
Impact:low-volume PEG/ascorbic acid: 90.6% willing; 2 L PEG+bisacodyl: 96.9% willing
Trust score:3/5

A 2-L PEG+ascorbate solution produced similar high-quality colon cleansing but better tolerability and fewer adverse events than standard 4-L PEG.

Trust comment: Large randomized clinical trial with clear endpoints showing improved acceptability for the ascorbate-containing low-volume prep.

Study Details

PMID:23769755
Participants:400
Impact:87% (2-L) vs 51% (4-L) (p<0.001)
Trust score:4/5

health-related quality of life (SF-36/GHQ-12)

1 evidences

Long-term daily supplementation with a capsule containing vitamins and minerals (including 20 mg zinc) did not improve health-related quality of life versus placebo.

Trust comment: Large, long-duration randomized double-blind trial but used a multi-nutrient supplement so effects cannot be ascribed to vitamin C alone.

Study Details

PMID:22158670
Participants:8112
Impact:no significant difference in change over ~76 months between supplement (includes vitamin C) and placebo
Trust score:4/5

all-cause mortality

5 evidences

In postmenopausal women with coronary disease, antioxidant vitamins (including vitamin C) did not slow artery narrowing and were associated with a suggestion of harm including more deaths.

Trust comment: Large randomized double-blind RCT (n=423) providing high-quality evidence, but vitamins were given combined so effects cannot be attributed to vitamin C alone.

Study Details

PMID:12435256
Participants:423
Impact:16 deaths in vitamin group vs 6 in placebo (HR 2.8; 95% CI 1.1–7.2)
Trust score:4/5

Large randomized placebo-controlled trial in high-risk adults: combined antioxidant regimen (including vitamin C 250 mg/day) produced no significant reduction in mortality, major vascular events, or cancer over ~5 years.

Trust comment: Very large, randomized placebo-controlled trial with long follow-up and good adherence, providing high-quality evidence.

Study Details

PMID:12114037
Participants:20536
Impact:no significant effect over 5 years
Trust score:5/5

Large randomized placebo-controlled trial in a high-risk Chinese population; long-term (7.3 years) vitamin supplementation (included 250 mg vitamin C with vitamin E and selenium) reduced gastric cancer incidence and gastric cancer mortality over 22.3 years.

Trust comment: Large randomized, placebo-controlled factorial trial with excellent compliance and 22-year follow-up; vitamin arm included vitamin C as a component.

Study Details

PMID:31511230
Participants:3365
Impact:marginal decrease (HR 0.87, P=0.07)
Trust score:5/5

Higher blood vitamin C levels were associated with lower mortality risk in older adults.

Trust comment: Large cohort with objective blood measures and multivariable adjustment, but observational design limits causal inference.

Study Details

PMID:14594788
Participants:1214
Impact:-46% (HR = 0.54 for highest vs lowest blood ascorbate quintile)
Trust score:4/5

In this cohort of middle-aged men, higher combined intake of vitamin C and beta-carotene was associated with lower cancer, coronary, and all-cause mortality over long-term follow-up.

Trust comment: Large long-term observational cohort showing associations but subject to confounding and combined-nutrient exposure (vitamin C + beta-carotene) limits causal attribution to vitamin C alone.

Study Details

PMID:7503047
Participants:1556
Impact:relative risk 0.69 (−31% for specified intake increment)
Trust score:3/5

major vascular events (coronary, stroke, revascularisation)

1 evidences

Large randomized placebo-controlled trial in high-risk adults: combined antioxidant regimen (including vitamin C 250 mg/day) produced no significant reduction in mortality, major vascular events, or cancer over ~5 years.

Trust comment: Very large, randomized placebo-controlled trial with long follow-up and good adherence, providing high-quality evidence.

Study Details

PMID:12114037
Participants:20536
Impact:no significant effect (event rate ratio 1.00)
Trust score:5/5

cancer incidence

2 evidences

Large randomized placebo-controlled trial in high-risk adults: combined antioxidant regimen (including vitamin C 250 mg/day) produced no significant reduction in mortality, major vascular events, or cancer over ~5 years.

Trust comment: Very large, randomized placebo-controlled trial with long follow-up and good adherence, providing high-quality evidence.

Study Details

PMID:12114037
Participants:20536
Impact:no significant effect
Trust score:5/5

A randomized dietary trial showed the Mediterranean-type diet group had fewer deaths and cancers over 4 years; plasma vitamin C levels increased in the diet group, but the effect cannot be attributed solely to vitamin C.

Trust comment: Randomized trial with clinically important outcomes, but diet changes were multifactorial so vitamin C-specific attribution is limited.

Study Details

PMID:9625397
Participants:605
Impact:−61% (reduction in experimental vs control after adjustment)
Trust score:3/5

lymphocyte 8-OHdG (DNA oxidative damage)

1 evidences

Randomized placebo-controlled study in hemodialysis patients: IV vitamin C (300 mg postdialysis thrice weekly) reduced lymphocyte DNA oxidation and intracellular ROS and increased hOGG1 expression.

Trust comment: Randomized placebo-controlled trial with biochemical endpoints and reasonable completer count (51), though specific clinical impact is limited.

Study Details

PMID:15253739
Participants:51
Impact:decreased (22.9 to 18.8 per 10^6 dG)
Trust score:4/5

intracellular ROS production

1 evidences

Randomized placebo-controlled study in hemodialysis patients: IV vitamin C (300 mg postdialysis thrice weekly) reduced lymphocyte DNA oxidation and intracellular ROS and increased hOGG1 expression.

Trust comment: Randomized placebo-controlled trial with biochemical endpoints and reasonable completer count (51), though specific clinical impact is limited.

Study Details

PMID:15253739
Participants:51
Impact:decreased (spontaneous and PMA-stimulated)
Trust score:4/5

hOGG1 mRNA expression

1 evidences

Randomized placebo-controlled study in hemodialysis patients: IV vitamin C (300 mg postdialysis thrice weekly) reduced lymphocyte DNA oxidation and intracellular ROS and increased hOGG1 expression.

Trust comment: Randomized placebo-controlled trial with biochemical endpoints and reasonable completer count (51), though specific clinical impact is limited.

Study Details

PMID:15253739
Participants:51
Impact:up-regulated at 24 hours
Trust score:4/5

systolic blood pressure (24 h)

1 evidences

Double-blind RCT in 110 men with grade 1 hypertension: combined vitamins C (1 g/day) and E lowered 24 h ambulatory systolic, diastolic, and mean arterial blood pressure and increased antioxidant capacity.

Trust comment: Randomized double-blind placebo-controlled trial with objective BP and biochemical measures; effect is for combined C+E so attribution to vitamin C alone is uncertain.

Study Details

PMID:17999638
Participants:110
Impact:decreased (significantly vs placebo)
Trust score:4/5

diastolic blood pressure (24 h)

1 evidences

Double-blind RCT in 110 men with grade 1 hypertension: combined vitamins C (1 g/day) and E lowered 24 h ambulatory systolic, diastolic, and mean arterial blood pressure and increased antioxidant capacity.

Trust comment: Randomized double-blind placebo-controlled trial with objective BP and biochemical measures; effect is for combined C+E so attribution to vitamin C alone is uncertain.

Study Details

PMID:17999638
Participants:110
Impact:decreased (significantly vs placebo)
Trust score:4/5

erythrocyte and serum antioxidant capacity

1 evidences

Double-blind RCT in 110 men with grade 1 hypertension: combined vitamins C (1 g/day) and E lowered 24 h ambulatory systolic, diastolic, and mean arterial blood pressure and increased antioxidant capacity.

Trust comment: Randomized double-blind placebo-controlled trial with objective BP and biochemical measures; effect is for combined C+E so attribution to vitamin C alone is uncertain.

Study Details

PMID:17999638
Participants:110
Impact:increased (significantly vs placebo)
Trust score:4/5

quadriceps muscle thickness (MT)

1 evidences

Placebo-controlled randomized study in young women: vitamins C (1 g/day) + E during 10 weeks strength training increased muscle thickness and strength measures but appeared to attenuate strength/work improvements compared with placebo.

Trust comment: Randomized placebo-controlled trial with objective performance measures but small sample and mixed/attenuating effects of antioxidant supplementation.

Study Details

PMID:29939770
Participants:42
Impact:increased (vitamins 37.2 ± 5.4 to 40.3 ± 5.6 mm)
Trust score:3/5

peak torque (PT)

1 evidences

Placebo-controlled randomized study in young women: vitamins C (1 g/day) + E during 10 weeks strength training increased muscle thickness and strength measures but appeared to attenuate strength/work improvements compared with placebo.

Trust comment: Randomized placebo-controlled trial with objective performance measures but small sample and mixed/attenuating effects of antioxidant supplementation.

Study Details

PMID:29939770
Participants:42
Impact:increased (vitamins 146.0 ± 29.1 to 170.1 ± 30.3 N·m) but improvement attenuated vs placebo
Trust score:3/5

total work (TW)

1 evidences

Placebo-controlled randomized study in young women: vitamins C (1 g/day) + E during 10 weeks strength training increased muscle thickness and strength measures but appeared to attenuate strength/work improvements compared with placebo.

Trust comment: Randomized placebo-controlled trial with objective performance measures but small sample and mixed/attenuating effects of antioxidant supplementation.

Study Details

PMID:29939770
Participants:42
Impact:increased (vitamins 2068.3 ± 401.2 to 2295.5 ± 426.8 J) but improvement attenuated vs placebo
Trust score:3/5

overall successful bowel preparation

1 evidences

A low-volume PEG solution containing ascorbic acid provided effective bowel cleansing and better proximal colon cleansing versus comparator in this pilot study.

Trust comment: Single-blind randomized pilot (n=65); clinically relevant endpoints but modest sample size and pilot design.

Study Details

PMID:18179734
Participants:65
Impact:84.4% vs 72.7% (PEG+ascorbic acid vs comparator), treatment difference +11.6% (p=0.367, not significant)
Trust score:3/5

lipid peroxidation

1 evidences

Multivitamin/mineral supplements given to women undergoing IVF were associated with decreased oxidative stress markers and higher antioxidant vitamin levels in serum and follicular fluid.

Trust comment: Moderate-sized human study with biological measures but unclear blinding/controls and combined multivitamin intervention limits attribution to vitamin C alone.

Study Details

PMID:20226443
Participants:69
Impact:decreased (reduced oxidative stress reported)
Trust score:3/5

bowel cleansing efficacy (fecal properties at 2 hours)

1 evidences

Randomized trial comparing AJG522 (contains ascorbic acid) with PEG+E for bowel prep: AJG522 produced faster/better early cleansing, lower preparation volume and higher acceptability.

Trust comment: Randomized trial with blinded outcome assessment and clinically relevant endpoints, but single-center pilot with modest sample size.

Study Details

PMID:25688357
Participants:75
Impact:significantly better with AJG522 at 2 hours (P<0.05)
Trust score:4/5

preparation volume consumed

1 evidences

Randomized trial comparing AJG522 (contains ascorbic acid) with PEG+E for bowel prep: AJG522 produced faster/better early cleansing, lower preparation volume and higher acceptability.

Trust comment: Randomized trial with blinded outcome assessment and clinically relevant endpoints, but single-center pilot with modest sample size.

Study Details

PMID:25688357
Participants:75
Impact:median 1000 mL (AJG522) vs 2000 mL (PEG+E); P<0.0001
Trust score:4/5

acceptability (willingness to take more)

1 evidences

Randomized trial comparing AJG522 (contains ascorbic acid) with PEG+E for bowel prep: AJG522 produced faster/better early cleansing, lower preparation volume and higher acceptability.

Trust comment: Randomized trial with blinded outcome assessment and clinically relevant endpoints, but single-center pilot with modest sample size.

Study Details

PMID:25688357
Participants:75
Impact:AJG522 65.6% vs PEG+E 33.3% (P=0.010)
Trust score:4/5

fasting blood sugar (FBS)

2 evidences

Randomized allocation to 500 mg or 1000 mg vitamin C daily for 6 weeks in type 2 diabetic patients; 1000 mg/day produced metabolic improvements whereas 500 mg did not.

Trust comment: Randomized human study with clear metabolic endpoints but relatively small size, short duration (6 weeks) and limited methodological detail reported.

Study Details

PMID:18160753
Participants:84
Impact:significant decrease with 1000 mg/day (no change with 500 mg)
Trust score:3/5

In type 2 diabetic patients on metformin, adding 500 mg vitamin C daily for 12 months improved fasting glucose, HbA1c and albumin-to-creatinine ratio versus metformin alone.

Trust comment: Well-powered 12-month randomized multicenter trial with monthly monitoring and objective biochemical endpoints, though single-blind and lacking ITT/repeated-measures in final analysis.

Study Details

PMID:28807030
Participants:422
Impact:Decreased from 7.65 ±2.52 to 5.18 ±1.66 mmol/L (−2.47 mmol/L) in ascorbic acid arm (P<0.01)
Trust score:4/5

glycated hemoglobin (HbA1c)

1 evidences

Randomized allocation to 500 mg or 1000 mg vitamin C daily for 6 weeks in type 2 diabetic patients; 1000 mg/day produced metabolic improvements whereas 500 mg did not.

Trust comment: Randomized human study with clear metabolic endpoints but relatively small size, short duration (6 weeks) and limited methodological detail reported.

Study Details

PMID:18160753
Participants:84
Impact:significant decrease with 1000 mg/day (no change with 500 mg)
Trust score:3/5

LDL cholesterol (and triglycerides)

1 evidences

Randomized allocation to 500 mg or 1000 mg vitamin C daily for 6 weeks in type 2 diabetic patients; 1000 mg/day produced metabolic improvements whereas 500 mg did not.

Trust comment: Randomized human study with clear metabolic endpoints but relatively small size, short duration (6 weeks) and limited methodological detail reported.

Study Details

PMID:18160753
Participants:84
Impact:significant decrease with 1000 mg/day (no change with 500 mg)
Trust score:3/5

F2-isoprostanes (oxidative stress marker)

1 evidences

Double-blind RCT of blackcurrant juice rich in vitamin C and polyphenols for 6 weeks: raised plasma vitamin C, lowered oxidative stress and improved endothelial function.

Trust comment: Well-conducted double-blind RCT with objective vascular and biochemical outcomes, but intervention combined vitamin C with polyphenols so effects of vitamin C alone are uncertain.

Study Details

PMID:24742818
Participants:66
Impact:lower in high-dose group (225 pg/ml) versus low (257) and placebo (254); P≤0.003
Trust score:4/5

H. pylori eradication rate (intention-to-treat)

1 evidences

Randomized trial adding vitamins C (500 mg b.i.d.) and E to standard H. pylori therapy increased eradication rates compared with standard therapy alone.

Trust comment: Randomized controlled trial with large, clinically important effect on eradication rates, though details on blinding/multicenter status are limited.

Study Details

PMID:19674132
Participants:153
Impact:AJG (vitamins C+E) 73/80 (91.25%) vs control 48/80 (60%) — +31.25 percentage points
Trust score:4/5

H. pylori eradication rate (per-protocol)

1 evidences

Randomized trial adding vitamins C (500 mg b.i.d.) and E to standard H. pylori therapy increased eradication rates compared with standard therapy alone.

Trust comment: Randomized controlled trial with large, clinically important effect on eradication rates, though details on blinding/multicenter status are limited.

Study Details

PMID:19674132
Participants:153
Impact:AJG (vitamins C+E) 73/78 (93.5%) vs control 48/75 (64%) — +29.5 percentage points
Trust score:4/5

semen parameters (volume, concentration, motility, count, viability)

1 evidences

Randomized double-blind trial in infertile men given high-dose vitamin C (1000 mg) + vitamin E for 56 days showed no improvement in conventional semen parameters or 24-h sperm survival.

Trust comment: Double-blind randomized trial but small sample size and negative findings reduce confidence in positive effects.

Study Details

PMID:10221237
Participants:31
Impact:no change with high-dose vitamins C+E versus placebo
Trust score:3/5

24-hour sperm survival

1 evidences

Randomized double-blind trial in infertile men given high-dose vitamin C (1000 mg) + vitamin E for 56 days showed no improvement in conventional semen parameters or 24-h sperm survival.

Trust comment: Double-blind randomized trial but small sample size and negative findings reduce confidence in positive effects.

Study Details

PMID:10221237
Participants:31
Impact:no change with high-dose vitamins C+E versus placebo
Trust score:3/5

plasma lipid peroxide (lipid peroxidation)

1 evidences

An antioxidant-rich (vitamin C–containing) diet after acute MI increased plasma vitamin C and reduced lipid peroxidation and cardiac enzyme rise versus control diet.

Trust comment: Large randomized controlled diet intervention in MI patients with clear biochemical endpoints and adequate sample size, increasing confidence.

Study Details

PMID:7797808
Participants:406
Impact:greater decrease in intervention vs control (0.59 → vs 0.10 change; difference ≈0.49 pmol/L)
Trust score:4/5

lactate dehydrogenase (cardiac enzyme)

1 evidences

An antioxidant-rich (vitamin C–containing) diet after acute MI increased plasma vitamin C and reduced lipid peroxidation and cardiac enzyme rise versus control diet.

Trust comment: Large randomized controlled diet intervention in MI patients with clear biochemical endpoints and adequate sample size, increasing confidence.

Study Details

PMID:7797808
Participants:406
Impact:smaller increase in intervention (427.7 U/L) vs control (561.2 U/L); difference ≈-133.5 U/L
Trust score:4/5

natriuretic effect of furosemide

1 evidences

Intravenous vitamin C reduced oxidative stress and, in enalapril-treated moderate CHF patients, augmented the natriuretic effect of furosemide.

Trust comment: Small study with multiple small protocols and crossover elements showing physiologic effects, but limited power and group sizes reduce confidence.

Study Details

PMID:12514674
Participants:35
Impact:in enalapril-treated CHF patients: urine natriuresis ↑ from 179 ±98 to 192 ±104 μmol/min (≈+13 μmol/min, P<.01)
Trust score:3/5

peak oxygen consumption (peak VO2)

1 evidences

A single 2 g dose of vitamin C before exercise increased heart-rate and norepinephrine responses and improved peak VO2 in post-MI patients.

Trust comment: Randomized crossover design in post-MI patients shows consistent physiological effects but small sample size limits generalizability.

Study Details

PMID:16246442
Participants:21
Impact:increase (improved peak VO2 after ascorbic acid administration; exact magnitude not provided)
Trust score:3/5

heart rate and norepinephrine response to exercise (DeltaHR/logDeltaNE)

1 evidences

A single 2 g dose of vitamin C before exercise increased heart-rate and norepinephrine responses and improved peak VO2 in post-MI patients.

Trust comment: Randomized crossover design in post-MI patients shows consistent physiological effects but small sample size limits generalizability.

Study Details

PMID:16246442
Participants:21
Impact:increase (enhanced DeltaHR/logDeltaNE with ascorbic acid)
Trust score:3/5

fruit consumption

1 evidences

A low-cost cafeteria nudge intervention made children take and eat more fruit at lunchtime.

Trust comment: Cluster randomized design with validated individual consumption measures, but only two clusters per arm and short follow-up limit generalizability.

Study Details

PMID:30760296
Participants:176
Impact:+4.47 g (mean increase from 7.88 g to 12.35 g at lunchtime)
Trust score:4/5

vitamin C intake

16 evidences

Randomized trial comparing GUMLi formula vs cows' milk in toddlers; reports nutrient intake differences including higher vitamin D intake in the GUMLi group.

Trust comment: Multi-centre, double-blind RCT with repeated dietary assessments and adequate sample size.

Study Details

PMID:30912737
Participants:160
Impact:higher in GUMLi group at 2 years (vs cows' milk)
Trust score:4/5

A low-cost cafeteria nudge intervention made children take and eat more fruit at lunchtime.

Trust comment: Cluster randomized design with validated individual consumption measures, but only two clusters per arm and short follow-up limit generalizability.

Study Details

PMID:30760296
Participants:176
Impact:+2.98 mg (mean increase from 6.60 mg to 9.58 mg at lunchtime)
Trust score:4/5

Cross-sectional analysis relating dietary vitamins (including vitamin C) to early AMD signs; higher vitamin A (not vitamin C) intake associated with larger drusen in certain genotypes.

Trust comment: Well-sized cross-sectional human study; vitamin C was assessed but no clear association with early AMD was reported.

Study Details

PMID:27502478
Participants:848
Impact:no clear association with early AMD reported in text (no significant effect described)
Trust score:3/5

An 18‑week worksite plant‑based dietary intervention increased reported vitamin C intake and other micronutrients among completers.

Trust comment: Large multicenter randomized cluster trial with objective design and adequate sample (183 completers) though nutrient intakes were self‑reported, limiting precision.

Study Details

PMID:23942177
Participants:183
Impact:increased (significant in intervention vs control)
Trust score:4/5

In this cohort, nonanemic children had higher vitamin C intake than anemic children, suggesting an association between vitamin C intake and lower anemia prevalence.

Trust comment: Large cohort with dietary assessment showing association, but observational (not randomized to vitamin C).

Study Details

PMID:17279280
Participants:369
Impact:higher in nonanemic vs anemic children (P = 0.001)
Trust score:3/5

A 6‑month lifestyle intervention led to weight loss and increased physical activity; measured vitamin C intake (marker of fruit/vegetable intake) showed no difference between groups.

Trust comment: Small randomized trial (n=45 randomized; ~38 completers) with meaningful clinical endpoints but limited power for nutrient intake differences.

Study Details

PMID:18243282
Participants:38
Impact:no significant change (no difference between groups)
Trust score:3/5

Close dietetic supervision of a Mediterranean-style diet increased antioxidant intake, including vitamin C, and raised plasma antioxidant capacity over 2 months.

Trust comment: Randomized human trial (n=90) with clear outcome measures and significant results; moderate-high quality.

Study Details

PMID:22237557
Participants:90
Impact:+increased (P<0.05)
Trust score:4/5

Eating two kiwifruit daily increased vitamin C intake and lowered systolic blood pressure by ~2.7 mmHg over 7 weeks, without changing fasting insulin or other metabolic markers.

Trust comment: Randomized controlled trial with objective measures and documented vitamin C intake increase; modest sample size and short duration limit generalizability.

Study Details

PMID:35807858
Participants:43
Impact:Increased in the kiwifruit group during intervention
Trust score:4/5

Individualized nutritional counseling after HSCT improved intake adequacy of several micronutrients, including vitamin C, by day 100.

Trust comment: Small randomized trial showing improved reported intake, but it assesses intake adequacy not direct clinical effects of vitamin C.

Study Details

PMID:33257778
Participants:46
Impact:improved adequacy at 100 days post-HSCT in counseling group (no numeric value reported)
Trust score:3/5

Adults with metabolic syndrome counseled on DASH diet plus low-sodium vegetable juice (a source of vitamin C) increased vitamin C intake and experienced modestly greater weight loss; oxidative stress markers did not change.

Trust comment: Randomized trial with objective measures but small sample, short duration and industry involvement which may affect bias.

Study Details

PMID:20178625
Participants:81
Impact:increased (significant vs no-juice; p<0.05)
Trust score:3/5

A feeding trial comparing diets raised vitamin C intake and produced substantially greater systolic blood pressure reduction, but the study assessed a whole-diet intervention (not isolated vitamin C).

Trust comment: Randomized feeding trial with objective intake and BP outcomes, but vitamin C change is part of a multifactorial diet so causal attribution to vitamin C alone is limited.

Study Details

PMID:38445388
Participants:53
Impact:CHH diet 152.22 mg/d vs control 120.75 mg/d (+31.5 mg/d)
Trust score:4/5

Randomized trial of DNA-based dietary advice found no significant changes in vitamin C intake at 3 or 12 months compared to controls.

Trust comment: Randomized controlled design with 12-month follow-up and adjusted analyses, but dietary intake was self-reported via FFQ.

Study Details

PMID:25398084
Participants:123
Impact:no significant change from baseline at 3 or 12 months compared to control (no between-group difference)
Trust score:4/5

In this cross-sectional study, people with diet-related beliefs about colorectal cancer prevention reported higher vitamin C intake.

Trust comment: Moderate-quality cross-sectional study (n=169) showing association between beliefs and reported vitamin C intake, but no causal inference.

Study Details

PMID:25528326
Participants:169
Impact:higher intake in those with diet-related CRC prevention beliefs (p=0.039)
Trust score:3/5

A school nutrition intervention increased fruit and vegetable intake by 47% in 7-9-year-olds and produced a borderline increase in vitamin C intake.

Trust comment: Controlled school intervention with weighed dietary records and paired baseline/follow-up data (n=106), though some nutrient changes were only borderline significant.

Study Details

PMID:20409359
Participants:106
Impact:borderline increase (not quantified)
Trust score:4/5

In 589 individuals from 169 families, a multifaceted family-based intervention (personalized goal setting + cooking + education) increased dietary vitamin C intake at 3 and 18 months versus education alone.

Trust comment: Large randomized parallel-design community trial with multiple follow-ups and clear dietary outcomes, though long-term retention dropped substantially.

Study Details

PMID:22017999
Participants:589
Impact:increased in intervention C vs A at 3 months (P = 0.002) and at 18 months (P = 0.01)
Trust score:4/5

In women, interpersonal stressors were associated with higher ghrelin, lower leptin, and small/marginal increases in several dietary components including vitamin C intake.

Trust comment: Small observational study (n=50) with repeated measures linking stressors to hormones and diet; vitamin C appears only as part of dietary associations.

Study Details

PMID:25032903
Participants:50
Impact:marginally higher intake associated with more interpersonal stressors
Trust score:3/5

fibre intake

1 evidences

A low-cost cafeteria nudge intervention made children take and eat more fruit at lunchtime.

Trust comment: Cluster randomized design with validated individual consumption measures, but only two clusters per arm and short follow-up limit generalizability.

Study Details

PMID:30760296
Participants:176
Impact:+0.66 g (mean increase from 2.55 g to 3.21 g at lunchtime)
Trust score:4/5

vitamin C intake (from fruit)

1 evidences

Monthly volunteer home visits did not change infant vitamin C intake but improved some feeding practices and increased certain fruit/vegetable consumption.

Trust comment: Randomized controlled trial with a substantial initial sample but moderate attrition (68% completed) and nutrient outcomes reported as non-significant.

Study Details

PMID:19141661
Participants:212
Impact:no significant change at 12 and 18 months
Trust score:4/5

specific fruit and vegetable consumption

1 evidences

Monthly volunteer home visits did not change infant vitamin C intake but improved some feeding practices and increased certain fruit/vegetable consumption.

Trust comment: Randomized controlled trial with a substantial initial sample but moderate attrition (68% completed) and nutrient outcomes reported as non-significant.

Study Details

PMID:19141661
Participants:212
Impact:increased (statistically significant; no numeric intake provided)
Trust score:4/5

alpha- and gamma-tocopherol disappearance rates

1 evidences

In smokers, short-term vitamin C supplements reduced the faster loss of vitamin E seen with smoking.

Trust comment: Double-blind, placebo-controlled crossover with mechanistic labeled-tocopherol measures but small sample size limits precision.

Study Details

PMID:16458200
Participants:24
Impact:smoking-associated increased disappearance rates were reduced/normalized by ascorbic acid supplementation (500 mg twice daily)
Trust score:4/5

plasma F2alpha-isoprostanes

1 evidences

In smokers, short-term vitamin C supplements reduced the faster loss of vitamin E seen with smoking.

Trust comment: Double-blind, placebo-controlled crossover with mechanistic labeled-tocopherol measures but small sample size limits precision.

Study Details

PMID:16458200
Participants:24
Impact:no change with supplementation
Trust score:4/5

serum adiponectin concentration

1 evidences

Irvingia gabonensis kernel extract (300 mg/day) in overweight/obese women for 12 weeks raised plasma vitamin C and maintained adiponectin but did not change fat oxidation, body composition, telomere length, or aerobic capacity.

Trust comment: Randomized, double-blind placebo-controlled RCT with appropriate methods and adequate completion (66), though single-sex sample and limited duration constrain generalizability.

Study Details

PMID:36364907
Participants:66
Impact:+2.22 μg/mL (IG vs placebo at 3 weeks); overall adiponectin maintained in IG vs decreases in placebo
Trust score:4/5

fat oxidation rate

1 evidences

Irvingia gabonensis kernel extract (300 mg/day) in overweight/obese women for 12 weeks raised plasma vitamin C and maintained adiponectin but did not change fat oxidation, body composition, telomere length, or aerobic capacity.

Trust comment: Randomized, double-blind placebo-controlled RCT with appropriate methods and adequate completion (66), though single-sex sample and limited duration constrain generalizability.

Study Details

PMID:36364907
Participants:66
Impact:no significant change
Trust score:4/5

6-minute walk distance

1 evidences

Twenty-eight days of L-arginine (1.66 g twice daily) plus liposomal vitamin C (500 mg twice daily) improved 6-minute walk distance, handgrip strength, endothelial function and markedly reduced fatigue in adults with long COVID.

Trust comment: Randomized, placebo-controlled trial adequately powered for primary endpoint with objective outcomes; single-blind and single-center limit robustness but results are consistent and statistically significant.

Study Details

PMID:36501014
Participants:46
Impact:+30 m median change from baseline in active group vs +0 m in placebo; mean difference ≈ +50 m (95% CI 20–80 m), p=0.001
Trust score:4/5

handgrip strength

2 evidences

Twenty-eight days of L-arginine (1.66 g twice daily) plus liposomal vitamin C (500 mg twice daily) improved 6-minute walk distance, handgrip strength, endothelial function and markedly reduced fatigue in adults with long COVID.

Trust comment: Randomized, placebo-controlled trial adequately powered for primary endpoint with objective outcomes; single-blind and single-center limit robustness but results are consistent and statistically significant.

Study Details

PMID:36501014
Participants:46
Impact:+3.4 kg mean difference vs placebo (95% CI 0.5–9.4 kg), p=0.03
Trust score:4/5

Daily fortified yogurt containing HMB, 1000 IU vitamin D, and vitamin C improved handgrip strength, gait speed, vitamin D and IGF-1 levels, and reduced inflammation markers versus control in sarcopenic older adults.

Trust comment: Well-conducted double-blind RCT (n=66) with clear benefits, but vitamin C was given in combination with HMB and vitamin D so effects cannot be attributed to vitamin C alone.

Study Details

PMID:33067129
Participants:66
Impact:intervention mean change 4.36 vs control 0.97 (mean difference ≈ +3.39; P<0.001)
Trust score:4/5

flow-mediated dilation (endothelial function)

1 evidences

Twenty-eight days of L-arginine (1.66 g twice daily) plus liposomal vitamin C (500 mg twice daily) improved 6-minute walk distance, handgrip strength, endothelial function and markedly reduced fatigue in adults with long COVID.

Trust comment: Randomized, placebo-controlled trial adequately powered for primary endpoint with objective outcomes; single-blind and single-center limit robustness but results are consistent and statistically significant.

Study Details

PMID:36501014
Participants:46
Impact:+3.4% mean difference vs placebo (95% CI 0.4–6.5%), p=0.03
Trust score:4/5

hearing threshold (pure tone audiometry)

1 evidences

In 120 patients randomized to several antioxidant regimens (one arm received α-lipoic acid plus vitamin C), none of the treatments, including the vitamin C-containing arm, improved hearing outcomes after six months.

Trust comment: Randomized, double-blind, placebo-controlled design with moderate sample size; subgroup sizes per arm reduce power to detect small effects.

Study Details

PMID:23318104
Participants:120
Impact:no significant change vs placebo after 6 months
Trust score:3/5

speech recognition threshold

1 evidences

In 120 patients randomized to several antioxidant regimens (one arm received α-lipoic acid plus vitamin C), none of the treatments, including the vitamin C-containing arm, improved hearing outcomes after six months.

Trust comment: Randomized, double-blind, placebo-controlled design with moderate sample size; subgroup sizes per arm reduce power to detect small effects.

Study Details

PMID:23318104
Participants:120
Impact:no significant change vs placebo after 6 months
Trust score:3/5

speech recognition percentage index

1 evidences

In 120 patients randomized to several antioxidant regimens (one arm received α-lipoic acid plus vitamin C), none of the treatments, including the vitamin C-containing arm, improved hearing outcomes after six months.

Trust comment: Randomized, double-blind, placebo-controlled design with moderate sample size; subgroup sizes per arm reduce power to detect small effects.

Study Details

PMID:23318104
Participants:120
Impact:no significant change vs placebo after 6 months
Trust score:3/5

pain VAS (visual analog scale)

1 evidences

Tested calcium ascorbate (vitamin C) in osteoarthritis; small reduction in pain versus placebo.

Trust comment: Well-conducted randomized, double-blind crossover trial with adequate sample and intention-to-treat analysis, but effect sizes are small and clinical relevance modest.

Study Details

PMID:12854267
Participants:133
Impact:mean reduction 4.6 mm vs placebo (95% CI 1.2–8.0), p=0.0078
Trust score:4/5

Lequesne index (function)

1 evidences

Tested calcium ascorbate (vitamin C) in osteoarthritis; small reduction in pain versus placebo.

Trust comment: Well-conducted randomized, double-blind crossover trial with adequate sample and intention-to-treat analysis, but effect sizes are small and clinical relevance modest.

Study Details

PMID:12854267
Participants:133
Impact:improvement mean difference 0.56 (95% CI 0.04–1.08), p=0.036
Trust score:4/5

patient preference

1 evidences

Tested calcium ascorbate (vitamin C) in osteoarthritis; small reduction in pain versus placebo.

Trust comment: Well-conducted randomized, double-blind crossover trial with adequate sample and intention-to-treat analysis, but effect sizes are small and clinical relevance modest.

Study Details

PMID:12854267
Participants:133
Impact:greater preference for calcium ascorbate vs placebo (p=0.012)
Trust score:4/5

bone formation markers (osteocalcin, alkaline phosphatase)

1 evidences

In elderly postmenopausal women, 12 weeks of treatment including vitamin C showed no clear effect of vitamin C on bone or metabolic markers.

Trust comment: Randomized but open-label, small sample and short duration—adequate for safety but limited for efficacy conclusions.

Study Details

PMID:11444086
Participants:68
Impact:no significant change
Trust score:3/5

bone resorption (serum and urinary CTX)

1 evidences

In elderly postmenopausal women, 12 weeks of treatment including vitamin C showed no clear effect of vitamin C on bone or metabolic markers.

Trust comment: Randomized but open-label, small sample and short duration—adequate for safety but limited for efficacy conclusions.

Study Details

PMID:11444086
Participants:68
Impact:no significant difference versus comparator (weak within-group decrease from baseline only)
Trust score:3/5

serum lipids (total cholesterol, LDL)

1 evidences

In elderly postmenopausal women, 12 weeks of treatment including vitamin C showed no clear effect of vitamin C on bone or metabolic markers.

Trust comment: Randomized but open-label, small sample and short duration—adequate for safety but limited for efficacy conclusions.

Study Details

PMID:11444086
Participants:68
Impact:no significant effect attributed to vitamin C
Trust score:3/5

arterial compliance

1 evidences

In young healthy men, 12 weeks of vitamin C+E+folate reduced systolic blood pressure but showed no other clear cardiovascular changes.

Trust comment: Small randomized trial with objective measures but limited sample size and combined-vitamin intervention confounds vitamin C–specific attribution.

Study Details

PMID:15580811
Participants:31
Impact:no statistically significant change (possible increase indicated)
Trust score:3/5

postprandial hepatic venous pressure gradient (HVPG) increase

1 evidences

In patients with cirrhosis, IV ascorbic acid reduced oxidative marker MDA and markedly blunted the postprandial rise in portal pressure.

Trust comment: Randomized human study with objective hemodynamic endpoints and significant effects, though sample size is modest.

Study Details

PMID:16496307
Participants:37
Impact:attenuated: 4% ± 7% vs 18% ± 10% in placebo at 30 min (p < .001)
Trust score:4/5

malondialdehyde (MDA, lipid peroxidation marker)

1 evidences

In patients with cirrhosis, IV ascorbic acid reduced oxidative marker MDA and markedly blunted the postprandial rise in portal pressure.

Trust comment: Randomized human study with objective hemodynamic endpoints and significant effects, though sample size is modest.

Study Details

PMID:16496307
Participants:37
Impact:decrease (statistically significant)
Trust score:4/5

FEF25-75 (forced expiratory flow)

1 evidences

Offspring of pregnant smokers given 500 mg/day vitamin C had better lung function at age 5 and less wheeze than offspring of placebo mothers.

Trust comment: Large double-blind randomized trial with objective spirometry outcomes and clinically meaningful, statistically robust results.

Study Details

PMID:36409489
Participants:192
Impact:increase +17.2% (adjusted mean difference 0.21 L/s; p < .001)
Trust score:5/5

FEV1 (forced expiratory volume in 1 s)

1 evidences

Offspring of pregnant smokers given 500 mg/day vitamin C had better lung function at age 5 and less wheeze than offspring of placebo mothers.

Trust comment: Large double-blind randomized trial with objective spirometry outcomes and clinically meaningful, statistically robust results.

Study Details

PMID:36409489
Participants:192
Impact:increase +4.4% (adjusted mean difference 0.05 L; p = .02)
Trust score:5/5

wheeze occurrence in offspring

1 evidences

Offspring of pregnant smokers given 500 mg/day vitamin C had better lung function at age 5 and less wheeze than offspring of placebo mothers.

Trust comment: Large double-blind randomized trial with objective spirometry outcomes and clinically meaningful, statistically robust results.

Study Details

PMID:36409489
Participants:192
Impact:decrease 28.3% vs 47.2% (OR 0.41; p = .003)
Trust score:5/5

CMT neuropathy score (CMTNS, primary outcome)

1 evidences

In adults with CMT1A, 1.5 g/day ascorbic acid for 24 months did not improve the primary neuropathy score or prespecified secondary outcomes versus placebo.

Trust comment: Large, multicenter, double-blind randomized trial adequately powered and well conducted, producing clear null results.

Study Details

PMID:21393063
Participants:271
Impact:no significant effect (between-group difference 0.0; p = 0.93)
Trust score:5/5

CMT examination score (CMTES) and secondary clinical measures

1 evidences

In adults with CMT1A, 1.5 g/day ascorbic acid for 24 months did not improve the primary neuropathy score or prespecified secondary outcomes versus placebo.

Trust comment: Large, multicenter, double-blind randomized trial adequately powered and well conducted, producing clear null results.

Study Details

PMID:21393063
Participants:271
Impact:no significant differences
Trust score:5/5

electrophysiological measurements

1 evidences

In adults with CMT1A, 1.5 g/day ascorbic acid for 24 months did not improve the primary neuropathy score or prespecified secondary outcomes versus placebo.

Trust comment: Large, multicenter, double-blind randomized trial adequately powered and well conducted, producing clear null results.

Study Details

PMID:21393063
Participants:271
Impact:no significant differences
Trust score:5/5

plasma ascorbic acid and alpha-tocopherol concentrations

1 evidences

In SLE patients, 12 weeks of combined vitamins C and E increased plasma vitamin levels and reduced MDA but did not change endothelial function measures.

Trust comment: Double-blind randomized pilot with objective biochemical endpoints but small sample and combined-vitamin intervention limit attribution to vitamin C alone.

Study Details

PMID:15693087
Participants:39
Impact:increase (statistically significant in treatment group)
Trust score:3/5

flow-mediated dilatation (FMD, endothelial function)

1 evidences

In SLE patients, 12 weeks of combined vitamins C and E increased plasma vitamin levels and reduced MDA but did not change endothelial function measures.

Trust comment: Double-blind randomized pilot with objective biochemical endpoints but small sample and combined-vitamin intervention limit attribution to vitamin C alone.

Study Details

PMID:15693087
Participants:39
Impact:no significant change
Trust score:3/5

total energy intake

1 evidences

Oral nutritional supplements plus dietary counseling increased energy and micronutrient intakes (including calcium), and improved appetite versus counseling alone in picky-eating children over 90 days.

Trust comment: Large randomized, double‑blind trial with complete dietary assessment showing robust increases in vitamin C intake from the supplements, but effects are for multi‑nutrient ONS rather than isolated Vitamin C.

Study Details

PMID:37299491
Participants:321
Impact:increased (ONS groups +≈278–282 kcal/day vs +130.6 kcal in control) leading to improved nutrient adequacy
Trust score:3/5

sperm concentration

1 evidences

In obese men, alternate-day 1,000 mg vitamin C improved sperm concentration and motility but did not change semen volume or normal morphology.

Trust comment: Randomized with a control group and reasonable sample size but effect sizes not reported and methodology/details limited in abstract.

Study Details

PMID:27085565
Participants:250
Impact:significant increase (across BMI groups)
Trust score:3/5

semen volume

1 evidences

In obese men, alternate-day 1,000 mg vitamin C improved sperm concentration and motility but did not change semen volume or normal morphology.

Trust comment: Randomized with a control group and reasonable sample size but effect sizes not reported and methodology/details limited in abstract.

Study Details

PMID:27085565
Participants:250
Impact:no significant change
Trust score:3/5

oxidative DNA damage (urinary 8-oxodG)

1 evidences

In smokers, 2 months of vitamin C supplementation increased plasma antioxidant levels but did not change urinary 8-oxodG (oxidative DNA damage marker).

Trust comment: Randomized placebo-controlled trial with adequate sample size and clear biomarker endpoints, though short duration (2 months).

Study Details

PMID:9022536
Participants:142
Impact:no significant change after 2 months
Trust score:4/5

plasma antioxidant concentration

1 evidences

In smokers, 2 months of vitamin C supplementation increased plasma antioxidant levels but did not change urinary 8-oxodG (oxidative DNA damage marker).

Trust comment: Randomized placebo-controlled trial with adequate sample size and clear biomarker endpoints, though short duration (2 months).

Study Details

PMID:9022536
Participants:142
Impact:substantial increase (reported)
Trust score:4/5

systolic/diastolic blood pressure

2 evidences

Daily consumption of a dairy product enriched with calcium, vitamin D and other bone‑supporting nutrients for 24 weeks improved bone mass and bone turnover markers and mitigated BMD loss in menopausal women at risk of osteoporosis.

Trust comment: Randomized double-blind RCT with moderate sample size but tests a multi-nutrient product so effects cannot be attributed to vitamin C alone.

Study Details

PMID:32722015
Participants:65
Impact:SBP 112.85 → 104.12 mmHg; DBP 77.12 → 71.79 mmHg in EG (within-group p < 0.05/0.01)
Trust score:4/5

In subjects with resistant hypertension and dyslipidemia, 500 mg/day vitamin C for 8 weeks produced no significant improvements in blood pressure, LDL, or endothelial function.

Trust comment: Randomized trial but small sample and short duration; clear negative result for vitamin C arm while active comparator showed benefit.

Study Details

PMID:15609886
Participants:48
Impact:no significant change with vitamin C
Trust score:3/5

brachial artery flow-mediated dilation (endothelial function)

1 evidences

In subjects with resistant hypertension and dyslipidemia, 500 mg/day vitamin C for 8 weeks produced no significant improvements in blood pressure, LDL, or endothelial function.

Trust comment: Randomized trial but small sample and short duration; clear negative result for vitamin C arm while active comparator showed benefit.

Study Details

PMID:15609886
Participants:48
Impact:no significant change with vitamin C
Trust score:3/5

glutathione peroxidase (GPx) activity

3 evidences

In women using oral contraceptives, combined low-dose vitamin C and E supplementation decreased lipid peroxidation (MDA) and increased GPx and GR activities.

Trust comment: Reasonable sample and biochemical endpoints but combined vitamin intervention (C+E) prevents isolation of vitamin C-specific effects.

Study Details

PMID:22494786
Participants:120
Impact:significant increase
Trust score:3/5

Randomized double-blind trial of daily multivitamin and trace element supplement (including zinc 20 mg) vs placebo in adults measuring serum nutrient levels and antioxidant markers over 6 months.

Trust comment: Large randomized double-blind trial (n=401) demonstrating expected biomarker changes but effects are from a multinutrient formulation, not vitamin C alone.

Study Details

PMID:9627910
Participants:401
Impact:Plasma and red cell GPx activity increased with supplementation
Trust score:4/5

Six-month double-blind RCT in institutionalized elderly: vitamin supplementation (including vitamin C) increased serum vitamin levels and improved enzymatic antioxidant activity.

Trust comment: Large randomized, double-blind, placebo-controlled trial with objective biochemical endpoints, though clinical outcomes limited.

Study Details

PMID:8862480
Participants:575
Impact:Increased (P < 0.01)
Trust score:4/5

glutathione reductase (GR) activity

1 evidences

In women using oral contraceptives, combined low-dose vitamin C and E supplementation decreased lipid peroxidation (MDA) and increased GPx and GR activities.

Trust comment: Reasonable sample and biochemical endpoints but combined vitamin intervention (C+E) prevents isolation of vitamin C-specific effects.

Study Details

PMID:22494786
Participants:120
Impact:significant increase
Trust score:3/5

plasma F2-isoprostanes (oxidative stress)

1 evidences

In cyclists, regimens containing vitamin C (with flavonoids ± n-3) attenuated the immediate postexercise rise in F2-isoprostanes (oxidative stress marker) compared with placebo.

Trust comment: Randomized small study in athletes showing physiological effects on an oxidative stress marker, but multi-ingredient arms complicate attribution to vitamin C alone.

Study Details

PMID:21813916
Participants:39
Impact:attenuated postexercise increase (QC and QFO vs placebo)
Trust score:3/5

sICAM-1 (endothelial activation)

1 evidences

Fourteen days of 500 mg twice-daily vitamin C did not change circulating sICAM-1, neopterin, or neutrophil elastase activity in smokers or non-smokers.

Trust comment: Randomized double-blind placebo-controlled trial but small sample and short duration; outcomes were negative.

Study Details

PMID:15883748
Participants:40
Impact:no change with vitamin C
Trust score:3/5

neopterin (monocyte activation)

1 evidences

Fourteen days of 500 mg twice-daily vitamin C did not change circulating sICAM-1, neopterin, or neutrophil elastase activity in smokers or non-smokers.

Trust comment: Randomized double-blind placebo-controlled trial but small sample and short duration; outcomes were negative.

Study Details

PMID:15883748
Participants:40
Impact:no change with vitamin C
Trust score:3/5

neutrophil elastase activity (neutrophil activation)

1 evidences

Fourteen days of 500 mg twice-daily vitamin C did not change circulating sICAM-1, neopterin, or neutrophil elastase activity in smokers or non-smokers.

Trust comment: Randomized double-blind placebo-controlled trial but small sample and short duration; outcomes were negative.

Study Details

PMID:15883748
Participants:40
Impact:no change with vitamin C
Trust score:3/5

postoperative atrial fibrillation

1 evidences

Oral vitamin C given before and after CABG reduced postoperative atrial fibrillation and shortened ICU and hospital stays.

Trust comment: Randomized clinical trial with 100 patients and significant p-values supports moderate-to-high trustworthiness.

Study Details

PMID:24293167
Participants:100
Impact:-24 percentage points (32% → 8%)
Trust score:4/5

ICU stay duration

1 evidences

Oral vitamin C given before and after CABG reduced postoperative atrial fibrillation and shortened ICU and hospital stays.

Trust comment: Randomized clinical trial with 100 patients and significant p-values supports moderate-to-high trustworthiness.

Study Details

PMID:24293167
Participants:100
Impact:-0.31 days (2.10 → 1.79 days)
Trust score:4/5

hospital stay duration

1 evidences

Oral vitamin C given before and after CABG reduced postoperative atrial fibrillation and shortened ICU and hospital stays.

Trust comment: Randomized clinical trial with 100 patients and significant p-values supports moderate-to-high trustworthiness.

Study Details

PMID:24293167
Participants:100
Impact:-0.42 days (5.74 → 5.32 days)
Trust score:4/5

wound closure (closure rate)

1 evidences

Supplemental ascorbic acid (500 mg twice daily) did not speed healing of pressure ulcers compared with low-dose control in an 88-patient randomized trial.

Trust comment: Multicenter, blinded randomized trial (n=88) with negative results; good design but modest sample size.

Study Details

PMID:8543959
Participants:88
Impact:no significant difference (Cox HR 0.78; 90% PI 0.44–1.39)
Trust score:4/5

mean wound healing rate

1 evidences

Supplemental ascorbic acid (500 mg twice daily) did not speed healing of pressure ulcers compared with low-dose control in an 88-patient randomized trial.

Trust comment: Multicenter, blinded randomized trial (n=88) with negative results; good design but modest sample size.

Study Details

PMID:8543959
Participants:88
Impact:intervention 0.21 vs control 0.27 cm²/week (difference not significant)
Trust score:4/5

24-h stool weight output

1 evidences

Low-volume PEG formulations with increased ascorbate produced high 24-h stool output and effective colon cleansing at lower fluid volumes with tolerable adverse events.

Trust comment: Randomized, endoscopist-blinded Phase 2 trial with objective endpoints and good compliance; not powered for definitive between-group comparisons.

Study Details

PMID:31146679
Participants:240
Impact:LVPEG-3: 3399 g (Part1); LVPEG-3: 3050 g and LVPEG-4: 3215 g (Part2) — exceeded 2750 g target for lead formulations
Trust score:4/5

overall bowel cleansing success (HCS)

1 evidences

Low-volume PEG formulations with increased ascorbate produced high 24-h stool output and effective colon cleansing at lower fluid volumes with tolerable adverse events.

Trust comment: Randomized, endoscopist-blinded Phase 2 trial with objective endpoints and good compliance; not powered for definitive between-group comparisons.

Study Details

PMID:31146679
Participants:240
Impact:LVPEG-3 and LVPEG-4: 100% success (Part2) vs control 90%
Trust score:4/5

vomiting/tolerability

1 evidences

Low-volume PEG formulations with increased ascorbate produced high 24-h stool output and effective colon cleansing at lower fluid volumes with tolerable adverse events.

Trust comment: Randomized, endoscopist-blinded Phase 2 trial with objective endpoints and good compliance; not powered for definitive between-group comparisons.

Study Details

PMID:31146679
Participants:240
Impact:low and similar rates to control (vomiting mostly 0–3.3% in Part2)
Trust score:4/5

plasma ascorbic acid (AA) level

1 evidences

High-dose vitamins E and C raised blood antioxidant levels but did not change serum cytokines or muscle strength after ACL surgery.

Trust comment: Randomized trial with clear biochemical endpoints but small sample (n=29) limits power for clinical outcomes.

Study Details

PMID:25890874
Participants:29
Impact:+~50% (supplement vs placebo)
Trust score:3/5

serum cytokine concentrations

1 evidences

High-dose vitamins E and C raised blood antioxidant levels but did not change serum cytokines or muscle strength after ACL surgery.

Trust comment: Randomized trial with clear biochemical endpoints but small sample (n=29) limits power for clinical outcomes.

Study Details

PMID:25890874
Participants:29
Impact:no significant change vs placebo
Trust score:3/5

peak isometric muscle force/time to exhaustion

1 evidences

High-dose vitamins E and C raised blood antioxidant levels but did not change serum cytokines or muscle strength after ACL surgery.

Trust comment: Randomized trial with clear biochemical endpoints but small sample (n=29) limits power for clinical outcomes.

Study Details

PMID:25890874
Participants:29
Impact:no significant change vs placebo
Trust score:3/5

postoperative pain (VAS) on day 1

1 evidences

Postoperative vitamin C reduced early pain, morphine use, inflammatory CRP levels, swelling and improved short-term hip function similar to dexamethasone but without increasing blood glucose.

Trust comment: Prospective randomized trial (n=107) with clinically relevant endpoints and demonstrated differences; single-center context limits generalizability slightly.

Study Details

PMID:40208930
Participants:107
Impact:significantly lower vs control (vitamin C and dexamethasone groups)
Trust score:4/5

perioperative morphine consumption

1 evidences

Postoperative vitamin C reduced early pain, morphine use, inflammatory CRP levels, swelling and improved short-term hip function similar to dexamethasone but without increasing blood glucose.

Trust comment: Prospective randomized trial (n=107) with clinically relevant endpoints and demonstrated differences; single-center context limits generalizability slightly.

Study Details

PMID:40208930
Participants:107
Impact:significantly lower vs control
Trust score:4/5

CRP (inflammation) on days 1–2

1 evidences

Postoperative vitamin C reduced early pain, morphine use, inflammatory CRP levels, swelling and improved short-term hip function similar to dexamethasone but without increasing blood glucose.

Trust comment: Prospective randomized trial (n=107) with clinically relevant endpoints and demonstrated differences; single-center context limits generalizability slightly.

Study Details

PMID:40208930
Participants:107
Impact:significantly lower vs control
Trust score:4/5

oxidative stress (marker)

1 evidences

In smokers with higher BMI, 500 mg/day vitamin C for 2 months lowered a blood marker of lipid oxidation; no effect in low-BMI smokers.

Trust comment: Randomized double-blind placebo-controlled trial with clear biomarker outcome and adequate sample size, though effect limited to a BMI-defined subgroup.

Study Details

PMID:11815395
Participants:126
Impact:decrease in lipid peroxidation marker in high-BMI subgroup
Trust score:4/5

no effect (low BMI)

1 evidences

In smokers with higher BMI, 500 mg/day vitamin C for 2 months lowered a blood marker of lipid oxidation; no effect in low-BMI smokers.

Trust comment: Randomized double-blind placebo-controlled trial with clear biomarker outcome and adequate sample size, though effect limited to a BMI-defined subgroup.

Study Details

PMID:11815395
Participants:126
Impact:no treatment effect observed in low-BMI smokers
Trust score:4/5

duration of URTI symptoms

1 evidences

Children given a probiotic consortium plus 50 mg/day vitamin C for 6 months had fewer and shorter upper respiratory infections and less preschool absence versus placebo; study used a combined product so effects cannot be ascribed to vitamin C alone.

Trust comment: Randomized double-blind pilot trial with modest sample size and a combined probiotic+vitamin C intervention, so attribution to vitamin C alone is uncertain.

Study Details

PMID:25205320
Participants:66
Impact:mean difference −21.0 days (PP) vs placebo; −17.9 days (ITT)
Trust score:3/5

incidence rate of URTI symptoms

1 evidences

Children given a probiotic consortium plus 50 mg/day vitamin C for 6 months had fewer and shorter upper respiratory infections and less preschool absence versus placebo; study used a combined product so effects cannot be ascribed to vitamin C alone.

Trust comment: Randomized double-blind pilot trial with modest sample size and a combined probiotic+vitamin C intervention, so attribution to vitamin C alone is uncertain.

Study Details

PMID:25205320
Participants:66
Impact:33% reduction in incidence rate (active vs placebo)
Trust score:3/5

preschool absence incidence

1 evidences

Children given a probiotic consortium plus 50 mg/day vitamin C for 6 months had fewer and shorter upper respiratory infections and less preschool absence versus placebo; study used a combined product so effects cannot be ascribed to vitamin C alone.

Trust comment: Randomized double-blind pilot trial with modest sample size and a combined probiotic+vitamin C intervention, so attribution to vitamin C alone is uncertain.

Study Details

PMID:25205320
Participants:66
Impact:~30% lower incidence rate of absence (active vs placebo)
Trust score:3/5

HD cramp reduction (vitamin C)

1 evidences

Haemodialysis patients receiving 250 mg/day vitamin C for 8 weeks had large reductions in cramp frequency/intensity compared with placebo; greatest reduction seen with vitamins C+E combined.

Trust comment: Randomized double-blind placebo-controlled study with clear clinical outcomes though sample size per arm was small (n=15).

Study Details

PMID:11427639
Participants:60
Impact:61% cramp reduction at end of trial (vitamin C group)
Trust score:4/5

HD cramp reduction (vitamin E)

1 evidences

Haemodialysis patients receiving 250 mg/day vitamin C for 8 weeks had large reductions in cramp frequency/intensity compared with placebo; greatest reduction seen with vitamins C+E combined.

Trust comment: Randomized double-blind placebo-controlled study with clear clinical outcomes though sample size per arm was small (n=15).

Study Details

PMID:11427639
Participants:60
Impact:54% cramp reduction (vitamin E group)
Trust score:4/5

HD cramp reduction (combination)

1 evidences

Haemodialysis patients receiving 250 mg/day vitamin C for 8 weeks had large reductions in cramp frequency/intensity compared with placebo; greatest reduction seen with vitamins C+E combined.

Trust comment: Randomized double-blind placebo-controlled study with clear clinical outcomes though sample size per arm was small (n=15).

Study Details

PMID:11427639
Participants:60
Impact:97% cramp reduction (vitamin C+E group)
Trust score:4/5

percent change in fasting blood glucose

1 evidences

Vitamin C alone or with rutin reduced the percent change in fasting blood glucose over 8 weeks; no clear effect on HbA1c, insulin resistance or oxidative stress; some cholesterol and quality-of-life domains improved in specific groups.

Trust comment: Small randomized controlled study (n=53) with appropriate outcomes but limited sample size and short duration.

Study Details

PMID:31987106
Participants:53
Impact:decrease vs control (statistically significant)
Trust score:3/5

LDL-cholesterol and total cholesterol

1 evidences

Vitamin C alone or with rutin reduced the percent change in fasting blood glucose over 8 weeks; no clear effect on HbA1c, insulin resistance or oxidative stress; some cholesterol and quality-of-life domains improved in specific groups.

Trust comment: Small randomized controlled study (n=53) with appropriate outcomes but limited sample size and short duration.

Study Details

PMID:31987106
Participants:53
Impact:improved in vitamin C alone group (vs baseline, p<0.05)
Trust score:3/5

quality of life (physical functioning, energy)

1 evidences

Vitamin C alone or with rutin reduced the percent change in fasting blood glucose over 8 weeks; no clear effect on HbA1c, insulin resistance or oxidative stress; some cholesterol and quality-of-life domains improved in specific groups.

Trust comment: Small randomized controlled study (n=53) with appropriate outcomes but limited sample size and short duration.

Study Details

PMID:31987106
Participants:53
Impact:improved in combination group vs control (p<0.05)
Trust score:3/5

immediate memory (Logical Memory I)

1 evidences

In sepsis survivors, early IV vitamin C with thiamine and hydrocortisone did not improve 6-month outcomes and was associated with worse immediate memory and higher PTSD rates.

Trust comment: Large multicenter randomized, double-blind trial with robust outcome assessment though this is a secondary analysis of survivors (213 completed follow-up).

Study Details

PMID:36853612
Participants:213
Impact:worse with treatment (aOR 0.49, 95% CI 0.26–0.89, p=0.02)
Trust score:4/5

posttraumatic stress disorder (PTSD) incidence

1 evidences

In sepsis survivors, early IV vitamin C with thiamine and hydrocortisone did not improve 6-month outcomes and was associated with worse immediate memory and higher PTSD rates.

Trust comment: Large multicenter randomized, double-blind trial with robust outcome assessment though this is a secondary analysis of survivors (213 completed follow-up).

Study Details

PMID:36853612
Participants:213
Impact:increased with treatment (16.7% vs 9.5%; aOR 3.51, 95% CI 1.18–10.40, p=0.02)
Trust score:4/5

functional status (ADL/FAQ/EQ-5D-3L)

1 evidences

In sepsis survivors, early IV vitamin C with thiamine and hydrocortisone did not improve 6-month outcomes and was associated with worse immediate memory and higher PTSD rates.

Trust comment: Large multicenter randomized, double-blind trial with robust outcome assessment though this is a secondary analysis of survivors (213 completed follow-up).

Study Details

PMID:36853612
Participants:213
Impact:no significant difference
Trust score:4/5

delayed graft function incidence

1 evidences

Perfusion of renal grafts with ascorbic acid did not produce significant improvements in graft outcomes (incidence of delayed graft function similar to control).

Trust comment: Controlled clinical perfusion study with within-donor contralateral controls but modest sample size and no statistically significant benefits.

Study Details

PMID:12719802
Participants:31
Impact:32% AA vs 29% control (no significant difference)
Trust score:3/5

duration of delayed graft function

1 evidences

Perfusion of renal grafts with ascorbic acid did not produce significant improvements in graft outcomes (incidence of delayed graft function similar to control).

Trust comment: Controlled clinical perfusion study with within-donor contralateral controls but modest sample size and no statistically significant benefits.

Study Details

PMID:12719802
Participants:31
Impact:trend toward shorter duration with AA (not statistically conclusive)
Trust score:3/5

major vascular outcomes with antioxidant vitamins

1 evidences

In this large randomized trial, a long-term antioxidant vitamin cocktail (including 250 mg vitamin C) showed no benefit on major vascular outcomes (preliminary), while simvastatin produced clear benefit.

Trust comment: Very large, randomized, double-blind controlled trial with long follow-up and high-quality design; results for vitamins reported as preliminary but reliable.

Study Details

PMID:11831837
Participants:20500
Impact:no benefit observed (preliminary)
Trust score:5/5

safety of vitamins

1 evidences

In this large randomized trial, a long-term antioxidant vitamin cocktail (including 250 mg vitamin C) showed no benefit on major vascular outcomes (preliminary), while simvastatin produced clear benefit.

Trust comment: Very large, randomized, double-blind controlled trial with long follow-up and high-quality design; results for vitamins reported as preliminary but reliable.

Study Details

PMID:11831837
Participants:20500
Impact:no harm detected over ~5 years
Trust score:5/5

ΔSOFA score (72 h)

1 evidences

In 111 septic shock patients, IV vitamin C plus thiamine for 48 h raised blood vitamin levels but did not improve organ dysfunction (ΔSOFA) or mortality compared with placebo.

Trust comment: Multi-centre, double‑blind RCT with pre-specified primary outcome and clear reporting; moderate sample size for septic shock limits power for some secondary endpoints.

Study Details

PMID:32780166
Participants:111
Impact:no change (median 3 vs 3; p = 0.96)
Trust score:4/5

serum vitamin C level at 72 h

1 evidences

In 111 septic shock patients, IV vitamin C plus thiamine for 48 h raised blood vitamin levels but did not improve organ dysfunction (ΔSOFA) or mortality compared with placebo.

Trust comment: Multi-centre, double‑blind RCT with pre-specified primary outcome and clear reporting; moderate sample size for septic shock limits power for some secondary endpoints.

Study Details

PMID:32780166
Participants:111
Impact:increased (median 44 μmol/L vs 9 μmol/L; p < 0.01); vitamin C deficiency 0% vs 55.4% in placebo
Trust score:4/5

gastric cancer incidence/mortality (population-level)

1 evidences

Cross-sectional multicentre study (~1,400 people) found no population-level association between fasting plasma vitamin C and gastric cancer rates or markers of gastritis/H. pylori.

Trust comment: Large multicentre cross-sectional study provides robust correlation data but cannot establish causality and uses population averages.

Study Details

PMID:9398046
Participants:1400
Impact:no association with average plasma vitamin C
Trust score:3/5

H. pylori infection / gastritis markers (pepsinogen A, DNA adducts)

1 evidences

Cross-sectional multicentre study (~1,400 people) found no population-level association between fasting plasma vitamin C and gastric cancer rates or markers of gastritis/H. pylori.

Trust comment: Large multicentre cross-sectional study provides robust correlation data but cannot establish causality and uses population averages.

Study Details

PMID:9398046
Participants:1400
Impact:no association with plasma vitamin C
Trust score:3/5

determinants of plasma vitamin C

1 evidences

Cross-sectional multicentre study (~1,400 people) found no population-level association between fasting plasma vitamin C and gastric cancer rates or markers of gastritis/H. pylori.

Trust comment: Large multicentre cross-sectional study provides robust correlation data but cannot establish causality and uses population averages.

Study Details

PMID:9398046
Participants:1400
Impact:positively associated with female sex, higher education, never smoking; negatively with cigarettes/day and higher weight
Trust score:3/5

biochemical vitamin and trace element status (after 2 years)

1 evidences

Large randomized, double‑blind placebo-controlled primary prevention trial (n=12,735) testing daily nutritional-dose antioxidant supplementation including vitamin C (120 mg); after 2 years biochemical markers rose to nutritional but not excessive levels.

Trust comment: Large, long-term randomized double‑blind placebo-controlled trial designed for primary prevention, though this excerpt reports biochemical status rather than clinical endpoints.

Study Details

PMID:10541446
Participants:12735
Impact:increased to reasonable/nutritional levels (did not reach high concentrations seen in high-dose trials)
Trust score:4/5

coronary atherosclerosis progression (MLD annual change)

1 evidences

In postmenopausal women with coronary disease, antioxidant vitamins (including vitamin C) did not slow artery narrowing and were associated with a suggestion of harm including more deaths.

Trust comment: Large randomized double-blind RCT (n=423) providing high-quality evidence, but vitamins were given combined so effects cannot be attributed to vitamin C alone.

Study Details

PMID:12435256
Participants:423
Impact:Antioxidant vitamins: +0.044 mm/y vs placebo: +0.028 mm/y (difference +0.016 mm/y; P=0.32)
Trust score:4/5

composite (death, nonfatal MI, or stroke)

1 evidences

In postmenopausal women with coronary disease, antioxidant vitamins (including vitamin C) did not slow artery narrowing and were associated with a suggestion of harm including more deaths.

Trust comment: Large randomized double-blind RCT (n=423) providing high-quality evidence, but vitamins were given combined so effects cannot be attributed to vitamin C alone.

Study Details

PMID:12435256
Participants:423
Impact:26 events in vitamin group vs 18 in controls (HR 1.5; 95% CI 0.80–2.9)
Trust score:4/5

plasma linoleic acid (18:2 ω-6)

1 evidences

In children with heterozygous familial hypercholesterolemia, combined vitamin C and E therapy altered plasma fatty acid composition but did not change lipid profile or inflammatory markers.

Trust comment: Randomized (single-blind) trial in 40 children showing biochemical changes; small sample and vitamins combined limit attribution to vitamin C alone.

Study Details

PMID:16948972
Participants:40
Impact:Significant increase with antioxidant vitamins (vitamin C + E)
Trust score:3/5

essential fatty acid deficiency ratio (Mead/arachidonic acid)

1 evidences

In children with heterozygous familial hypercholesterolemia, combined vitamin C and E therapy altered plasma fatty acid composition but did not change lipid profile or inflammatory markers.

Trust comment: Randomized (single-blind) trial in 40 children showing biochemical changes; small sample and vitamins combined limit attribution to vitamin C alone.

Study Details

PMID:16948972
Participants:40
Impact:Significant decrease with antioxidant vitamins
Trust score:3/5

cardiovascular mortality

1 evidences

Higher blood vitamin C levels were associated with lower mortality risk in older adults.

Trust comment: Large cohort with objective blood measures and multivariable adjustment, but observational design limits causal inference.

Study Details

PMID:14594788
Participants:1214
Impact:-49% (HR = 0.51 after excluding baseline CVD/cancer)
Trust score:4/5

blood ascorbate concentration

1 evidences

Higher blood vitamin C levels were associated with lower mortality risk in older adults.

Trust comment: Large cohort with objective blood measures and multivariable adjustment, but observational design limits causal inference.

Study Details

PMID:14594788
Participants:1214
Impact:inverse trend with mortality (higher levels associated with lower mortality)
Trust score:4/5

gestational hypertension / preeclampsia

1 evidences

Daily vitamin C (1 g) plus vitamin E did not reduce gestational hypertension or preeclampsia and was associated with some increased fetal/perinatal risks.

Trust comment: Large multicenter randomized controlled trial with intention-to-treat analysis, providing high-quality evidence.

Study Details

PMID:20207239
Participants:2363
Impact:no effect (RR = 0.99; 95% CI 0.78–1.26)
Trust score:5/5

fetal loss or perinatal death

1 evidences

Daily vitamin C (1 g) plus vitamin E did not reduce gestational hypertension or preeclampsia and was associated with some increased fetal/perinatal risks.

Trust comment: Large multicenter randomized controlled trial with intention-to-treat analysis, providing high-quality evidence.

Study Details

PMID:20207239
Participants:2363
Impact:increased risk (reported increase; no RR provided in text)
Trust score:5/5

preterm prelabor rupture of membranes

1 evidences

Daily vitamin C (1 g) plus vitamin E did not reduce gestational hypertension or preeclampsia and was associated with some increased fetal/perinatal risks.

Trust comment: Large multicenter randomized controlled trial with intention-to-treat analysis, providing high-quality evidence.

Study Details

PMID:20207239
Participants:2363
Impact:increased risk (reported increase; no RR provided in text)
Trust score:5/5

systemic oxidative stress (urine F2-isoprostanes)

1 evidences

Targeted vitamin C supplementation reduced oxidative stress and improved performance in individuals with low vitamin C status but not in unselected controls.

Trust comment: Crossover randomized design is strong, but small sample size and selected phenotypes limit generalizability.

Study Details

PMID:32682929
Participants:36
Impact:reduced in Low VitC group after vitamin C (no numeric value provided)
Trust score:3/5

VO2max / exercise performance

1 evidences

Targeted vitamin C supplementation reduced oxidative stress and improved performance in individuals with low vitamin C status but not in unselected controls.

Trust comment: Crossover randomized design is strong, but small sample size and selected phenotypes limit generalizability.

Study Details

PMID:32682929
Participants:36
Impact:improved in Low VitC group after targeted vitamin C (no numeric value provided)
Trust score:3/5

fatigue index

1 evidences

Targeted vitamin C supplementation reduced oxidative stress and improved performance in individuals with low vitamin C status but not in unselected controls.

Trust comment: Crossover randomized design is strong, but small sample size and selected phenotypes limit generalizability.

Study Details

PMID:32682929
Participants:36
Impact:no improvement after vitamin C (improved after NAC instead)
Trust score:3/5

contrast-induced nephropathy (CIN) incidence

2 evidences

Intravenous hydration plus oral ascorbic acid did not significantly change contrast-induced nephropathy rates but reduced postprocedural worsening of renal function.

Trust comment: Randomized controlled trial with clear outcomes but modest sample size limits precision for rare events.

Study Details

PMID:23931876
Participants:81
Impact:no significant difference: 3.0% (ascorbic acid) vs 7.3% (placebo), P = 0.512
Trust score:4/5

Adding ascorbic acid to saline + N-acetylcysteine did not reduce contrast-induced nephropathy compared with saline + N-acetylcysteine alone; bicarbonate + NAC was superior.

Trust comment: Large randomized trial with clear clinical endpoint showing no added benefit of ascorbic acid in this protocol.

Study Details

PMID:17309916
Participants:326
Impact:saline+NAC 9.9%; bicarbonate+NAC 1.9% (significantly lower); saline+ascorbic acid+NAC 10.3% (no benefit vs saline+NAC)
Trust score:4/5

postprocedural worsening of renal function

1 evidences

Intravenous hydration plus oral ascorbic acid did not significantly change contrast-induced nephropathy rates but reduced postprocedural worsening of renal function.

Trust comment: Randomized controlled trial with clear outcomes but modest sample size limits precision for rare events.

Study Details

PMID:23931876
Participants:81
Impact:-11.1 percentage points (12.3% vs 23.4%), P = 0.038
Trust score:4/5

incidence of CRPS-1 at 12 weeks

1 evidences

Adding 500 mg vitamin C to the Bier block reduced the incidence of CRPS after distal radius fracture surgery compared with control.

Trust comment: Randomized design with significant effect size, though both groups also received oral vitamin C which may affect interpretation.

Study Details

PMID:33119790
Participants:74
Impact:22.9% (vitamin C) vs 45.5% (control); absolute reduction 22.6 percentage points, P = 0.04 (OR 0.26; 95% CI 0.08–0.85)
Trust score:4/5

vegetable-related micronutrient intake

1 evidences

Large observational cohort: heavier soup consumers had higher dietary vitamin C intake; serum vitamin C was slightly higher but not significantly.

Trust comment: Large cohort with repeated 24-h records supports dietary associations, but observational design limits causal inference.

Study Details

PMID:14639794
Participants:4988
Impact:higher (folate, beta-carotene also increased)
Trust score:3/5

plasma ascorbate concentration

1 evidences

Large randomized trial in pregnant women with type 1 diabetes: vitamins C+E increased blood vitamin levels but did not reduce pre-eclampsia or gestational hypertension overall.

Trust comment: Large, multicentre randomized placebo-controlled trial with predefined outcomes and high methodological quality.

Study Details

PMID:20580423
Participants:761
Impact:increased (significantly higher at 26 and 34 weeks)
Trust score:5/5

VO2 max / performance

1 evidences

Randomized trial: vitamins C+E did not alter improvements in VO2max or performance but blocked increases in mitochondrial biogenesis markers in trained muscle.

Trust comment: Well-controlled randomized trial with muscle biopsies and molecular endpoints; moderate sample size limits detection of some performance effects.

Study Details

PMID:24492839
Participants:54
Impact:increased similarly in both groups (no difference)
Trust score:4/5

mitochondrial biogenesis markers (COX4, PGC‑1α)

1 evidences

Randomized trial: vitamins C+E did not alter improvements in VO2max or performance but blocked increases in mitochondrial biogenesis markers in trained muscle.

Trust comment: Well-controlled randomized trial with muscle biopsies and molecular endpoints; moderate sample size limits detection of some performance effects.

Study Details

PMID:24492839
Participants:54
Impact:attenuated increase with vitamins (placebo +59% COX4 vs vitamin group -13% COX4; P ≤ 0.03)
Trust score:4/5

muscle gene expression (CDC42, MAPK1)

1 evidences

Randomized trial: vitamins C+E did not alter improvements in VO2max or performance but blocked increases in mitochondrial biogenesis markers in trained muscle.

Trust comment: Well-controlled randomized trial with muscle biopsies and molecular endpoints; moderate sample size limits detection of some performance effects.

Study Details

PMID:24492839
Participants:54
Impact:lower expression in vitamin group vs placebo
Trust score:4/5

new gout diagnoses

1 evidences

Daily 500 mg vitamin C modestly reduced new gout diagnoses in middle-aged male physicians.

Trust comment: Large randomized double‑blind placebo‑controlled trial (post hoc analysis) with self‑reported gout outcome and modest effect size.

Study Details

PMID:35575611
Participants:14641
Impact:-12% risk (HR 0.88; incidence 8.0 vs 9.1 per 1000 person-years; P = 0.04)
Trust score:4/5

vitamin C intake (dietary)

2 evidences

Community dietary education increased reported vitamin C intake modestly but produced only minimal change in serum ascorbic acid.

Trust comment: Randomized community trial with objective biomarkers but intake measured by questionnaire and biomarker changes were modest/non‑significant.

Study Details

PMID:14572428
Participants:550
Impact:+13 mg/day net (intervention vs control; p < 0.05)
Trust score:3/5

Cross‑sectional baseline data from 159 urban African Americans with uncontrolled hypertension showed overall vitamin C intake higher than recommendations, but below‑median intake was associated with greater albuminuria.

Trust comment: Cross‑sectional, self‑reported dietary data; associations reported but cannot infer causality.

Study Details

PMID:30709714
Participants:159
Impact:overall higher than recommendations (descriptive)
Trust score:3/5

acute adverse reactions to Lugol staining

1 evidences

Spraying vitamin C solution after Lugol iodine staining reduced acute adverse reactions and sped decolorization of the esophageal mucosa compared with distilled water and performed similarly to sodium thiosulfate.

Trust comment: Large multicenter randomized controlled trial with objective clinical endpoints and consistent comparator arms.

Study Details

PMID:34406172
Participants:2965
Impact:-significantly reduced (VCS vs distilled water; similar effect to sodium thiosulfate; P < 0.05)
Trust score:5/5

heartburn within 1 week (0.5% LIS)

1 evidences

Spraying vitamin C solution after Lugol iodine staining reduced acute adverse reactions and sped decolorization of the esophageal mucosa compared with distilled water and performed similarly to sodium thiosulfate.

Trust comment: Large multicenter randomized controlled trial with objective clinical endpoints and consistent comparator arms.

Study Details

PMID:34406172
Participants:2965
Impact:-reduced (P < 0.05)
Trust score:5/5

decolorization speed of iodine-stained mucosa

1 evidences

Spraying vitamin C solution after Lugol iodine staining reduced acute adverse reactions and sped decolorization of the esophageal mucosa compared with distilled water and performed similarly to sodium thiosulfate.

Trust comment: Large multicenter randomized controlled trial with objective clinical endpoints and consistent comparator arms.

Study Details

PMID:34406172
Participants:2965
Impact:faster decolorization (~90% faded at 120s with VCS vs ~50.97% with DW; P < 0.05)
Trust score:5/5

antioxidant enzymes (SOD, catalase)

1 evidences

Vitamin C (1000 mg/day) reduced lipid peroxidation markers and increased some antioxidant enzymes and certain hematological parameters in power plant workers.

Trust comment: Double‑blind randomized trial with objective biochemical measures but small per‑arm sample sizes and some inconsistent reporting.

Study Details

PMID:32191586
Participants:91
Impact:+significant increase (vitamin-treated groups)
Trust score:3/5

hematological parameters (RBC, hematocrit, MCH/MCHC)

1 evidences

Vitamin C (1000 mg/day) reduced lipid peroxidation markers and increased some antioxidant enzymes and certain hematological parameters in power plant workers.

Trust comment: Double‑blind randomized trial with objective biochemical measures but small per‑arm sample sizes and some inconsistent reporting.

Study Details

PMID:32191586
Participants:91
Impact:+significant increase
Trust score:3/5

endothelial function (flow‑mediated dilation, FMD)

1 evidences

In young healthy adults simulated train noise worsened sleep and endothelial function; oral vitamin C (2 g) given acutely improved endothelial function after noise nights in women but not men.

Trust comment: Randomized, double‑blind crossover field study with 70 enrolled (66 analyzed) and objective vascular measures; subgroup vitamin C given to 30 participants—good design though limited to young healthy adults.

Study Details

PMID:36360723
Participants:66
Impact:women: relative change after vitamin C +2.59±1.45% (Noise30) and +2.50±1.43% (Noise60) vs +1.49±1.13% (control); improvement significant
Trust score:4/5

sleep quality (VAS)

1 evidences

In young healthy adults simulated train noise worsened sleep and endothelial function; oral vitamin C (2 g) given acutely improved endothelial function after noise nights in women but not men.

Trust comment: Randomized, double‑blind crossover field study with 70 enrolled (66 analyzed) and objective vascular measures; subgroup vitamin C given to 30 participants—good design though limited to young healthy adults.

Study Details

PMID:36360723
Participants:66
Impact:worsened after Noise30 and Noise60 vs control (e.g., women control 3.43±2.02 vs Noise60 7.26±1.5)
Trust score:4/5

stress hormones / routine labs

1 evidences

In young healthy adults simulated train noise worsened sleep and endothelial function; oral vitamin C (2 g) given acutely improved endothelial function after noise nights in women but not men.

Trust comment: Randomized, double‑blind crossover field study with 70 enrolled (66 analyzed) and objective vascular measures; subgroup vitamin C given to 30 participants—good design though limited to young healthy adults.

Study Details

PMID:36360723
Participants:66
Impact:no meaningful differences reported after exposures or vitamin C
Trust score:4/5

adequate small bowel visualization quality (SBVQ)

1 evidences

In a multicenter randomized trial 1‑L PEG with ascorbic acid was non‑inferior to 2‑L PEG+AA for bowel cleaning before small bowel capsule endoscopy.

Trust comment: Prospective, multicenter randomized controlled non‑inferiority trial with appropriate sample size and per‑protocol analysis.

Study Details

PMID:39628348
Participants:137
Impact:94.0% (1‑L) vs 94.3% (2‑L); non‑inferior (risk difference −0.3%; 95% CI −8.1 to 7.6)
Trust score:5/5

diagnostic yield

1 evidences

In a multicenter randomized trial 1‑L PEG with ascorbic acid was non‑inferior to 2‑L PEG+AA for bowel cleaning before small bowel capsule endoscopy.

Trust comment: Prospective, multicenter randomized controlled non‑inferiority trial with appropriate sample size and per‑protocol analysis.

Study Details

PMID:39628348
Participants:137
Impact:49.3% (1‑L) vs 48.6% (2‑L); no significant difference (p=0.936)
Trust score:5/5

adverse events (nausea, bloating, electrolyte imbalance)

1 evidences

In a multicenter randomized trial 1‑L PEG with ascorbic acid was non‑inferior to 2‑L PEG+AA for bowel cleaning before small bowel capsule endoscopy.

Trust comment: Prospective, multicenter randomized controlled non‑inferiority trial with appropriate sample size and per‑protocol analysis.

Study Details

PMID:39628348
Participants:137
Impact:11.9% (1‑L) vs 12.9% (2‑L); no significant difference
Trust score:5/5

cerebral blood flow (CBF)

1 evidences

In Fabry patients and controls IV ascorbate reduced cerebral blood flow; patients had lower baseline plasma ascorbate and higher myeloperoxidase levels.

Trust comment: Randomized double‑blind placebo‑controlled context but small sample (19 patients, 15 controls); mechanistic imaging study with plausible biomarkers.

Study Details

PMID:15390234
Participants:34
Impact:decreased after ascorbate infusion in both controls and treated patients (timing differences vs placebo)
Trust score:3/5

plasma ascorbate levels

1 evidences

In Fabry patients and controls IV ascorbate reduced cerebral blood flow; patients had lower baseline plasma ascorbate and higher myeloperoxidase levels.

Trust comment: Randomized double‑blind placebo‑controlled context but small sample (19 patients, 15 controls); mechanistic imaging study with plausible biomarkers.

Study Details

PMID:15390234
Participants:34
Impact:lower in Fabry patients vs healthy controls (baseline)
Trust score:3/5

myeloperoxidase (inflammatory marker)

1 evidences

In Fabry patients and controls IV ascorbate reduced cerebral blood flow; patients had lower baseline plasma ascorbate and higher myeloperoxidase levels.

Trust comment: Randomized double‑blind placebo‑controlled context but small sample (19 patients, 15 controls); mechanistic imaging study with plausible biomarkers.

Study Details

PMID:15390234
Participants:34
Impact:elevated in Fabry patients (consistent with inflammation)
Trust score:3/5

plasma cfDNA (NET marker)

1 evidences

Post-hoc biomarker analysis of a multicenter randomized placebo-controlled trial (CITRIS-ALI) in sepsis-induced ARDS: high-dose IV vitamin C attenuated rises in plasma cfDNA and syndecan-1 at 48 h and these biomarker changes correlated with oxygenation and 28-day mortality.

Trust comment: Post-hoc biomarker analysis of a large randomized, double-blind, placebo-controlled multicenter trial with reasonable sample size but some missing data due to early deaths.

Study Details

PMID:36297099
Participants:167
Impact:mean 48h change −0.45 ng/µL with HDIVC vs +0.57 ng/µL placebo; adjusted mean decrease vs placebo −1.02 ng/µL (p=0.05)
Trust score:4/5

plasma syndecan-1 (glycocalyx degradation)

1 evidences

Post-hoc biomarker analysis of a multicenter randomized placebo-controlled trial (CITRIS-ALI) in sepsis-induced ARDS: high-dose IV vitamin C attenuated rises in plasma cfDNA and syndecan-1 at 48 h and these biomarker changes correlated with oxygenation and 28-day mortality.

Trust comment: Post-hoc biomarker analysis of a large randomized, double-blind, placebo-controlled multicenter trial with reasonable sample size but some missing data due to early deaths.

Study Details

PMID:36297099
Participants:167
Impact:+0.75 ng/mL at 48h with HDIVC vs +1.53 ng/mL with placebo (difference p=0.05)
Trust score:4/5

oxygenation (PaO2/FiO2) association

1 evidences

Post-hoc biomarker analysis of a multicenter randomized placebo-controlled trial (CITRIS-ALI) in sepsis-induced ARDS: high-dose IV vitamin C attenuated rises in plasma cfDNA and syndecan-1 at 48 h and these biomarker changes correlated with oxygenation and 28-day mortality.

Trust comment: Post-hoc biomarker analysis of a large randomized, double-blind, placebo-controlled multicenter trial with reasonable sample size but some missing data due to early deaths.

Study Details

PMID:36297099
Participants:167
Impact:syndecan-1 increase associated with −8.85 in PaO2/FiO2 per 1 ng/mL; HDIVC group showed larger association (−18.9) vs placebo (−4.4)
Trust score:4/5

H. pylori eradication rate (overall)

1 evidences

Randomized study of 104 H. pylori–infected patients: adding vitamin C (250 mg) and E to standard triple therapy did not improve eradication and was associated with lower eradication rates in metronidazole-susceptible infections.

Trust comment: Randomized clinical trial of moderate size with clear clinical endpoints, but mechanism for reduced eradication with vitamins not established.

Study Details

PMID:12390211
Participants:104
Impact:triple-plus-vitamin ITT 40.0% vs triple-only ITT 59.1%; per-protocol 44% vs 64.4%
Trust score:3/5

eradication rate in metronidazole-susceptible strains

1 evidences

Randomized study of 104 H. pylori–infected patients: adding vitamin C (250 mg) and E to standard triple therapy did not improve eradication and was associated with lower eradication rates in metronidazole-susceptible infections.

Trust comment: Randomized clinical trial of moderate size with clear clinical endpoints, but mechanism for reduced eradication with vitamins not established.

Study Details

PMID:12390211
Participants:104
Impact:53.1% with vitamins vs 80% without (p<0.01)
Trust score:3/5

gastric inflammation (histology)

1 evidences

Randomized study of 104 H. pylori–infected patients: adding vitamin C (250 mg) and E to standard triple therapy did not improve eradication and was associated with lower eradication rates in metronidazole-susceptible infections.

Trust comment: Randomized clinical trial of moderate size with clear clinical endpoints, but mechanism for reduced eradication with vitamins not established.

Study Details

PMID:12390211
Participants:104
Impact:no difference between groups
Trust score:3/5

melanin index

1 evidences

Randomized single-blind trial in patients with melasma found both treatments reduced severity; hydroquinone+ascorbic acid gave greater melanin index reduction.

Trust comment: Randomized controlled design but single-blind and modest sample size; vitamin C was part of a combination product so isolated effect cannot be determined.

Study Details

PMID:35510765
Participants:65
Impact:greater reduction with hydroquinone+ascorbic acid vs cysteamine (between-group difference; P=0.002)
Trust score:3/5

wrinkle depth (R3z)

1 evidences

Double-blind RCT in post-menopausal women (159 completers) testing an oral multi-ingredient supplement (not collagen); reported reduced wrinkle depth and increased skin collagen deposition in biopsies.

Trust comment: Well-conducted double-blind RCT with good sample and objective measures, but multi-ingredient product prevents attribution of effects to vitamin C alone.

Study Details

PMID:23927381
Participants:159
Impact:≈10% reduction in wrinkle depth in active groups vs placebo
Trust score:3/5

dermal collagen quantity

1 evidences

Double-blind RCT in post-menopausal women (159 completers) testing an oral multi-ingredient supplement (not collagen); reported reduced wrinkle depth and increased skin collagen deposition in biopsies.

Trust comment: Well-conducted double-blind RCT with good sample and objective measures, but multi-ingredient product prevents attribution of effects to vitamin C alone.

Study Details

PMID:23927381
Participants:159
Impact:significant increase in collagen quantity/quality in test group 2 (p≈0.026)
Trust score:3/5

LDL resistance to Cu2+-catalyzed oxidation

1 evidences

In male smokers with mixed high lipids, antioxidant supplementation (including vitamin C) raised serum vitamin E and made LDL less prone to oxidative modification in vitro.

Trust comment: Randomized, double-blind, placebo-controlled trial with clear biochemical outcomes but small sample size.

Study Details

PMID:9409230
Participants:41
Impact:increased lag time; reduced lipid peroxide formation
Trust score:4/5

Serum vitamin E concentration

1 evidences

In male smokers with mixed high lipids, antioxidant supplementation (including vitamin C) raised serum vitamin E and made LDL less prone to oxidative modification in vitro.

Trust comment: Randomized, double-blind, placebo-controlled trial with clear biochemical outcomes but small sample size.

Study Details

PMID:9409230
Participants:41
Impact:increased
Trust score:4/5

Mononuclear cell–mediated LDL oxidation

1 evidences

In male smokers with mixed high lipids, antioxidant supplementation (including vitamin C) raised serum vitamin E and made LDL less prone to oxidative modification in vitro.

Trust comment: Randomized, double-blind, placebo-controlled trial with clear biochemical outcomes but small sample size.

Study Details

PMID:9409230
Participants:41
Impact:no change
Trust score:4/5

Creatine kinase (CK)

1 evidences

Six weeks of high-dose vitamin C plus vitamin E raised blood antioxidant levels but did not reduce exercise-induced muscle damage or loss of strength after a 50-km run.

Trust comment: Randomized trial with repeated measures but small sample and specific extreme-exercise population limits generalizability.

Study Details

PMID:16394956
Participants:22
Impact:increased postrace; no effect of antioxidant treatment
Trust score:3/5

Lactate dehydrogenase (LDH)

1 evidences

Six weeks of high-dose vitamin C plus vitamin E raised blood antioxidant levels but did not reduce exercise-induced muscle damage or loss of strength after a 50-km run.

Trust comment: Randomized trial with repeated measures but small sample and specific extreme-exercise population limits generalizability.

Study Details

PMID:16394956
Participants:22
Impact:increased postrace; no effect of antioxidant treatment
Trust score:3/5

Maximal voluntary contraction (MVC)

1 evidences

Six weeks of high-dose vitamin C plus vitamin E raised blood antioxidant levels but did not reduce exercise-induced muscle damage or loss of strength after a 50-km run.

Trust comment: Randomized trial with repeated measures but small sample and specific extreme-exercise population limits generalizability.

Study Details

PMID:16394956
Participants:22
Impact:decreased 14–26% postrace; no effect of antioxidant treatment
Trust score:3/5

Bowel preparation adequacy (BBPS)

1 evidences

In outpatients undergoing colonoscopy, the low-volume PEG with ascorbic acid prep had similar bowel cleansing efficacy and detection rates to comparator but higher compliance.

Trust comment: Large randomized controlled trial with clinically relevant endpoints; ascorbic acid included as part of the prep formulation.

Study Details

PMID:25410648
Participants:388
Impact:no significant difference between 2-L PEG/Asc and comparator
Trust score:4/5

Polyp and adenoma detection rates (PDR/ADR)

1 evidences

In outpatients undergoing colonoscopy, the low-volume PEG with ascorbic acid prep had similar bowel cleansing efficacy and detection rates to comparator but higher compliance.

Trust comment: Large randomized controlled trial with clinically relevant endpoints; ascorbic acid included as part of the prep formulation.

Study Details

PMID:25410648
Participants:388
Impact:similar in both groups (>60% PDR, >40% ADR)
Trust score:4/5

Patient compliance

3 evidences

In outpatients undergoing colonoscopy, the low-volume PEG with ascorbic acid prep had similar bowel cleansing efficacy and detection rates to comparator but higher compliance.

Trust comment: Large randomized controlled trial with clinically relevant endpoints; ascorbic acid included as part of the prep formulation.

Study Details

PMID:25410648
Participants:388
Impact:higher with 2-L PEG/Asc
Trust score:4/5

A 2-L PEG solution plus ascorbic acid cleaned the colon as well as 4-L PEG, with better taste and higher patient compliance.

Trust comment: Large randomized trial with blinded endoscopists and complete outcome reporting for cleansing, tolerability, and compliance.

Study Details

PMID:21900786
Participants:461
Impact:higher with 2-L PEG+ascorbic acid vs 4-L PEG
Trust score:4/5

1-L PEG plus ascorbate was noninferior to 4-L PEG for colon cleansing, had higher patient compliance, and similar safety.

Trust comment: Large multicenter randomized phase IV trial with blinded assessment and adequate sample size.

Study Details

PMID:33940043
Participants:388
Impact:+11.6 percentage points (92.7% vs 81.1%)
Trust score:4/5

neutrophil oxygen free radical production

1 evidences

In patients with acute MI, combined vitamin C+E supplementation reduced neutrophil oxidative radical production and limited lipid peroxidation versus usual care.

Trust comment: Randomized study in MI patients shows significant biochemical effects but combined C+E supplementation and small sample limit attribution to vitamin C alone.

Study Details

PMID:9110940
Participants:45
Impact:decreased (P<0.01)
Trust score:3/5

serum lipid peroxides (TBARS)

1 evidences

In patients with acute MI, combined vitamin C+E supplementation reduced neutrophil oxidative radical production and limited lipid peroxidation versus usual care.

Trust comment: Randomized study in MI patients shows significant biochemical effects but combined C+E supplementation and small sample limit attribution to vitamin C alone.

Study Details

PMID:9110940
Participants:45
Impact:stable in supplemented group vs increased in controls (P<0.05)
Trust score:3/5

serum ascorbic acid level

1 evidences

In patients with acute MI, combined vitamin C+E supplementation reduced neutrophil oxidative radical production and limited lipid peroxidation versus usual care.

Trust comment: Randomized study in MI patients shows significant biochemical effects but combined C+E supplementation and small sample limit attribution to vitamin C alone.

Study Details

PMID:9110940
Participants:45
Impact:increased with supplementation (expected rise)
Trust score:3/5

duration of reactive hyperaemia

1 evidences

Oral ascorbic acid (2 g) increased the duration of forearm reactive hyperaemia in hypercholesterolaemic patients but did not change peak blood flow.

Trust comment: Controlled study with healthy and hypercholesterolaemic groups showing acute hemodynamic improvement after single high-dose vitamin C, but sample sizes are modest and effects are short-term.

Study Details

PMID:15187819
Participants:72
Impact:increased by ~35 s (from ~69.1 to ~104.1 s; P<0.05)
Trust score:3/5

peak reactive hyperaemic forearm blood flow

1 evidences

Oral ascorbic acid (2 g) increased the duration of forearm reactive hyperaemia in hypercholesterolaemic patients but did not change peak blood flow.

Trust comment: Controlled study with healthy and hypercholesterolaemic groups showing acute hemodynamic improvement after single high-dose vitamin C, but sample sizes are modest and effects are short-term.

Study Details

PMID:15187819
Participants:72
Impact:no significant change
Trust score:3/5

cancer mortality

2 evidences

Large double‑blind randomized trial of vitamin C (500 mg daily) ± other antioxidants assessing long‑term cancer incidence and mortality in women.

Trust comment: Large, long‑term, double‑blind randomized trial with hard clinical endpoints; high quality evidence showing no benefit for cancer prevention.

Study Details

PMID:19116389
Participants:7627
Impact:no significant effect (RR 1.28, 95% CI 0.95–1.73 for vitamin C)
Trust score:5/5

In this cohort of middle-aged men, higher combined intake of vitamin C and beta-carotene was associated with lower cancer, coronary, and all-cause mortality over long-term follow-up.

Trust comment: Large long-term observational cohort showing associations but subject to confounding and combined-nutrient exposure (vitamin C + beta-carotene) limits causal attribution to vitamin C alone.

Study Details

PMID:7503047
Participants:1556
Impact:relative risk 0.60 (−40% for specified intake increment)
Trust score:3/5

coronary heart disease mortality

1 evidences

In this cohort of middle-aged men, higher combined intake of vitamin C and beta-carotene was associated with lower cancer, coronary, and all-cause mortality over long-term follow-up.

Trust comment: Large long-term observational cohort showing associations but subject to confounding and combined-nutrient exposure (vitamin C + beta-carotene) limits causal attribution to vitamin C alone.

Study Details

PMID:7503047
Participants:1556
Impact:relative risk 0.70 (−30% for specified intake increment)
Trust score:3/5

haemoglobin (day 90 change)

1 evidences

In pregnant women with moderate IDA, ferrous ascorbate produced the largest mean hemoglobin rise and had fewer gastrointestinal adverse effects than ferrous sulphate over 90 days.

Trust comment: Randomized parallel-group trial in pregnant women with adequate completion (n=150); open-label design and co-formulation of iron with ascorbate mean effects cannot be solely attributed to vitamin C.

Study Details

PMID:34782532
Participants:150
Impact:FeA +2.69 g/dl from baseline (highest among groups); FeA > FS (P<0.05 at day 90)
Trust score:4/5

serum ferritin (day 90)

1 evidences

In pregnant women with moderate IDA, ferrous ascorbate produced the largest mean hemoglobin rise and had fewer gastrointestinal adverse effects than ferrous sulphate over 90 days.

Trust comment: Randomized parallel-group trial in pregnant women with adequate completion (n=150); open-label design and co-formulation of iron with ascorbate mean effects cannot be solely attributed to vitamin C.

Study Details

PMID:34782532
Participants:150
Impact:increased in all groups; FeA 31.80 μg/l (comparable across groups)
Trust score:4/5

adverse effect incidence

1 evidences

In pregnant women with moderate IDA, ferrous ascorbate produced the largest mean hemoglobin rise and had fewer gastrointestinal adverse effects than ferrous sulphate over 90 days.

Trust comment: Randomized parallel-group trial in pregnant women with adequate completion (n=150); open-label design and co-formulation of iron with ascorbate mean effects cannot be solely attributed to vitamin C.

Study Details

PMID:34782532
Participants:150
Impact:FeA 42% vs FS 62% (fewer GI effects with FeA)
Trust score:4/5

blood pressure (pre- and post-exercise)

1 evidences

Six weeks of 1000 mg/day vitamin C in poorly controlled T2D lowered blood pressure and reduced oxidative stress markers while increasing plasma ascorbate and NO compared with placebo.

Trust comment: Randomized placebo-controlled crossover with clear biochemical and physiological effects, but small sample size and short intervention limit generalizability.

Study Details

PMID:33642340
Participants:24
Impact:decreased (SBP and DBP significantly lower vs placebo)
Trust score:4/5

oxidative stress markers (MDA, F2-isoprostanes)

1 evidences

Six weeks of 1000 mg/day vitamin C in poorly controlled T2D lowered blood pressure and reduced oxidative stress markers while increasing plasma ascorbate and NO compared with placebo.

Trust comment: Randomized placebo-controlled crossover with clear biochemical and physiological effects, but small sample size and short intervention limit generalizability.

Study Details

PMID:33642340
Participants:24
Impact:decreased (P<0.05)
Trust score:4/5

plasma nitric oxide and ascorbate

1 evidences

Six weeks of 1000 mg/day vitamin C in poorly controlled T2D lowered blood pressure and reduced oxidative stress markers while increasing plasma ascorbate and NO compared with placebo.

Trust comment: Randomized placebo-controlled crossover with clear biochemical and physiological effects, but small sample size and short intervention limit generalizability.

Study Details

PMID:33642340
Participants:24
Impact:increased (ascorbate P<0.05 at all times; NO increased at rest and immediately post-exercise)
Trust score:4/5

bowel cleansing success

2 evidences

Two 1-L bowel‑prep solutions containing ascorbic acid cleaned the colon equally well; one (CleanViewAL) tasted slightly better and no serious side effects occurred.

Trust comment: Randomized prospective phase‑4 trial with objective endpoints and reasonable sample size; open‑label design is a limitation.

Study Details

PMID:36004636
Participants:173
Impact:CleanViewAL 97.6% vs Plenvu 98.8% (difference −1.2 percentage points; no significant difference)
Trust score:4/5

PEG with ascorbate components (2 L) produced substantially higher successful bowel cleansing than sodium phosphate and was well tolerated.

Trust comment: Randomized controlled trial with blinded expert panel assessment and clear, large differences in primary outcome.

Study Details

PMID:25180609
Participants:356
Impact:PEG+Asc 93.4% vs NaP 22.8% (p < 0.0001).
Trust score:4/5

BBPS score

1 evidences

Two 1-L bowel‑prep solutions containing ascorbic acid cleaned the colon equally well; one (CleanViewAL) tasted slightly better and no serious side effects occurred.

Trust comment: Randomized prospective phase‑4 trial with objective endpoints and reasonable sample size; open‑label design is a limitation.

Study Details

PMID:36004636
Participants:173
Impact:8.67±1.00 vs 8.70±0.76 (no significant difference)
Trust score:4/5

taste satisfaction

1 evidences

Two 1-L bowel‑prep solutions containing ascorbic acid cleaned the colon equally well; one (CleanViewAL) tasted slightly better and no serious side effects occurred.

Trust comment: Randomized prospective phase‑4 trial with objective endpoints and reasonable sample size; open‑label design is a limitation.

Study Details

PMID:36004636
Participants:173
Impact:CleanViewAL +0.30 points (2.90 vs 2.60, p=0.028)
Trust score:4/5

plasma total antioxidant capacity

1 evidences

A 3-week fruit/vegetable concentrate raised blood vitamin C and some antioxidants but did not change markers of oxidative damage in male smokers.

Trust comment: Randomized crossover trial directly measured serum vitamin C with clear outcomes but had a small sample and used a complex concentrate, limiting attribution solely to vitamin C.

Study Details

PMID:11385058
Participants:22
Impact:increased
Trust score:3/5

adequate bowel preparation

2 evidences

In elderly outpatients, 2‑L PEG‑ascorbic acid was non‑inferior to oral sulfate solution for colon cleansing and had lower rates of vomiting and thirst.

Trust comment: Prospective multicenter randomized trial in the target population with clinically relevant endpoints; analysis used nearly complete data.

Study Details

PMID:34562328
Participants:189
Impact:PEG‑Asc 93.6% vs OSS 89.5% (non‑inferior; difference within prespecified margin)
Trust score:4/5

1 L PEG with ascorbic acid achieved similarly high adequate bowel-prep rates to oral sodium sulfate but caused more thirst and dizziness.

Trust comment: Multicenter prospective randomized trial with clear reported outcomes and reasonable sample size; some outcomes borderline significant.

Study Details

PMID:36107563
Participants:172
Impact:98.8% vs 96.6% (no significant difference)
Trust score:4/5

vomiting

1 evidences

In elderly outpatients, 2‑L PEG‑ascorbic acid was non‑inferior to oral sulfate solution for colon cleansing and had lower rates of vomiting and thirst.

Trust comment: Prospective multicenter randomized trial in the target population with clinically relevant endpoints; analysis used nearly complete data.

Study Details

PMID:34562328
Participants:189
Impact:PEG‑Asc 2.1% vs OSS 11.6% (higher with OSS)
Trust score:4/5

thirst

1 evidences

In elderly outpatients, 2‑L PEG‑ascorbic acid was non‑inferior to oral sulfate solution for colon cleansing and had lower rates of vomiting and thirst.

Trust comment: Prospective multicenter randomized trial in the target population with clinically relevant endpoints; analysis used nearly complete data.

Study Details

PMID:34562328
Participants:189
Impact:PEG‑Asc 11.7% vs OSS 24.2% (higher with OSS)
Trust score:4/5

strength loss

1 evidences

High‑dose vitamin C (3×1000 mg/day for 8 days) did not reduce markers or symptoms of delayed onset muscle soreness after eccentric exercise.

Trust comment: Randomized placebo‑controlled design but small sample reduces power to detect modest effects.

Study Details

PMID:16998453
Participants:24
Impact:No significant between‑group difference (P = 0.202)
Trust score:3/5

point tenderness

1 evidences

High‑dose vitamin C (3×1000 mg/day for 8 days) did not reduce markers or symptoms of delayed onset muscle soreness after eccentric exercise.

Trust comment: Randomized placebo‑controlled design but small sample reduces power to detect modest effects.

Study Details

PMID:16998453
Participants:24
Impact:No significant between‑group difference (P = 0.824)
Trust score:3/5

subjective pain and range of motion

1 evidences

High‑dose vitamin C (3×1000 mg/day for 8 days) did not reduce markers or symptoms of delayed onset muscle soreness after eccentric exercise.

Trust comment: Randomized placebo‑controlled design but small sample reduces power to detect modest effects.

Study Details

PMID:16998453
Participants:24
Impact:No significant between‑group differences (pain P = 0.342; ROM P = 0.208)
Trust score:3/5

serum ferritin (premenopausal women)

1 evidences

Higher intake of vitamin C–rich fruits and vegetables was associated with slightly higher hemoglobin in the whole sample and higher ferritin in premenopausal women.

Trust comment: Large observational cohort with repeated dietary records supports associations but cannot prove causality.

Study Details

PMID:18469253
Participants:4358
Impact:Up to ~10% higher in the third vs first tertile
Trust score:3/5

association by FVJ fiber content

1 evidences

Higher intake of vitamin C–rich fruits and vegetables was associated with slightly higher hemoglobin in the whole sample and higher ferritin in premenopausal women.

Trust comment: Large observational cohort with repeated dietary records supports associations but cannot prove causality.

Study Details

PMID:18469253
Participants:4358
Impact:Fiber‑poor FVJ linked to higher ferritin in premenopausal women and higher hemoglobin in whole sample
Trust score:3/5

comet assay indices (DNA damage: tail intensity/length)

1 evidences

In power-plant workers, daily vitamin C (1,000 mg) reduced markers of DNA damage measured by comet assay but did not change apoptosis measures.

Trust comment: Double-blind randomized controlled trial in humans with clear participant number and objective assays, though subgroup detail and exact effect sizes for vitamin C alone are limited.

Study Details

PMID:32247559
Participants:81
Impact:- significant decrease after vitamin C (and vitamin E+C) vs baseline
Trust score:4/5

apoptosis (early/late/necrosis)

1 evidences

In power-plant workers, daily vitamin C (1,000 mg) reduced markers of DNA damage measured by comet assay but did not change apoptosis measures.

Trust comment: Double-blind randomized controlled trial in humans with clear participant number and objective assays, though subgroup detail and exact effect sizes for vitamin C alone are limited.

Study Details

PMID:32247559
Participants:81
Impact:no change
Trust score:4/5

superoxide dismutase (SOD)

2 evidences

Vitamin A+C given for 1 month produced mixed effects on oxidative-stress markers: some markers improved in HIV-only patients but worsened or did not improve in HIV-TB co-infected patients.

Trust comment: Moderate-quality non-blinded clinical supplementation study with short duration and mixed/contradictory biomarker results.

Study Details

PMID:29062324
Participants:90
Impact:↓ after supplementation in HIV/TB co-infected and decreased vs baseline in some groups
Trust score:3/5

In HNC patients on cisplatin, the control group given vitamins C+E showed increases in SOD and decreases in MDA, but astaxanthin produced larger MDA reductions.

Trust comment: Small double-blind randomized trial with clear pre/post biochemical measures, but small sample (n=42) and comparison was against astaxanthin rather than placebo.

Study Details

PMID:39487992
Participants:42
Impact:increase in vit C+E group: Δ +28.8 U/mL (pre→post), pre vs post p=0.003
Trust score:3/5

platelet aggregation

1 evidences

In healthy volunteers, vitamin E supplementation markedly raised platelet alpha-tocopherol and reduced platelet function; vitamin C and beta-carotene showed no significant effects.

Trust comment: Double-blind randomized placebo-controlled trial but small sample size and null results.

Study Details

PMID:9051202
Participants:40
Impact:no significant change; trend toward decreased aggregability
Trust score:4/5

sICAM-1

1 evidences

In patients with intermittent claudication, vitamin C administration prevented exercise-induced impairment of endothelial function and rises in oxidative stress markers.

Trust comment: Small human trial with physiological and biochemical endpoints and randomized subset assignment, but limited sample size.

Study Details

PMID:12417278
Participants:31
Impact:exercise-induced increase (282→323 ng/ml) was abolished by vitamin C in treated patients
Trust score:3/5

OBPS adequate bowel preparation rate

1 evidences

In this randomized investigator-blind trial in Korean patients, oral sulfate solution produced superior overall bowel cleansing compared with 2-L ascorbic acid plus PEG.

Trust comment: Large randomized investigator-blind trial with clear endpoints and adequate sample size (173), high methodological quality for the comparison of bowel preps.

Study Details

PMID:30685963
Participants:173
Impact:OSS 93.0% vs AA+PEG 77.0% (p=0.005); AA+PEG inferior
Trust score:4/5

BBPS total score

1 evidences

In this randomized investigator-blind trial in Korean patients, oral sulfate solution produced superior overall bowel cleansing compared with 2-L ascorbic acid plus PEG.

Trust comment: Large randomized investigator-blind trial with clear endpoints and adequate sample size (173), high methodological quality for the comparison of bowel preps.

Study Details

PMID:30685963
Participants:173
Impact:OSS 7.43±1.49 vs AA+PEG 6.51±1.76 (p<0.001); AA+PEG lower score
Trust score:4/5

tolerability (nausea, cramping)

1 evidences

In this randomized investigator-blind trial in Korean patients, oral sulfate solution produced superior overall bowel cleansing compared with 2-L ascorbic acid plus PEG.

Trust comment: Large randomized investigator-blind trial with clear endpoints and adequate sample size (173), high methodological quality for the comparison of bowel preps.

Study Details

PMID:30685963
Participants:173
Impact:AA+PEG had less nausea/abdominal cramping than OSS (differences small; scores <2)
Trust score:4/5

plasma cortisol

2 evidences

In women with functional hypercortisolemia, 1000 mg/day vitamin C for 2 months significantly lowered elevated cortisol and DHEA-S levels compared with untreated controls.

Trust comment: Human study with clear hormonal endpoints and sample of 69 women, but limited detail on randomization and blinding in excerpt.

Study Details

PMID:38010274
Participants:69
Impact:Group I: 780±57→446±26 nmol/L (p=0.000065); Group II: 657±47→515±29 nmol/L (p=0.005)
Trust score:3/5

Intravenous ascorbic acid did not attenuate etomidate-induced suppression of adrenal steroid production in this small clinical study.

Trust comment: Controlled clinical setting but small sample (n=30) and limited power to detect modest effects.

Study Details

PMID:8842654
Participants:30
Impact:no clinically relevant attenuation of etomidate-induced suppression with ascorbic acid
Trust score:3/5

DHEA-S

1 evidences

In women with functional hypercortisolemia, 1000 mg/day vitamin C for 2 months significantly lowered elevated cortisol and DHEA-S levels compared with untreated controls.

Trust comment: Human study with clear hormonal endpoints and sample of 69 women, but limited detail on randomization and blinding in excerpt.

Study Details

PMID:38010274
Participants:69
Impact:Group II: 13.9±1.6→9.9±1.2 (p=0.0007); Group III: 12.8±1.0→7.8±1.4 (p=0.003)
Trust score:3/5

bowel cleansing efficacy (modified Ottawa, Aronchick)

1 evidences

Randomized trial (n=200) comparing low-volume PEG+ascorbic acid vs sodium picosulfate+magnesium citrate for colon cleansing; similar efficacy but better tolerance with PEG+ascorbic.

Trust comment: Randomized, endoscopist-blinded RCT with adequate sample (n=200); single-center but well-reported outcomes.

Study Details

PMID:26945825
Participants:200
Impact:no significant difference (OBPS: 4.01±2.29 vs 3.86±2.47; P=0.62; Aronchick P=0.42)
Trust score:4/5

patient overall tolerance/taste

1 evidences

Randomized trial (n=200) comparing low-volume PEG+ascorbic acid vs sodium picosulfate+magnesium citrate for colon cleansing; similar efficacy but better tolerance with PEG+ascorbic.

Trust comment: Randomized, endoscopist-blinded RCT with adequate sample (n=200); single-center but well-reported outcomes.

Study Details

PMID:26945825
Participants:200
Impact:higher with PEG+ascorbic (P=0.01)
Trust score:4/5

adverse events (dizziness, nausea)

1 evidences

Randomized trial (n=200) comparing low-volume PEG+ascorbic acid vs sodium picosulfate+magnesium citrate for colon cleansing; similar efficacy but better tolerance with PEG+ascorbic.

Trust comment: Randomized, endoscopist-blinded RCT with adequate sample (n=200); single-center but well-reported outcomes.

Study Details

PMID:26945825
Participants:200
Impact:dizziness more frequent with PEG+ascorbic (P=0.03); nausea more frequent with SPMC (P=0.02)
Trust score:4/5

haemoglobin

1 evidences

Two related studies in haemodialysis patients (small RCT n=21 and larger 3-month cohort n=153) found no improvement in haemoglobin or iron availability with oral or IV ascorbic acid; plasma AA rose and serum oxalate increased.

Trust comment: Small randomized comparison and a larger non‑blinded cohort; objective outcomes but limited power and mixed designs.

Study Details

PMID:16109077
Participants:174
Impact:no change following oral or IV ascorbic acid
Trust score:3/5

iron availability / ferritin

1 evidences

Two related studies in haemodialysis patients (small RCT n=21 and larger 3-month cohort n=153) found no improvement in haemoglobin or iron availability with oral or IV ascorbic acid; plasma AA rose and serum oxalate increased.

Trust comment: Small randomized comparison and a larger non‑blinded cohort; objective outcomes but limited power and mixed designs.

Study Details

PMID:16109077
Participants:174
Impact:no change
Trust score:3/5

rEPO dose

1 evidences

Two related studies in haemodialysis patients (small RCT n=21 and larger 3-month cohort n=153) found no improvement in haemoglobin or iron availability with oral or IV ascorbic acid; plasma AA rose and serum oxalate increased.

Trust comment: Small randomized comparison and a larger non‑blinded cohort; objective outcomes but limited power and mixed designs.

Study Details

PMID:16109077
Participants:174
Impact:no change
Trust score:3/5

kidney function markers (urea, creatinine, uric acid)

1 evidences

6-week randomized prospective study in 80 postmenopausal women (40 with T2D) showing HRT ± vitamin C/E associated with improved kidney and liver biochemical markers in diabetic women but no change in thyroid hormones.

Trust comment: Small randomized short-term study; biochemical changes reported but attribution specifically to vitamins versus HRT is not fully isolated.

Study Details

PMID:19917523
Participants:80
Impact:decreased in diabetic women receiving HRT or HRT+vitamins
Trust score:3/5

liver enzymes (AST, ALT, LDH, bilirubin)

1 evidences

6-week randomized prospective study in 80 postmenopausal women (40 with T2D) showing HRT ± vitamin C/E associated with improved kidney and liver biochemical markers in diabetic women but no change in thyroid hormones.

Trust comment: Small randomized short-term study; biochemical changes reported but attribution specifically to vitamins versus HRT is not fully isolated.

Study Details

PMID:19917523
Participants:80
Impact:decreased in diabetic women receiving HRT or HRT+vitamins
Trust score:3/5

thyroid hormones (free T4, T3)

1 evidences

6-week randomized prospective study in 80 postmenopausal women (40 with T2D) showing HRT ± vitamin C/E associated with improved kidney and liver biochemical markers in diabetic women but no change in thyroid hormones.

Trust comment: Small randomized short-term study; biochemical changes reported but attribution specifically to vitamins versus HRT is not fully isolated.

Study Details

PMID:19917523
Participants:80
Impact:no significant change
Trust score:3/5

vagal control of heart rate

1 evidences

Randomized, placebo‑controlled crossover study in 30 male smokers found minor acute cardiovascular effects; moderate vitamins increased vagal HR control but antioxidants did not change baroreflex sensitivity.

Trust comment: Well-controlled crossover design with objective autonomic measures but small, single‑sex sample limits generalizability.

Study Details

PMID:17895912
Participants:30
Impact:+23% with moderate vitamins (P<0.05)
Trust score:4/5

baroreflex sensitivity (BRS)

1 evidences

Randomized, placebo‑controlled crossover study in 30 male smokers found minor acute cardiovascular effects; moderate vitamins increased vagal HR control but antioxidants did not change baroreflex sensitivity.

Trust comment: Well-controlled crossover design with objective autonomic measures but small, single‑sex sample limits generalizability.

Study Details

PMID:17895912
Participants:30
Impact:no significant effect from circulating antioxidants
Trust score:4/5

systolic blood pressure / heart rate (post‑fat challenge)

1 evidences

Randomized, placebo‑controlled crossover study in 30 male smokers found minor acute cardiovascular effects; moderate vitamins increased vagal HR control but antioxidants did not change baroreflex sensitivity.

Trust comment: Well-controlled crossover design with objective autonomic measures but small, single‑sex sample limits generalizability.

Study Details

PMID:17895912
Participants:30
Impact:cream (high fat) increased SBP ~+2 mmHg and HR ~+2 bpm (P<0.05)
Trust score:4/5

pain (Visual Analogue Scale)

1 evidences

Rehab plus oral collagen-containing supplement produced greater and more sustained improvements in pain, disability, and physical QoL than rehab alone.

Trust comment: Randomized but likely unblinded, small sample and combined multi-ingredient supplement limit attribution to vitamin C alone.

Study Details

PMID:33568038
Participants:60
Impact:greater improvement with supplement+exercise at end of treatment and sustained at follow-up
Trust score:3/5

function (Oswestry Disability Index)

1 evidences

Rehab plus oral collagen-containing supplement produced greater and more sustained improvements in pain, disability, and physical QoL than rehab alone.

Trust comment: Randomized but likely unblinded, small sample and combined multi-ingredient supplement limit attribution to vitamin C alone.

Study Details

PMID:33568038
Participants:60
Impact:greater improvement with supplement+exercise and sustained vs rehabilitation alone
Trust score:3/5

physical quality of life (SF-12 physical)

1 evidences

Rehab plus oral collagen-containing supplement produced greater and more sustained improvements in pain, disability, and physical QoL than rehab alone.

Trust comment: Randomized but likely unblinded, small sample and combined multi-ingredient supplement limit attribution to vitamin C alone.

Study Details

PMID:33568038
Participants:60
Impact:sustained improvement with supplement+exercise; rehabilitation alone worsened by follow-up
Trust score:3/5

total cancer incidence (men)

3 evidences

Long-term low-dose antioxidant/multi-mineral supplementation (including 20 mg zinc) reduced total cancer incidence and all-cause mortality in men but not in women over ~7.5 years.

Trust comment: Large randomized double-blind placebo-controlled primary prevention trial with long follow-up, providing high-quality evidence.

Study Details

PMID:15557412
Participants:13017
Impact:decreased ~31% (RR 0.69, 95% CI 0.53–0.91)
Trust score:5/5

Large randomized trial of daily low-dose antioxidant supplement (included 20 mg Zn) showed lower total cancer incidence in men but not in women after 7.5 years.

Trust comment: Large, long-duration randomized double‑blind primary prevention trial with robust sample size and pre-specified analyses.

Study Details

PMID:16115341
Participants:12741
Impact:reduced after 7.5 years of low‑dose antioxidant supplementation (effect observed in men, not women)
Trust score:5/5

Long-term low-dose antioxidant supplementation (including 120 mg vitamin C) did not affect vascular disease but lowered total cancer incidence in men.

Trust comment: Large, long-duration double-blind RCT offering high-quality evidence for the combination, but multiple nutrients were given so effects cannot be ascribed to vitamin C alone.

Study Details

PMID:17119469
Participants:12741
Impact:decrease — significant
Trust score:4/5

baseline serum vitamin C / E levels and cancer risk

1 evidences

Large randomized trial of daily low-dose antioxidant supplement (included 20 mg Zn) showed lower total cancer incidence in men but not in women after 7.5 years.

Trust comment: Large, long-duration randomized double‑blind primary prevention trial with robust sample size and pre-specified analyses.

Study Details

PMID:16115341
Participants:12741
Impact:men with baseline vitamin C or E below cut-offs had higher cancer risk; supplementation effect larger in low‑baseline men
Trust score:5/5

sex difference in supplementation effect

1 evidences

Large randomized trial of daily low-dose antioxidant supplement (included 20 mg Zn) showed lower total cancer incidence in men but not in women after 7.5 years.

Trust comment: Large, long-duration randomized double‑blind primary prevention trial with robust sample size and pre-specified analyses.

Study Details

PMID:16115341
Participants:12741
Impact:no beneficial effect seen in women
Trust score:5/5

iron absorption (relative bioavailability)

1 evidences

In a randomized crossover study in male blood donors, elemental iron powders were less well absorbed than ferrous sulfate; electrolytic iron given with 50 mg ascorbic acid showed absorption similar to ferrous sulfate.

Trust comment: Well-conducted double-blind randomized crossover in humans; direct measures of serum iron support conclusions though sample size moderate.

Study Details

PMID:15864409
Participants:48
Impact:elemental iron powders RBV range 0.36–0.65 (significantly lower than FeSO4)
Trust score:4/5

plasma lipids and lipoproteins

1 evidences

Adults advised to eat more fruit and vegetables for eight weeks had higher plasma vitamin C and carotenoids but no change in lipids.

Trust comment: Randomized controlled trial with clear dietary intervention and measured plasma antioxidants, but exact vitamin C change not numerically reported in the summary.

Study Details

PMID:9224079
Participants:87
Impact:no significant change
Trust score:4/5

hemoglobin concentration

9 evidences

A 6-month school feeding intervention with cowpea-based food plus a vitamin C-rich drink increased hemoglobin and reduced anemia prevalence in children.

Trust comment: Randomized school feeding intervention with 150 children in a malaria-endemic setting; reasonable size though infectious disease confounding present.

Study Details

PMID:26385950
Participants:150
Impact:change +8.3 g/L (fish meal + vitamin C) vs +4.2 g/L (control)
Trust score:4/5

Fortified porridge given for 6 months raised hemoglobin and ferritin and improved motor development in infants.

Trust comment: Large randomized trial with good completion (292); includes ascorbic acid as part of a multi-micronutrient fortification so effects are attributable to the combined formulation, not vitamin C alone.

Study Details

PMID:16280435
Participants:292
Impact:+9 g/L intervention effect (95% CI: 6 to 12 g/L)
Trust score:4/5

A fortified drink given 6 days/week for 8 weeks reduced vitamin B12 deficiency prevalence and increased vitamin B12 concentration and hemoglobin in schoolchildren.

Trust comment: Checklist: confirmed Vitamin C included in the fortified drink; primary outcomes (vitamin C status, Hb, ferritin) identified; participant count confirmed—randomized double-blind placebo-controlled trial with strong internal validity.

Study Details

PMID:23232585
Participants:246
Impact:increase (significantly higher in intervention, P<0.001)
Trust score:4/5

Weekly or daily micronutrient supplements including zinc raised hemoglobin, serum zinc, and retinol versus placebo; growth improved only in children who were stunted at baseline.

Trust comment: Checklist: Vitamin C present in both supplementation regimens (not isolated); key outcomes (Hb, retinol, zinc) identified; participant count confirmed—well-conducted randomized placebo-controlled trial.

Study Details

PMID:9925127
Participants:163
Impact:increase vs placebo (P<0.001)
Trust score:4/5

Children given improved gruel with or without a multi-micronutrient mix (including iodine) both showed Hb increases; the micronutrient mix added no significant benefit.

Trust comment: Randomized community trial with modest sample size and clear outcomes; multi-nutrient composition limits attribution to vitamin C alone.

Study Details

PMID:20529401
Participants:131
Impact:Endpoint Hb: GG 104.1 g/L vs MMGG 107.6 g/L; between-group difference +3.5 g/L (95% CI -1.0, 8.1), not significant
Trust score:3/5

Anemic children given iron/folate improved hemoglobin; adding vitamins A and C helped restore iron stores faster.

Trust comment: Randomized, double-blind trial with moderate-to-large sample and clinically relevant hematologic endpoints.

Study Details

PMID:11442213
Participants:215
Impact:increase +3.6 g/dL (mean 6.6 → 10.2 g/dL across groups)
Trust score:4/5

Daily mungbean meal with guava (high vitamin C) for 7 months increased hemoglobin and reduced anemia prevalence but did not increase body iron stores.

Trust comment: Large, randomized, registered trial in children with supervised feeding and clearly reported outcomes and CIs.

Study Details

PMID:39481541
Participants:200
Impact:+3.7 g/L (95% CI: 1.6 to 5.6; P = 0.001)
Trust score:5/5

In 324 anemic adolescent girls, once- or twice-weekly multiple micronutrient supplements (including vitamin C) improved vitamin C status and several other micronutrients compared with iron+folic acid over 52 weeks; hemoglobin differences were minimal overall.

Trust comment: Checklist: Vitamin C measured as part of MMN vs IFA comparison; main outcomes (vitamin C status, Hb, ferritin) identified; participant count confirmed—large randomized double-blind trial with appropriate follow-up.

Study Details

PMID:20702745
Participants:324
Impact:no significant difference overall between treatments
Trust score:4/5

Home fortification micronutrient powder (contains vitamin C among others) was at least as effective as iron–folic acid tablets in maintaining hemoglobin during pregnancy, though adherence was lower.

Trust comment: Large cluster-randomized noninferiority trial with pragmatic design, but intervention is a multi-nutrient powder so effects cannot be isolated to vitamin C.

Study Details

PMID:22908696
Participants:478
Impact:micronutrient powder 109.5 ± 12.9 g/L vs tablets 112.0 ± 11.2 g/L (non-inferior; 95% CI −0.757 to 5.716)
Trust score:4/5

body iron stores

2 evidences

Daily low-dose MNP containing bioavailable iron and 2.5 mg zinc reduced iron and zinc deficiencies and modestly improved weight-for-age over 23 weeks.

Trust comment: Randomized double-blind trial (n=200) with clear effects on iron/zinc status, but vitamin C was a component of a combined formula so its isolated effect is not determined.

Study Details

PMID:21178093
Participants:200
Impact:Increased (P < 0.01)
Trust score:3/5

Daily mungbean meal with guava (high vitamin C) for 7 months increased hemoglobin and reduced anemia prevalence but did not increase body iron stores.

Trust comment: Large, randomized, registered trial in children with supervised feeding and clearly reported outcomes and CIs.

Study Details

PMID:39481541
Participants:200
Impact:no significant change (mean treatment effect 0.65 mg/kg; 95% CI: -0.34 to 1.63; P = 0.197)
Trust score:5/5

SOFA score change (0–72 h)

1 evidences

In adults with septic shock, combination therapy including ascorbic acid did not significantly reduce organ failure (SOFA score), kidney failure, or 30-day mortality versus placebo.

Trust comment: Multicenter, randomized, blinded trial with adequate sample size and clear reporting showing no significant benefit of the combination including ascorbic acid.

Study Details

PMID:32809003
Participants:200
Impact:adjusted mean difference -0.8 (95% CI: -1.7 to 0.2); no significant improvement (P = .12)
Trust score:5/5

kidney failure incidence

1 evidences

In adults with septic shock, combination therapy including ascorbic acid did not significantly reduce organ failure (SOFA score), kidney failure, or 30-day mortality versus placebo.

Trust comment: Multicenter, randomized, blinded trial with adequate sample size and clear reporting showing no significant benefit of the combination including ascorbic acid.

Study Details

PMID:32809003
Participants:200
Impact:31.7% with intervention vs 27.3% with placebo (no significant difference)
Trust score:5/5

plasma antioxidant profile

1 evidences

Older adults received vitamin C/E with or without resistance training for 6 months; antioxidant profile improved but strength did not change and body composition changed significantly.

Trust comment: Randomized double-blind study in older adults but modest sample size and limited reporting of effect sizes.

Study Details

PMID:22159777
Participants:57
Impact:Improved with combined resistance training + antioxidant supplementation
Trust score:3/5

pro-oxidant status

1 evidences

Older adults received vitamin C/E with or without resistance training for 6 months; antioxidant profile improved but strength did not change and body composition changed significantly.

Trust comment: Randomized double-blind study in older adults but modest sample size and limited reporting of effect sizes.

Study Details

PMID:22159777
Participants:57
Impact:No effect
Trust score:3/5

muscle strength

1 evidences

Older adults received vitamin C/E with or without resistance training for 6 months; antioxidant profile improved but strength did not change and body composition changed significantly.

Trust comment: Randomized double-blind study in older adults but modest sample size and limited reporting of effect sizes.

Study Details

PMID:22159777
Participants:57
Impact:No difference in strength gain between groups
Trust score:3/5

plasma homocysteine concentration

1 evidences

In men with mildly elevated homocysteine, B‑group vitamin supplementation (including cyanocobalamin) reduced plasma homocysteine over 8 weeks.

Trust comment: Double-blind, randomized factorial trial with completion data (n=101), but vitamin C was given as part of a multinutrient antioxidant mix.

Study Details

PMID:9583842
Participants:101
Impact:antioxidant vitamins alone: nonsignificant increase of 5.1% (95% CI -2.8% to 13.6%; P = 0.21)
Trust score:4/5

Endothelium-dependent vasodilator response to acetylcholine

1 evidences

Vitamin C co-infusion tended to improve endothelial responses in some treatment groups but changes were not statistically significant versus placebo.

Trust comment: Double-blind, randomized, placebo-controlled trial with moderate sample size, but the vitamin C effect reported was not statistically significant versus placebo.

Study Details

PMID:22053074
Participants:44
Impact:Improved with vitamin C co-infusion (not statistically significant vs placebo)
Trust score:4/5

Acute exercise-induced plasma IL-6 response

1 evidences

Combined vitamin C+E prevented the training-related reduction in exercise-induced plasma IL-6 and increased some oxidative stress markers.

Trust comment: Small randomized allocation and use of combined vitamin C+E limits attribution to vitamin C alone despite statistically reported effects.

Study Details

PMID:22207723
Participants:21
Impact:No attenuation after training in vitamin group (P = 0.82) versus attenuation in placebo
Trust score:3/5

Plasma protein carbonyls (oxidative stress marker)

1 evidences

Combined vitamin C+E prevented the training-related reduction in exercise-induced plasma IL-6 and increased some oxidative stress markers.

Trust comment: Small randomized allocation and use of combined vitamin C+E limits attribution to vitamin C alone despite statistically reported effects.

Study Details

PMID:22207723
Participants:21
Impact:Overall increase in vitamin group (group effect P < 0.005)
Trust score:3/5

ICAM-1

1 evidences

Vitamin C alone lowered P-selectin and combined vitamin E+C lowered ICAM-1 over 6 months in patients with aortic stenosis.

Trust comment: Randomized trial with adequate sample size but open-label design and unclear clinical significance of biomarker changes.

Study Details

PMID:16086935
Participants:100
Impact:Reduced from 298 ±12 to 272 ±12 ng/mL at 6 months with vitamin E+C (–26 ng/mL, P = .0015)
Trust score:3/5

P-selectin

1 evidences

Vitamin C alone lowered P-selectin and combined vitamin E+C lowered ICAM-1 over 6 months in patients with aortic stenosis.

Trust comment: Randomized trial with adequate sample size but open-label design and unclear clinical significance of biomarker changes.

Study Details

PMID:16086935
Participants:100
Impact:Reduced from 134 ±10 to 118 ±10 ng/mL at 6 months with vitamin C alone (–16 ng/mL, P = .033)
Trust score:3/5

Exercise-induced lipid peroxidation (PBN adducts)

1 evidences

Oral 1 g vitamin C increased plasma vitamin C and attenuated exercise-induced oxidative stress markers in type 1 diabetic patients and healthy controls.

Trust comment: Randomized double-blind placebo-controlled trial but small sample size and mixed groups limit generalizability.

Study Details

PMID:18769906
Participants:26
Impact:Attenuated by 1 g vitamin C (statistically significant, P < 0.05)
Trust score:3/5

fasting blood glucose

2 evidences

In 30 HCV patients, adding black cumin and vitamin C to standard antivirals showed small improvements in hematologic and antioxidant markers and a significant drop in fasting glucose, but most comparisons were not statistically significant.

Trust comment: Prospective randomized trial but very small sample (n=30) with mostly non-significant differences limiting confidence.

Study Details

PMID:32566096
Participants:30
Impact:significant decrease in treated group (P = 0.001)
Trust score:3/5

In a randomized double-blind crossover trial, diabetics received magnesium or vitamin C to assess effects on blood pressure, glucose and lipids.

Trust comment: Randomized double-blind crossover RCT in 56 diabetics showing statistically significant changes in glycemia and lipids in NIDDM, but sample is modest and subgroup-specific.

Study Details

PMID:8546437
Participants:56
Impact:from 10.1 to 9.1 mmol/L (−1.0 mmol/L; P < 0.05)
Trust score:4/5

HbA1c

4 evidences

In a randomized double-blind crossover trial, diabetics received magnesium or vitamin C to assess effects on blood pressure, glucose and lipids.

Trust comment: Randomized double-blind crossover RCT in 56 diabetics showing statistically significant changes in glycemia and lipids in NIDDM, but sample is modest and subgroup-specific.

Study Details

PMID:8546437
Participants:56
Impact:from 9.3% to 8.5% (−0.8 percentage points; P < 0.05)
Trust score:4/5

In type 2 diabetic men on metformin, daily vitamin C (alone or with vitamin E) for 90 days improved glycemic control, insulin resistance measures, and some oxidative stress markers versus placebo.

Trust comment: Randomized single-blind trial showing beneficial signals, but small sample size per arm and single-blind design limit confidence and generalizability.

Study Details

PMID:29571976
Participants:40
Impact:improvement compared with placebo (reported qualitatively)
Trust score:3/5

In type 2 diabetic patients on metformin, adding 500 mg vitamin C daily for 12 months improved fasting glucose, HbA1c and albumin-to-creatinine ratio versus metformin alone.

Trust comment: Well-powered 12-month randomized multicenter trial with monthly monitoring and objective biochemical endpoints, though single-blind and lacking ITT/repeated-measures in final analysis.

Study Details

PMID:28807030
Participants:422
Impact:Decreased from 8.83 ±2.41 to 6.45 ±1.21 percentage points (≈−2.38 pp) in ascorbic acid arm (P<0.01)
Trust score:4/5

In a randomized trial of T2DM patients, combined vitamin C (500 mg) and chromium (200 µg) for the treatment group (n=30) improved glycemic control (HbA1c), lipid profile, liver enzymes and BMI versus placebo.

Trust comment: Small randomized controlled trial (n=60) testing a combined supplement (vitamin C + chromium) so effects cannot be attributed to vitamin C alone; limited methodological detail reported.

Study Details

PMID:38747270
Participants:60
Impact:Normalized to 5.45% ± 0.2 in treatment group (P<0.001 vs control)
Trust score:3/5

blood lipids (cholesterol and triglycerides)

1 evidences

In a randomized double-blind crossover trial, diabetics received magnesium or vitamin C to assess effects on blood pressure, glucose and lipids.

Trust comment: Randomized double-blind crossover RCT in 56 diabetics showing statistically significant changes in glycemia and lipids in NIDDM, but sample is modest and subgroup-specific.

Study Details

PMID:8546437
Participants:56
Impact:cholesterol: 6.2 to 5.9 mmol/L (−0.3 mmol/L; P < 0.05); triglycerides: 2.5 to 2.2 mmol/L (−0.3 mmol/L; P < 0.05)
Trust score:4/5

micronucleus frequency (chromosomal damage)

1 evidences

A 12-week trial of combined antioxidants including vitamin C (100 mg/day) reduced oxidative damage markers and prevented micronucleus increases versus placebo, with effects influenced by folate status.

Trust comment: Randomized trial but vitamin C was given as part of a multinutrient antioxidant combination, so effects cannot be attributed to vitamin C alone.

Study Details

PMID:15548759
Participants:86
Impact:prevented increase seen in placebo; decreased after supplementation (strongest in subjects with normal folate; P = 0.015)
Trust score:3/5

ferric reducing ability of plasma (FRAP)

1 evidences

A 12-week trial of combined antioxidants including vitamin C (100 mg/day) reduced oxidative damage markers and prevented micronucleus increases versus placebo, with effects influenced by folate status.

Trust comment: Randomized trial but vitamin C was given as part of a multinutrient antioxidant combination, so effects cannot be attributed to vitamin C alone.

Study Details

PMID:15548759
Participants:86
Impact:increased in supplemented myocardial infarction survivors (P < 0.001)
Trust score:3/5

bowel preparation efficacy (OBPS and 4-point scale)

1 evidences

In 62 inpatients, low-volume PEG with ascorbic acid had comparable bowel-cleansing efficacy and tolerability to 2 L PEG plus bisacodyl when given split-dose.

Trust comment: Small randomized trial directly testing an ascorbic acid–containing bowel prep with clear endpoints but limited sample size.

Study Details

PMID:25862428
Participants:62
Impact:comparable between groups (OBPS P = 0.071; 4-point scale P = 0.056; no significant difference)
Trust score:3/5

adverse events

1 evidences

In 62 inpatients, low-volume PEG with ascorbic acid had comparable bowel-cleansing efficacy and tolerability to 2 L PEG plus bisacodyl when given split-dose.

Trust comment: Small randomized trial directly testing an ascorbic acid–containing bowel prep with clear endpoints but limited sample size.

Study Details

PMID:25862428
Participants:62
Impact:no significant difference between groups (P = 1.000)
Trust score:3/5

bowel cleansing quality (BBPS total score)

1 evidences

Multicenter randomized trial (per-protocol n=211) found OST noninferior to 2 L-PEG with ascorbic acid for bowel cleansing and showed better tolerability measures for OST.

Trust comment: Large multicenter randomized, colonoscopist-blinded trial using validated scales and robust sample (PP n=211), yielding high internal validity.

Study Details

PMID:39688329
Participants:211
Impact:OST 8.2 ± 1.5 vs. 2 L-PEG/ASC 7.8 ± 1.4 (difference +0.4; P = 0.040)
Trust score:5/5

high-quality cleansing (right/transverse/left colon)

1 evidences

Multicenter randomized trial (per-protocol n=211) found OST noninferior to 2 L-PEG with ascorbic acid for bowel cleansing and showed better tolerability measures for OST.

Trust comment: Large multicenter randomized, colonoscopist-blinded trial using validated scales and robust sample (PP n=211), yielding high internal validity.

Study Details

PMID:39688329
Participants:211
Impact:right colon: 73.2% vs 50.5% (P = 0.002); transverse: 80.6% vs 68.0% (P = 0.016); left: 81.5% vs 67.0% (P = 0.004)
Trust score:5/5

tolerability (taste/ease/willingness)

1 evidences

Multicenter randomized trial (per-protocol n=211) found OST noninferior to 2 L-PEG with ascorbic acid for bowel cleansing and showed better tolerability measures for OST.

Trust comment: Large multicenter randomized, colonoscopist-blinded trial using validated scales and robust sample (PP n=211), yielding high internal validity.

Study Details

PMID:39688329
Participants:211
Impact:taste 7.9 vs 6.5 (P < 0.001); ease 7.8 vs 6.5 (P < 0.001); willingness 89.8% vs 78.6% (P = 0.026)
Trust score:5/5

duration of scab/persistent symptoms

1 evidences

Small randomized double-blind placebo-controlled trial of topical ascorbic acid solution showed faster lesion healing and reduced virus culture positivity.

Trust comment: Randomized double-blind placebo RCT shows significant clinical and antiviral effects but is small (32 episodes) and topical application limits generalizability.

Study Details

PMID:8540748
Participants:32
Impact:patient records: significantly fewer cumulative days with scab or symptoms (P < 0.02); nurse records: scab persistence 3.4 vs 5.9 days (P = 0.03)
Trust score:3/5

virus culture positivity

1 evidences

Small randomized double-blind placebo-controlled trial of topical ascorbic acid solution showed faster lesion healing and reduced virus culture positivity.

Trust comment: Randomized double-blind placebo RCT shows significant clinical and antiviral effects but is small (32 episodes) and topical application limits generalizability.

Study Details

PMID:8540748
Participants:32
Impact:less frequent herpes simplex isolation after first day in active treatment group (P < 0.01)
Trust score:3/5

fat intake

2 evidences

In 589 individuals from 169 families, a multifaceted family-based intervention (personalized goal setting + cooking + education) increased dietary vitamin C intake at 3 and 18 months versus education alone.

Trust comment: Large randomized parallel-design community trial with multiple follow-ups and clear dietary outcomes, though long-term retention dropped substantially.

Study Details

PMID:22017999
Participants:589
Impact:reduced in intervention C vs A at 3 months (P = 0.02)
Trust score:4/5

Nutrition education classes reduced fat intake and increased fiber and ascorbic acid (vitamin C) intake among postmenopausal women, especially in those motivated to change.

Trust comment: Large behavioral trial with clear group sizes and repeated measures, but dietary intake measured by FFQ and effect sizes not provided in excerpt.

Study Details

PMID:15020177
Participants:866
Impact:decreased (magnitude not reported)
Trust score:3/5

total carbohydrate/starch intake

1 evidences

In 589 individuals from 169 families, a multifaceted family-based intervention (personalized goal setting + cooking + education) increased dietary vitamin C intake at 3 and 18 months versus education alone.

Trust comment: Large randomized parallel-design community trial with multiple follow-ups and clear dietary outcomes, though long-term retention dropped substantially.

Study Details

PMID:22017999
Participants:589
Impact:increased in intervention C vs A at 3 months (total carbohydrate P = 0.001; starch P = 0.04)
Trust score:4/5

postoperative acute kidney injury incidence

1 evidences

Perioperative vitamin C did not reduce postoperative acute kidney injury or change key renal function measures after elective on-pump CABG.

Trust comment: Randomized prospective single-center trial with 100 well-matched patients; pilot size and single-center design limit broad generalizability.

Study Details

PMID:29087285
Participants:100
Impact:+2 percentage points (16% vs 14%; P = .779; not significant)
Trust score:4/5

peak postoperative serum creatinine

1 evidences

Perioperative vitamin C did not reduce postoperative acute kidney injury or change key renal function measures after elective on-pump CABG.

Trust comment: Randomized prospective single-center trial with 100 well-matched patients; pilot size and single-center design limit broad generalizability.

Study Details

PMID:29087285
Participants:100
Impact:0 µmol/L difference (83 vs 83 µmol/L; P = .434; not significant)
Trust score:4/5

postoperative creatinine clearance

1 evidences

Perioperative vitamin C did not reduce postoperative acute kidney injury or change key renal function measures after elective on-pump CABG.

Trust comment: Randomized prospective single-center trial with 100 well-matched patients; pilot size and single-center design limit broad generalizability.

Study Details

PMID:29087285
Participants:100
Impact:+5.5 mL/min (96.40 vs 90.89 mL/min; P = .766; not significant)
Trust score:4/5

anxiety level

1 evidences

In type 2 diabetic patients, 1000 mg/day vitamin C for six weeks significantly reduced anxiety compared with vitamin E and placebo, with no effect on stress or depression.

Trust comment: Randomized single-blind trial with small sample (n=45) and short duration; randomization supports validity but limited size and single-blind design weaken strength.

Study Details

PMID:24511708
Participants:45
Impact:Decreased (significant vs other groups; P = 0.005)
Trust score:3/5

stress level

1 evidences

In type 2 diabetic patients, 1000 mg/day vitamin C for six weeks significantly reduced anxiety compared with vitamin E and placebo, with no effect on stress or depression.

Trust comment: Randomized single-blind trial with small sample (n=45) and short duration; randomization supports validity but limited size and single-blind design weaken strength.

Study Details

PMID:24511708
Participants:45
Impact:No significant change
Trust score:3/5

depression score

1 evidences

In type 2 diabetic patients, 1000 mg/day vitamin C for six weeks significantly reduced anxiety compared with vitamin E and placebo, with no effect on stress or depression.

Trust comment: Randomized single-blind trial with small sample (n=45) and short duration; randomization supports validity but limited size and single-blind design weaken strength.

Study Details

PMID:24511708
Participants:45
Impact:No significant change
Trust score:3/5

LDL oxidation (TBARS LDL)

1 evidences

In patients starting hemodialysis, 1000 mg/day vitamin C for one year attenuated the rise in LDL oxidation products (TBARS) compared with placebo, with mixed results for other oxidation markers.

Trust comment: Randomized one-year study in 41 patients showing significant attenuation of LDL TBARS but overall mixed and limited by small sample size.

Study Details

PMID:18803940
Participants:41
Impact:Smaller increase with vitamin C: +0.13 ng/g LDL (0.25 → 0.38) vs placebo +0.18 ng/g LDL (0.28 → 0.46); between-group difference P < .007
Trust score:3/5

HDL oxidation (TBARS HDL)

1 evidences

In patients starting hemodialysis, 1000 mg/day vitamin C for one year attenuated the rise in LDL oxidation products (TBARS) compared with placebo, with mixed results for other oxidation markers.

Trust comment: Randomized one-year study in 41 patients showing significant attenuation of LDL TBARS but overall mixed and limited by small sample size.

Study Details

PMID:18803940
Participants:41
Impact:Trend to smaller increase with vitamin C (+0.12 vs +0.08; P = .071; not significant)
Trust score:3/5

standard lipid profile

1 evidences

In patients starting hemodialysis, 1000 mg/day vitamin C for one year attenuated the rise in LDL oxidation products (TBARS) compared with placebo, with mixed results for other oxidation markers.

Trust comment: Randomized one-year study in 41 patients showing significant attenuation of LDL TBARS but overall mixed and limited by small sample size.

Study Details

PMID:18803940
Participants:41
Impact:No significant differences between vitamin C and placebo groups
Trust score:3/5

skin pigmentation

1 evidences

Topical sodium ascorbyl phosphate (a vitamin C derivative) combined with PKEK reduced skin pigmentation more than SAP alone in several small controlled cohorts.

Trust comment: Multiple small double-blind controlled cohorts using a topical vitamin C derivative showed consistent cosmetic effects, but sample sizes per cohort were small.

Study Details

PMID:22142309
Participants:95
Impact:Reduced with PKEK + sodium ascorbyl phosphate versus SAP alone (e.g., −26% and −18% SCINEXA score reductions reported in Japanese cohort; significant)
Trust score:3/5

bowel cleansing efficacy

2 evidences

Low-volume PEG with ascorbic acid cleans as well as standard PEG, tastes better, and split dosing gives the best cleansing.

Trust comment: Large randomized, single-blind multicenter trial with objective endpoints and good sample size, though not double-blind.

Study Details

PMID:20561621
Participants:868
Impact:Equivalent efficacy: split-dosage 77% vs 73.4% (PEG+ascorbic acid vs standard PEG); non-split 41.7% vs 44.3%.
Trust score:4/5

In healthy adults, low-dose ascorbic acid added to 1‑L PEG gave similar bowel cleansing, better tolerability than 2‑L PEG‑Asc, and less residual gastric fluid than standard 1‑L PEG‑Asc.

Trust comment: Randomized, double‑blinded, multicenter noninferiority RCT in healthy adults — well designed and reported.

Study Details

PMID:35288148
Participants:215
Impact:no significant difference vs standard 1‑L and 2‑L PEG‑Asc (noninferior; all P>0.1)
Trust score:4/5

tolerability

4 evidences

In healthy adults, low-dose ascorbic acid added to 1‑L PEG gave similar bowel cleansing, better tolerability than 2‑L PEG‑Asc, and less residual gastric fluid than standard 1‑L PEG‑Asc.

Trust comment: Randomized, double‑blinded, multicenter noninferiority RCT in healthy adults — well designed and reported.

Study Details

PMID:35288148
Participants:215
Impact:improved vs 2‑L PEG‑Asc (better tolerability)
Trust score:4/5

Compared colonoscopy preparations; the low-volume PEG with ascorbic acid (PEGA) had similar cleansing efficacy to PEG when regimens matched and was better tolerated than PEG.

Trust comment: Large multicentre RCT but vitamin C is present as a formulation component (ascorbic acid), not isolated as a sole intervention.

Study Details

PMID:28944412
Participants:973
Impact:PEGA better tolerated than PEG (p<0.006)
Trust score:3/5

Compared bowel preparations including polyethylene glycol with ascorbic acid and found similar optimal preparation intervals and overall efficacy; tolerability depended on product type.

Trust comment: Large randomized, endoscopist-blinded multicentre trial providing objective bowel-prep outcomes; direct vitamin C role is as a component of a prep solution rather than a systemic health effect.

Study Details

PMID:29102524
Participants:612
Impact:No effect of timing; tolerability depended on product type (SPMC) only
Trust score:4/5

12-week triple-blind randomized placebo-controlled trial in women showed that a drinkable supplement containing collagen peptides and dermonutrients improved dermal collagen structure and subjective skin measures without adverse events.

Trust comment: Randomized, triple-blind trial with objective and subjective endpoints but the product contained multiple active nutrients including collagen peptides, so vitamin C's individual contribution is unclear.

Study Details

PMID:32017646
Participants:60
Impact:no adverse effects reported; product well tolerated
Trust score:3/5

residual gastric fluid retention

1 evidences

In healthy adults, low-dose ascorbic acid added to 1‑L PEG gave similar bowel cleansing, better tolerability than 2‑L PEG‑Asc, and less residual gastric fluid than standard 1‑L PEG‑Asc.

Trust comment: Randomized, double‑blinded, multicenter noninferiority RCT in healthy adults — well designed and reported.

Study Details

PMID:35288148
Participants:215
Impact:reduced with lower ascorbic acid dose (less residual fluid)
Trust score:4/5

corticosteroid dosage

1 evidences

In corticosteroid‑dependent asthma patients, adding antioxidants including CoQ10, vitamin E and 250 mg vitamin C/day was associated with reduced corticosteroid requirements.

Trust comment: Open, randomized crossover clinical study with small sample and limited blinding; outcome reported but magnitude not quantified.

Study Details

PMID:16873952
Participants:41
Impact:reduced after antioxidant supplementation (magnitude not reported)
Trust score:3/5

successful bowel preparation rate

2 evidences

An ascorbic acid–enriched PEG solution prepared the bowel as well as standard PEG with a lower total drinking volume.

Trust comment: Phase III multicenter randomized non-inferiority trial with adequate sample and clear endpoints.

Study Details

PMID:37462794
Participants:173
Impact:no meaningful difference (0.93 vs 0.92; non-inferior)
Trust score:5/5

In patients with inactive ulcerative colitis, OSS was non‑inferior to 2‑L PEG+ascorbic acid for bowel preparation, with similar tolerability and no effect on disease activity.

Trust comment: Prospective randomized multicenter single‑blind trial with appropriate endpoints and reasonable sample size; well reported.

Study Details

PMID:36588527
Participants:185
Impact:OSS 96.7% vs 2‑L PEG+Asc 97.8% (no significant difference, p=0.64)
Trust score:4/5

bowel cleanliness (BBPS)

1 evidences

In patients with inactive ulcerative colitis, OSS was non‑inferior to 2‑L PEG+ascorbic acid for bowel preparation, with similar tolerability and no effect on disease activity.

Trust comment: Prospective randomized multicenter single‑blind trial with appropriate endpoints and reasonable sample size; well reported.

Study Details

PMID:36588527
Participants:185
Impact:mean BBPS 8.3 vs 8.1 (no significant difference, p=0.33)
Trust score:4/5

tolerability (nausea score)

1 evidences

In patients with inactive ulcerative colitis, OSS was non‑inferior to 2‑L PEG+ascorbic acid for bowel preparation, with similar tolerability and no effect on disease activity.

Trust comment: Prospective randomized multicenter single‑blind trial with appropriate endpoints and reasonable sample size; well reported.

Study Details

PMID:36588527
Participants:185
Impact:mean 1.8 vs 1.6 (trend higher with OSS, p=0.06)
Trust score:4/5

necroinflammatory activity / ALT

1 evidences

In NASH patients, combined vitamin E and vitamin C for 6 months improved liver fibrosis scores but did not change inflammation or ALT.

Trust comment: Double‑blind, randomized, placebo‑controlled trial with moderate sample and blinded histologic assessment; credible result though sample relatively small.

Study Details

PMID:14638353
Participants:45
Impact:no change observed
Trust score:4/5

fractional non‑heme iron absorption

1 evidences

In young women consuming whole diets, higher vitamin C content increased non‑heme iron absorption compared with low vitamin C diets.

Trust comment: Randomized cross‑over whole‑diet isotope study in women with direct whole‑body measurements; well controlled and directly relevant.

Study Details

PMID:16277774
Participants:32
Impact:low vitamin C 1.9% vs high vitamin C 3.4% (P=0.04) — higher absorption with more vitamin C
Trust score:4/5

total iron absorbed

1 evidences

In young women consuming whole diets, higher vitamin C content increased non‑heme iron absorption compared with low vitamin C diets.

Trust comment: Randomized cross‑over whole‑diet isotope study in women with direct whole‑body measurements; well controlled and directly relevant.

Study Details

PMID:16277774
Participants:32
Impact:varied from 0.43 mg to 1.09 mg across diets (P<0.001)
Trust score:4/5

reduced glutathione decrease

1 evidences

Two-week antioxidant supplementation (vitamin C + E or fruit/veg powder) reduced some exercise-induced oxidative stress markers in men and women.

Trust comment: Randomized human study with pre/post measures and exercise challenge, moderate sample size (48); outcomes are biochemical markers.

Study Details

PMID:18059586
Participants:48
Impact:attenuated decrease vs placebo
Trust score:4/5

oxidized glutathione and protein carbonyls increase

1 evidences

Two-week antioxidant supplementation (vitamin C + E or fruit/veg powder) reduced some exercise-induced oxidative stress markers in men and women.

Trust comment: Randomized human study with pre/post measures and exercise challenge, moderate sample size (48); outcomes are biochemical markers.

Study Details

PMID:18059586
Participants:48
Impact:attenuated increase vs placebo
Trust score:4/5

coronary endothelial function

1 evidences

Six months of combined high-dose vitamins C and E raised plasma antioxidant levels but did not improve coronary or brachial endothelial function in CAD patients.

Trust comment: Double-blind RCT in CAD patients but small sample and some endpoints measured in subsets (coronary n=18, brachial n=25).

Study Details

PMID:14975474
Participants:30
Impact:no improvement vs placebo
Trust score:4/5

brachial (flow-mediated) endothelial function

1 evidences

Six months of combined high-dose vitamins C and E raised plasma antioxidant levels but did not improve coronary or brachial endothelial function in CAD patients.

Trust comment: Double-blind RCT in CAD patients but small sample and some endpoints measured in subsets (coronary n=18, brachial n=25).

Study Details

PMID:14975474
Participants:30
Impact:no improvement vs placebo
Trust score:4/5

platelet-derived microparticles

1 evidences

Immediate vitamin C (1 g/day) during MI reduced platelet-derived microparticles more than control and markedly reduced endothelial-derived microparticles in higher-risk subgroups.

Trust comment: Prospective randomized trial in MI patients with clinically relevant surrogate endpoints but modest sample size and short follow-up.

Study Details

PMID:12871555
Participants:61
Impact:reduction ~10% greater with vitamin C (overall); ~13% reduction in high-risk subgroup
Trust score:3/5

endothelial-derived microparticles

1 evidences

Immediate vitamin C (1 g/day) during MI reduced platelet-derived microparticles more than control and markedly reduced endothelial-derived microparticles in higher-risk subgroups.

Trust comment: Prospective randomized trial in MI patients with clinically relevant surrogate endpoints but modest sample size and short follow-up.

Study Details

PMID:12871555
Participants:61
Impact:≈70% decrease in high-risk subgroups (diabetes, dyslipidemia or >2 risk factors)
Trust score:3/5

procoagulant circulating microparticles (overall)

1 evidences

Immediate vitamin C (1 g/day) during MI reduced platelet-derived microparticles more than control and markedly reduced endothelial-derived microparticles in higher-risk subgroups.

Trust comment: Prospective randomized trial in MI patients with clinically relevant surrogate endpoints but modest sample size and short follow-up.

Study Details

PMID:12871555
Participants:61
Impact:decreased with vitamin C in higher-risk patients
Trust score:3/5

wound-healing rate

1 evidences

A wound-specific oral supplement containing arginine, vitamin C and zinc was less effective for wound-healing than a standard nutrition supplement in patients with chronic wounds.

Trust comment: Small pragmatic randomized trial; vitamin C was part of a multi-nutrient formula so individual effect of vitamin C cannot be isolated.

Study Details

PMID:23627791
Participants:24
Impact:standard supplement superior to wound-specific (contains vitamin C) (p = 0.044)
Trust score:3/5

nutritional status

1 evidences

A wound-specific oral supplement containing arginine, vitamin C and zinc was less effective for wound-healing than a standard nutrition supplement in patients with chronic wounds.

Trust comment: Small pragmatic randomized trial; vitamin C was part of a multi-nutrient formula so individual effect of vitamin C cannot be isolated.

Study Details

PMID:23627791
Participants:24
Impact:no significant effect
Trust score:3/5

Apolipoprotein A1 (apo A1)

1 evidences

In type 2 diabetic patients, combined mineral (Mg+Zn) plus vitamins C+E increased HDL cholesterol and apolipoprotein A1 over 3 months; Mg+Zn alone showed no significant changes.

Trust comment: Randomized double-blind placebo-controlled human RCT with clear biochemical outcomes but small total sample (n=69) and short duration (3 months).

Study Details

PMID:15163474
Participants:69
Impact:+8.8% (MV group vs baseline; 169.8 vs 156.1 mg/dl; significant)
Trust score:4/5

Total cholesterol / LDL / Triglycerides / apo B

1 evidences

In type 2 diabetic patients, combined mineral (Mg+Zn) plus vitamins C+E increased HDL cholesterol and apolipoprotein A1 over 3 months; Mg+Zn alone showed no significant changes.

Trust comment: Randomized double-blind placebo-controlled human RCT with clear biochemical outcomes but small total sample (n=69) and short duration (3 months).

Study Details

PMID:15163474
Participants:69
Impact:No significant change
Trust score:4/5

Modification of β-carotene harm by vitamin C intake

1 evidences

Secondary analysis of a large RCT (ATBC) shows that dietary vitamin C intake modifies harms from high-dose β-carotene supplementation in specific smoker subgroups; this is an interaction analysis rather than a vitamin C trial.

Trust comment: Large randomized trial dataset with robust follow-up; vitamin C effects are observational/subgroup modifiers here (not randomized), so causal inference about vitamin C alone is limited.

Study Details

PMID:32215208
Participants:29126
Impact:In heavy smokers who started ≥21 yrs and smoked ≥21/d, β-carotene increased mortality markedly in those with vitamin C <90 mg/d (RR 2.26) versus no harm in other subgroups
Trust score:3/5

β-carotene effect in heavy late-start smokers

1 evidences

Secondary analysis of a large RCT (ATBC) shows that dietary vitamin C intake modifies harms from high-dose β-carotene supplementation in specific smoker subgroups; this is an interaction analysis rather than a vitamin C trial.

Trust comment: Large randomized trial dataset with robust follow-up; vitamin C effects are observational/subgroup modifiers here (not randomized), so causal inference about vitamin C alone is limited.

Study Details

PMID:32215208
Participants:29126
Impact:Overall RR 1.56 higher mortality for β-carotene in this subgroup (no-vitamin E participants)
Trust score:3/5

Bowel cleansing (Aronchick scale)

1 evidences

In adults undergoing colonoscopy, a 2-L PEG solution with ascorbic acid achieved at least as good (and in some metrics better) bowel cleansing and higher acceptability than standard 4-L PEG.

Trust comment: Single-blind randomized non-inferiority trial with adequate sample (n=339) showing statistically significant improvements in cleansing and acceptability for ascorbic-acid containing prep.

Study Details

PMID:22119219
Participants:339
Impact:Excellent-good cleansing: 2-L PEG+ascorbic acid 84.6% vs 4-L PEG 75.3% (absolute +9.3%; p=0.04)
Trust score:4/5

Patient acceptability

1 evidences

In adults undergoing colonoscopy, a 2-L PEG solution with ascorbic acid achieved at least as good (and in some metrics better) bowel cleansing and higher acceptability than standard 4-L PEG.

Trust comment: Single-blind randomized non-inferiority trial with adequate sample (n=339) showing statistically significant improvements in cleansing and acceptability for ascorbic-acid containing prep.

Study Details

PMID:22119219
Participants:339
Impact:Acceptability: 83% (2-L+AA) vs 76% (4-L) (absolute +7%; p=0.02)
Trust score:4/5

serum PSA

1 evidences

In men with untreated prostate cancer, a combined supplement including vitamin C produced no change in PSA or sex-hormone levels over 21 weeks.

Trust comment: Randomized placebo-controlled trial but used a multi-nutrient supplement (attribution to vitamin C alone unclear) and modest sample (70 completions).

Study Details

PMID:15774238
Participants:70
Impact:no significant change vs placebo over 21 weeks
Trust score:3/5

sex hormones (testosterone, DHT, LH, SHBG)

1 evidences

In men with untreated prostate cancer, a combined supplement including vitamin C produced no change in PSA or sex-hormone levels over 21 weeks.

Trust comment: Randomized placebo-controlled trial but used a multi-nutrient supplement (attribution to vitamin C alone unclear) and modest sample (70 completions).

Study Details

PMID:15774238
Participants:70
Impact:no significant change vs placebo over 21 weeks
Trust score:3/5

endothelium-dependent vasodilation (ACh-induced)

1 evidences

Local intra-arterial vitamin C prevented ischemia-reperfusion–induced impairment of endothelium-dependent vasodilation in healthy volunteers and patients with PAD.

Trust comment: Randomized placebo-controlled human study with direct vascular physiology endpoints, though sample size is small.

Study Details

PMID:17645881
Participants:34
Impact:impaired by IR in placebo but completely prevented/restored by vitamin C
Trust score:4/5

endothelium-independent vasodilation (NTG-induced)

1 evidences

Local intra-arterial vitamin C prevented ischemia-reperfusion–induced impairment of endothelium-dependent vasodilation in healthy volunteers and patients with PAD.

Trust comment: Randomized placebo-controlled human study with direct vascular physiology endpoints, though sample size is small.

Study Details

PMID:17645881
Participants:34
Impact:no effect from IR or vitamin C
Trust score:4/5

NO synthase–dependent responses (L-NMMA)

1 evidences

Local intra-arterial vitamin C prevented ischemia-reperfusion–induced impairment of endothelium-dependent vasodilation in healthy volunteers and patients with PAD.

Trust comment: Randomized placebo-controlled human study with direct vascular physiology endpoints, though sample size is small.

Study Details

PMID:17645881
Participants:34
Impact:blunted during reperfusion and reversed by vitamin C
Trust score:4/5

oxidative stress markers (nitrotyrosine, 8-iso-PGF2α)

1 evidences

In a crossover human experiment, vitamin C infusion during recovery from hypoglycemia with hyperglycemia attenuated the worsening of endothelial function and increases in oxidative stress and inflammation.

Trust comment: Randomized crossover experiments in humans with direct vascular and biochemical measures and moderate sample size (n=42 total).

Study Details

PMID:22891214
Participants:42
Impact:hyperglycemia increased markers; vitamin C attenuated these increases
Trust score:4/5

inflammatory markers (sICAM-1, IL-6)

1 evidences

In a crossover human experiment, vitamin C infusion during recovery from hypoglycemia with hyperglycemia attenuated the worsening of endothelial function and increases in oxidative stress and inflammation.

Trust comment: Randomized crossover experiments in humans with direct vascular and biochemical measures and moderate sample size (n=42 total).

Study Details

PMID:22891214
Participants:42
Impact:increases with hyperglycemic recovery were attenuated by vitamin C infusion
Trust score:4/5

PROM (premature rupture of membranes)

1 evidences

In a placebo-controlled RCT in pregnant high-risk women, daily vitamin C (1000 mg) + vitamin E increased rates of PROM and PPROM compared with placebo.

Trust comment: Large double-blind randomized trial (secondary analysis) with high-quality design and clear outcome data (697 completed), though findings are from a secondary outcome analysis.

Study Details

PMID:18928997
Participants:697
Impact:increase: 10.6% vs 5.5% (adjusted RR 1.89; P=0.015)
Trust score:4/5

PPROM (preterm PROM)

1 evidences

In a placebo-controlled RCT in pregnant high-risk women, daily vitamin C (1000 mg) + vitamin E increased rates of PROM and PPROM compared with placebo.

Trust comment: Large double-blind randomized trial (secondary analysis) with high-quality design and clear outcome data (697 completed), though findings are from a secondary outcome analysis.

Study Details

PMID:18928997
Participants:697
Impact:increase: 4.6% vs 1.7% (RR 2.68; P=0.025)
Trust score:4/5

hs-CRP (inflammation)

2 evidences

Randomized cross-over trial in hemodialysis patients with low vitamin C showed that 200 mg/day oral vitamin C raised plasma vitamin C and reduced hs-CRP; some nutritional markers trended upward.

Trust comment: Randomized controlled cross-over with selected deficient patients and measurable biomarker changes; modest sample (100) and some dropouts/no placebo limit certainty.

Study Details

PMID:24228847
Participants:100
Impact:decrease: group1 median 9.6 → 4.9 mg/L during treatment (p<0.01); group2 6.2 → 5.1 mg/L during treated period (p<0.01)
Trust score:4/5

Daily fortified yogurt containing HMB, 1000 IU vitamin D, and vitamin C improved handgrip strength, gait speed, vitamin D and IGF-1 levels, and reduced inflammation markers versus control in sarcopenic older adults.

Trust comment: Well-conducted double-blind RCT (n=66) with clear benefits, but vitamin C was given in combination with HMB and vitamin D so effects cannot be attributed to vitamin C alone.

Study Details

PMID:33067129
Participants:66
Impact:prevented increase (significant vs control, P=0.033)
Trust score:4/5

prealbumin (nutritional marker)

1 evidences

Randomized cross-over trial in hemodialysis patients with low vitamin C showed that 200 mg/day oral vitamin C raised plasma vitamin C and reduced hs-CRP; some nutritional markers trended upward.

Trust comment: Randomized controlled cross-over with selected deficient patients and measurable biomarker changes; modest sample (100) and some dropouts/no placebo limit certainty.

Study Details

PMID:24228847
Participants:100
Impact:increase: group2 mean 315.3 → 336.9 mg/L at end of treated period (p<0.05)
Trust score:4/5

plasma glutathione (GSH)

1 evidences

Single-blind randomized trial in male COPD patients found that vitamin C (alone) improved antioxidant status (notably plasma glutathione) and helped nutritional measures over six months.

Trust comment: Parallel single-blind RCT with small sample size (79) and multiple arms; positive biomarker changes but limited power for some clinical endpoints.

Study Details

PMID:27117852
Participants:79
Impact:increase (significant in vitamin C group; P=0.005)
Trust score:3/5

body mass index (BMI) / nutritional status

1 evidences

Single-blind randomized trial in male COPD patients found that vitamin C (alone) improved antioxidant status (notably plasma glutathione) and helped nutritional measures over six months.

Trust comment: Parallel single-blind RCT with small sample size (79) and multiple arms; positive biomarker changes but limited power for some clinical endpoints.

Study Details

PMID:27117852
Participants:79
Impact:interaction effect on BMI (p=0.046) with improvements noted in intervention arms
Trust score:3/5

organ dysfunction (day 7)

1 evidences

In this small RCT of severe acute pancreatitis, daily antioxidant vitamins including 1 g vitamin C did not significantly change organ dysfunction or oxidative stress markers versus standard care.

Trust comment: Randomized trial with blinded endpoint assessment and independent analysis, but small single-center sample and open-label treatment introduce limitations.

Study Details

PMID:21546719
Participants:39
Impact:No significant difference (antioxidant 37% vs control 40%)
Trust score:4/5

oxidative stress markers (MDA, GSH, SOD)

1 evidences

In this small RCT of severe acute pancreatitis, daily antioxidant vitamins including 1 g vitamin C did not significantly change organ dysfunction or oxidative stress markers versus standard care.

Trust comment: Randomized trial with blinded endpoint assessment and independent analysis, but small single-center sample and open-label treatment introduce limitations.

Study Details

PMID:21546719
Participants:39
Impact:Markers changed in both groups by day 7 with no significant between-group differences
Trust score:4/5

oxidized glutathione (GSSG) / GSH/GSSG ratio

1 evidences

In older adults undertaking regular exercise, a multi-ingredient antioxidant beverage (containing vitamin C among others) prevented exercise-induced increases in markers of lipid, protein and DNA oxidation and normalized glutathione and vitamin C levels.

Trust comment: Large, long-term intervention but used a multi-ingredient product (not isolated vitamin C), so effects cannot be attributed solely to vitamin C.

Study Details

PMID:19857542
Participants:400
Impact:Exercise ↑ GSSG +112% and ↓ GSH/GSSG −43%; supplementation normalized GSSG and GSH/GSSG
Trust score:3/5

scar roughness

1 evidences

Laser-assisted delivery followed by topical growth factors+vitamin C or vitamin C alone reduced scar roughness and volume; adding growth factors produced significantly better scar improvement.

Trust comment: Randomized, double-blind clinical trial with objective measurements, but described as an early/short-term study.

Study Details

PMID:33881605
Participants:132
Impact:Significant reduction in both groups (p<0.01); greater improvement with growth factors + vitamin C vs vitamin C alone (p<0.01)
Trust score:4/5

scar volume

1 evidences

Laser-assisted delivery followed by topical growth factors+vitamin C or vitamin C alone reduced scar roughness and volume; adding growth factors produced significantly better scar improvement.

Trust comment: Randomized, double-blind clinical trial with objective measurements, but described as an early/short-term study.

Study Details

PMID:33881605
Participants:132
Impact:Significant reduction in both groups (p<0.01); growth factors + vitamin C superior to vitamin C alone (p<0.01)
Trust score:4/5

postoperative pulmonary complications incidence (PPC ≥3)

1 evidences

High‑dose IV vitamin C for 48 h after cardiac surgery greatly reduced serious postoperative lung complications, improved oxygenation, and lowered mortality.

Trust comment: Randomized single‑blinded RCT with 150 analyzed and statistically significant effects, but single‑center and partial masking limit external validity.

Study Details

PMID:38542673
Participants:150
Impact:reduced from 60.0% to 13.3% (−46.7 percentage points; p<0.001)
Trust score:4/5

pulmonary oxygenation (PaO2/FiO2, Horowitz index)

1 evidences

High‑dose IV vitamin C for 48 h after cardiac surgery greatly reduced serious postoperative lung complications, improved oxygenation, and lowered mortality.

Trust comment: Randomized single‑blinded RCT with 150 analyzed and statistically significant effects, but single‑center and partial masking limit external validity.

Study Details

PMID:38542673
Participants:150
Impact:+43.7 units (312.6 vs 268.9; +16%; p=0.008)
Trust score:4/5

hospital mortality

1 evidences

High‑dose IV vitamin C for 48 h after cardiac surgery greatly reduced serious postoperative lung complications, improved oxygenation, and lowered mortality.

Trust comment: Randomized single‑blinded RCT with 150 analyzed and statistically significant effects, but single‑center and partial masking limit external validity.

Study Details

PMID:38542673
Participants:150
Impact:reduced from 10.7% to 1.3% (−9.4 percentage points; p=0.034)
Trust score:4/5

colorectal cancer risk

2 evidences

Dietary vitamin C intake was not associated with colorectal cancer risk in this case–control study.

Trust comment: Large case‑control study with adequate sample size but observational design and potential residual confounding.

Study Details

PMID:22716281
Participants:1631
Impact:no association with dietary vitamin C intake (no relation found)
Trust score:3/5

Large prospective cohort of male smokers found no link between dietary or serum antioxidant vitamins (including vitamin C) and colorectal cancer risk.

Trust comment: Large prospective cohort with adjustment for major confounders; high sample size supports reliability.

Study Details

PMID:12080400
Participants:26951
Impact:no significant association with dietary vitamin C
Trust score:4/5

contrast‑induced nephropathy (CIN) incidence

1 evidences

Adding IV N‑acetylcysteine plus vitamin C did not lower overall contrast‑induced nephropathy incidence but reduced oxidative stress markers and lessened cystatin‑C rises in affected patients.

Trust comment: Randomized trial but open‑label, single‑center, and modest sample size limit strength of conclusions.

Study Details

PMID:29089038
Participants:124
Impact:no reduction: 18.33% (Nac+Aa) vs 15.6% (control); p=0.81
Trust score:3/5

oxidative stress (8‑isoprostane)

1 evidences

Adding IV N‑acetylcysteine plus vitamin C did not lower overall contrast‑induced nephropathy incidence but reduced oxidative stress markers and lessened cystatin‑C rises in affected patients.

Trust comment: Randomized trial but open‑label, single‑center, and modest sample size limit strength of conclusions.

Study Details

PMID:29089038
Participants:124
Impact:lower in antioxidant group at 2 h and 24 h (statistically significant timepoints)
Trust score:3/5

renal injury marker (serum cystatin‑C change in CIN patients)

1 evidences

Adding IV N‑acetylcysteine plus vitamin C did not lower overall contrast‑induced nephropathy incidence but reduced oxidative stress markers and lessened cystatin‑C rises in affected patients.

Trust comment: Randomized trial but open‑label, single‑center, and modest sample size limit strength of conclusions.

Study Details

PMID:29089038
Participants:124
Impact:median % change 37.23%±12.54 (Nac+Aa) vs 93.20%±33.54 (control); p=0.03
Trust score:3/5

IL-6/IL-10 ratio

1 evidences

Preoperative multi-vitamin/mineral supplementation (which tended to raise 25(OH)D) significantly blunted the postoperative rise in the IL-6/IL-10 ratio after total knee arthroplasty.

Trust comment: Randomized double-blind placebo-controlled trial but small sample (n=21) limits precision.

Study Details

PMID:33497870
Participants:21
Impact:Blunted post-operative increase (significant)
Trust score:4/5

plasma ascorbic acid (vitamin C)

1 evidences

Preoperative multi-vitamin/mineral supplementation (which tended to raise 25(OH)D) significantly blunted the postoperative rise in the IL-6/IL-10 ratio after total knee arthroplasty.

Trust comment: Randomized double-blind placebo-controlled trial but small sample (n=21) limits precision.

Study Details

PMID:33497870
Participants:21
Impact:Increased before surgery (significant)
Trust score:4/5

hsCRP / IL-6 postoperative rise

1 evidences

Preoperative multi-vitamin/mineral supplementation (which tended to raise 25(OH)D) significantly blunted the postoperative rise in the IL-6/IL-10 ratio after total knee arthroplasty.

Trust comment: Randomized double-blind placebo-controlled trial but small sample (n=21) limits precision.

Study Details

PMID:33497870
Participants:21
Impact:Post-op IL-6 and hsCRP still increased (no mitigation)
Trust score:4/5

post-PTCA restenosis incidence

1 evidences

Oral ascorbic acid 500 mg/day was associated with a lower incidence of restenosis after PTCA compared with controls in this preliminary study.

Trust comment: Clinical preliminary study with moderate sample but limited methodological detail and unclear randomization.

Study Details

PMID:8960592
Participants:101
Impact:Reduced incidence in vitamin C group (significant)
Trust score:3/5

lesion hypopigmentation (solar lentigines)

1 evidences

Topical formulations including 5% ascorbyl glucosamine (vitamin C derivative) showed no clear benefit on solar lentigines in this pilot study.

Trust comment: Pilot cosmetic study with objective measures but limited sample and short duration.

Study Details

PMID:12077522
Participants:50
Impact:No significant lightening effect for ascorbyl glucosamine formulation (inefficacious)
Trust score:3/5

serum electrolytes

1 evidences

PEG with ascorbic acid bowel prep had similar electrolyte changes to 4-L PEG but better taste and higher willingness to repeat.

Trust comment: Large randomized multicenter trial with objective labs and patient-reported outcomes.

Study Details

PMID:25780304
Participants:226
Impact:No significant changes (no difference between groups)
Trust score:4/5

patient satisfaction / willingness to repeat

2 evidences

1 L polyethylene glycol with ascorbic acid plus a low-residue diet provided similar or better bowel cleansing and greater patient satisfaction than 2 L PEGA.

Trust comment: Endoscopist-blinded randomized controlled trial (n=173) with objective bowel-prep scoring and patient-reported outcomes.

Study Details

PMID:30278110
Participants:173
Impact:increased (P<0.01)
Trust score:4/5

PEG with ascorbic acid bowel prep had similar electrolyte changes to 4-L PEG but better taste and higher willingness to repeat.

Trust comment: Large randomized multicenter trial with objective labs and patient-reported outcomes.

Study Details

PMID:25780304
Participants:226
Impact:Improved with PEG-Asc (higher willingness; taste better)
Trust score:4/5

clinical clearance of genital warts

1 evidences

Adding pidotimod plus vitamin C after laser vaporization showed a higher clinical clearance rate of warts (81% vs 67%) but the difference was not statistically significant.

Trust comment: Prospective randomized allocation with blinded assessors but small sample and no statistical significance for main outcome.

Study Details

PMID:20945819
Participants:62
Impact:+14 percentage points (81% vs 67%), not statistically significant (p=0.2)
Trust score:3/5

Days of bleeding (menstrual irregularity)

1 evidences

Vitamin C supplementation did not prevent Depo-Provera-related menstrual irregularities or weight changes in adolescent girls.

Trust comment: Randomized trial but modest sample size and outcomes mostly self-reported, limiting precision.

Study Details

PMID:12106752
Participants:55
Impact:no change
Trust score:3/5

Body mass index (BMI)

2 evidences

Vitamin C supplementation did not prevent Depo-Provera-related menstrual irregularities or weight changes in adolescent girls.

Trust comment: Randomized trial but modest sample size and outcomes mostly self-reported, limiting precision.

Study Details

PMID:12106752
Participants:55
Impact:no change
Trust score:3/5

Addition of L-ascorbic acid (with chitosan) for 8 weeks accentuated weight and BMI reduction compared with chitosan alone or placebo; BMI decrease was greater with ascorbic acid plus chitosan.

Trust comment: Moderate-sized controlled intervention with significant BMI differences, but short duration and combination with chitosan limit generalizability to vitamin C alone.

Study Details

PMID:25835230
Participants:80
Impact:Chito: −1.0 kg/m2 vs Chito-vita: −1.6 kg/m2 (Chito-vita significantly greater decrease vs Chito, p<0.05)
Trust score:3/5

Patient concern/satisfaction (reported)

1 evidences

Vitamin C supplementation did not prevent Depo-Provera-related menstrual irregularities or weight changes in adolescent girls.

Trust comment: Randomized trial but modest sample size and outcomes mostly self-reported, limiting precision.

Study Details

PMID:12106752
Participants:55
Impact:no clinically meaningful improvement
Trust score:3/5

Functional outcome (Harris Hip Score)

1 evidences

Peri- and postoperative vitamin C reduced subjective pain and analgesic use after hip fracture surgery but did not change hip function scores.

Trust comment: Prospective randomized full-scale study with objective consumption and pain measures; blinding not clearly reported.

Study Details

PMID:40355782
Participants:74
Impact:no change
Trust score:4/5

Proportion with significant MASI reduction

1 evidences

Adding topical magnesium ascorbyl phosphate (a vitamin C derivative) to TCA peels produced greater reduction in melasma severity than peel alone.

Trust comment: Randomized controlled trial with adequate sample size and clinically relevant outcome, though topical-application blinding unclear.

Study Details

PMID:27504543
Participants:148
Impact:81.1% vs 66.2% (combined vs peel alone; p=0.040)
Trust score:4/5

MASI score reduction (overall)

1 evidences

Adding topical magnesium ascorbyl phosphate (a vitamin C derivative) to TCA peels produced greater reduction in melasma severity than peel alone.

Trust comment: Randomized controlled trial with adequate sample size and clinically relevant outcome, though topical-application blinding unclear.

Study Details

PMID:27504543
Participants:148
Impact:greater in combined treatment
Trust score:4/5

Glutathione peroxidase activity

1 evidences

Vitamin C+E supplementation (with or without exercise) reduced oxidative stress markers and increased antioxidant measures in fibromyalgia patients, but symptoms did not improve.

Trust comment: Controlled pilot study with small sample size limits generalizability and statistical power.

Study Details

PMID:20666654
Participants:32
Impact:Increased with VCE supplementation (with or without exercise)
Trust score:3/5

Newborn TPTEF:TE (tidal flow ratio)

1 evidences

Maternal vitamin C (500 mg/day) given to pregnant smokers improved newborn lung function and reduced wheezing through age 1 year.

Trust comment: Randomized, double-blind multicenter trial with objective newborn PFTs and clinically meaningful respiratory outcomes.

Study Details

PMID:24838476
Participants:159
Impact:increased (0.383 vs 0.345; adjusted diff significant; p=0.006)
Trust score:5/5

Newborn passive respiratory compliance (Crs/kg)

1 evidences

Maternal vitamin C (500 mg/day) given to pregnant smokers improved newborn lung function and reduced wheezing through age 1 year.

Trust comment: Randomized, double-blind multicenter trial with objective newborn PFTs and clinically meaningful respiratory outcomes.

Study Details

PMID:24838476
Participants:159
Impact:increased (1.32 vs 1.20 mL/cm H2O/kg; p=0.01)
Trust score:5/5

Wheezing through 1 year

1 evidences

Maternal vitamin C (500 mg/day) given to pregnant smokers improved newborn lung function and reduced wheezing through age 1 year.

Trust comment: Randomized, double-blind multicenter trial with objective newborn PFTs and clinically meaningful respiratory outcomes.

Study Details

PMID:24838476
Participants:159
Impact:reduced (21% vs 40%; RR 0.56; p=0.03)
Trust score:5/5

Incidence of contrast-mediated nephropathy

1 evidences

Oral ascorbic acid around the time of coronary angiography reduced the incidence of contrast-induced nephropathy and attenuated the rise in serum creatinine.

Trust comment: Randomized, double-blind, placebo-controlled trial in high-risk patients with clinically relevant endpoints.

Study Details

PMID:15492300
Participants:231
Impact:9% (ascorbic) vs 20% (placebo); OR 0.38; p=0.02
Trust score:5/5

Mean serum creatinine increase

1 evidences

Oral ascorbic acid around the time of coronary angiography reduced the incidence of contrast-induced nephropathy and attenuated the rise in serum creatinine.

Trust comment: Randomized, double-blind, placebo-controlled trial in high-risk patients with clinically relevant endpoints.

Study Details

PMID:15492300
Participants:231
Impact:smaller in ascorbic group (difference 0.09 mg/dL; p=0.049)
Trust score:5/5

CPT-induced coronary luminal area change

1 evidences

In 31 patients, acute IV ascorbic acid (3 g) reversed cold-pressor-induced coronary vasoconstriction in chronic smokers.

Trust comment: Randomized infusion study with objective angiographic endpoints in humans; small sample but clear physiological effect.

Study Details

PMID:11326145
Participants:31
Impact:from -18.5% to +7.7% (net +26.2 percentage points; vasoconstriction → vasodilation)
Trust score:4/5

apo A-I

1 evidences

An 8-month randomized double-blind placebo-controlled trial (n=138 completers) found no overall effect of 1 g/day vitamin C on HDL, LDL, total cholesterol or triglycerides; a small subgroup (n=43, low baseline AA) showed HDL +0.10 mmol/L.

Trust comment: Large randomized double-blind placebo-controlled trial with 138 completers; overall null primary results and subgroup findings are exploratory.

Study Details

PMID:7728285
Participants:138
Impact:+1.9 μmol/L (5.3 mg/dL) (marginal significance, P<0.10)
Trust score:4/5

bowel cleansing success rate

1 evidences

In elderly patients, 2L PEG with ascorbic acid cleaned bowels as well as 4L PEG, with less liquid to drink and better tolerability.

Trust comment: Randomized trial with adequate sample size and clear endpoints; results appear reliable.

Study Details

PMID:35048226
Participants:347
Impact:92% (2L PEG+Asc) vs 96% (4L PEG); no significant difference (P=0.118)
Trust score:4/5

total ingested liquid

1 evidences

In elderly patients, 2L PEG with ascorbic acid cleaned bowels as well as 4L PEG, with less liquid to drink and better tolerability.

Trust comment: Randomized trial with adequate sample size and clear endpoints; results appear reliable.

Study Details

PMID:35048226
Participants:347
Impact:2.9 L vs 4.2 L; -1.3 L (P<0.001)
Trust score:4/5

tolerability (overall satisfaction/willingness to reuse)

1 evidences

In elderly patients, 2L PEG with ascorbic acid cleaned bowels as well as 4L PEG, with less liquid to drink and better tolerability.

Trust comment: Randomized trial with adequate sample size and clear endpoints; results appear reliable.

Study Details

PMID:35048226
Participants:347
Impact:improved in 2L PEG+Asc (P<0.001)
Trust score:4/5

sensitivity to PGE1 (platelet inhibition)

1 evidences

In healthy volunteers, vitamin E supplementation markedly raised platelet alpha-tocopherol and reduced platelet function; vitamin C and beta-carotene showed no significant effects.

Trust comment: Double-blind randomized placebo-controlled trial but small sample size and null results.

Study Details

PMID:9051202
Participants:40
Impact:no significant change; trend toward increased sensitivity
Trust score:4/5

serum alpha-tocopherol, beta-carotene, zinc, selenium

1 evidences

Double-blind randomized trial in 106 alcohol-dependent inpatients comparing 21 days of micronutrient supplementation (including zinc 20 mg) versus placebo and measuring serum vitamin and trace element levels.

Trust comment: Randomized double-blind trial with moderate size but used a multi-nutrient supplement so vitamin C–specific effects are not isolated.

Study Details

PMID:12897045
Participants:106
Impact:improved in supplement group vs placebo
Trust score:3/5

delivery within 14 days (prolongation of pregnancy)

1 evidences

In women with severe early pre-eclampsia, combined antioxidant therapy (including vitamin C) did not clearly improve biochemical markers or clinical prolongation of pregnancy.

Trust comment: Randomized placebo-controlled trial but small sample and multi-agent intervention limit attribution to vitamin C alone.

Study Details

PMID:9197872
Participants:56
Impact:52% (antioxidant) vs 76% (placebo); RR 0.68 (95% CI 0.45-1.04) — not clearly significant
Trust score:3/5

lipid peroxide levels

1 evidences

In women with severe early pre-eclampsia, combined antioxidant therapy (including vitamin C) did not clearly improve biochemical markers or clinical prolongation of pregnancy.

Trust comment: Randomized placebo-controlled trial but small sample and multi-agent intervention limit attribution to vitamin C alone.

Study Details

PMID:9197872
Participants:56
Impact:no significant change
Trust score:3/5

successful overall bowel preparation (HCS A/B)

1 evidences

A low-volume PEG–ascorbic acid (contains vitamin C) bowel prep (0.8 L) was as effective and safe as standard 2 L PEG–Asc for colonoscopy, with fewer bubbles and similar tolerability.

Trust comment: Multicenter, randomized, investigator-blinded phase III trial with objective blinded video review supports high trustworthiness.

Study Details

PMID:40704430
Participants:133
Impact:100% successful overall preparation (PPS, N=133); 0.8-L PEG‑Asc noninferior to 2-L PEG‑Asc
Trust score:5/5

high-quality overall preparation rate (HCS grade A)

1 evidences

A low-volume PEG–ascorbic acid (contains vitamin C) bowel prep (0.8 L) was as effective and safe as standard 2 L PEG–Asc for colonoscopy, with fewer bubbles and similar tolerability.

Trust comment: Multicenter, randomized, investigator-blinded phase III trial with objective blinded video review supports high trustworthiness.

Study Details

PMID:40704430
Participants:133
Impact:92.9% (0.8-L split-dose) vs 84.4% (2-L split-dose) in PPS
Trust score:5/5

colonic bubble score (Grade 0)

1 evidences

A low-volume PEG–ascorbic acid (contains vitamin C) bowel prep (0.8 L) was as effective and safe as standard 2 L PEG–Asc for colonoscopy, with fewer bubbles and similar tolerability.

Trust comment: Multicenter, randomized, investigator-blinded phase III trial with objective blinded video review supports high trustworthiness.

Study Details

PMID:40704430
Participants:133
Impact:100% Grade 0 in 0.8-L groups vs 46.7% in 2-L group (P<0.0001)
Trust score:5/5

lipid peroxidation (oxidative stress)

1 evidences

Vitamin C+E supplementation (with or without exercise) reduced oxidative stress markers and increased antioxidant measures in fibromyalgia patients, but symptoms did not improve.

Trust comment: Controlled pilot study with small sample size limits generalizability and statistical power.

Study Details

PMID:20666654
Participants:32
Impact:Plasma and erythrocyte lipid peroxidation decreased after 12 weeks in VCE and EX groups vs baseline
Trust score:3/5

reduced glutathione and antioxidant vitamins

1 evidences

Vitamin C+E supplementation (with or without exercise) reduced oxidative stress markers and increased antioxidant measures in fibromyalgia patients, but symptoms did not improve.

Trust comment: Controlled pilot study with small sample size limits generalizability and statistical power.

Study Details

PMID:20666654
Participants:32
Impact:Plasma vitamins A/E and reduced glutathione increased with VCE and EX
Trust score:3/5

lumbar spine bone mineral density (BMD)

1 evidences

In postmenopausal women, daily antioxidant supplementation including 1000 mg vitamin C prevented the small lumbar spine bone loss seen in the placebo group over 6 months.

Trust comment: Small randomized pilot trial with limited sample sizes per arm; results are suggestive but underpowered for definitive conclusions.

Study Details

PMID:19020919
Participants:34
Impact:Placebo group decreased from 1.01±0.17 to 1.00±0.16 g/cm² (P<0.05); antioxidant and exercise groups remained stable over 6 months
Trust score:3/5

tendon non-healing rate

1 evidences

In 98 patients after rotator cuff repair, postoperative vitamin C (500 mg/day for 45 days) showed a non-significant trend toward lower non-healing rate at 6 months (11% vs 23%).

Trust comment: Randomized monocenter preliminary study with modest sample size and non-significant primary result limits confidence; larger trials needed.

Study Details

PMID:33725178
Participants:98
Impact:Non-healing: 11% in VC+ vs 23% in VC-; overall non-healing 17% (P=0.20, not significant)
Trust score:3/5

clinical shoulder outcomes (Constant score, mobility)

1 evidences

In 98 patients after rotator cuff repair, postoperative vitamin C (500 mg/day for 45 days) showed a non-significant trend toward lower non-healing rate at 6 months (11% vs 23%).

Trust comment: Randomized monocenter preliminary study with modest sample size and non-significant primary result limits confidence; larger trials needed.

Study Details

PMID:33725178
Participants:98
Impact:No difference between supplemented and non-supplemented groups at ~6 months
Trust score:3/5

exercise-induced oxidative stress (lipid peroxidation, MDA)

1 evidences

Short-term supplementation with vitamins C (500 mg/day) and E reduced exercise-induced oxidative stress in young football players but did not improve performance or reduce muscle soreness/damage.

Trust comment: Randomized double-blind small trial with objective biochemical outcomes but limited sample size for performance endpoints.

Study Details

PMID:30927644
Participants:21
Impact:Supplementation reduced markers of lipid peroxidation (MDA, total lipid peroxidation) and preserved GSH/GSSG ratio after exercise
Trust score:3/5

performance, DOMS and muscle damage markers

1 evidences

Short-term supplementation with vitamins C (500 mg/day) and E reduced exercise-induced oxidative stress in young football players but did not improve performance or reduce muscle soreness/damage.

Trust comment: Randomized double-blind small trial with objective biochemical outcomes but limited sample size for performance endpoints.

Study Details

PMID:30927644
Participants:21
Impact:No improvement in lower body power, agility, anaerobic power, DOMS, or plasma creatine kinase during recovery
Trust score:3/5

overall bowel cleansing success (BBPS)

1 evidences

In colonoscopy patients, 1 L PEG with ascorbic acid was noninferior to 2 L for bowel cleansing but caused more thirst.

Trust comment: Large, registered randomized controlled trial (240 completed) with clinically relevant endpoints and clear reporting.

Study Details

PMID:36113016
Participants:240
Impact:1 L: 92.5% vs 2 L: 90.8% (noninferior; treatment difference 1.7%, 95% CI −5.4 to 8.7)
Trust score:5/5

Harefield Cleansing Scale success (HCS)

1 evidences

In colonoscopy patients, 1 L PEG with ascorbic acid was noninferior to 2 L for bowel cleansing but caused more thirst.

Trust comment: Large, registered randomized controlled trial (240 completed) with clinically relevant endpoints and clear reporting.

Study Details

PMID:36113016
Participants:240
Impact:1 L: 92.5% vs 2 L: 89.2% (noninferior)
Trust score:5/5

thirst (adverse event)

2 evidences

In colonoscopy patients, 1 L PEG with ascorbic acid was noninferior to 2 L for bowel cleansing but caused more thirst.

Trust comment: Large, registered randomized controlled trial (240 completed) with clinically relevant endpoints and clear reporting.

Study Details

PMID:36113016
Participants:240
Impact:More frequent with 1 L (29.2%) vs 2 L (17.5%), P = 0.033
Trust score:5/5

1 L PEG with ascorbic acid achieved similarly high adequate bowel-prep rates to oral sodium sulfate but caused more thirst and dizziness.

Trust comment: Multicenter prospective randomized trial with clear reported outcomes and reasonable sample size; some outcomes borderline significant.

Study Details

PMID:36107563
Participants:172
Impact:+13.4 percentage points (30.6% vs 17.2%; P = 0.04)
Trust score:4/5

average intimal index (plaque/vessel area)

1 evidences

In cardiac transplant patients, vitamins C+E slowed early progression of coronary intimal thickening.

Trust comment: Double-blind randomized trial with objective IVUS outcome but small sample (n=40).

Study Details

PMID:11943259
Participants:40
Impact:Placebo: increased by 8% (SE 2); Vitamin C+E: no significant change (0.8% ±1); difference P = 0.008
Trust score:4/5

coronary endothelium-dependent vasoreactivity

1 evidences

In cardiac transplant patients, vitamins C+E slowed early progression of coronary intimal thickening.

Trust comment: Double-blind randomized trial with objective IVUS outcome but small sample (n=40).

Study Details

PMID:11943259
Participants:40
Impact:Remained stable in both treatment and placebo groups (no significant change)
Trust score:4/5

serum vitamin C and other nutrient concentrations

1 evidences

Randomized double-blind trial of daily multivitamin and trace element supplement (including zinc 20 mg) vs placebo in adults measuring serum nutrient levels and antioxidant markers over 6 months.

Trust comment: Large randomized double-blind trial (n=401) demonstrating expected biomarker changes but effects are from a multinutrient formulation, not vitamin C alone.

Study Details

PMID:9627910
Participants:401
Impact:Serum vitamin C, alpha-tocopherol, beta-carotene, zinc and selenium increased significantly after 3 months of supplementation
Trust score:4/5

malondialdehyde (MDA, oxidative damage marker)

1 evidences

Randomized double-blind trial of daily multivitamin and trace element supplement (including zinc 20 mg) vs placebo in adults measuring serum nutrient levels and antioxidant markers over 6 months.

Trust comment: Large randomized double-blind trial (n=401) demonstrating expected biomarker changes but effects are from a multinutrient formulation, not vitamin C alone.

Study Details

PMID:9627910
Participants:401
Impact:No significant change after 6 months
Trust score:4/5

pain (verbal rating score)

1 evidences

A double-blind trial in 100 volunteers tested a nitrite+ascorbic acid gel system (with/without lidocaine) and found the active formulation reduced pain during hand vein cannulation.

Trust comment: Well-designed placebo-controlled double-blind trial with 100 volunteers showing significant analgesic effects; intervention included ascorbic acid as component.

Study Details

PMID:11966551
Participants:100
Impact:decrease (statistically significant, p<0.001)
Trust score:4/5

pain (visual analogue score)

1 evidences

A double-blind trial in 100 volunteers tested a nitrite+ascorbic acid gel system (with/without lidocaine) and found the active formulation reduced pain during hand vein cannulation.

Trust comment: Well-designed placebo-controlled double-blind trial with 100 volunteers showing significant analgesic effects; intervention included ascorbic acid as component.

Study Details

PMID:11966551
Participants:100
Impact:>40% decrease vs placebo (p<0.001)
Trust score:4/5

erythema score

1 evidences

Fifty patients applied a serum containing 15% vitamin C to one side of the face after Fraxel laser; the vitamin-C–containing side showed less redness, lower erythema index, improved short-term hydration and less pain vs saline on the other side.

Trust comment: Randomized, investigator-blinded split-face RCT with complete follow-up (n=50); industry funding and provided product create potential conflict of interest.

Study Details

PMID:40414817
Participants:50
Impact:T4–T0 difference −0.14 points (CEF vs NS) on Day 7 (p=0.011)
Trust score:4/5

erythema index (EI)

1 evidences

Fifty patients applied a serum containing 15% vitamin C to one side of the face after Fraxel laser; the vitamin-C–containing side showed less redness, lower erythema index, improved short-term hydration and less pain vs saline on the other side.

Trust comment: Randomized, investigator-blinded split-face RCT with complete follow-up (n=50); industry funding and provided product create potential conflict of interest.

Study Details

PMID:40414817
Participants:50
Impact:mean % change Day 7 −9.77% (CEF vs NS) (p<0.001)
Trust score:4/5

skin hydration (percentage change)

1 evidences

Fifty patients applied a serum containing 15% vitamin C to one side of the face after Fraxel laser; the vitamin-C–containing side showed less redness, lower erythema index, improved short-term hydration and less pain vs saline on the other side.

Trust comment: Randomized, investigator-blinded split-face RCT with complete follow-up (n=50); industry funding and provided product create potential conflict of interest.

Study Details

PMID:40414817
Participants:50
Impact:Day 1 +9.53% (p=0.007) and Day 3 +11.80% (p=0.002) on CEF side vs NS
Trust score:4/5

ulcer size

1 evidences

In 43 non-malnourished patients with severe pressure ulcers, a high-protein, arginine- and micronutrient-enriched oral supplement (which included vitamin C) accelerated ulcer healing and reduced dressing needs compared with control; blood vitamin C levels rose in the supplement group.

Trust comment: Randomized, double-blind trial but supplement combined multiple nutrients (so effects cannot be attributed to vitamin C alone) with modest sample size.

Study Details

PMID:20598855
Participants:43
Impact:greater decrease over 8 weeks vs control (P≤0.016)
Trust score:3/5

pressure ulcer severity (PUSH) score

1 evidences

In 43 non-malnourished patients with severe pressure ulcers, a high-protein, arginine- and micronutrient-enriched oral supplement (which included vitamin C) accelerated ulcer healing and reduced dressing needs compared with control; blood vitamin C levels rose in the supplement group.

Trust comment: Randomized, double-blind trial but supplement combined multiple nutrients (so effects cannot be attributed to vitamin C alone) with modest sample size.

Study Details

PMID:20598855
Participants:43
Impact:significantly greater decrease vs control (P≤0.033)
Trust score:3/5

blood vitamin C level

2 evidences

In 43 non-malnourished patients with severe pressure ulcers, a high-protein, arginine- and micronutrient-enriched oral supplement (which included vitamin C) accelerated ulcer healing and reduced dressing needs compared with control; blood vitamin C levels rose in the supplement group.

Trust comment: Randomized, double-blind trial but supplement combined multiple nutrients (so effects cannot be attributed to vitamin C alone) with modest sample size.

Study Details

PMID:20598855
Participants:43
Impact:increase vs control at end of study (P=0.015)
Trust score:3/5

Providing 350 g/day vegetables and using water-free (multi-ply) cookware increased blood vitamin C and reduced oxidized LDL and LDL cholesterol over 2 weeks compared with ordinary cooking or usual diet.

Trust comment: Randomized study with objective biomarker changes (n=57) showing short-term increases in blood vitamin C and improvements in lipid/oxidative markers; moderate sample and short duration.

Study Details

PMID:22229802
Participants:57
Impact:Group A: 9.2 → 11.0 μg/ml (+1.8 μg/ml; P < 0.01); Group B: 9.8 → 10.7 μg/ml (+0.9 μg/ml; P < 0.05)
Trust score:4/5

carotid intima-media thickness progression

1 evidences

Analysis of 146 men in an arterial imaging trial found no association between higher self-selected supplementary vitamin C intake (≥250 mg/day subgroup) and reduced carotid intima-media thickness progression.

Trust comment: Controlled arterial imaging study but analysis of self-selected supplement use (observational within trial) and limited high-user subgroup (n=29) limits causal inference.

Study Details

PMID:8921775
Participants:146
Impact:no effect of supplementary vitamin C detected (no difference vs low users)
Trust score:3/5

positive psychotic symptoms (PANSS positive subscale)

1 evidences

In a 2×2 factorial RCT (n=99) adding vitamins E+C (including vitamin C ~1000 mg/day) to antipsychotics worsened psychotic positive symptoms in patients with low baseline RBC PUFA; combining vitamins with EPA neutralized the effect.

Trust comment: Randomized, double-blind trial but complex subgroup effects (PUFA stratification), smaller than planned sample and heterogeneous responses limit certainty.

Study Details

PMID:24346133
Participants:99
Impact:worsened in low-PUFA patients on vitamins E+C (e.g., positive subscale ~16.4 with vitamins vs 11.0 with double placebo over 16 weeks)
Trust score:3/5

drop-out risk

1 evidences

In a 2×2 factorial RCT (n=99) adding vitamins E+C (including vitamin C ~1000 mg/day) to antipsychotics worsened psychotic positive symptoms in patients with low baseline RBC PUFA; combining vitamins with EPA neutralized the effect.

Trust comment: Randomized, double-blind trial but complex subgroup effects (PUFA stratification), smaller than planned sample and heterogeneous responses limit certainty.

Study Details

PMID:24346133
Participants:99
Impact:vitamins (given alone) increased risk of drop-out (odds ratio reported)
Trust score:3/5

IL-6 (pro-inflammatory cytokine)

1 evidences

In 131 patients with septic shock randomized to antioxidant arms, vitamin C treatment (oral 1 g q6h for 5 days) was associated with marked SOFA score improvement and reductions in some oxidative stress markers and inflammatory cytokines.

Trust comment: Prospective randomized, blinded trial with 131 septic shock patients showing clinically meaningful SOFA improvement with vitamin C; multiple antioxidant arms and short follow-up are limitations.

Study Details

PMID:38068931
Participants:131
Impact:decrease with Vit C (p=0.006)
Trust score:4/5

plasma NO3−/NO2− levels (oxidative marker)

1 evidences

In 131 patients with septic shock randomized to antioxidant arms, vitamin C treatment (oral 1 g q6h for 5 days) was associated with marked SOFA score improvement and reductions in some oxidative stress markers and inflammatory cytokines.

Trust comment: Prospective randomized, blinded trial with 131 septic shock patients showing clinically meaningful SOFA improvement with vitamin C; multiple antioxidant arms and short follow-up are limitations.

Study Details

PMID:38068931
Participants:131
Impact:statistically significant decrease with Vit C (p reported)
Trust score:4/5

signal-averaged ECG indices (QRS duration / low-amplitude signal duration)

1 evidences

In 61 AMI patients, supplementation with vitamins C and E (600 mg/day each) for 14 days prevented worsening of SAECG indices seen in controls and reduced leukocyte oxygen free radical production.

Trust comment: Randomized clinical study with objective electrophysiologic and biochemical endpoints; modest sample size but clear biochemical confirmation of supplementation.

Study Details

PMID:8607400
Participants:61
Impact:indices remained unchanged with vitamins vs increases in control (e.g., QRS 99→111 ms in controls; unchanged in supplemented group)
Trust score:4/5

leukocyte oxygen-free radical production

1 evidences

In 61 AMI patients, supplementation with vitamins C and E (600 mg/day each) for 14 days prevented worsening of SAECG indices seen in controls and reduced leukocyte oxygen free radical production.

Trust comment: Randomized clinical study with objective electrophysiologic and biochemical endpoints; modest sample size but clear biochemical confirmation of supplementation.

Study Details

PMID:8607400
Participants:61
Impact:decreased vs control (p<0.02)
Trust score:4/5

best-corrected visual acuity (BCVA)

1 evidences

An oral supplement containing lutein, zeaxanthin and coantioxidants (including vitamin C) produced functional and morphologic benefits in early AMD over 36 months.

Trust comment: Randomized placebo-controlled trial in humans with clear positive secondary outcomes, but vitamin C was given as part of a multi-nutrient supplement so its individual effect is not isolated.

Study Details

PMID:23218821
Participants:433
Impact:+4.8 letters (active vs placebo at 36 months; P=0.04)
Trust score:3/5

progression along AMD severity scale

1 evidences

An oral supplement containing lutein, zeaxanthin and coantioxidants (including vitamin C) produced functional and morphologic benefits in early AMD over 36 months.

Trust comment: Randomized placebo-controlled trial in humans with clear positive secondary outcomes, but vitamin C was given as part of a multi-nutrient supplement so its individual effect is not isolated.

Study Details

PMID:23218821
Participants:433
Impact:slower progression (P=0.014)
Trust score:3/5

contrast sensitivity

1 evidences

An oral supplement containing lutein, zeaxanthin and coantioxidants (including vitamin C) produced functional and morphologic benefits in early AMD over 36 months.

Trust comment: Randomized placebo-controlled trial in humans with clear positive secondary outcomes, but vitamin C was given as part of a multi-nutrient supplement so its individual effect is not isolated.

Study Details

PMID:23218821
Participants:433
Impact:improved (secondary outcome; magnitude not reported)
Trust score:3/5

incidence of post-contrast acute kidney injury (PC-AKI)

1 evidences

Statin plus ascorbic acid reduced the incidence of post-contrast acute kidney injury compared to placebo, though serum creatinine and eGFR changes were not improved between groups.

Trust comment: Randomized clinical trial with adequate sample but ascorbic acid was given together with high‑dose atorvastatin, so effect of vitamin C alone is not separable.

Study Details

PMID:37742328
Participants:213
Impact:placebo 9.8% vs statin+ascorbic acid 3.0% (absolute −6.8 percentage points; P=0.04)
Trust score:3/5

WOMAC index (symptoms/function)

1 evidences

A 6-month randomized trial found the product containing undenatured type II collagen (Artneo) improved pain, stiffness, and some MRI signs of synovitis and was not inferior to glucosamine+chondroitin.

Trust comment: Randomized small trial showing benefit of a combination product that includes vitamin C; the contribution of vitamin C alone cannot be determined.

Study Details

PMID:38785054
Participants:70
Impact:improved in both groups with no significant intergroup difference
Trust score:3/5

morning stiffness / synovitis area

1 evidences

A 6-month randomized trial found the product containing undenatured type II collagen (Artneo) improved pain, stiffness, and some MRI signs of synovitis and was not inferior to glucosamine+chondroitin.

Trust comment: Randomized small trial showing benefit of a combination product that includes vitamin C; the contribution of vitamin C alone cannot be determined.

Study Details

PMID:38785054
Participants:70
Impact:greater decrease in stiffness and larger reduction in synovitis area with Artneo (synovitis area reduction ~2.95× vs 1.37× for comparator)
Trust score:3/5

urine NGAL

1 evidences

Adding NAC and vitamin C did not significantly change urine IL-18 or NGAL or the incidence/duration of delayed graft function after living-donor kidney transplant in this trial.

Trust comment: Randomized human study but small group sizes and vitamin C was given in combination with NAC, with no significant biomarker changes observed.

Study Details

PMID:25599738
Participants:84
Impact:decreased in NAC and NAC+vitamin C groups but reductions were not statistically significant
Trust score:3/5

urine interleukin-18 (IL-18)

1 evidences

Adding NAC and vitamin C did not significantly change urine IL-18 or NGAL or the incidence/duration of delayed graft function after living-donor kidney transplant in this trial.

Trust comment: Randomized human study but small group sizes and vitamin C was given in combination with NAC, with no significant biomarker changes observed.

Study Details

PMID:25599738
Participants:84
Impact:decreased in NAC and NAC+vitamin C groups but reductions were not statistically significant
Trust score:3/5

delayed graft function (DGF) prevalence/duration

1 evidences

Adding NAC and vitamin C did not significantly change urine IL-18 or NGAL or the incidence/duration of delayed graft function after living-donor kidney transplant in this trial.

Trust comment: Randomized human study but small group sizes and vitamin C was given in combination with NAC, with no significant biomarker changes observed.

Study Details

PMID:25599738
Participants:84
Impact:no significant differences between groups
Trust score:3/5

serum IL-1β and IL-6

1 evidences

In term infants with perinatal asphyxia, early intravenous ascorbic acid plus oral ibuprofen did not improve cytokines, mortality, neurologic discharge status, or 6-month developmental outcomes versus placebo.

Trust comment: Randomized neonatal trial but small sample and vitamin C was co-administered with ibuprofen; no benefit demonstrated.

Study Details

PMID:19242485
Participants:60
Impact:no significant difference between intervention and control at enrollment or follow-up
Trust score:3/5

developmental delay at 6 months

1 evidences

In term infants with perinatal asphyxia, early intravenous ascorbic acid plus oral ibuprofen did not improve cytokines, mortality, neurologic discharge status, or 6-month developmental outcomes versus placebo.

Trust comment: Randomized neonatal trial but small sample and vitamin C was co-administered with ibuprofen; no benefit demonstrated.

Study Details

PMID:19242485
Participants:60
Impact:32% (intervention) vs 40% (control); no significant difference
Trust score:3/5

reactive hyperemia (% change, RH%)

1 evidences

Short-term vitamin C (2 g/day) plus high-dose vitamin E (800 IU/day) improved reactive hyperemia and reduced several inflammatory markers in smokers, whereas vitamin C alone was ineffective.

Trust comment: Randomized human study with small sample sizes per arm; shows benefit when vitamin C is combined with high-dose vitamin E but vitamin C monotherapy was ineffective.

Study Details

PMID:14612206
Participants:43
Impact:significant increase in groups receiving vitamin C plus vitamin E (400 and 800 IU) but not with vitamin C alone; largest effect in 800 IU group
Trust score:3/5

inflammatory markers (IL-1β, IL-6, sVCAM-1, sICAM-1)

1 evidences

Short-term vitamin C (2 g/day) plus high-dose vitamin E (800 IU/day) improved reactive hyperemia and reduced several inflammatory markers in smokers, whereas vitamin C alone was ineffective.

Trust comment: Randomized human study with small sample sizes per arm; shows benefit when vitamin C is combined with high-dose vitamin E but vitamin C monotherapy was ineffective.

Study Details

PMID:14612206
Participants:43
Impact:significant reductions observed in group receiving vitamin C 2 g/day + vitamin E 800 IU/day (group C); no change with vitamin C alone
Trust score:3/5

clinically successful bowel preparation

1 evidences

A 2-L PEG solution containing ascorbic acid produced at least comparable bowel cleansing to sodium phosphate and was better tolerated.

Trust comment: Prospective randomized multicentre trial with a large sample and blinded video scoring; single-blind design and CI crossing zero moderate confidence.

Study Details

PMID:17094774
Participants:352
Impact:72.5% vs 63.9% (treatment difference +8.6%, 95% CI -2.3% to +19.4%)
Trust score:4/5

tolerability / patient acceptability

1 evidences

A 2-L PEG solution containing ascorbic acid produced at least comparable bowel cleansing to sodium phosphate and was better tolerated.

Trust comment: Prospective randomized multicentre trial with a large sample and blinded video scoring; single-blind design and CI crossing zero moderate confidence.

Study Details

PMID:17094774
Participants:352
Impact:better tolerated (qualitative)
Trust score:4/5

right colon BBPS score

1 evidences

1 L PEG with ascorbic acid achieved similarly high adequate bowel-prep rates to oral sodium sulfate but caused more thirst and dizziness.

Trust comment: Multicenter prospective randomized trial with clear reported outcomes and reasonable sample size; some outcomes borderline significant.

Study Details

PMID:36107563
Participants:172
Impact:+0.20 points (2.22 vs 2.02; P = 0.08)
Trust score:4/5

dizziness (adverse event)

1 evidences

1 L PEG with ascorbic acid achieved similarly high adequate bowel-prep rates to oral sodium sulfate but caused more thirst and dizziness.

Trust comment: Multicenter prospective randomized trial with clear reported outcomes and reasonable sample size; some outcomes borderline significant.

Study Details

PMID:36107563
Participants:172
Impact:+12.1 percentage points (25.9% vs 13.8%; P = 0.047)
Trust score:4/5

general fatigue

1 evidences

Strength training reduced perceived and performance fatigue in breast cancer survivors; adding vitamins C (500 mg/day) and E gave no additional benefit.

Trust comment: Randomized double-blind placebo-controlled trial but very small sample (n=25).

Study Details

PMID:32348688
Participants:25
Impact:decreased (similar to placebo)
Trust score:4/5

physical fatigue

1 evidences

Strength training reduced perceived and performance fatigue in breast cancer survivors; adding vitamins C (500 mg/day) and E gave no additional benefit.

Trust comment: Randomized double-blind placebo-controlled trial but very small sample (n=25).

Study Details

PMID:32348688
Participants:25
Impact:decreased (similar to placebo)
Trust score:4/5

performance fatigability

1 evidences

Strength training reduced perceived and performance fatigue in breast cancer survivors; adding vitamins C (500 mg/day) and E gave no additional benefit.

Trust comment: Randomized double-blind placebo-controlled trial but very small sample (n=25).

Study Details

PMID:32348688
Participants:25
Impact:decreased (similar to placebo)
Trust score:4/5

peak serum creatinine increase

1 evidences

High‑dose IV and short-term oral ascorbic acid did not reduce serum creatinine rise or incidence of contrast-induced nephropathy in patients with renal insufficiency undergoing coronary angiography.

Trust comment: Prospective randomized controlled trial with adequate sample size and clear negative primary result.

Study Details

PMID:22449658
Participants:156
Impact:no significant difference (0.012 vs 0.022 mg/dL; p=0.216)
Trust score:4/5

incidence of contrast-induced nephropathy

1 evidences

High‑dose IV and short-term oral ascorbic acid did not reduce serum creatinine rise or incidence of contrast-induced nephropathy in patients with renal insufficiency undergoing coronary angiography.

Trust comment: Prospective randomized controlled trial with adequate sample size and clear negative primary result.

Study Details

PMID:22449658
Participants:156
Impact:no significant difference (5.4% vs 6.3%; p=0.690)
Trust score:4/5

gastric antral atrophy

1 evidences

Over 72 months, cure of H. pylori improved gastric antral atrophy; dietary ascorbic acid supplementation showed no significant independent effect.

Trust comment: Randomized long-term trial with morphometric endpoints; ascorbic acid provided no measurable benefit after accounting for H. pylori therapy.

Study Details

PMID:11774937
Participants:132
Impact:no significant effect from ascorbic acid (effect driven by H. pylori treatment)
Trust score:4/5

insulin-stimulated glucose uptake

1 evidences

In young men undergoing intense endurance training, antioxidant supplementation (vitamin C 500 mg + vitamin E) did not alter the training-induced increase in insulin sensitivity or improvements in fitness.

Trust comment: Randomized controlled trial with gold-standard metabolic testing but small sample (n=21).

Study Details

PMID:21325105
Participants:21
Impact:+17.2% with antioxidants (training effect), no difference vs placebo (18.9%)
Trust score:4/5

cardiorespiratory fitness (Vo2max/Pmax)

1 evidences

In young men undergoing intense endurance training, antioxidant supplementation (vitamin C 500 mg + vitamin E) did not alter the training-induced increase in insulin sensitivity or improvements in fitness.

Trust comment: Randomized controlled trial with gold-standard metabolic testing but small sample (n=21).

Study Details

PMID:21325105
Participants:21
Impact:increased with training; no difference vs placebo
Trust score:4/5

cellular reduced glutathione

1 evidences

In elderly patients with type 2 diabetes, vitamin C (0.5–1 g/day) increased cellular glutathione and LDL vitamin E content but did not reduce LDL susceptibility to peroxidation.

Trust comment: Randomized biomarker trial with clear dose-response on antioxidant measures but small sample and no clinical outcomes.

Study Details

PMID:18077012
Participants:36
Impact:increased (0.5 g: 0.60 vs 0.33; 1 g: 0.93 vs 0.33)
Trust score:4/5

intracellular vitamin C

1 evidences

In elderly patients with type 2 diabetes, vitamin C (0.5–1 g/day) increased cellular glutathione and LDL vitamin E content but did not reduce LDL susceptibility to peroxidation.

Trust comment: Randomized biomarker trial with clear dose-response on antioxidant measures but small sample and no clinical outcomes.

Study Details

PMID:18077012
Participants:36
Impact:increased (1 g: 5.66 vs 2.72)
Trust score:4/5

vitamin E content of LDL

1 evidences

In elderly patients with type 2 diabetes, vitamin C (0.5–1 g/day) increased cellular glutathione and LDL vitamin E content but did not reduce LDL susceptibility to peroxidation.

Trust comment: Randomized biomarker trial with clear dose-response on antioxidant measures but small sample and no clinical outcomes.

Study Details

PMID:18077012
Participants:36
Impact:increased (1 g: 1.98 vs 1.48)
Trust score:4/5

ischemia zone volume

2 evidences

Elderly stroke patients received ascorbic acid or Cytoflavin; vitamin C showed no morphologic benefit.

Trust comment: Multicenter randomized prospective study (185 pts); randomized design and clinical endpoints increase trustworthiness though ascorbic acid was inferior to comparator.

Study Details

PMID:25946854
Participants:185
Impact:no change (ascorbic acid showed no effect on morphologic parameters)
Trust score:4/5

In ischemic stroke patients, ascorbic acid showed no effect on ischemic lesion volume or morphologic parameters, whereas cytoflavin produced volume reductions and better clinical outcomes.

Trust comment: Multicenter randomized trial with moderate sample size but limited detail in abstract and ascorbic acid was not the effective intervention.

Study Details

PMID:25591516
Participants:185
Impact:no effect of ascorbic acid (cytoflavin decreased volume by 25.2–29.0%)
Trust score:3/5

neurologic/functional status

2 evidences

Elderly stroke patients received ascorbic acid or Cytoflavin; vitamin C showed no morphologic benefit.

Trust comment: Multicenter randomized prospective study (185 pts); randomized design and clinical endpoints increase trustworthiness though ascorbic acid was inferior to comparator.

Study Details

PMID:25946854
Participants:185
Impact:no change (no improvement with ascorbic acid)
Trust score:4/5

In ischemic stroke patients, ascorbic acid showed no effect on ischemic lesion volume or morphologic parameters, whereas cytoflavin produced volume reductions and better clinical outcomes.

Trust comment: Multicenter randomized trial with moderate sample size but limited detail in abstract and ascorbic acid was not the effective intervention.

Study Details

PMID:25591516
Participants:185
Impact:no improvement with ascorbic acid (improved with cytoflavin)
Trust score:3/5

daily fruit and vegetable servings

1 evidences

A mobile intervention or providing fruits/vegetables increased daily intake (~+0.9 servings/day) and raised plasma vitamin C compared to control in young adults.

Trust comment: Randomized trial with objective biomarker confirmation and moderate sample size; effect is dietary (increases vitamin C intake) rather than supplementation.

Study Details

PMID:27642037
Participants:171
Impact:increased by ~+0.9 servings/day (EMI/FVI 3.7 vs control 2.8)
Trust score:4/5

common cold symptom score

1 evidences

A multi‑component product that includes caffeine improved common‑cold symptom scores more than controls, though caffeine was not tested alone.

Trust comment: Large randomized double‑blind multicenter trial (high quality), but no placebo arm and vitamin C was present in all groups so isolated vitamin C effects are not clearly quantified.

Study Details

PMID:12665160
Participants:1167
Impact:ascorbic acid alone showed less improvement vs Grippostad‑C (Grippostad‑C statistically superior; exact magnitude not reported)
Trust score:4/5

systolic blood pressure reactivity

1 evidences

High‑dose sustained‑release vitamin C for 14 days reduced BP reactivity and subjective stress and sped cortisol recovery during an acute laboratory stress test.

Trust comment: Randomized double‑blind placebo‑controlled trial with reasonable sample and objective measures; outcomes reported clearly though some values not fully detailed in provided text.

Study Details

PMID:11862365
Participants:108
Impact:smaller increase by 8 mmHg (23 vs 31 mmHg increase in ascorbate vs placebo)
Trust score:4/5

diastolic blood pressure reactivity

1 evidences

High‑dose sustained‑release vitamin C for 14 days reduced BP reactivity and subjective stress and sped cortisol recovery during an acute laboratory stress test.

Trust comment: Randomized double‑blind placebo‑controlled trial with reasonable sample and objective measures; outcomes reported clearly though some values not fully detailed in provided text.

Study Details

PMID:11862365
Participants:108
Impact:reduced increase vs placebo (exact value not reported)
Trust score:4/5

subjective stress response

1 evidences

High‑dose sustained‑release vitamin C for 14 days reduced BP reactivity and subjective stress and sped cortisol recovery during an acute laboratory stress test.

Trust comment: Randomized double‑blind placebo‑controlled trial with reasonable sample and objective measures; outcomes reported clearly though some values not fully detailed in provided text.

Study Details

PMID:11862365
Participants:108
Impact:reduced subjective stress responses vs placebo (exact magnitude not reported)
Trust score:4/5

alpha-tocopherol (vitamin E)

2 evidences

After 2 years of daily antioxidant supplementation (including 120 mg vitamin C), plasma concentrations of vitamin C, vitamin E, beta-carotene, selenium and zinc were significantly higher than placebo in a 1000-person subsample.

Trust comment: Large randomized double-blind placebo-controlled trial with substantial sample and clear biomarker changes, though this report is preliminary on a subsample.

Study Details

PMID:11718454
Participants:1000
Impact:increased (men 35.3 µmol/L; women 34.9 µmol/L)
Trust score:4/5

Chlorella supplementation increased plasma vitamin C and other antioxidant markers and improved erythrocyte antioxidant enzymes in smokers, though DNA damage also decreased with placebo.

Trust comment: Randomized double-blind placebo-controlled trial (n=52) showing clear increases in plasma antioxidant nutrients, but primary intervention was Chlorella (contains vitamin C) and DNA damage findings were not specific to active treatment.

Study Details

PMID:19660910
Participants:52
Impact:+15.7% after supplementation
Trust score:3/5

erythrocyte antioxidant enzyme activity

1 evidences

Chlorella supplementation increased plasma vitamin C and other antioxidant markers and improved erythrocyte antioxidant enzymes in smokers, though DNA damage also decreased with placebo.

Trust comment: Randomized double-blind placebo-controlled trial (n=52) showing clear increases in plasma antioxidant nutrients, but primary intervention was Chlorella (contains vitamin C) and DNA damage findings were not specific to active treatment.

Study Details

PMID:19660910
Participants:52
Impact:increased (catalase and superoxide dismutase activities increased)
Trust score:3/5

procollagen I N-propeptide (PINP)

1 evidences

Smokers had smaller, more superficial punch wounds and lower vitamin C and PINP (a collagen synthesis marker); smoking cessation increased wound depth, vitamin C, and PINP; nicotine patch had no detectable effect.

Trust comment: Well-characterized randomized/controlled wound study with biomarker measures and sufficient sample size to show significant vitamin C differences by smoking status.

Study Details

PMID:20347467
Participants:78
Impact:lower in smokers (52.7 ±6.6 ng/mL) vs never smokers (64.7 ±4.7 ng/mL); increased after smoking cessation (P≈.07 vs never smokers)
Trust score:4/5

wound depth

1 evidences

Smokers had smaller, more superficial punch wounds and lower vitamin C and PINP (a collagen synthesis marker); smoking cessation increased wound depth, vitamin C, and PINP; nicotine patch had no detectable effect.

Trust comment: Well-characterized randomized/controlled wound study with biomarker measures and sufficient sample size to show significant vitamin C differences by smoking status.

Study Details

PMID:20347467
Participants:78
Impact:smokers had shallower wounds vs never smokers and wound depth increased after smoking cessation (P=.02)
Trust score:4/5

exercise-induced lipid hydroperoxide (DeltaPEROX)

1 evidences

An antioxidant supplement regimen including vitamin C reduced exercise-induced oxidative stress and improved adiponectin and some inflammatory/lipid responses in overweight young adults.

Trust comment: Randomized double-blind controlled trial (n=48) using a combination antioxidant supplement including vitamin C; effects cannot be solely ascribed to vitamin C.

Study Details

PMID:17189550
Participants:48
Impact:reduced to 0.09 nM/kg/min in overweight-AOX group vs 0.98 (placebo-overweight) and 0.53 (placebo-normal) at 8 weeks (P<0.05)
Trust score:3/5

adiponectin

1 evidences

An antioxidant supplement regimen including vitamin C reduced exercise-induced oxidative stress and improved adiponectin and some inflammatory/lipid responses in overweight young adults.

Trust comment: Randomized double-blind controlled trial (n=48) using a combination antioxidant supplement including vitamin C; effects cannot be solely ascribed to vitamin C.

Study Details

PMID:17189550
Participants:48
Impact:increased 22.1% in AOX groups vs 3.1% in placebo (P<0.05)
Trust score:3/5

exercise-induced IL-6 and lipid changes

1 evidences

An antioxidant supplement regimen including vitamin C reduced exercise-induced oxidative stress and improved adiponectin and some inflammatory/lipid responses in overweight young adults.

Trust comment: Randomized double-blind controlled trial (n=48) using a combination antioxidant supplement including vitamin C; effects cannot be solely ascribed to vitamin C.

Study Details

PMID:17189550
Participants:48
Impact:DeltaIL-6, total cholesterol, and LDL reductions observed in AOX groups (all P<0.05)
Trust score:3/5

serum insulin

1 evidences

In adolescent girls with metabolic syndrome, 6 weeks of DASH recommendations increased vitamin C levels, lowered insulin and prevented rise in diastolic blood pressure versus usual advice.

Trust comment: Randomised crossover trial with objective biochemical measures but moderate sample size and short intervention period.

Study Details

PMID:23773316
Participants:60
Impact:-11.4 pmol/l (-11%), 101.4 to 90.0 pmol/l, P=0.04
Trust score:4/5

prevalence of metabolic syndrome

1 evidences

In adolescent girls with metabolic syndrome, 6 weeks of DASH recommendations increased vitamin C levels, lowered insulin and prevented rise in diastolic blood pressure versus usual advice.

Trust comment: Randomised crossover trial with objective biochemical measures but moderate sample size and short intervention period.

Study Details

PMID:23773316
Participants:60
Impact:reduced prevalence vs UDA (P<0.05)
Trust score:4/5

dietary vitamin C intake/quality

1 evidences

Four years after a community dietary program, participants largely maintained a low-salt, high-carotene and high–vitamin C diet compared with pre-intervention.

Trust comment: Community randomized intervention with long follow-up but analyses based on a subset (308) which may introduce selection bias.

Study Details

PMID:16707149
Participants:308
Impact:maintained post-intervention improvements vs pre-intervention (P<0.01); only small nonsignificant reversal at follow-up (P=0.082–0.824)
Trust score:3/5

serum leptin

1 evidences

In people with type 2 diabetes, 8 weeks of 500 mg/day vitamin C raised leptin and restored a significant leptin–CRP correlation compared with placebo.

Trust comment: Randomized, double-blind placebo-controlled trial with clear primary findings but modest sample size (57 completers).

Study Details

PMID:37612864
Participants:57
Impact:+24% (MD=3.48), p=0.001
Trust score:4/5

CRP–leptin correlation

1 evidences

In people with type 2 diabetes, 8 weeks of 500 mg/day vitamin C raised leptin and restored a significant leptin–CRP correlation compared with placebo.

Trust comment: Randomized, double-blind placebo-controlled trial with clear primary findings but modest sample size (57 completers).

Study Details

PMID:37612864
Participants:57
Impact:restored to significant correlation (rs=0.730, p<0.001) after vitamin C
Trust score:4/5

inflammatory and metabolic markers (FPG, HbA1c, CRP, lipids)

1 evidences

In people with type 2 diabetes, 8 weeks of 500 mg/day vitamin C raised leptin and restored a significant leptin–CRP correlation compared with placebo.

Trust comment: Randomized, double-blind placebo-controlled trial with clear primary findings but modest sample size (57 completers).

Study Details

PMID:37612864
Participants:57
Impact:no significant change (p>0.05)
Trust score:4/5

intestinal metaplasia regression

1 evidences

After H. pylori eradication, 6 months of 500 mg/day ascorbic acid led to greater regression of gastric intestinal metaplasia versus no treatment.

Trust comment: Prospective randomized study with clear histological outcome measures but relatively small sample.

Study Details

PMID:11012475
Participants:59
Impact:9/29 (31%) resolved vs 1/29 (3.4%) in control, P=0.006
Trust score:4/5

extent of antral gastritis with intestinal metaplasia

1 evidences

After H. pylori eradication, 6 months of 500 mg/day ascorbic acid led to greater regression of gastric intestinal metaplasia versus no treatment.

Trust comment: Prospective randomized study with clear histological outcome measures but relatively small sample.

Study Details

PMID:11012475
Participants:59
Impact:improvement in 6/29 (20.7%) vs 1 patient in control, P=0.051
Trust score:4/5

hospitalization/ICU stay and time to rhythm restoration

1 evidences

Perioperative vitamin C supplementation reduced incidence of postoperative atrial fibrillation and shortened hospital and ICU stays compared with control.

Trust comment: Randomized single-center pilot with adequate sample but limited by single-center design and being a pilot study.

Study Details

PMID:21098510
Participants:170
Impact:significantly shorter in vitamin C group (no exact group means reported)
Trust score:3/5

maximum serum creatinine change

1 evidences

In patients with renal impairment undergoing angiography, high-dose ascorbic acid produced a small rise in creatinine and tended to higher CIN rates compared with high-dose NAC; diabetics on ascorbic acid had higher CIN.

Trust comment: Prospective randomized controlled trial with a substantial sample (n=212); comparisons favor NAC over ascorbic acid with statistically significant creatinine difference.

Study Details

PMID:19249432
Participants:212
Impact:+0.04 ± 0.20 mg/dL (ascorbic acid), greater rise vs NAC (-0.03 ± 0.18 mg/dL), P=0.026
Trust score:4/5

contrast-induced nephropathy incidence

2 evidences

In patients with renal impairment undergoing angiography, high-dose ascorbic acid produced a small rise in creatinine and tended to higher CIN rates compared with high-dose NAC; diabetics on ascorbic acid had higher CIN.

Trust comment: Prospective randomized controlled trial with a substantial sample (n=212); comparisons favor NAC over ascorbic acid with statistically significant creatinine difference.

Study Details

PMID:19249432
Participants:212
Impact:4.4% with ascorbic acid vs 1.2% with NAC overall (P=0.370); in diabetics 12.5% with ascorbic acid vs 0% with NAC, P=0.039
Trust score:4/5

In CKD patients having catheterization, IV sodium bicarbonate plus IV ascorbic acid reduced contrast-induced kidney injury versus saline.

Trust comment: Prospective clinical study with a large sample (n=429) and a significant result, though randomization/blinding details are not specified in the text provided.

Study Details

PMID:28003574
Participants:429
Impact:-5.9 percentage points (8.7% saline vs 2.8% combo; P=0.008)
Trust score:4/5

superoxide dismutase (SOD) activity

2 evidences

A 4-month high-antioxidant diet (designed to raise vitamins A, C and E) increased plasma and leukocyte vitamin C, boosted antioxidant enzyme activities, and lowered lipid oxidative markers in women with endometriosis.

Trust comment: Randomized diet intervention with objective biochemical endpoints and moderate completion rates, but unblinded and with some dropouts.

Study Details

PMID:19476631
Participants:72
Impact:+40% (after 2 months)
Trust score:3/5

Six-month double-blind RCT in institutionalized elderly: vitamin supplementation (including vitamin C) increased serum vitamin levels and improved enzymatic antioxidant activity.

Trust comment: Large randomized, double-blind, placebo-controlled trial with objective biochemical endpoints, though clinical outcomes limited.

Study Details

PMID:8862480
Participants:575
Impact:Increased (P < 0.05)
Trust score:4/5

preeclampsia risk

1 evidences

Large randomized trial of vitamin C (1000 mg) plus vitamin E vs placebo in pregnancy found no reduction in preeclampsia or major perinatal adverse outcomes.

Trust comment: Large, multicenter randomized controlled trial with robust sample size and clinically relevant endpoints.

Study Details

PMID:16641396
Participants:1877
Impact:+20% (6.0% vs 5.0%; RR 1.20)
Trust score:5/5

infant death or serious outcomes

1 evidences

Large randomized trial of vitamin C (1000 mg) plus vitamin E vs placebo in pregnancy found no reduction in preeclampsia or major perinatal adverse outcomes.

Trust comment: Large, multicenter randomized controlled trial with robust sample size and clinically relevant endpoints.

Study Details

PMID:16641396
Participants:1877
Impact:-21% (9.5% vs 12.1%; RR 0.79)
Trust score:5/5

small-for-gestational-age (<10th percentile)

1 evidences

Large randomized trial of vitamin C (1000 mg) plus vitamin E vs placebo in pregnancy found no reduction in preeclampsia or major perinatal adverse outcomes.

Trust comment: Large, multicenter randomized controlled trial with robust sample size and clinically relevant endpoints.

Study Details

PMID:16641396
Participants:1877
Impact:-12% (8.7% vs 9.9%; RR 0.87)
Trust score:5/5

interleukin-6

1 evidences

Doubling antioxidant intake via supplements (including vitamin C) or foods for 8 weeks did not change measured inflammatory markers in adults at CVD risk.

Trust comment: Randomized pilot RCT with objective biomarker outcomes but modest sample size limits power.

Study Details

PMID:29540273
Participants:88
Impact:no significant change
Trust score:3/5

monocyte chemotactic protein-1

1 evidences

Doubling antioxidant intake via supplements (including vitamin C) or foods for 8 weeks did not change measured inflammatory markers in adults at CVD risk.

Trust comment: Randomized pilot RCT with objective biomarker outcomes but modest sample size limits power.

Study Details

PMID:29540273
Participants:88
Impact:no significant change
Trust score:3/5

soluble intercellular adhesion molecule-1

1 evidences

Doubling antioxidant intake via supplements (including vitamin C) or foods for 8 weeks did not change measured inflammatory markers in adults at CVD risk.

Trust comment: Randomized pilot RCT with objective biomarker outcomes but modest sample size limits power.

Study Details

PMID:29540273
Participants:88
Impact:no significant change
Trust score:3/5

lipid peroxide (TBARS)

1 evidences

In CHD patients over 30 days, vitamin C (1,000 mg) reduced lipid peroxide (TBARS) but did not change lipid concentrations.

Trust comment: Randomized controlled design (Latin-square) in CHD patients with objective biochemical endpoints; short duration (30 days) limits long-term inference.

Study Details

PMID:11291971
Participants:175
Impact:-19.8% (mean change in vitamin C group)
Trust score:4/5

lipid profile (total/HDL/LDL/triglycerides)

1 evidences

In CHD patients over 30 days, vitamin C (1,000 mg) reduced lipid peroxide (TBARS) but did not change lipid concentrations.

Trust comment: Randomized controlled design (Latin-square) in CHD patients with objective biochemical endpoints; short duration (30 days) limits long-term inference.

Study Details

PMID:11291971
Participants:175
Impact:no significant change
Trust score:4/5

infant wheeze

1 evidences

Higher maternal dietary vitamin C in pregnancy was associated with lower risk of infant wheeze at 1 year; no protective effect was seen for total vitamin C intake including supplements.

Trust comment: Prospective cohort of 300 mother–infant pairs with clinical assessments and multivariate adjustment; observational design limits causal inference.

Study Details

PMID:23201845
Participants:300
Impact:-60% (adjusted OR 0.40 for highest vs lowest dietary vitamin C quartile; 95% CI 0.16–0.98)
Trust score:4/5

any allergic disease (infant)

1 evidences

Higher maternal dietary vitamin C in pregnancy was associated with lower risk of infant wheeze at 1 year; no protective effect was seen for total vitamin C intake including supplements.

Trust comment: Prospective cohort of 300 mother–infant pairs with clinical assessments and multivariate adjustment; observational design limits causal inference.

Study Details

PMID:23201845
Participants:300
Impact:-52% (crude OR 0.48 for highest vs lowest dietary vitamin C quartile; 95% CI 0.25–0.93); adjusted analysis not statistically significant
Trust score:4/5

plasma antioxidant capacity / LDL oxidation (ex vivo)

1 evidences

A fruit/vegetable purée drink acutely raised plasma vitamin C and plasma antioxidant capacity and showed a trend toward improved endothelium-dependent vasodilation.

Trust comment: Randomized, single-blind crossover but small sample (n=24) and short-term (acute) outcomes.

Study Details

PMID:23017441
Participants:24
Impact:increased antioxidant capacity (P = 0.003) and longer LDL oxidation lag phase (trend P = 0.068)
Trust score:3/5

brachial artery flow-mediated dilation (endothelium-dependent)

1 evidences

Oral ascorbic acid markedly raised plasma ascorbate levels but did not improve brachial artery flow‑mediated (endothelium-dependent) dilation in hypertensive patients; chronic treatment previously reported to lower blood pressure.

Trust comment: Randomized, double-blind, placebo-controlled trial in hypertensive patients with objective vascular measures, but modest sample size.

Study Details

PMID:11158948
Participants:39
Impact:no change (no improvement with acute or chronic ascorbic acid)
Trust score:4/5

systolic and mean blood pressure

1 evidences

Oral ascorbic acid markedly raised plasma ascorbate levels but did not improve brachial artery flow‑mediated (endothelium-dependent) dilation in hypertensive patients; chronic treatment previously reported to lower blood pressure.

Trust comment: Randomized, double-blind, placebo-controlled trial in hypertensive patients with objective vascular measures, but modest sample size.

Study Details

PMID:11158948
Participants:39
Impact:chronic ascorbic acid therapy was reported to reduce systolic and mean BP (reduction reported by authors; magnitude not provided in excerpt)
Trust score:4/5

systolic and diastolic blood pressure

1 evidences

Combined antioxidant supplementation including 500 mg/day vitamin C for 2–4 months had no significant effect on blood pressure, serum lipids or fasting glucose in older adults.

Trust comment: Large randomized placebo-controlled trial (n=297) with clear null results for traditional CVD risk factors.

Study Details

PMID:9215516
Participants:297
Impact:no significant change after supplementation
Trust score:4/5

fasting serum lipids (total, HDL, LDL)

1 evidences

Combined antioxidant supplementation including 500 mg/day vitamin C for 2–4 months had no significant effect on blood pressure, serum lipids or fasting glucose in older adults.

Trust comment: Large randomized placebo-controlled trial (n=297) with clear null results for traditional CVD risk factors.

Study Details

PMID:9215516
Participants:297
Impact:no significant change after supplementation
Trust score:4/5

fasting glucose

2 evidences

Combined antioxidant supplementation including 500 mg/day vitamin C for 2–4 months had no significant effect on blood pressure, serum lipids or fasting glucose in older adults.

Trust comment: Large randomized placebo-controlled trial (n=297) with clear null results for traditional CVD risk factors.

Study Details

PMID:9215516
Participants:297
Impact:no significant change after supplementation
Trust score:4/5

Three months of community yoga lowered oxidative stress (MDA) and improved BMI, waist, systolic BP and fasting glucose but did not change vitamin C levels.

Trust comment: Small RCT with objective oxidative stress measures; vitamin C was measured as an antioxidant but showed no effect.

Study Details

PMID:24280463
Participants:29
Impact:decrease — significant
Trust score:3/5

serum ferritin and iron deficiency prevalence

1 evidences

Adding guava to a supplemental meal increased vitamin C and improved iron status in preschoolers; the study measured B12 but did not report a B12 effect.

Trust comment: Cluster-RCT (n=399) with objective biomarker outcomes and clear statistically significant effects on iron status.

Study Details

PMID:33385184
Participants:399
Impact:serum ferritin increased (P < 0.001) with decreased iron deficiency prevalence (P = 0.003)
Trust score:4/5

sustained attention (CPT‑IP d')

1 evidences

In patients with schizophrenia, vitamins E+C (including vitamin C 1000 mg/day) impaired sustained attention in a subgroup and produced adverse neurocognitive effects unless combined with ethyl‑EPA.

Trust comment: Randomized controlled trial but small sample and subgroup effects; findings limited to specific neurocognitive measure and patient subgroups.

Study Details

PMID:29079039
Participants:53
Impact:impairment with Vitamins E+C alone in high PUFA patients, effect size d = 0.69 (statistically significant)
Trust score:3/5

other neurocognitive tests

1 evidences

In patients with schizophrenia, vitamins E+C (including vitamin C 1000 mg/day) impaired sustained attention in a subgroup and produced adverse neurocognitive effects unless combined with ethyl‑EPA.

Trust comment: Randomized controlled trial but small sample and subgroup effects; findings limited to specific neurocognitive measure and patient subgroups.

Study Details

PMID:29079039
Participants:53
Impact:no significant effects reported
Trust score:3/5

24 h PCA morphine consumption

1 evidences

A single 2 g oral vitamin C given 1 hour before major abdominal surgery reduced pain scores, lowered morphine use, and decreased need for extra analgesic compared with placebo.

Trust comment: Prospective, double-blind randomized controlled trial with adequate sample size and clinically relevant endpoints.

Study Details

PMID:31465720
Participants:165
Impact:22.2 ± 6.5 mg (vit C) vs 24.6 ± 8.4 mg (placebo) at 24 h; lower with vitamin C (absolute −2.4 mg)
Trust score:4/5

supplement analgesic requirement (diclofenac)

1 evidences

A single 2 g oral vitamin C given 1 hour before major abdominal surgery reduced pain scores, lowered morphine use, and decreased need for extra analgesic compared with placebo.

Trust comment: Prospective, double-blind randomized controlled trial with adequate sample size and clinically relevant endpoints.

Study Details

PMID:31465720
Participants:165
Impact:23.6% (vit C) vs 41.8% (placebo); absolute −18.2 percentage points
Trust score:4/5

MDA-TBARS (marker of lipid peroxidation)

1 evidences

Intraoperative antioxidant infusion containing tocopherol and ascorbate attenuated the immediate rise in lipid-peroxidation marker after reperfusion and improved prothrombin time.

Trust comment: Randomized prospective trial with objective biomarkers but small N and combined antioxidant (tocopherol+ascorbate) limits attribution to vitamin C alone.

Study Details

PMID:10400458
Participants:50
Impact:Attenuated rise at 30 min after reperfusion in treatment group vs significant increase in control (between-group p = 0.007)
Trust score:3/5

prothrombin time

1 evidences

Intraoperative antioxidant infusion containing tocopherol and ascorbate attenuated the immediate rise in lipid-peroxidation marker after reperfusion and improved prothrombin time.

Trust comment: Randomized prospective trial with objective biomarkers but small N and combined antioxidant (tocopherol+ascorbate) limits attribution to vitamin C alone.

Study Details

PMID:10400458
Participants:50
Impact:Prothrombin time significantly better in treatment group (p = 0.003)
Trust score:3/5

postoperative complications

2 evidences

Randomized, triple‑blind trial of perioperative ascorbic acid vs placebo in CABG patients; monitored postoperative atrial fibrillation and complications.

Trust comment: Randomized, triple‑blind trial with adequate sample and clear clinical endpoints; well‑reported negative finding.

Study Details

PMID:23022248
Participants:185
Impact:no difference (no significant differences reported)
Trust score:4/5

Intraoperative antioxidant infusion containing tocopherol and ascorbate attenuated the immediate rise in lipid-peroxidation marker after reperfusion and improved prothrombin time.

Trust comment: Randomized prospective trial with objective biomarkers but small N and combined antioxidant (tocopherol+ascorbate) limits attribution to vitamin C alone.

Study Details

PMID:10400458
Participants:50
Impact:Fewer prolonged liver failure/bleeding/infections in treatment group (reported qualitatively)
Trust score:3/5

presence of carotid plaques

1 evidences

Long-term low-dose combined antioxidant supplementation (including 120 mg vitamin C) showed no benefit on carotid intima-media thickness or arterial stiffness and had a higher proportion of carotid plaques in the intervention group.

Trust comment: Large, long-term randomized trial substudy but tested a multi-nutrient combination (including vitamin C), so effects cannot be attributed to vitamin C alone.

Study Details

PMID:15217803
Participants:1162
Impact:35.2% (intervention) vs 29.5% (placebo); P = 0.04 (higher in supplementation group)
Trust score:3/5

common carotid intima-media thickness (cIMT)

1 evidences

Long-term low-dose combined antioxidant supplementation (including 120 mg vitamin C) showed no benefit on carotid intima-media thickness or arterial stiffness and had a higher proportion of carotid plaques in the intervention group.

Trust comment: Large, long-term randomized trial substudy but tested a multi-nutrient combination (including vitamin C), so effects cannot be attributed to vitamin C alone.

Study Details

PMID:15217803
Participants:1162
Impact:No difference between groups (0.70 ± 0.08 mm vs 0.70 ± 0.08 mm; P = 0.38)
Trust score:3/5

carotid-femoral pulse-wave velocity (PWV)

1 evidences

Long-term low-dose combined antioxidant supplementation (including 120 mg vitamin C) showed no benefit on carotid intima-media thickness or arterial stiffness and had a higher proportion of carotid plaques in the intervention group.

Trust comment: Large, long-term randomized trial substudy but tested a multi-nutrient combination (including vitamin C), so effects cannot be attributed to vitamin C alone.

Study Details

PMID:15217803
Participants:1162
Impact:Trend toward lower PWV in intervention but not statistically significant (P = 0.13)
Trust score:3/5

all-cause mortality (age ≥71)

1 evidences

In this secondary analysis of the ATBC trial, vitamin E extended lifespan in older men (≥71 years) and particularly in the subgroup with higher dietary vitamin C intake who smoked <1 pack/day.

Trust comment: Large randomized trial with subgroup analyses indicating interaction with dietary vitamin C, but findings are subgroup-specific and observational in nature within the trial.

Study Details

PMID:21242192
Participants:10837
Impact:Vitamin E reduced mortality by 24% among participants aged 71+
Trust score:3/5

lifespan extension in subgroup

1 evidences

In this secondary analysis of the ATBC trial, vitamin E extended lifespan in older men (≥71 years) and particularly in the subgroup with higher dietary vitamin C intake who smoked <1 pack/day.

Trust comment: Large randomized trial with subgroup analyses indicating interaction with dietary vitamin C, but findings are subgroup-specific and observational in nature within the trial.

Study Details

PMID:21242192
Participants:10837
Impact:In men with dietary vitamin C above median and <1 pack/day smoking, vitamin E extended lifespan by ~2 years (divergence at age 71)
Trust score:3/5

leukocyte vitamin C level

1 evidences

In adults with stable asthma, 1000 mg/day vitamin C for 1 month increased leukocyte vitamin C levels but did not improve lung function.

Trust comment: Double-blind randomized trial in 60 patients but short (1 month) and relatively small, limiting generalizability.

Study Details

PMID:22592572
Participants:60
Impact:+0.0497 µg/10^8 leukocytes (+55%)
Trust score:4/5

FEV1 (spirometry)

1 evidences

In adults with stable asthma, 1000 mg/day vitamin C for 1 month increased leukocyte vitamin C levels but did not improve lung function.

Trust comment: Double-blind randomized trial in 60 patients but short (1 month) and relatively small, limiting generalizability.

Study Details

PMID:22592572
Participants:60
Impact:no change with vitamin C
Trust score:4/5

CCE excretion rate

1 evidences

Randomized trial comparing 2L PEG+ascorbic acid versus 4L PEG for colon capsule prep found similar cleansing but higher capsule excretion rate with the ascorbic-acid regimen.

Trust comment: Prospective randomized study with moderate sample size (n=58); endpoints clinically relevant though sample is small.

Study Details

PMID:25287233
Participants:58
Impact:+23 percentage points (93% vs 70%, P=0.043)
Trust score:3/5

colonic cleansing (excellent-good)

1 evidences

Randomized trial comparing 2L PEG+ascorbic acid versus 4L PEG for colon capsule prep found similar cleansing but higher capsule excretion rate with the ascorbic-acid regimen.

Trust comment: Prospective randomized study with moderate sample size (n=58); endpoints clinically relevant though sample is small.

Study Details

PMID:25287233
Participants:58
Impact:78% vs 64% (no significant difference, P=0.252)
Trust score:3/5

ROS release from inflammatory cells

1 evidences

In chronic bronchitis patients, 500 mg vitamin C twice daily (alone or with NAC) for 3 months did not reduce inflammatory cell ROS release, change glutathione, or improve symptoms/ spirometry.

Trust comment: Randomized double-blind placebo-controlled trial with 100 patients; well-designed though outcomes were negative.

Study Details

PMID:15761783
Participants:100
Impact:no change
Trust score:4/5

intracellular glutathione levels

1 evidences

In chronic bronchitis patients, 500 mg vitamin C twice daily (alone or with NAC) for 3 months did not reduce inflammatory cell ROS release, change glutathione, or improve symptoms/ spirometry.

Trust comment: Randomized double-blind placebo-controlled trial with 100 patients; well-designed though outcomes were negative.

Study Details

PMID:15761783
Participants:100
Impact:no change
Trust score:4/5

spirometry and symptoms

1 evidences

In chronic bronchitis patients, 500 mg vitamin C twice daily (alone or with NAC) for 3 months did not reduce inflammatory cell ROS release, change glutathione, or improve symptoms/ spirometry.

Trust comment: Randomized double-blind placebo-controlled trial with 100 patients; well-designed though outcomes were negative.

Study Details

PMID:15761783
Participants:100
Impact:no change
Trust score:4/5

time to resolution of vasoplegia

1 evidences

High-dose IV vitamin C after cardiac surgery was feasible and safe but did not significantly speed resolution of vasoplegia.

Trust comment: Small, double-blind randomized pilot RCT (50 patients) with appropriate design but underpowered to detect modest effects.

Study Details

PMID:31526557
Participants:50
Impact:-7.7 hours (mean: 27.0 vs 34.7 h), p=0.40 (not significant)
Trust score:3/5

norepinephrine equivalent dose (first 2 days)

1 evidences

High-dose IV vitamin C after cardiac surgery was feasible and safe but did not significantly speed resolution of vasoplegia.

Trust comment: Small, double-blind randomized pilot RCT (50 patients) with appropriate design but underpowered to detect modest effects.

Study Details

PMID:31526557
Participants:50
Impact:median 64.9 vs 47.4 µg/kg (vitamin C vs placebo), p=0.75 (no significant change)
Trust score:3/5

ICU length of stay

2 evidences

High-dose IV vitamin C after cardiac surgery was feasible and safe but did not significantly speed resolution of vasoplegia.

Trust comment: Small, double-blind randomized pilot RCT (50 patients) with appropriate design but underpowered to detect modest effects.

Study Details

PMID:31526557
Participants:50
Impact:median 1.4 vs 1.5 days, p=0.36 (no significant change)
Trust score:3/5

Double-blind randomized trial giving high-dose IV and cardioplegia vitamin C in CABG patients found no change in cardiac enzymes but improved ejection fraction and shorter ICU stay.

Trust comment: Randomized double-blind surgical trial with clear vitamin C dosing but small sample size and single-center design limit generalizability.

Study Details

PMID:31719005
Participants:50
Impact:shorter in vitamin C group (1.22 vs 1.58 days; significant)
Trust score:3/5

antioxidative/prooxidative status (plasma)

1 evidences

In older women doing 6 weeks of moderate training, 1000 mg/day vitamin C raised blood vitamin C but did not produce clear changes in antioxidant balance or inflammatory gene expression.

Trust comment: Randomized, double-blind trial but very small sample (n=24) with baseline composition differences limiting generalizability.

Study Details

PMID:33653365
Participants:24
Impact:no significant beneficial change; SUP had higher antioxidative status than CON at end (298.5 vs 278.4 µmol/L, p=0.03) but overall no clear improvement
Trust score:3/5

inflammatory gene expression (IL-6, IL-10, CCL2)

1 evidences

In older women doing 6 weeks of moderate training, 1000 mg/day vitamin C raised blood vitamin C but did not produce clear changes in antioxidant balance or inflammatory gene expression.

Trust comment: Randomized, double-blind trial but very small sample (n=24) with baseline composition differences limiting generalizability.

Study Details

PMID:33653365
Participants:24
Impact:no significant changes in SUP; IL-6 tended to decrease and IL-10 tended to increase (not significant); CCL2 decreased significantly only in control group (p=0.01)
Trust score:3/5

overall quality of cleansing

1 evidences

A low-volume PEG solution containing ascorbic acid provided effective bowel cleansing and better proximal colon cleansing versus comparator in this pilot study.

Trust comment: Single-blind randomized pilot (n=65); clinically relevant endpoints but modest sample size and pilot design.

Study Details

PMID:18179734
Participants:65
Impact:higher with PEG+ascorbic acid (p=0.018); significantly better cleansing in ascending colon (p=0.024) and caecum (p=0.003)
Trust score:3/5

time to neutrophil recovery (engraftment)

1 evidences

In autologous SCT patients, vitamin C supplementation raised serum vitamin C but did not shorten time to neutrophil recovery; transient higher cytotoxic T cells and a lower (non-significant) bacteremia rate were observed.

Trust comment: Well-designed triple-blind randomized trial (44 patients) with appropriate endpoints; limited size reduces power for some clinical outcomes.

Study Details

PMID:36432471
Participants:44
Impact:no difference; mean 11.2 days in both groups (no effect)
Trust score:4/5

cytotoxic T-cell count at repopulation

1 evidences

In autologous SCT patients, vitamin C supplementation raised serum vitamin C but did not shorten time to neutrophil recovery; transient higher cytotoxic T cells and a lower (non-significant) bacteremia rate were observed.

Trust comment: Well-designed triple-blind randomized trial (44 patients) with appropriate endpoints; limited size reduces power for some clinical outcomes.

Study Details

PMID:36432471
Participants:44
Impact:higher in vitamin C group at repopulation (statistically significant at repopulation but not at end of study); transient effect
Trust score:4/5

mucosal inflammation/ulceration

1 evidences

In outpatients undergoing colonoscopy, low-volume PEG with vitamin C gave similar overall cleansing and mucosal injury rates but more residual colonic fluid and better patient acceptance.

Trust comment: Randomized, investigator-blinded RCT with adequate sample size but single-center and limited generalizability.

Study Details

PMID:26260754
Participants:319
Impact:SD-PEG 3.1% (5/160) vs LV-PEG+Asc 3.7% (6/159); no significant difference
Trust score:4/5

overall bowel cleansing score (Ottawa)

1 evidences

In outpatients undergoing colonoscopy, low-volume PEG with vitamin C gave similar overall cleansing and mucosal injury rates but more residual colonic fluid and better patient acceptance.

Trust comment: Randomized, investigator-blinded RCT with adequate sample size but single-center and limited generalizability.

Study Details

PMID:26260754
Participants:319
Impact:4.19±2.261 vs 4.41±2.066; no significant difference (p=0.376)
Trust score:4/5

colonic fluid quantity

1 evidences

In outpatients undergoing colonoscopy, low-volume PEG with vitamin C gave similar overall cleansing and mucosal injury rates but more residual colonic fluid and better patient acceptance.

Trust comment: Randomized, investigator-blinded RCT with adequate sample size but single-center and limited generalizability.

Study Details

PMID:26260754
Participants:319
Impact:0.66±0.623 vs 0.81±0.542; greater fluid with LV-PEG+Asc (p=0.023)
Trust score:4/5

patient acceptance/preference

1 evidences

In outpatients undergoing colonoscopy, low-volume PEG with vitamin C gave similar overall cleansing and mucosal injury rates but more residual colonic fluid and better patient acceptance.

Trust comment: Randomized, investigator-blinded RCT with adequate sample size but single-center and limited generalizability.

Study Details

PMID:26260754
Participants:319
Impact:better for LV-PEG+Asc (p=0.001)
Trust score:4/5

HCV viral load

1 evidences

In 30 HCV patients, adding black cumin and vitamin C to standard antivirals showed small improvements in hematologic and antioxidant markers and a significant drop in fasting glucose, but most comparisons were not statistically significant.

Trust comment: Prospective randomized trial but very small sample (n=30) with mostly non-significant differences limiting confidence.

Study Details

PMID:32566096
Participants:30
Impact:eradicated to undetectable in all patients in both groups after 8 weeks
Trust score:3/5

total antioxidant status (TAS) / GSH / SOD / MDA

1 evidences

In 30 HCV patients, adding black cumin and vitamin C to standard antivirals showed small improvements in hematologic and antioxidant markers and a significant drop in fasting glucose, but most comparisons were not statistically significant.

Trust comment: Prospective randomized trial but very small sample (n=30) with mostly non-significant differences limiting confidence.

Study Details

PMID:32566096
Participants:30
Impact:slight improvement in treated vs control but not statistically significant (P > 0.05)
Trust score:3/5

hematological parameters (RBC, WBC, Hb, platelets)

1 evidences

In 30 HCV patients, adding black cumin and vitamin C to standard antivirals showed small improvements in hematologic and antioxidant markers and a significant drop in fasting glucose, but most comparisons were not statistically significant.

Trust comment: Prospective randomized trial but very small sample (n=30) with mostly non-significant differences limiting confidence.

Study Details

PMID:32566096
Participants:30
Impact:increased trends in treated group vs control; differences not significant (P > 0.05)
Trust score:3/5

oxidative stress / reactive oxygen species

1 evidences

In 25 men, daily blond orange juice produced a marked antioxidant effect (linked to hesperetin) and trends toward improved endothelial function and modest apoA-I increase compared with a control beverage that contained vitamin C but lacked phytomicronutrients.

Trust comment: Randomized cross-over pilot with small sample; effects attributed to phytochemicals rather than vitamin C alone.

Study Details

PMID:25865966
Participants:25
Impact:marked antioxidant effect with orange juice; decrease in reactive oxygen species (correlated with hesperetin)
Trust score:3/5

endothelial function

1 evidences

In 25 men, daily blond orange juice produced a marked antioxidant effect (linked to hesperetin) and trends toward improved endothelial function and modest apoA-I increase compared with a control beverage that contained vitamin C but lacked phytomicronutrients.

Trust comment: Randomized cross-over pilot with small sample; effects attributed to phytochemicals rather than vitamin C alone.

Study Details

PMID:25865966
Participants:25
Impact:tendency toward improvement (not definitive)
Trust score:3/5

plasma apoA-I concentration

1 evidences

In 25 men, daily blond orange juice produced a marked antioxidant effect (linked to hesperetin) and trends toward improved endothelial function and modest apoA-I increase compared with a control beverage that contained vitamin C but lacked phytomicronutrients.

Trust comment: Randomized cross-over pilot with small sample; effects attributed to phytochemicals rather than vitamin C alone.

Study Details

PMID:25865966
Participants:25
Impact:modest increase observed
Trust score:3/5

IL-6 level at 72 h

1 evidences

IV vitamin C plus thiamine in early septic shock did not change prognostic biomarker levels (IL-6, IL-10, angiopoietin-II, S100β) at 72 hours.

Trust comment: Multicenter double-blind RCT dataset used for post-hoc biomarker analysis; negative result but reasonably powered for clinical trial context.

Study Details

PMID:34482319
Participants:97
Impact:no significant difference between treatment and placebo
Trust score:4/5

IL-10 level at 72 h

1 evidences

IV vitamin C plus thiamine in early septic shock did not change prognostic biomarker levels (IL-6, IL-10, angiopoietin-II, S100β) at 72 hours.

Trust comment: Multicenter double-blind RCT dataset used for post-hoc biomarker analysis; negative result but reasonably powered for clinical trial context.

Study Details

PMID:34482319
Participants:97
Impact:no significant difference between treatment and placebo
Trust score:4/5

angiopoietin-II and S100β at 72 h

1 evidences

IV vitamin C plus thiamine in early septic shock did not change prognostic biomarker levels (IL-6, IL-10, angiopoietin-II, S100β) at 72 hours.

Trust comment: Multicenter double-blind RCT dataset used for post-hoc biomarker analysis; negative result but reasonably powered for clinical trial context.

Study Details

PMID:34482319
Participants:97
Impact:no significant differences or reduction-rate differences between groups
Trust score:4/5

endothelium-dependent vasodilation (acetylcholine response)

1 evidences

In a controlled crossover study (24 subjects across three groups), acute vitamin C infusion improved acetylcholine-mediated endothelial responses in type 1 diabetes patients and regular smokers.

Trust comment: Small, well-controlled physiologic crossover study showing acute effects; limited by small sample and single-dose setting.

Study Details

PMID:17065352
Participants:24
Impact:improved after 1,000 mg vitamin C infusion in patients with type 1 diabetes and in regular smokers (P < 0.05–0.01)
Trust score:3/5

flow-mediated dilatation (endothelial function)

1 evidences

Controlled exposure to fine particulates (± ozone) increased diastolic blood pressure and, in one location, impaired endothelial function; high-dose vitamin C (2 g) pretreatment did not prevent the BP rise or endothelial impairment.

Trust comment: Randomized, double-blind, crossover human exposure study with objective vascular and BP measures; moderate sample size and clear negative finding for high-dose vitamin C as a mitigator.

Study Details

PMID:19620518
Participants:81
Impact:Decreased 2.0% and 2.9% 24 h after particle-containing exposures in Toronto; in Ann Arbor FMD was unaltered and not mitigated by pretreatments including vitamin C
Trust score:4/5

nausea frequency

1 evidences

Adding orange juice to PEG–ascorbic acid bowel prep improved taste and reduced nausea without reducing cleansing efficacy.

Trust comment: Single-blind randomized trial in ambulatory patients showing improved tolerability with orange juice added to ascorbic-acid–containing prep; sample moderate size but limited to ambulatory setting.

Study Details

PMID:25203380
Participants:107
Impact:26.4% vs 59.3% (p=0.001), reduced with orange juice
Trust score:3/5

contrast-induced nephropathy (CIN) rate

1 evidences

Adding oral vitamin C to standard saline hydration did not significantly reduce contrast-induced kidney injury compared with hydration alone.

Trust comment: Single-center randomized trial with adequate sample size (n=243) but found no significant benefit of ascorbic acid.

Study Details

PMID:22994682
Participants:243
Impact:Ascorbic acid group 3.6% vs control 7.7% (difference not statistically significant)
Trust score:4/5

serum creatinine increase ≥0.5 mg/dL

1 evidences

Adding oral vitamin C to standard saline hydration did not significantly reduce contrast-induced kidney injury compared with hydration alone.

Trust comment: Single-center randomized trial with adequate sample size (n=243) but found no significant benefit of ascorbic acid.

Study Details

PMID:22994682
Participants:243
Impact:3.6% (ascorbic acid) vs 6.2% (control); no significant difference
Trust score:4/5

cognitive performance (MMSE)

1 evidences

Daily vitamins E+C for 1 year improved antioxidant biomarkers but did not improve cognitive test scores in elderly with mild cognitive impairment.

Trust comment: Large double-blind randomized placebo-controlled trial with objective biomarkers but no cognitive benefit observed.

Study Details

PMID:24326981
Participants:256
Impact:No significant improvement after 6 or 12 months (e.g., 12-month MMSE ~26.8 vs 26.59 for control; not significant)
Trust score:4/5

total antioxidant capacity / glutathione

1 evidences

Daily vitamins E+C for 1 year improved antioxidant biomarkers but did not improve cognitive test scores in elderly with mild cognitive impairment.

Trust comment: Large double-blind randomized placebo-controlled trial with objective biomarkers but no cognitive benefit observed.

Study Details

PMID:24326981
Participants:256
Impact:Total antioxidant capacity increased (P < 0.001); glutathione increased (P < 0.01)
Trust score:4/5

hemoglobin (older adults ≥65)

1 evidences

Daily oral iron plus vitamin C for ~30 days prevented hemoglobin loss in older adults awaiting orthopedic surgery; overall effects in the whole cohort were limited.

Trust comment: Randomized but open-label and relatively small with subgroup-dependent effects; vitamin C was used as an enhancer with iron rather than tested alone.

Study Details

PMID:32024027
Participants:73
Impact:Intervention prevented Hb loss: intervention ~13.6 → 13.7 g/dL vs control 13.8 → 13.4 g/dL (older adults Δ +0.7% vs −2.8%; p = 0.019)
Trust score:3/5

overall cohort hematologic markers

1 evidences

Daily oral iron plus vitamin C for ~30 days prevented hemoglobin loss in older adults awaiting orthopedic surgery; overall effects in the whole cohort were limited.

Trust comment: Randomized but open-label and relatively small with subgroup-dependent effects; vitamin C was used as an enhancer with iron rather than tested alone.

Study Details

PMID:32024027
Participants:73
Impact:No statistically significant changes across entire cohort after treatment
Trust score:3/5

quadriceps DOMS

1 evidences

In moderately trained men, 2 weeks of vitamin C (1000 mg/day) plus vitamin E reduced quadriceps soreness and markers of muscle damage and increased antioxidant capacity after repeated downhill runs.

Trust comment: Randomized placebo-controlled trial but small sample and co‑supplementation with vitamin E limits attribution to vitamin C alone.

Study Details

PMID:25607519
Participants:22
Impact:−1.1 points (1.1 vs 2.2, supplement vs placebo)
Trust score:3/5

creatine kinase (CK) at 24 h after 2nd downhill run

1 evidences

In moderately trained men, 2 weeks of vitamin C (1000 mg/day) plus vitamin E reduced quadriceps soreness and markers of muscle damage and increased antioxidant capacity after repeated downhill runs.

Trust comment: Randomized placebo-controlled trial but small sample and co‑supplementation with vitamin E limits attribution to vitamin C alone.

Study Details

PMID:25607519
Participants:22
Impact:reduced at 24 h POST after the 2nd run (vs 1st run; P<0.01)
Trust score:3/5

antioxidant capacity (ORAC)

1 evidences

In moderately trained men, 2 weeks of vitamin C (1000 mg/day) plus vitamin E reduced quadriceps soreness and markers of muscle damage and increased antioxidant capacity after repeated downhill runs.

Trust comment: Randomized placebo-controlled trial but small sample and co‑supplementation with vitamin E limits attribution to vitamin C alone.

Study Details

PMID:25607519
Participants:22
Impact:increased at 24 h POST after the 2nd run (P<0.05)
Trust score:3/5

F2‑isoprostanes

1 evidences

In healthy adults, serum vitamin C concentrations differed by GST genotype and were associated with differences in oxidative stress biomarkers.

Trust comment: Large cross-sectional biomarker study with genotyping; observational associations cannot prove causation.

Study Details

PMID:21813807
Participants:383
Impact:lower in GSTM1‑0 but significance lost after adjustment for serum vitamin C
Trust score:4/5

malondialdehyde

1 evidences

In healthy adults, serum vitamin C concentrations differed by GST genotype and were associated with differences in oxidative stress biomarkers.

Trust comment: Large cross-sectional biomarker study with genotyping; observational associations cannot prove causation.

Study Details

PMID:21813807
Participants:383
Impact:lower in GSTT1‑0 but significance lost after adjustment for serum vitamin C
Trust score:4/5

hemolysis markers (hemoglobin/hematocrit/erythrocyte morphology)

1 evidences

In 51 high‑risk premature infants, daily ascorbic acid (100 mg/kg) during the first week prevented the normal postnatal drop in levels and was not associated with increased hemolysis or short‑term adverse outcomes.

Trust comment: Double‑blind randomized trial in premature infants but small sample limits power to detect differences in clinical outcomes.

Study Details

PMID:9514139
Participants:51
Impact:no evidence of increased hemolysis
Trust score:4/5

clinical adverse outcomes (renal function, infection, BPD, IVH)

1 evidences

In 51 high‑risk premature infants, daily ascorbic acid (100 mg/kg) during the first week prevented the normal postnatal drop in levels and was not associated with increased hemolysis or short‑term adverse outcomes.

Trust comment: Double‑blind randomized trial in premature infants but small sample limits power to detect differences in clinical outcomes.

Study Details

PMID:9514139
Participants:51
Impact:no significant differences between groups
Trust score:4/5

albumin‑to‑creatinine ratio ≥30

1 evidences

Cross‑sectional baseline data from 159 urban African Americans with uncontrolled hypertension showed overall vitamin C intake higher than recommendations, but below‑median intake was associated with greater albuminuria.

Trust comment: Cross‑sectional, self‑reported dietary data; associations reported but cannot infer causality.

Study Details

PMID:30709714
Participants:159
Impact:below‑median vitamin C intake associated with higher odds (adjusted OR 3.4; 95% CI 1.5–7.8)
Trust score:3/5

estimated GFR <60

1 evidences

Cross‑sectional baseline data from 159 urban African Americans with uncontrolled hypertension showed overall vitamin C intake higher than recommendations, but below‑median intake was associated with greater albuminuria.

Trust comment: Cross‑sectional, self‑reported dietary data; associations reported but cannot infer causality.

Study Details

PMID:30709714
Participants:159
Impact:no significant association with vitamin C intake
Trust score:3/5

urinary oxalate excretion

1 evidences

In calcium stone formers, vitamin C intake correlated with urinary oxalate excretion; an oxalate food load without calcium raised urinary oxalate by ~20%.

Trust comment: Prospective dietary assessment with urine measures but observational correlation and modest sample size limit inference about causation.

Study Details

PMID:12563622
Participants:111
Impact:positively correlated with vitamin C intake in calcium stone formers
Trust score:3/5

oxalate excretion after dark chocolate (oxalate load)

1 evidences

In calcium stone formers, vitamin C intake correlated with urinary oxalate excretion; an oxalate food load without calcium raised urinary oxalate by ~20%.

Trust comment: Prospective dietary assessment with urine measures but observational correlation and modest sample size limit inference about causation.

Study Details

PMID:12563622
Participants:111
Impact:+20% (36 vs 30 mg/24 hr) after dark chocolate; co‑ingestion of calcium mitigated increase
Trust score:3/5

insulin resistance (HOMA-IR)

4 evidences

In a randomized crossover trial of overweight/obese adolescents (58 completers), an anti-inflammatory supplement containing vitamin C maintained high-molecular-weight adiponectin but did not change insulin resistance overall; a subgroup (n=23) showed ≥10% improvement in HOMA-IR.

Trust comment: Randomized, double-blind, placebo-controlled crossover with biologic measures and compliance data, though sample size is modest and supplement was multi-nutrient (vitamin C not isolated).

Study Details

PMID:29665620
Participants:58
Impact:no change in total cohort; in a responder subgroup (n=23) HOMA-IR decreased ≥10% with AINS (responder-by-intervention p=0.001; vs placebo p=0.004)
Trust score:4/5

In children with NAFLD, adding vitamin E plus vitamin C to diet/exercise did not improve liver enzymes, insulin resistance, or weight loss compared with placebo.

Trust comment: Double-blind RCT in 90 pediatric NAFLD patients; well-conducted but vitamin C was given with vitamin E so individual C effect is not isolated.

Study Details

PMID:17206944
Participants:90
Impact:no significant difference between antioxidant and placebo at 12 months (P = NS)
Trust score:4/5

A combined nutraceutical containing bergamot extract and phytosterols improved triglycerides, LDL-C, and insulin resistance markers versus placebo in overweight dyslipidemic subjects.

Trust comment: Well-designed double-blind placebo-controlled RCT but the intervention was a multi-ingredient nutraceutical (including vitamin C), so individual contribution of vitamin C is not isolated.

Study Details

PMID:31225673
Participants:90
Impact:decrease — significant
Trust score:4/5

In type 2 diabetic men on metformin, daily vitamin C (alone or with vitamin E) for 90 days improved glycemic control, insulin resistance measures, and some oxidative stress markers versus placebo.

Trust comment: Randomized single-blind trial showing beneficial signals, but small sample size per arm and single-blind design limit confidence and generalizability.

Study Details

PMID:29571976
Participants:40
Impact:improvement compared with placebo (reported qualitatively)
Trust score:3/5

weight loss (percent excessive body weight)

1 evidences

In children with NAFLD, adding vitamin E plus vitamin C to diet/exercise did not improve liver enzymes, insulin resistance, or weight loss compared with placebo.

Trust comment: Double-blind RCT in 90 pediatric NAFLD patients; well-conducted but vitamin C was given with vitamin E so individual C effect is not isolated.

Study Details

PMID:17206944
Participants:90
Impact:no significant difference between antioxidant and placebo at 12 months (32% vs 35%; P = NS)
Trust score:4/5

maternal adiponectin at delivery

1 evidences

Secondary analysis of a prenatal vitamin C+E trial: maternal adiponectin at delivery was slightly higher with vitamins overall, while cord blood adiponectin did not differ; effects varied by baseline adiponectin tertile.

Trust comment: Secondary analysis of a randomized prenatal trial with decent sample size, but being secondary limits causal interpretation for adiponectin outcomes.

Study Details

PMID:40049594
Participants:198
Impact:higher with vitamins (29.4 vs 27.5 µg/mL; p = 0.04)
Trust score:4/5

cord blood adiponectin

1 evidences

Secondary analysis of a prenatal vitamin C+E trial: maternal adiponectin at delivery was slightly higher with vitamins overall, while cord blood adiponectin did not differ; effects varied by baseline adiponectin tertile.

Trust comment: Secondary analysis of a randomized prenatal trial with decent sample size, but being secondary limits causal interpretation for adiponectin outcomes.

Study Details

PMID:40049594
Participants:198
Impact:no significant difference (26.6 vs 27.4 µg/mL; p = 0.47)
Trust score:4/5

treatment × baseline interaction

1 evidences

Secondary analysis of a prenatal vitamin C+E trial: maternal adiponectin at delivery was slightly higher with vitamins overall, while cord blood adiponectin did not differ; effects varied by baseline adiponectin tertile.

Trust comment: Secondary analysis of a randomized prenatal trial with decent sample size, but being secondary limits causal interpretation for adiponectin outcomes.

Study Details

PMID:40049594
Participants:198
Impact:vitamin effect differed by baseline tertile: higher maternal adiponectin in high-baseline tertile; lower cord adiponectin in low-baseline tertile (p for interaction <0.05)
Trust score:4/5

plasma vitamin C and E concentrations

1 evidences

Antioxidant vitamins, with or without B-group vitamins (including B12), improved antioxidant capacity, lowered oxidative damage markers and reduced CRP after acute ischemic stroke; B vitamins reduced homocysteine.

Trust comment: Randomized controlled trial in 96 acute stroke patients with clear biomarker changes; sample modest and effects are biochemical/short-term.

Study Details

PMID:16517955
Participants:96
Impact:significantly increased with antioxidant supplementation (reported as significant increases)
Trust score:4/5

malondialdehyde (MDA) and C-reactive protein (CRP)

1 evidences

Antioxidant vitamins, with or without B-group vitamins (including B12), improved antioxidant capacity, lowered oxidative damage markers and reduced CRP after acute ischemic stroke; B vitamins reduced homocysteine.

Trust comment: Randomized controlled trial in 96 acute stroke patients with clear biomarker changes; sample modest and effects are biochemical/short-term.

Study Details

PMID:16517955
Participants:96
Impact:significant reductions in MDA and CRP in supplement groups compared with control
Trust score:4/5

VAS pain scores (early postoperative: 2,6,12,24 h)

1 evidences

A randomized double-blind trial found a single 3 g IV vitamin C dose at induction reduced 0–24 h morphine use, early VAS pain scores, early IL-6 and CRP, and improved early hip flexion after total hip arthroplasty.

Trust comment: Prospective, preregistered double-blind RCT with 100 patients and objective outcomes, though effect sizes are modest and clinical significance debated by authors.

Study Details

PMID:39487511
Participants:100
Impact:significantly lower with vitamin C (e.g., motion at 2 h: 4.72 vs 5.48; −0.76 points; p ≤0.001)
Trust score:4/5

inflammatory markers (IL-6 and CRP at 24 h)

1 evidences

A randomized double-blind trial found a single 3 g IV vitamin C dose at induction reduced 0–24 h morphine use, early VAS pain scores, early IL-6 and CRP, and improved early hip flexion after total hip arthroplasty.

Trust comment: Prospective, preregistered double-blind RCT with 100 patients and objective outcomes, though effect sizes are modest and clinical significance debated by authors.

Study Details

PMID:39487511
Participants:100
Impact:IL-6 24 h: 51.36 vs 60.35 (control) (−8.99 units; p = 0.000); CRP 24 h: 22.33 vs 37.49 (control) (−15.16 units; p = 0.000)
Trust score:4/5

fasting plasma glucose

1 evidences

Daily antioxidant capsule containing 20 mg zinc (among other antioxidants) for 7.5 years had no effect on fasting plasma glucose compared with placebo.

Trust comment: Large randomized primary prevention trial with long follow-up and clear outcome measures; high-quality but combined antioxidants limit isolation of vitamin C effect.

Study Details

PMID:16895889
Participants:3146
Impact:no significant change after 7.5 years of antioxidant (including vitamin C) supplementation
Trust score:4/5

baseline plasma vitamin C (association)

1 evidences

Daily antioxidant capsule containing 20 mg zinc (among other antioxidants) for 7.5 years had no effect on fasting plasma glucose compared with placebo.

Trust comment: Large randomized primary prevention trial with long follow-up and clear outcome measures; high-quality but combined antioxidants limit isolation of vitamin C effect.

Study Details

PMID:16895889
Participants:3146
Impact:baseline plasma vitamin C negatively associated with fasting plasma glucose (higher vitamin C → lower FPG; P=0.0455)
Trust score:4/5

rate of successful bowel preparation

1 evidences

Multicenter randomized trial comparing PEG with ascorbic acid versus oral sulfate solution for colonoscopy bowel prep; no difference in success rates, slightly less vomiting intensity with PEG+ascorbic acid.

Trust comment: Randomized multicenter phase III trial with adequate follow-up and analyzed completers; moderate sample size limits power for tolerability endpoints.

Study Details

PMID:28267011
Participants:167
Impact:no significant difference (91.7% vs 96.4%; P=0.20)
Trust score:4/5

vomiting intensity

1 evidences

Multicenter randomized trial comparing PEG with ascorbic acid versus oral sulfate solution for colonoscopy bowel prep; no difference in success rates, slightly less vomiting intensity with PEG+ascorbic acid.

Trust comment: Randomized multicenter phase III trial with adequate follow-up and analyzed completers; moderate sample size limits power for tolerability endpoints.

Study Details

PMID:28267011
Participants:167
Impact:lower mean vomiting intensity with polyethylene glycol + ascorbic acid (1.6 ± 0.9) vs oral sulfate (1.9 ± 1.1); P=0.02
Trust score:4/5

mMASI score (melasma severity)

1 evidences

Randomized single-blind trial in patients with melasma found both treatments reduced severity; hydroquinone+ascorbic acid gave greater melanin index reduction.

Trust comment: Randomized controlled design but single-blind and modest sample size; vitamin C was part of a combination product so isolated effect cannot be determined.

Study Details

PMID:35510765
Participants:65
Impact:decreased in both groups over 4 months (cysteamine: 6.69→4.47, −2.22; HC (hydroquinone+ascorbic acid): 6.26→3.87, −2.39)
Trust score:3/5

Tinnitus Handicap Inventory (THI) score

1 evidences

Randomized, blinded trial in older adults with tinnitus tested several antioxidant regimens (one included vitamin C) and found no significant benefit on tinnitus scores after six months.

Trust comment: Randomized and blinded with appropriate validated outcome (THI) but small group sizes and multiple agents (vitamin C given in combination) limit attribution to vitamin C.

Study Details

PMID:26547700
Participants:53
Impact:no significant change after treatment and no difference between groups (THI before vs after P=0.848; between-groups P=0.715)
Trust score:3/5

quality of life (related to tinnitus)

1 evidences

Randomized, blinded trial in older adults with tinnitus tested several antioxidant regimens (one included vitamin C) and found no significant benefit on tinnitus scores after six months.

Trust comment: Randomized and blinded with appropriate validated outcome (THI) but small group sizes and multiple agents (vitamin C given in combination) limit attribution to vitamin C.

Study Details

PMID:26547700
Participants:53
Impact:reported improvement in quality-of-life measures across groups (authors note improvement, P≈0.05), but THI changes were not significant
Trust score:3/5

incidence of acute kidney injury (AKI)

1 evidences

Randomized clinical trial in off-pump CABG patients found perioperative oral vitamin C (with other arms) did not reduce incidence or severity of acute kidney injury or related morbidity.

Trust comment: Prospective randomized clinical trial with reasonable sample and clear AKI definitions; oral dosing and low-risk population limit generalizability.

Study Details

PMID:29898141
Participants:272
Impact:no significant reduction with vitamin C (14/67, 20.9%) versus control (10/71, 14.1%); overall AKI incidence 22.1%; P non-significant
Trust score:4/5

PAI-1/PAI-2 ratio

1 evidences

Vitamin C (1000 mg) plus vitamin E given from 16–22 weeks reduced markers of placental dysfunction and lowered pre-eclampsia risk in high‑risk women.

Trust comment: Randomized controlled trial with adequate sample size and clinically relevant endpoints; single-population study so generalizability needs confirmation.

Study Details

PMID:10485722
Participants:283
Impact:-21% during gestation (95% CI 4–35, p=0.015)
Trust score:4/5

pre-eclampsia occurrence

1 evidences

Vitamin C (1000 mg) plus vitamin E given from 16–22 weeks reduced markers of placental dysfunction and lowered pre-eclampsia risk in high‑risk women.

Trust comment: Randomized controlled trial with adequate sample size and clinically relevant endpoints; single-population study so generalizability needs confirmation.

Study Details

PMID:10485722
Participants:283
Impact:17% → 8% (absolute -9 percentage points); adjusted OR 0.39, p=0.02
Trust score:4/5

total antioxidant capacity (TEAC)

1 evidences

A twice-daily enriched drink increased plasma antioxidant levels including vitamin C in frail elderly people over six months.

Trust comment: Six‑month randomized double‑blind placebo‑controlled trial in frail elderly with clear biochemical outcomes, moderate sample size.

Study Details

PMID:12805250
Participants:55
Impact:increased (change 38 ±15 vs -10 ±11 mmol/L Trolox eq)
Trust score:4/5

overall cleansing success

1 evidences

1 L PEG plus ascorbate achieved higher overall and right‑colon cleansing success than 4 L PEG with similar tolerability and safety.

Trust comment: Large multicentre randomized non-inferiority trial with clear primary endpoint and statistically significant differences.

Study Details

PMID:37574430
Participants:478
Impact:91.8% vs 83.6% (+8.2 percentage points, P=0.01)
Trust score:5/5

high-quality right‑colon cleansing

1 evidences

1 L PEG plus ascorbate achieved higher overall and right‑colon cleansing success than 4 L PEG with similar tolerability and safety.

Trust comment: Large multicentre randomized non-inferiority trial with clear primary endpoint and statistically significant differences.

Study Details

PMID:37574430
Participants:478
Impact:52.3% vs 38.5% (+13.8 percentage points, P=0.004)
Trust score:5/5

interleukin-10 (IL-10)

1 evidences

In chronic hemodialysis patients, supplementation including vitamin C (250 mg) and vitamin E with whey protein reduced IL‑10 after 8 weeks; other inflammatory markers showed no significant between‑group changes.

Trust comment: Randomized double‑blind pilot with small completed sample (n=23); signals reported but underpowered for many outcomes.

Study Details

PMID:37598813
Participants:23
Impact:decrease in supplementation group after 8 weeks (P=0.0382)
Trust score:3/5

markers of haemolysis

1 evidences

High-dose vitamins C+E raised serum vitamin levels but unexpectedly increased markers of haemolysis without improving haemoglobin in sickle cell patients.

Trust comment: Randomized, double-blind, placebo-controlled trial with a moderate sample (n=83); clear and clinically important outcomes.

Study Details

PMID:23278176
Participants:83
Impact:significantly increased with supplementation
Trust score:4/5

hemoglobin level

1 evidences

High-dose vitamins C+E raised serum vitamin levels but unexpectedly increased markers of haemolysis without improving haemoglobin in sickle cell patients.

Trust comment: Randomized, double-blind, placebo-controlled trial with a moderate sample (n=83); clear and clinically important outcomes.

Study Details

PMID:23278176
Participants:83
Impact:no significant change
Trust score:4/5

transferrin receptor:serum ferritin ratio

1 evidences

An intensive dietary program that increased vitamin C intake (among other changes) improved iron intake and produced modest increases in iron stores compared with placebo, while iron supplementation produced larger increases.

Trust comment: Randomized controlled 16‑week intervention with objective iron outcomes, but vitamin C was part of a multi-component dietary change so effects are indirect.

Study Details

PMID:11601562
Participants:75
Impact:decreased 51% in Supplement group (p=0.001); non-significant 22% decrease in Diet group
Trust score:3/5

plasma carotenoids (α- and β-carotene)

1 evidences

Daily fruit-and-vegetable puree drinks raised dietary vitamin C and plasma carotenoids and produced a trend toward improved endothelium-dependent vasodilation.

Trust comment: Randomized crossover with 39 completers and objective biochemical and vascular measures; reasonably reliable though vasodilation effect was borderline.

Study Details

PMID:22831286
Participants:39
Impact:significantly increased (P<0.001)
Trust score:4/5

tissue malondialdehyde (oxidative marker)

1 evidences

Adding oral antioxidants (including vitamin C) to intranasal steroid treatment reduced tissue and serum oxidative marker levels more than steroid alone in patients with nasal polyps.

Trust comment: Controlled clinical intervention with objective marker changes but small sample (n=34) and combined antioxidant therapy prevents isolating vitamin C effect.

Study Details

PMID:21669016
Participants:34
Impact:decreased in both groups; greater decrease with steroid+antioxidants (significant)
Trust score:3/5

serum malondialdehyde

1 evidences

Adding oral antioxidants (including vitamin C) to intranasal steroid treatment reduced tissue and serum oxidative marker levels more than steroid alone in patients with nasal polyps.

Trust comment: Controlled clinical intervention with objective marker changes but small sample (n=34) and combined antioxidant therapy prevents isolating vitamin C effect.

Study Details

PMID:21669016
Participants:34
Impact:decreased in both groups; greater fall in steroid+antioxidant group
Trust score:3/5

polyp clinical scores (CT/endoscopy)

1 evidences

Adding oral antioxidants (including vitamin C) to intranasal steroid treatment reduced tissue and serum oxidative marker levels more than steroid alone in patients with nasal polyps.

Trust comment: Controlled clinical intervention with objective marker changes but small sample (n=34) and combined antioxidant therapy prevents isolating vitamin C effect.

Study Details

PMID:21669016
Participants:34
Impact:scores decreased after treatment in both groups
Trust score:3/5

organ dysfunction-free days (28 d)

1 evidences

In 60 children with septic shock, IV vitamin C plus hydrocortisone and thiamin was feasible to deliver but did not improve organ-dysfunction-free days and showed a numerically higher 28-day mortality.

Trust comment: Multicenter randomized open-label pilot RCT (n=60) with good data monitoring but underpowered for clinical efficacy and unblinded.

Study Details

PMID:38240537
Participants:60
Impact:-1 day (median: 20.0 intervention vs 21.0 control)
Trust score:4/5

survival free of inotrope support at 7 d

1 evidences

In 60 children with septic shock, IV vitamin C plus hydrocortisone and thiamin was feasible to deliver but did not improve organ-dysfunction-free days and showed a numerically higher 28-day mortality.

Trust comment: Multicenter randomized open-label pilot RCT (n=60) with good data monitoring but underpowered for clinical efficacy and unblinded.

Study Details

PMID:38240537
Participants:60
Impact:+0.4 days (median: 6.3 intervention vs 5.9 control)
Trust score:4/5

adequate bowel cleansing (Ottawa ≤7)

1 evidences

In 341 outpatients with physical disabilities, an ascorbic acid–enriched PEG solution produced adequate bowel cleansing in most patients; an alternative low-volume prep was noninferior and safety was similar.

Trust comment: Randomized, endoscopist-blinded trial (n=341) with objective cleansing scores and 30-day safety follow-up.

Study Details

PMID:29337780
Participants:341
Impact:81.4% success with ascorbic acid–enriched PEG (vs 75.8% with comparator)
Trust score:4/5

successful ileocecal intubation

1 evidences

In 341 outpatients with physical disabilities, an ascorbic acid–enriched PEG solution produced adequate bowel cleansing in most patients; an alternative low-volume prep was noninferior and safety was similar.

Trust comment: Randomized, endoscopist-blinded trial (n=341) with objective cleansing scores and 30-day safety follow-up.

Study Details

PMID:29337780
Participants:341
Impact:95% in both groups
Trust score:4/5

medication-related adverse events

1 evidences

In 341 outpatients with physical disabilities, an ascorbic acid–enriched PEG solution produced adequate bowel cleansing in most patients; an alternative low-volume prep was noninferior and safety was similar.

Trust comment: Randomized, endoscopist-blinded trial (n=341) with objective cleansing scores and 30-day safety follow-up.

Study Details

PMID:29337780
Participants:341
Impact:none reported
Trust score:4/5

DASH score (functional outcome)

1 evidences

In 336 adults with distal radial fractures, 500 mg daily vitamin C for 50 days did not improve functional outcome at one year and showed some early subgroup harms.

Trust comment: Well-conducted double-blind RCT (n=336) with clear endpoints; no long-term benefit shown and some early subgroup adverse findings.

Study Details

PMID:25187584
Participants:336
Impact:no significant difference at 1 year
Trust score:4/5

complex regional pain syndrome (CRPS) rate

1 evidences

In 336 adults with distal radial fractures, 500 mg daily vitamin C for 50 days did not improve functional outcome at one year and showed some early subgroup harms.

Trust comment: Well-conducted double-blind RCT (n=336) with clear endpoints; no long-term benefit shown and some early subgroup adverse findings.

Study Details

PMID:25187584
Participants:336
Impact:increased at 6 weeks in vitamin C group for nondisplaced fractures (reported p=0.022)
Trust score:4/5

complications/pain at 26 weeks (displaced fractures)

1 evidences

In 336 adults with distal radial fractures, 500 mg daily vitamin C for 50 days did not improve functional outcome at one year and showed some early subgroup harms.

Trust comment: Well-conducted double-blind RCT (n=336) with clear endpoints; no long-term benefit shown and some early subgroup adverse findings.

Study Details

PMID:25187584
Participants:336
Impact:higher complications and greater pain with use (reported p≈0.043–0.045)
Trust score:4/5

urinary 8-iso-prostaglandin F2α

1 evidences

In 184 nonsmokers, 500 mg vitamin C daily reduced a marker of lipid peroxidation and increased antioxidant capacity, with no added benefit from combining vitamins C and E.

Trust comment: Placebo-controlled 2x2 factorial RCT (n=184) with objective biochemical endpoints and significant results for antioxidant capacity.

Study Details

PMID:12197998
Participants:184
Impact:-150 pg/mg creatinine (mean change with vitamin C alone)
Trust score:4/5

serum oxygen-radical absorbance capacity (ORAC)

1 evidences

In 184 nonsmokers, 500 mg vitamin C daily reduced a marker of lipid peroxidation and increased antioxidant capacity, with no added benefit from combining vitamins C and E.

Trust comment: Placebo-controlled 2x2 factorial RCT (n=184) with objective biochemical endpoints and significant results for antioxidant capacity.

Study Details

PMID:12197998
Participants:184
Impact:increased (vitamin C, P = 0.01)
Trust score:4/5

combined C+E vs single vitamins

1 evidences

In 184 nonsmokers, 500 mg vitamin C daily reduced a marker of lipid peroxidation and increased antioxidant capacity, with no added benefit from combining vitamins C and E.

Trust comment: Placebo-controlled 2x2 factorial RCT (n=184) with objective biochemical endpoints and significant results for antioxidant capacity.

Study Details

PMID:12197998
Participants:184
Impact:no additional benefit beyond either vitamin alone
Trust score:4/5

plasma alpha-/beta-carotene

1 evidences

In 122 premenopausal women, a high fruit-and-vegetable dietary intervention significantly increased plasma vitamin C and other carotenoids over one year.

Trust comment: Randomized dietary intervention (n=122) with serial biomarker measurements; dietary adherence and generalizability may limit inference.

Study Details

PMID:16766775
Participants:122
Impact:significantly increased with high fruit-vegetable intervention
Trust score:3/5

plasma beta-cryptoxanthin and zeaxanthin

1 evidences

In 122 premenopausal women, a high fruit-and-vegetable dietary intervention significantly increased plasma vitamin C and other carotenoids over one year.

Trust comment: Randomized dietary intervention (n=122) with serial biomarker measurements; dietary adherence and generalizability may limit inference.

Study Details

PMID:16766775
Participants:122
Impact:increased only with combined high FV + low-fat intervention
Trust score:3/5

IL-6 (inflammatory marker)

1 evidences

In 44 men with moderate-to-severe COPD, an 8-week fortified whey beverage containing 275 mg elemental magnesium improved inflammation, fat-free mass, muscle strength, and respiratory-quality-of-life measures versus control.

Trust comment: Single-blind RCT with low dropout showing multiple benefits, but multi-ingredient intervention (whey, magnesium, vitamin C) and lack of placebo beverage limit attribution specifically to vitamin C.

Study Details

PMID:32807165
Participants:44
Impact:−3.33 pg/ml (intervention change); between-group P=0.034
Trust score:3/5

fat-free mass

1 evidences

In 44 men with moderate-to-severe COPD, an 8-week fortified whey beverage containing 275 mg elemental magnesium improved inflammation, fat-free mass, muscle strength, and respiratory-quality-of-life measures versus control.

Trust comment: Single-blind RCT with low dropout showing multiple benefits, but multi-ingredient intervention (whey, magnesium, vitamin C) and lack of placebo beverage limit attribution specifically to vitamin C.

Study Details

PMID:32807165
Participants:44
Impact:+2.85 kg (intervention change); between-group P=0.025
Trust score:3/5

handgrip strength (right)

1 evidences

In 44 men with moderate-to-severe COPD, an 8-week fortified whey beverage containing 275 mg elemental magnesium improved inflammation, fat-free mass, muscle strength, and respiratory-quality-of-life measures versus control.

Trust comment: Single-blind RCT with low dropout showing multiple benefits, but multi-ingredient intervention (whey, magnesium, vitamin C) and lack of placebo beverage limit attribution specifically to vitamin C.

Study Details

PMID:32807165
Participants:44
Impact:+2.76 kg (intervention change); between-group P=0.023
Trust score:3/5

age-related cataract incidence

1 evidences

Large randomized trial in older male physicians found daily 500 mg vitamin C had no effect on risk of age-related cataract over 8 years.

Trust comment: Large, randomized, double-masked, placebo-controlled trial with long follow-up and robust outcome ascertainment showing no effect.

Study Details

PMID:21060040
Participants:11545
Impact:hazard ratio 1.02 (95% CI 0.91–1.14); no significant effect of vitamin C
Trust score:5/5

retinal vascular reactivity to hyperoxia

1 evidences

Healthy volunteers given LPS showed impaired retinal vascular reactivity that was normalized after 2 weeks of AREDS antioxidants (which include vitamin C) but not after placebo.

Trust comment: Randomized, double-masked small trial showing protective effect of an antioxidant mixture (includes vitamin C) against LPS-induced endothelial dysfunction, but effects cannot be attributed to vitamin C alone.

Study Details

PMID:19684008
Participants:21
Impact:restored to baseline after 2 weeks AREDS antioxidants following LPS challenge (e.g., vasoconstriction ≈13%)
Trust score:3/5

retinal blood flow reactivity

1 evidences

Healthy volunteers given LPS showed impaired retinal vascular reactivity that was normalized after 2 weeks of AREDS antioxidants (which include vitamin C) but not after placebo.

Trust comment: Randomized, double-masked small trial showing protective effect of an antioxidant mixture (includes vitamin C) against LPS-induced endothelial dysfunction, but effects cannot be attributed to vitamin C alone.

Study Details

PMID:19684008
Participants:21
Impact:normalized with AREDS mix vs persistent reduction with placebo
Trust score:3/5

palatability score

1 evidences

Adding orange juice to PEG–ascorbic acid bowel prep improved taste and reduced nausea without reducing cleansing efficacy.

Trust comment: Single-blind randomized trial in ambulatory patients showing improved tolerability with orange juice added to ascorbic-acid–containing prep; sample moderate size but limited to ambulatory setting.

Study Details

PMID:25203380
Participants:107
Impact:mean 2.36 vs 1.78 (p=0.005), improved with orange juice
Trust score:3/5

bowel cleansing quality (Aronchick)

1 evidences

Adding orange juice to PEG–ascorbic acid bowel prep improved taste and reduced nausea without reducing cleansing efficacy.

Trust comment: Single-blind randomized trial in ambulatory patients showing improved tolerability with orange juice added to ascorbic-acid–containing prep; sample moderate size but limited to ambulatory setting.

Study Details

PMID:25203380
Participants:107
Impact:no significant difference (mean 1.49 vs 1.43; p=0.94)
Trust score:3/5

serum vaspin concentration

1 evidences

Antioxidant supplementation including vitamin C (1000 mg/day) prevented the exercise-induced decrease in serum vaspin seen without antioxidants after 4 weeks of training.

Trust comment: Randomized supplementation in a modest-sized sample but effect reported for combined vitamins C+E (post-hoc analysis), so isolated vitamin C effect is not separable and analysis is limited.

Study Details

PMID:20975299
Participants:40
Impact:decrease after acute exercise and after 4 weeks of training without antioxidants; prevented/increased with antioxidant supplementation (vitamin C + E) during 4-week training
Trust score:3/5

oxidative stress marker (TBARS)

1 evidences

Antioxidant supplementation including vitamin C (1000 mg/day) prevented the exercise-induced decrease in serum vaspin seen without antioxidants after 4 weeks of training.

Trust comment: Randomized supplementation in a modest-sized sample but effect reported for combined vitamins C+E (post-hoc analysis), so isolated vitamin C effect is not separable and analysis is limited.

Study Details

PMID:20975299
Participants:40
Impact:increase after exercise correlated inversely with vaspin (r=-0.42 acute; r=-0.31 after 4 weeks)
Trust score:3/5

fasting blood glucose (FBS)

1 evidences

In type 2 diabetic men on metformin, daily vitamin C (alone or with vitamin E) for 90 days improved glycemic control, insulin resistance measures, and some oxidative stress markers versus placebo.

Trust comment: Randomized single-blind trial showing beneficial signals, but small sample size per arm and single-blind design limit confidence and generalizability.

Study Details

PMID:29571976
Participants:40
Impact:improvement compared with placebo (reported qualitatively; values not provided in extract)
Trust score:3/5

intestinal permeability (lactulose excretion)

1 evidences

In healthy female volunteers, ascorbic acid (500 mg) increased intestinal permeability (lactulose excretion) more than aspirin alone and had an additive effect when combined with aspirin.

Trust comment: Crossover study in healthy volunteers with direct measures of permeability and reasonable sample size for mechanistic work, though limited to short-term effects in healthy females.

Study Details

PMID:25641731
Participants:28
Impact:increase with ascorbic acid alone (greater than aspirin alone) and additive increase when given with aspirin
Trust score:4/5

mannitol excretion (small-molecule probe)

1 evidences

In healthy female volunteers, ascorbic acid (500 mg) increased intestinal permeability (lactulose excretion) more than aspirin alone and had an additive effect when combined with aspirin.

Trust comment: Crossover study in healthy volunteers with direct measures of permeability and reasonable sample size for mechanistic work, though limited to short-term effects in healthy females.

Study Details

PMID:25641731
Participants:28
Impact:no protective effect of ascorbic acid reported; timing had no significant effect on excretion patterns
Trust score:4/5

bowel cleansing adequacy (BBPS ≥2 per segment)

1 evidences

In outpatients undergoing colonoscopy, PEG plus ascorbic acid provided similar bowel cleansing efficacy to picosulphate/magnesium citrate but had lower tolerability and willingness-to-repeat.

Trust comment: Large randomized multicenter trial with clear clinical endpoints; ascorbic acid tested as part of a prep formulation rather than as isolated vitamin C intervention.

Study Details

PMID:23581277
Participants:285
Impact:adequate prep in 76.5% with PEG + ascorbic acid vs 75.7% with comparator (no meaningful difference)
Trust score:4/5

patient tolerability and willingness to repeat

1 evidences

In outpatients undergoing colonoscopy, PEG plus ascorbic acid provided similar bowel cleansing efficacy to picosulphate/magnesium citrate but had lower tolerability and willingness-to-repeat.

Trust comment: Large randomized multicenter trial with clear clinical endpoints; ascorbic acid tested as part of a prep formulation rather than as isolated vitamin C intervention.

Study Details

PMID:23581277
Participants:285
Impact:lower with PEG + ascorbic acid (84.8% no/mild discomfort; 83.4% willing to repeat) vs comparator (97.1% no/mild; 97.8% willing)
Trust score:4/5

adenoma detection rate

1 evidences

Bowel prep containing ascorbic acid cleaned the colon better and led to more adenomas being detected, with similar tolerability.

Trust comment: Randomized single-blind trial with validated outcomes and objective adenoma detection; reasonable quality.

Study Details

PMID:20626383
Participants:107
Impact:higher with PEG+Asc (39% vs 20%, P=0.04)
Trust score:4/5

SARS‑CoV‑2 viral load (RT‑PCR CT, RdRp)

1 evidences

Randomized open-label trial in asymptomatic COVID-19 patients comparing KSK decoction to standard care (vitamin C + zinc) for 7 days; measured viral load and cytokines.

Trust comment: Small (n=60), open‑label exploratory RCT; randomized and used objective PCR endpoints but limited sample size and short follow‑up.

Study Details

PMID:34526104
Participants:60
Impact:CT increase +2.60 (control group mean difference for RdRp) — viral load declined in control but less than KSK
Trust score:3/5

progression to symptomatic disease

1 evidences

Randomized open-label trial in asymptomatic COVID-19 patients comparing KSK decoction to standard care (vitamin C + zinc) for 7 days; measured viral load and cytokines.

Trust comment: Small (n=60), open‑label exploratory RCT; randomized and used objective PCR endpoints but limited sample size and short follow‑up.

Study Details

PMID:34526104
Participants:60
Impact:no progression in either group (0/30 progressed)
Trust score:3/5

IL‑10 (immunological marker)

1 evidences

Randomized open-label trial in asymptomatic COVID-19 patients comparing KSK decoction to standard care (vitamin C + zinc) for 7 days; measured viral load and cytokines.

Trust comment: Small (n=60), open‑label exploratory RCT; randomized and used objective PCR endpoints but limited sample size and short follow‑up.

Study Details

PMID:34526104
Participants:60
Impact:fewer patients had elevated IL‑10 at day 7 in control (28 → 13 elevated)
Trust score:3/5

late luminal loss (MLD) at follow‑up

1 evidences

Feasibility randomized, blinded study of IV ascorbic acid (300 mg or 600 mg thrice weekly) vs placebo after angioplasty in hemodialysis access patients; angiographic and clinical restenosis assessed.

Trust comment: Randomized, double‑blind design with objective angiographic outcomes; modest sample size (feasibility study) and short 3‑month follow‑up limit generalizability.

Study Details

PMID:31366980
Participants:89
Impact:reduced by 1.56 mm (3.15 mm placebo → 1.59 mm 600 mg AA), ≈49% reduction (600 mg vs placebo; P=0.006)
Trust score:4/5

target lesion restenosis rate

1 evidences

Feasibility randomized, blinded study of IV ascorbic acid (300 mg or 600 mg thrice weekly) vs placebo after angioplasty in hemodialysis access patients; angiographic and clinical restenosis assessed.

Trust comment: Randomized, double‑blind design with objective angiographic outcomes; modest sample size (feasibility study) and short 3‑month follow‑up limit generalizability.

Study Details

PMID:31366980
Participants:89
Impact:reduced from 40% (placebo) to 23% (600 mg AA) (absolute −17 percentage points)
Trust score:4/5

re‑intervention incidence

1 evidences

Feasibility randomized, blinded study of IV ascorbic acid (300 mg or 600 mg thrice weekly) vs placebo after angioplasty in hemodialysis access patients; angiographic and clinical restenosis assessed.

Trust comment: Randomized, double‑blind design with objective angiographic outcomes; modest sample size (feasibility study) and short 3‑month follow‑up limit generalizability.

Study Details

PMID:31366980
Participants:89
Impact:30% (600 mg) vs 53% (placebo) — lower but not statistically significant
Trust score:4/5

absolute risk of bleaching-induced tooth sensitivity

1 evidences

Oral ascorbic acid (500 mg every 8 hours) did not prevent or reduce tooth sensitivity after bleaching.

Trust comment: Triple-blind randomized placebo-controlled trial, small sample but well-controlled methodology.

Study Details

PMID:23802640
Participants:39
Impact:no significant difference (ascorbic acid vs placebo)
Trust score:4/5

intensity of tooth sensitivity

1 evidences

Oral ascorbic acid (500 mg every 8 hours) did not prevent or reduce tooth sensitivity after bleaching.

Trust comment: Triple-blind randomized placebo-controlled trial, small sample but well-controlled methodology.

Study Details

PMID:23802640
Participants:39
Impact:no significant difference
Trust score:4/5

color change after bleaching

1 evidences

Oral ascorbic acid (500 mg every 8 hours) did not prevent or reduce tooth sensitivity after bleaching.

Trust comment: Triple-blind randomized placebo-controlled trial, small sample but well-controlled methodology.

Study Details

PMID:23802640
Participants:39
Impact:no significant difference
Trust score:4/5

dietary ascorbic acid intake

1 evidences

A high-antioxidant diet increased dietary vitamin C intake and was associated with reduced CRP and some liver enzymes but no broad changes in oxidative stress markers.

Trust comment: Crossover dietary intervention with measured biochemical outcomes in healthy adults, but vitamin C was part of a multi-component dietary change.

Study Details

PMID:18469252
Participants:33
Impact:significantly higher on high-TAC diet (P < 0.001)
Trust score:4/5

plasma high-sensitivity C-reactive protein (hsCRP)

1 evidences

A high-antioxidant diet increased dietary vitamin C intake and was associated with reduced CRP and some liver enzymes but no broad changes in oxidative stress markers.

Trust comment: Crossover dietary intervention with measured biochemical outcomes in healthy adults, but vitamin C was part of a multi-component dietary change.

Study Details

PMID:18469252
Participants:33
Impact:decreased (HT: -0.72 mg/L vs LT: +1.05 mg/L; P < 0.01)
Trust score:4/5

plasma alpha-tocopherol

4 evidences

In surgical patients on TPN, plasma vitamin C and other non-supplemented antioxidants fell during TPN despite alpha-tocopherol supplementation normalizing tocopherol levels in one group.

Trust comment: Randomized clinical setting but small sample and short duration; vitamin C was measured but not manipulated as the primary intervention.

Study Details

PMID:10895108
Participants:33
Impact:increased by +20.0 µmol/L in the a-tocopherol-supplemented MLF group
Trust score:3/5

A 2-year RCT of combined antioxidants including vitamin C showed no improvement or stabilization of cognitive decline in individuals with Down syndrome and dementia.

Trust comment: Randomized double-blind placebo-controlled trial but used a combined antioxidant regimen, so vitamin C-specific effects cannot be isolated.

Study Details

PMID:21739598
Participants:53
Impact:increased ~2-fold in treatment group
Trust score:4/5

Critically ill patients receiving enteral formula enriched with vitamins A, C, and E showed increased plasma antioxidant vitamins and improved LDL resistance to oxidation, with no change in clinical outcomes.

Trust comment: Prospective randomized double-blind placebo-controlled ICU study with demonstrated biochemical effects but small completed sample and no clinical outcome differences.

Study Details

PMID:11153621
Participants:37
Impact:increased from 6.0 to 9.7 μg/mL (+3.7 μg/mL; p<0.05)
Trust score:4/5

A high-antioxidant diet increased dietary vitamin C intake and was associated with reduced CRP and some liver enzymes but no broad changes in oxidative stress markers.

Trust comment: Crossover dietary intervention with measured biochemical outcomes in healthy adults, but vitamin C was part of a multi-component dietary change.

Study Details

PMID:18469252
Participants:33
Impact:increased on high-TAC diet (P < 0.02)
Trust score:4/5

insulin requirement

1 evidences

Pregnant women with gestational diabetes given 1 g/day vitamin C needed less insulin and had improved placental oxidative markers and better neonatal glucose and fewer NICU admissions.

Trust comment: Large randomized controlled trial (n=200) with significant biochemical and clinical neonatal outcomes reported.

Study Details

PMID:26999688
Participants:200
Impact:decrease (25.6 ± 20.3 vs 40.5 ± 23.7; −14.9 units)
Trust score:4/5

placental malondialdehyde (MDA)

1 evidences

Pregnant women with gestational diabetes given 1 g/day vitamin C needed less insulin and had improved placental oxidative markers and better neonatal glucose and fewer NICU admissions.

Trust comment: Large randomized controlled trial (n=200) with significant biochemical and clinical neonatal outcomes reported.

Study Details

PMID:26999688
Participants:200
Impact:decrease (165.7 vs 264.15)
Trust score:4/5

neonatal blood glucose at 1 hour

1 evidences

Pregnant women with gestational diabetes given 1 g/day vitamin C needed less insulin and had improved placental oxidative markers and better neonatal glucose and fewer NICU admissions.

Trust comment: Large randomized controlled trial (n=200) with significant biochemical and clinical neonatal outcomes reported.

Study Details

PMID:26999688
Participants:200
Impact:increase/stabilization (56.7 ± 10.9 vs 39.7 ± 11.1 mg/dL)
Trust score:4/5

insulin resistance (HOMA index)

1 evidences

In elderly adults, 4 weeks of vitamin C supplementation reduced the adverse association between certain perfluorinated compounds and insulin resistance.

Trust comment: Well-designed double-blind randomized crossover (n=141) showing consistent protective effects on IR related to environmental exposures.

Study Details

PMID:25939797
Participants:141
Impact:protective effect vs placebo for high PFOS/PFDoDA exposure (reduced association)
Trust score:4/5

oxidative stress markers (MDA, 8-OHdG)

1 evidences

In elderly adults, 4 weeks of vitamin C supplementation reduced the adverse association between certain perfluorinated compounds and insulin resistance.

Trust comment: Well-designed double-blind randomized crossover (n=141) showing consistent protective effects on IR related to environmental exposures.

Study Details

PMID:25939797
Participants:141
Impact:PFOS/PFDoDA associated with increases; vitamin C attenuated related IR (no exact % reported)
Trust score:4/5

adequate bowel preparation rate

1 evidences

1 L polyethylene glycol with ascorbic acid plus a low-residue diet provided similar or better bowel cleansing and greater patient satisfaction than 2 L PEGA.

Trust comment: Endoscopist-blinded randomized controlled trial (n=173) with objective bowel-prep scoring and patient-reported outcomes.

Study Details

PMID:30278110
Participants:173
Impact:-4.7 percentage points (88.4% for 2L PEGA vs 93.1% for 1L PEGA+PLD; P=0.28, no significant difference)
Trust score:4/5

Boston Bowel Preparation Scale score

1 evidences

1 L polyethylene glycol with ascorbic acid plus a low-residue diet provided similar or better bowel cleansing and greater patient satisfaction than 2 L PEGA.

Trust comment: Endoscopist-blinded randomized controlled trial (n=173) with objective bowel-prep scoring and patient-reported outcomes.

Study Details

PMID:30278110
Participants:173
Impact:higher (P=0.02)
Trust score:4/5

overall survival (median)

1 evidences

In a small randomized phase 2 trial, adding high‑dose IV vitamin C to standard chemotherapy improved survival and reduced some chemotherapy toxicities.

Trust comment: Randomized phase 2 trial with objective survival endpoints and independent monitoring but limited by small sample size (34 analyzed) and limited diversity.

Study Details

PMID:39369582
Participants:34
Impact:+7.7 months (16.0 vs 8.3 months; HR 0.46, P=0.030)
Trust score:4/5

progression-free survival (median)

1 evidences

In a small randomized phase 2 trial, adding high‑dose IV vitamin C to standard chemotherapy improved survival and reduced some chemotherapy toxicities.

Trust comment: Randomized phase 2 trial with objective survival endpoints and independent monitoring but limited by small sample size (34 analyzed) and limited diversity.

Study Details

PMID:39369582
Participants:34
Impact:+2.3 months (6.2 vs 3.9 months; HR 0.43, P=0.029)
Trust score:4/5

grade 3/4 hematologic toxicity (e.g., neutropenia)

1 evidences

In a small randomized phase 2 trial, adding high‑dose IV vitamin C to standard chemotherapy improved survival and reduced some chemotherapy toxicities.

Trust comment: Randomized phase 2 trial with objective survival endpoints and independent monitoring but limited by small sample size (34 analyzed) and limited diversity.

Study Details

PMID:39369582
Participants:34
Impact:reduced (neutropenia 33.3% ASC vs 62.5% SOC)
Trust score:4/5

tuberculosis incidence — high dietary vitamin C

1 evidences

In the ATBC cohort of male smokers, higher dietary vitamin C was linked to lower tuberculosis risk; vitamin C intake modified the effect of vitamin E supplementation.

Trust comment: Large randomized trial cohort (ATBC) with reliable outcomes; this analysis reports observational associations and effect modification by dietary vitamin C.

Study Details

PMID:18279551
Participants:29023
Impact:-60% (adjusted risk lower in highest vs lowest vitamin C quartile; 95% CI 16%–81% lower)
Trust score:4/5

vitamin E effect modified by high dietary vitamin C

1 evidences

In the ATBC cohort of male smokers, higher dietary vitamin C was linked to lower tuberculosis risk; vitamin C intake modified the effect of vitamin E supplementation.

Trust comment: Large randomized trial cohort (ATBC) with reliable outcomes; this analysis reports observational associations and effect modification by dietary vitamin C.

Study Details

PMID:18279551
Participants:29023
Impact:vitamin E supplementation increased TB risk by +72% among those with ≥90 mg/day vitamin C who smoked heavily (95% CI 4%–185%)
Trust score:4/5

total dietary antioxidant intake

1 evidences

Close dietetic supervision of a Mediterranean-style diet increased antioxidant intake, including vitamin C, and raised plasma antioxidant capacity over 2 months.

Trust comment: Randomized human trial (n=90) with clear outcome measures and significant results; moderate-high quality.

Study Details

PMID:22237557
Participants:90
Impact:+significant increase (P=0.000)
Trust score:4/5

plasma total antioxidant capacity (TAC)

1 evidences

Close dietetic supervision of a Mediterranean-style diet increased antioxidant intake, including vitamin C, and raised plasma antioxidant capacity over 2 months.

Trust comment: Randomized human trial (n=90) with clear outcome measures and significant results; moderate-high quality.

Study Details

PMID:22237557
Participants:90
Impact:+increased (ORAC P=0.039; FRAP trend P=0.077)
Trust score:4/5

iron absorption from FeSO4

1 evidences

Ascorbic acid strongly enhanced iron absorption from FeSO4 but had a smaller effect on poorly soluble electrolytic iron in human volunteers.

Trust comment: Well-controlled human absorption study (n=56) with isotope labeling and clear quantitative results.

Study Details

PMID:16857836
Participants:56
Impact:+~4-fold increase with ~160 mg ascorbic acid
Trust score:4/5

iron absorption from irradiated electrolytic iron

1 evidences

Ascorbic acid strongly enhanced iron absorption from FeSO4 but had a smaller effect on poorly soluble electrolytic iron in human volunteers.

Trust comment: Well-controlled human absorption study (n=56) with isotope labeling and clear quantitative results.

Study Details

PMID:16857836
Participants:56
Impact:+~2-fold increase with ~160 mg ascorbic acid (absorption 5–15% of FeSO4 without enhancer)
Trust score:4/5

effect of phytic acid on iron absorption

1 evidences

Ascorbic acid strongly enhanced iron absorption from FeSO4 but had a smaller effect on poorly soluble electrolytic iron in human volunteers.

Trust comment: Well-controlled human absorption study (n=56) with isotope labeling and clear quantitative results.

Study Details

PMID:16857836
Participants:56
Impact:inhibited absorption (FeSO4 −73%, electrolytic iron −50%)
Trust score:4/5

incidence of acute mountain sickness (AMS)

1 evidences

Daily antioxidant supplement including 1 g vitamin C did not reduce incidence or severity of acute mountain sickness in healthy volunteers at high altitude.

Trust comment: Double-blind randomized placebo-controlled human trial (n=83) with clear negative findings; high internal validity.

Study Details

PMID:19273551
Participants:83
Impact:no difference (Day 2 at 5200 m: 69% antioxidant vs 66% placebo; P=0.74)
Trust score:4/5

AMS severity / oxygen saturation / PASP

1 evidences

Daily antioxidant supplement including 1 g vitamin C did not reduce incidence or severity of acute mountain sickness in healthy volunteers at high altitude.

Trust comment: Double-blind randomized placebo-controlled human trial (n=83) with clear negative findings; high internal validity.

Study Details

PMID:19273551
Participants:83
Impact:no differences between groups
Trust score:4/5

overall response rate (RR)

1 evidences

Adding high-dose multiple antioxidants (including ~6100 mg/day vitamin C) to chemotherapy showed no statistically significant improvement in response rate or survival in advanced NSCLC.

Trust comment: Randomized clinical trial (n=136) but used combined antioxidants (not vitamin C alone) and was not powered to detect small survival differences; moderate quality.

Study Details

PMID:15670980
Participants:136
Impact:chemotherapy 33% vs combination 37% (no significant difference)
Trust score:3/5

median survival

1 evidences

Adding high-dose multiple antioxidants (including ~6100 mg/day vitamin C) to chemotherapy showed no statistically significant improvement in response rate or survival in advanced NSCLC.

Trust comment: Randomized clinical trial (n=136) but used combined antioxidants (not vitamin C alone) and was not powered to detect small survival differences; moderate quality.

Study Details

PMID:15670980
Participants:136
Impact:chemotherapy 9 months vs combination 11 months (no significant difference; p=0.20)
Trust score:3/5

toxicity profile

1 evidences

Adding high-dose multiple antioxidants (including ~6100 mg/day vitamin C) to chemotherapy showed no statistically significant improvement in response rate or survival in advanced NSCLC.

Trust comment: Randomized clinical trial (n=136) but used combined antioxidants (not vitamin C alone) and was not powered to detect small survival differences; moderate quality.

Study Details

PMID:15670980
Participants:136
Impact:no meaningful difference between arms
Trust score:3/5

URTI symptom severity and duration (selected: head congestion, sore throat)

1 evidences

Eating gold kiwifruit daily increased plasma vitamin C and some antioxidants and reduced duration/severity of selected cold symptoms in older adults.

Trust comment: Randomized crossover human trial (n=32) with biologic measures and symptom outcomes; moderate-good quality though sample size is small.

Study Details

PMID:22172428
Participants:32
Impact:−reduced severity and shorter duration for head congestion and sore throat
Trust score:4/5

plasma lipid peroxidation

1 evidences

Eating gold kiwifruit daily increased plasma vitamin C and some antioxidants and reduced duration/severity of selected cold symptoms in older adults.

Trust comment: Randomized crossover human trial (n=32) with biologic measures and symptom outcomes; moderate-good quality though sample size is small.

Study Details

PMID:22172428
Participants:32
Impact:−significant reduction (improved oxidative stress marker)
Trust score:4/5

adequate bowel cleansing

1 evidences

Low-volume PEG+ascorbic acid provided similarly adequate bowel cleansing to high-volume PEG+simethicone but had worse bowel wall visualization and slightly fewer small adenoma detections.

Trust comment: Randomized, matched outpatient trial with clear outcome measures and reported dropouts (144→130 completed); direct comparison of ascorbic acid-containing prep.

Study Details

PMID:22180711
Participants:130
Impact:91% (PEG+Asc) vs 88% (PEG+Sim) (+3 percentage points)
Trust score:4/5

bowel wall visualization

1 evidences

Low-volume PEG+ascorbic acid provided similarly adequate bowel cleansing to high-volume PEG+simethicone but had worse bowel wall visualization and slightly fewer small adenoma detections.

Trust comment: Randomized, matched outpatient trial with clear outcome measures and reported dropouts (144→130 completed); direct comparison of ascorbic acid-containing prep.

Study Details

PMID:22180711
Participants:130
Impact:reduced with PEG+Asc versus PEG+Sim (significant)
Trust score:4/5

adenoma detection (≤10 mm)

1 evidences

Low-volume PEG+ascorbic acid provided similarly adequate bowel cleansing to high-volume PEG+simethicone but had worse bowel wall visualization and slightly fewer small adenoma detections.

Trust comment: Randomized, matched outpatient trial with clear outcome measures and reported dropouts (144→130 completed); direct comparison of ascorbic acid-containing prep.

Study Details

PMID:22180711
Participants:130
Impact:9 lesions (PEG+Asc) vs 12 lesions (PEG+Sim)
Trust score:4/5

plasma total antioxidant capacity (TAOC)

1 evidences

Chronic periodontitis patients had lower plasma total antioxidant capacity than controls; non-surgical periodontal therapy reduced oxidative stress, and adjunctive vitamin C showed no clear additional benefit in this small study.

Trust comment: Randomized allocation within the patient group but small subgroups (n=15 each) and short follow-up; vitamin C effect was inconclusive.

Study Details

PMID:20569170
Participants:60
Impact:lower in chronic periodontitis patients versus controls (P<0.05)
Trust score:3/5

adjunctive vitamin C effect

1 evidences

Chronic periodontitis patients had lower plasma total antioxidant capacity than controls; non-surgical periodontal therapy reduced oxidative stress, and adjunctive vitamin C showed no clear additional benefit in this small study.

Trust comment: Randomized allocation within the patient group but small subgroups (n=15 each) and short follow-up; vitamin C effect was inconclusive.

Study Details

PMID:20569170
Participants:60
Impact:no clear additional benefit observed (not conclusive)
Trust score:3/5

plasma folate

3 evidences

In CAD patients, folic acid supplementation markedly raised plasma folate and produced a modest homocysteine fall and a significant improvement in flow-mediated dilation versus placebo; adding antioxidants did not produce significant additional benefit.

Trust comment: Double-blind, placebo-controlled randomized trial with clear outcomes; high internal validity showing no added benefit from vitamins C+E.

Study Details

PMID:10987596
Participants:75
Impact:increased +475% (folic acid) and +438% (folic acid+antioxidants)
Trust score:4/5

Giving low consumers ~480 g/day fruit/veg + up to 300 ml juice for 12 weeks raised blood vitamin C and other nutrients but did not change measures of plasma antioxidant capacity or vascular risk markers.

Trust comment: Randomised controlled trial with objective biomarkers and good compliance; not blinded and modest sample size limits generalizability.

Study Details

PMID:28560503
Participants:45
Impact:+15% (approx.)
Trust score:4/5

In healthy middle-aged adults, 7-week supplementation with fruit/vegetable concentrates raised blood levels of several antioxidants including vitamin C.

Trust comment: Double-blind randomized crossover human study with moderate sample size but supplement contained many nutrients, so isolated vitamin C effect is indirect.

Study Details

PMID:15190044
Participants:59
Impact:increased (significant) after active supplementation
Trust score:3/5

plasma homocysteine

3 evidences

Supplementation with a fruit-and-vegetable concentrate increased plasma vitamin C and folate and modestly lowered homocysteine in men.

Trust comment: Randomized double-blind crossover (n=32) with biochemical endpoints; small sample but well controlled.

Study Details

PMID:12840177
Participants:32
Impact:decreased by −0.6 µmol/L (8.2 → 7.6 µmol/L; P<0.05)
Trust score:4/5

Isoflavone supplementation reduced homocysteine and some resting oxidative markers but did not change plasma vitamin C or prevent exercise-induced oxidative stress.

Trust comment: Randomized trial with clear biochemical endpoints but small N and the intervention was isoflavones, not vitamin C.

Study Details

PMID:15735366
Participants:30
Impact:decreased (p = 0.01) after 4-week isoflavone
Trust score:3/5

In CAD patients, folic acid supplementation markedly raised plasma folate and produced a modest homocysteine fall and a significant improvement in flow-mediated dilation versus placebo; adding antioxidants did not produce significant additional benefit.

Trust comment: Double-blind, placebo-controlled randomized trial with clear outcomes; high internal validity showing no added benefit from vitamins C+E.

Study Details

PMID:10987596
Participants:75
Impact:reduced −11% (folic acid) and −9% (folic acid+antioxidants)
Trust score:4/5

hip bone mineral density (BMD) / hip bone loss

1 evidences

One year of high-dose vitamin C (1,000 mg) plus vitamin E reduced oxidative stress markers and attenuated hip bone loss in elderly participants.

Trust comment: Double‑blind, controlled 12‑month trial with 90 participants; reasonably powered but combined vitamin C+E limits attribution to vitamin C alone.

Study Details

PMID:20617290
Participants:90
Impact:Attenuation of hip bone loss in Tx2 (1,000 mg ascorbic acid + 400 IU α‑tocopherol) vs placebo (Tx0) (p<0.05)
Trust score:4/5

lipid peroxidation (LPO/TBARS)

1 evidences

One year of high-dose vitamin C (1,000 mg) plus vitamin E reduced oxidative stress markers and attenuated hip bone loss in elderly participants.

Trust comment: Double‑blind, controlled 12‑month trial with 90 participants; reasonably powered but combined vitamin C+E limits attribution to vitamin C alone.

Study Details

PMID:20617290
Participants:90
Impact:Significantly lower decrease of LPO in Tx2 vs Tx0 (p<0.05)
Trust score:4/5

antioxidant enzymes (SOD, GPx) correlation with BMD

1 evidences

One year of high-dose vitamin C (1,000 mg) plus vitamin E reduced oxidative stress markers and attenuated hip bone loss in elderly participants.

Trust comment: Double‑blind, controlled 12‑month trial with 90 participants; reasonably powered but combined vitamin C+E limits attribution to vitamin C alone.

Study Details

PMID:20617290
Participants:90
Impact:Positive correlation: hip‑BMD with SOD (r=0.298) and GPx (r=0.214), p<0.05
Trust score:4/5

systemic free radical formation (ascorbate radical)

1 evidences

Antioxidant prophylaxis (vitamin C + E) reduced free‑radical signals during hypoxia/exercise but increased thrombin generation at rest.

Trust comment: Randomized double‑blind placebo‑controlled trial in healthy men but small sample (n=36) and used combination antioxidants, limiting attribution to vitamin C alone.

Study Details

PMID:29989171
Participants:36
Impact:Attenuated increase during hypoxia and exercise with antioxidant prophylaxis
Trust score:4/5

thrombin generation (coagulation)

1 evidences

Antioxidant prophylaxis (vitamin C + E) reduced free‑radical signals during hypoxia/exercise but increased thrombin generation at rest.

Trust comment: Randomized double‑blind placebo‑controlled trial in healthy men but small sample (n=36) and used combination antioxidants, limiting attribution to vitamin C alone.

Study Details

PMID:29989171
Participants:36
Impact:Increased at rest with antioxidant prophylaxis (normalized only under prevailing oxidation)
Trust score:4/5

atrial tissue antioxidant enzyme activity (catalase, SOD, GPx)

1 evidences

Supplementation with n‑3 PUFAs plus vitamins C (1 g/day) and E reduced post‑operative atrial fibrillation and increased cardiac antioxidant enzyme activity.

Trust comment: Large randomized trial with a clear clinical endpoint, but intervention combined n‑3 PUFA with vitamins C and E so effects cannot be ascribed to vitamin C alone.

Study Details

PMID:23916928
Participants:203
Impact:Increased by ~24.0%, 17.1%, and 19.7% vs placebo (p<0.05)
Trust score:4/5

incident visually significant age‑related macular degeneration (AMD)

1 evidences

Daily 500 mg vitamin C for 8 years did not affect risk of visually significant age‑related macular degeneration.

Trust comment: Large, long‑term randomized, double‑masked, placebo‑controlled trial with objective, medically‑confirmed outcomes; high methodological quality.

Study Details

PMID:22503302
Participants:14236
Impact:No significant effect (vitamin C vs placebo: 97 vs 96 cases; HR 0.99, 95% CI 0.75–1.31)
Trust score:5/5

antioxidant balance (GSH, MDA)

1 evidences

Children with β-thalassemia and low vitamins received combined vitamin therapy for 12 months and showed improved antioxidant markers and reduced liver iron.

Trust comment: Prospective clinical study with clear before/after measures in humans, but multi-vitamin intervention and non-randomized comparison limit attribution to vitamin C alone.

Study Details

PMID:23565660
Participants:60
Impact:↑ GSH and ↓ MDA (significant)
Trust score:3/5

hepatic fibrosis (TE >12 kPa)

1 evidences

Children with β-thalassemia and low vitamins received combined vitamin therapy for 12 months and showed improved antioxidant markers and reduced liver iron.

Trust comment: Prospective clinical study with clear before/after measures in humans, but multi-vitamin intervention and non-randomized comparison limit attribution to vitamin C alone.

Study Details

PMID:23565660
Participants:60
Impact:reduced proportion with TE>12 kPa (non-significant)
Trust score:3/5

FEF25-75 (small airway flow)

1 evidences

In children with moderate–severe asthma, daily vitamins C+E prevented ozone-associated decreases in lung function.

Trust comment: Randomized, double-blind trial with a clear clinical outcome and adequate sample size for the population studied.

Study Details

PMID:12204869
Participants:158
Impact:prevented ozone-associated decrease of -13.32 ml/s per 10 ppb (placebo showed this decrement)
Trust score:4/5

FEV1

1 evidences

In children with moderate–severe asthma, daily vitamins C+E prevented ozone-associated decreases in lung function.

Trust comment: Randomized, double-blind trial with a clear clinical outcome and adequate sample size for the population studied.

Study Details

PMID:12204869
Participants:158
Impact:prevented ozone-associated decrease of -4.59 ml per 10 ppb (placebo showed this decrement)
Trust score:4/5

PEF

1 evidences

In children with moderate–severe asthma, daily vitamins C+E prevented ozone-associated decreases in lung function.

Trust comment: Randomized, double-blind trial with a clear clinical outcome and adequate sample size for the population studied.

Study Details

PMID:12204869
Participants:158
Impact:prevented ozone-associated decrease of -15.01 ml/s per 10 ppb (placebo showed this decrement)
Trust score:4/5

overall bowel cleansing efficacy

2 evidences

2-L PEG with ascorbic acid and sodium picosulfate/magnesium citrate had similar overall cleansing; the SP/MC regimen had better tolerability and fewer adverse events.

Trust comment: Randomized controlled trial but vitamin C functions as part of a bowel-prep formulation rather than as an isolated supplement.

Study Details

PMID:29497812
Participants:223
Impact:no significant difference between PEG/Asc and SP/MC
Trust score:3/5

Compared colonoscopy preparations; the low-volume PEG with ascorbic acid (PEGA) had similar cleansing efficacy to PEG when regimens matched and was better tolerated than PEG.

Trust comment: Large multicentre RCT but vitamin C is present as a formulation component (ascorbic acid), not isolated as a sole intervention.

Study Details

PMID:28944412
Participants:973
Impact:no significant difference across agents when regimen matched (split-dose better overall)
Trust score:3/5

postoperative AKI incidence

1 evidences

Perioperative IV vitamin C did not reduce postoperative AKI or improve eGFR after on-pump cardiac surgery; MDA (oxidative stress marker) was not reduced and was higher on POD1 in a subgroup.

Trust comment: Large randomized prospective multicenter trial with predefined primary endpoint and appropriate analyses; MDA subgroup small and some secondary outcomes underpowered.

Study Details

PMID:35643076
Participants:332
Impact:20.9% (AA) vs 28.4% (control); -7.5 percentage points (not statistically significant, p=0.127)
Trust score:4/5

malondialdehyde (MDA) — oxidative stress marker

1 evidences

Perioperative IV vitamin C did not reduce postoperative AKI or improve eGFR after on-pump cardiac surgery; MDA (oxidative stress marker) was not reduced and was higher on POD1 in a subgroup.

Trust comment: Large randomized prospective multicenter trial with predefined primary endpoint and appropriate analyses; MDA subgroup small and some secondary outcomes underpowered.

Study Details

PMID:35643076
Participants:332
Impact:MDA higher in AA group on POD1: 45.16 vs 33.66 µg/L (P=0.029) in 50+50 subgroup; overall no consistent reduction
Trust score:4/5

ascorbic acid in bronchial/bronchoalveolar lavage fluid

1 evidences

In healthy volunteers, inhalation of NO2 transiently lowered ascorbic acid (vitamin C) in bronchial and bronchoalveolar lavage at 1.5 h, returning to baseline by 6 h.

Trust comment: Randomized, double-blind human exposure study with bronchoscopy and timed sampling; moderate sample size and direct biochemical measures.

Study Details

PMID:8970358
Participants:44
Impact:Decreased at 1.5 h after NO2 exposure, returned to control by 6 h
Trust score:4/5

uric acid in lavage fluid

1 evidences

In healthy volunteers, inhalation of NO2 transiently lowered ascorbic acid (vitamin C) in bronchial and bronchoalveolar lavage at 1.5 h, returning to baseline by 6 h.

Trust comment: Randomized, double-blind human exposure study with bronchoscopy and timed sampling; moderate sample size and direct biochemical measures.

Study Details

PMID:8970358
Participants:44
Impact:Decreased at 1.5 h then transiently increased above control at 6 h and returned to baseline by 24 h
Trust score:4/5

reduced glutathione (GSH) in bronchial lavage

1 evidences

In healthy volunteers, inhalation of NO2 transiently lowered ascorbic acid (vitamin C) in bronchial and bronchoalveolar lavage at 1.5 h, returning to baseline by 6 h.

Trust comment: Randomized, double-blind human exposure study with bronchoscopy and timed sampling; moderate sample size and direct biochemical measures.

Study Details

PMID:8970358
Participants:44
Impact:Increased at 1.5 and 6 h, returned to baseline by 24 h
Trust score:4/5

erythrocyte eicosapentaenoic acid (EPA) level

1 evidences

Combined supplementation with alpha-tocopherol and ascorbic acid attenuated the ribavirin-associated decrease in erythrocyte EPA but did not prevent ribavirin-induced anemia.

Trust comment: Randomized trial but small sample (n=32) and combined-vitamin intervention limits attribution to vitamin C alone.

Study Details

PMID:16872308
Participants:32
Impact:Vitamins attenuated the ribavirin-induced decrease in EPA (controls showed significant EPA drop at 8 and 26 weeks; vitamin group did not)
Trust score:3/5

hemoglobin / ribavirin-induced anemia

1 evidences

Combined supplementation with alpha-tocopherol and ascorbic acid attenuated the ribavirin-associated decrease in erythrocyte EPA but did not prevent ribavirin-induced anemia.

Trust comment: Randomized trial but small sample (n=32) and combined-vitamin intervention limits attribution to vitamin C alone.

Study Details

PMID:16872308
Participants:32
Impact:Vitamins did not prevent anemia (no inhibition of ribavirin-induced hemoglobin drop)
Trust score:3/5

cerebral ischemic lesion volume (CT)

1 evidences

In this multicenter randomized trial of ischemic stroke patients, ascorbic acid (given alone) produced no significant morphologic regression of cerebral ischemia or clear clinical benefit, whereas cytoflavin regimens showed lesion volume regression and better outcomes in more severe patients.

Trust comment: Large multicenter randomized trial but reporting lacks detail on blinding and full methodological transparency in the presented summary.

Study Details

PMID:26356615
Participants:373
Impact:No significant morphological changes observed in ascorbic acid group (132 patients) between day 1 and day 21
Trust score:3/5

proportion with lesion enlargement (day1–21)

1 evidences

In this multicenter randomized trial of ischemic stroke patients, ascorbic acid (given alone) produced no significant morphologic regression of cerebral ischemia or clear clinical benefit, whereas cytoflavin regimens showed lesion volume regression and better outcomes in more severe patients.

Trust comment: Large multicenter randomized trial but reporting lacks detail on blinding and full methodological transparency in the presented summary.

Study Details

PMID:26356615
Participants:373
Impact:Higher in ascorbic acid group (≈2-fold greater) compared with cytoflavin groups
Trust score:3/5

clinical/functional improvement in NIH ≥14 subgroup

1 evidences

In this multicenter randomized trial of ischemic stroke patients, ascorbic acid (given alone) produced no significant morphologic regression of cerebral ischemia or clear clinical benefit, whereas cytoflavin regimens showed lesion volume regression and better outcomes in more severe patients.

Trust comment: Large multicenter randomized trial but reporting lacks detail on blinding and full methodological transparency in the presented summary.

Study Details

PMID:26356615
Participants:373
Impact:No advantage reported for ascorbic acid; cytoflavin 20-day therapy showed more prominent improvement
Trust score:3/5

successful bowel cleansing

2 evidences

Low-volume PEG with ascorbic acid achieved comparable bowel cleansing to 4 L PEG (90.6% vs 96% success, difference not statistically significant); tolerability similar.

Trust comment: Prospective quasi-randomized single-blind study with adequate sample size but not fully randomized/blinded, limiting internal validity.

Study Details

PMID:20602568
Participants:307
Impact:90.6% (PEG+ascorbic acid, n=149) vs 96% (4 L PEG, n=158); difference not significant
Trust score:3/5

In patients undergoing colonoscopy, 2L-PEG/ascorbic acid and an oral sulfate solution had similar successful bowel cleansing rates; tolerability and adverse events were comparable.

Trust comment: Prospective randomized noninferiority trial with objective bowel-cleansing scoring; vitamin C present as part of a prep formulation rather than systemic therapy.

Study Details

PMID:30308546
Participants:187
Impact:OSS noninferior to 2L-PEG/Asc: 86.0% vs 88.3% (difference −2.3% by ITT)
Trust score:4/5

tolerability / side-effects

1 evidences

Low-volume PEG with ascorbic acid achieved comparable bowel cleansing to 4 L PEG (90.6% vs 96% success, difference not statistically significant); tolerability similar.

Trust comment: Prospective quasi-randomized single-blind study with adequate sample size but not fully randomized/blinded, limiting internal validity.

Study Details

PMID:20602568
Participants:307
Impact:Side-effects and patient experience similar between PEG+asc and PEG groups
Trust score:3/5

timing effect on cleansing

1 evidences

Low-volume PEG with ascorbic acid achieved comparable bowel cleansing to 4 L PEG (90.6% vs 96% success, difference not statistically significant); tolerability similar.

Trust comment: Prospective quasi-randomized single-blind study with adequate sample size but not fully randomized/blinded, limiting internal validity.

Study Details

PMID:20602568
Participants:307
Impact:Full evening dose of PEG+Asc gave worse cleansing for morning procedures vs split dose (split dose preferred)
Trust score:3/5

esophageal squamous cell carcinoma risk

1 evidences

Men with higher vitamin C intake (>100 mg/day) had lower rates of esophageal cancer.

Trust comment: Checklist: confirm Vitamin C effect on humans; list main outcomes (esophageal SCC, AC, dietary intake); extract participant count; rate study quality. Case-control pilot (n=149) with statistically significant associations but observational design and potential confounding.

Study Details

PMID:12384802
Participants:149
Impact:-67% (RR=0.33 for vitamin C >100 mg/day vs lower intake)
Trust score:3/5

esophageal adenocarcinoma risk

1 evidences

Men with higher vitamin C intake (>100 mg/day) had lower rates of esophageal cancer.

Trust comment: Checklist: confirm Vitamin C effect on humans; list main outcomes (esophageal SCC, AC, dietary intake); extract participant count; rate study quality. Case-control pilot (n=149) with statistically significant associations but observational design and potential confounding.

Study Details

PMID:12384802
Participants:149
Impact:similar significant risk reduction with higher vitamin C intake (RR approx 0.33)
Trust score:3/5

cataract progression (IPO % pixels opaque)

1 evidences

Daily antioxidant mixture including 750 mg vitamin C produced a small slowing of cataract progression over 3 years, mainly in the US cohort.

Trust comment: Large randomized double-masked multicenter trial (297 randomized) with objective imaging outcomes; subgroup differences between US and UK reduce generalizability.

Study Details

PMID:11815895
Participants:297
Impact:-84.5% IPO in US at 3 years (vitamin IPO=0.389 vs placebo IPO=2.517)
Trust score:4/5

early atrial fibrillation recurrence

1 evidences

Oral vitamin C after cardioversion reduced early AF recurrence and lowered some inflammation markers.

Trust comment: Small randomized clinical study (n=44) with clear randomization but limited size; results significant but require larger confirmation.

Study Details

PMID:15982504
Participants:44
Impact:-31.8 percentage points (4.5% recurrence with vitamin C vs 36.3% control at 1 week)
Trust score:3/5

C-reactive protein (day 7)

1 evidences

Oral vitamin C after cardioversion reduced early AF recurrence and lowered some inflammation markers.

Trust comment: Small randomized clinical study (n=44) with clear randomization but limited size; results significant but require larger confirmation.

Study Details

PMID:15982504
Participants:44
Impact:decreased (statistically significant, p<0.05)
Trust score:3/5

haematocrit

1 evidences

IV ascorbic acid improved haematocrit and iron availability and reduced erythropoietin dose in iron‑overloaded hemodialysis patients.

Trust comment: Randomized parallel comparative trial in humans (n=50) with objective laboratory endpoints; sample modest but findings are internally consistent.

Study Details

PMID:9829492
Participants:50
Impact:+4.8 percentage points (from 25.8% to 30.6% after 8 weeks of IV ascorbate)
Trust score:4/5

erythropoietin dose

1 evidences

IV ascorbic acid improved haematocrit and iron availability and reduced erythropoietin dose in iron‑overloaded hemodialysis patients.

Trust comment: Randomized parallel comparative trial in humans (n=50) with objective laboratory endpoints; sample modest but findings are internally consistent.

Study Details

PMID:9829492
Participants:50
Impact:-20% reduction after 8 weeks of IV ascorbate
Trust score:4/5

luminal diameter reduction

1 evidences

Multivitamins including vitamin C did not reduce restenosis after coronary angioplasty.

Trust comment: Double-blind randomized trial (n=317) with quantitative angiographic outcomes; high-quality design showing no vitamin benefit.

Study Details

PMID:9241125
Participants:317
Impact:mean reduction 0.33 ± 0.51 mm in multivitamin group (vs 0.38 ± 0.50 mm placebo); no significant effect
Trust score:4/5

restenosis rate per segment

1 evidences

Multivitamins including vitamin C did not reduce restenosis after coronary angioplasty.

Trust comment: Double-blind randomized trial (n=317) with quantitative angiographic outcomes; high-quality design showing no vitamin benefit.

Study Details

PMID:9241125
Participants:317
Impact:40.3% in multivitamin group vs 38.9% placebo (no significant benefit)
Trust score:4/5

acute hypoxic ventilatory response (AHR)

1 evidences

IV vitamin C (with vitamin E) prevented the halothane-induced drop in the acute hypoxic ventilatory response in healthy men.

Trust comment: Small, well-controlled volunteer study (n=32 total across protocols) with physiologic measurements; limited sample size but clear effect.

Study Details

PMID:12411535
Participants:32
Impact:AHR preserved at 0.77 l·min⁻¹·%⁻¹ with antioxidants vs depressed 0.36 l·min⁻¹·%⁻¹ with halothane alone (control 0.79)
Trust score:3/5

colorectal adenomatous polyp recurrence

1 evidences

Antioxidant vitamins (A, C, E) markedly reduced recurrence of colorectal polyps compared with no treatment.

Trust comment: Controlled clinical study (n=209 evaluable) showing large effect on polyp recurrence, but older study and details on randomization/dosing vary.

Study Details

PMID:9145453
Participants:209
Impact:-30.2 percentage points (5.7% recurrence with vitamins vs 35.9% in untreated controls)
Trust score:3/5

erythrocyte ATP/ADP ratio (EADR)

1 evidences

A single IV infusion of multivitamin/mineral formulas moved patients' red blood cell ATP/ADP ratios toward the mean, an effect not seen in controls.

Trust comment: Randomized patient groups with clear biochemical measures but heterogeneous clinical population and limited control detail.

Study Details

PMID:9988782
Participants:64
Impact:increased if initially low; decreased if initially high (regression to the mean); not seen in controls
Trust score:3/5

left ventricular ejection fraction (LVEF)

1 evidences

In elderly patients with chronic heart failure, long-term high-dose multiple micronutrient supplementation (including vitamin D) improved left ventricular volumes, increased LVEF and improved quality-of-life versus placebo.

Trust comment: Randomized double-blind trial with objective cardiac outcomes, but multiple nutrients were given so vitamin C–specific effects cannot be isolated.

Study Details

PMID:16081469
Participants:28
Impact:+5.3 ± 1.4% in intervention vs no change in placebo (P < 0.05)
Trust score:3/5

oxidant damage biomarkers (F2-isoprostanes, 8-isoprostanes, protein carbonyls)

1 evidences

Daily moderate antioxidant supplementation (including 272 mg vitamin C) raised plasma ascorbate but did not change measured markers of lipid or protein oxidative damage in healthy men.

Trust comment: Placebo-controlled supplementation in 77 men with objective biochemical endpoints; negative results are plausible and well measured.

Study Details

PMID:12612146
Participants:77
Impact:no change after supplementation
Trust score:4/5

overall bowel cleansing success (Harefield Cleansing Scale)

1 evidences

In a randomized phase 3 trial, low-volume PEG with high-dose ascorbate (TJP-008) produced noninferior or superior bowel cleansing compared with 2 L PEG with ascorbate.

Trust comment: Large randomized multicenter phase 3 trial with clear endpoints and high adherence/completion rates.

Study Details

PMID:34810296
Participants:285
Impact:TJP-008-2 99.0% and TJP-008-1 96.8% vs 2LPEG 94.8% (PPS)
Trust score:5/5

right colon high-quality cleansing

1 evidences

In a randomized phase 3 trial, low-volume PEG with high-dose ascorbate (TJP-008) produced noninferior or superior bowel cleansing compared with 2 L PEG with ascorbate.

Trust comment: Large randomized multicenter phase 3 trial with clear endpoints and high adherence/completion rates.

Study Details

PMID:34810296
Participants:285
Impact:83.2% (TJP-008-2) and 75.5% (TJP-008-1) vs 62.5% (2LPEG)
Trust score:5/5

methemoglobin concentration

1 evidences

Prophylactic 2,000 mg IV ascorbic acid given before plexus anesthesia with prilocaine did not reduce methemoglobin concentrations in patients.

Trust comment: Prospective randomized clinical study with adequate sample size showing a clear negative clinical result.

Study Details

PMID:14992088
Participants:72
Impact:no reduction with 2,000 mg IV ascorbic acid in vivo; high in vitro ascorbate only reduced formation at very high o-toluidine concentrations
Trust score:4/5

Retinopathy incidence

1 evidences

Ascorbic acid (600 mg/day) did not significantly prevent interferon-associated retinopathy compared with no ascorbic acid.

Trust comment: Randomized controlled trial (n=62) with ophthalmologic assessment but modest sample size and non-significant differences.

Study Details

PMID:11480793
Participants:62
Impact:29% (treated) vs 35% (control); −6 percentage points (not significant, P=0.186)
Trust score:3/5

Hemorrhage incidence

1 evidences

Ascorbic acid (600 mg/day) did not significantly prevent interferon-associated retinopathy compared with no ascorbic acid.

Trust comment: Randomized controlled trial (n=62) with ophthalmologic assessment but modest sample size and non-significant differences.

Study Details

PMID:11480793
Participants:62
Impact:Cumulative hemorrhage lower in treated group but difference not significant (P=0.186)
Trust score:3/5

Cotton-wool spots incidence

1 evidences

Ascorbic acid (600 mg/day) did not significantly prevent interferon-associated retinopathy compared with no ascorbic acid.

Trust comment: Randomized controlled trial (n=62) with ophthalmologic assessment but modest sample size and non-significant differences.

Study Details

PMID:11480793
Participants:62
Impact:No meaningful difference between groups
Trust score:3/5

Oxidized LDL (ox-LDL)

1 evidences

Providing 350 g/day vegetables and using water-free (multi-ply) cookware increased blood vitamin C and reduced oxidized LDL and LDL cholesterol over 2 weeks compared with ordinary cooking or usual diet.

Trust comment: Randomized study with objective biomarker changes (n=57) showing short-term increases in blood vitamin C and improvements in lipid/oxidative markers; moderate sample and short duration.

Study Details

PMID:22229802
Participants:57
Impact:Group A: 101.5 → 84.1 U/l (−17.4 U/l; P < 0.01)
Trust score:4/5

TNF-alpha (postprandial)

1 evidences

Giving vitamins including vitamin C with meals prevented post-meal rises in inflammatory and adhesion markers in healthy and type 2 diabetic people.

Trust comment: Randomized, observer-blinded crossover with matched controls and clear objective biomarkers, but vitamin C was given with vitamin E (co-intervention).

Study Details

PMID:11923038
Participants:40
Impact:increase prevented by vitamins (no significant rise vs baseline)
Trust score:4/5

IL-6 (postprandial)

1 evidences

Giving vitamins including vitamin C with meals prevented post-meal rises in inflammatory and adhesion markers in healthy and type 2 diabetic people.

Trust comment: Randomized, observer-blinded crossover with matched controls and clear objective biomarkers, but vitamin C was given with vitamin E (co-intervention).

Study Details

PMID:11923038
Participants:40
Impact:increase prevented by vitamins (no significant rise vs baseline)
Trust score:4/5

Adhesion molecules (ICAM-1/VCAM-1)

1 evidences

Giving vitamins including vitamin C with meals prevented post-meal rises in inflammatory and adhesion markers in healthy and type 2 diabetic people.

Trust comment: Randomized, observer-blinded crossover with matched controls and clear objective biomarkers, but vitamin C was given with vitamin E (co-intervention).

Study Details

PMID:11923038
Participants:40
Impact:post-meal increase prevented by vitamins (no significant change from baseline)
Trust score:4/5

Urinary oxalate

1 evidences

Taking 2 g/day vitamin C increased urinary oxalate and calcium-oxalate saturation but did not change urine pH.

Trust comment: Controlled metabolic-diet crossover with 24 subjects and objective urinary measures, but small sample size limits generalizability.

Study Details

PMID:12853784
Participants:24
Impact:increased: +20% (normals, 28.5→34.7 mg) and +33% (stone formers, 30.5→41.0 mg)
Trust score:4/5

Calcium-oxalate relative saturation

1 evidences

Taking 2 g/day vitamin C increased urinary oxalate and calcium-oxalate saturation but did not change urine pH.

Trust comment: Controlled metabolic-diet crossover with 24 subjects and objective urinary measures, but small sample size limits generalizability.

Study Details

PMID:12853784
Participants:24
Impact:significantly increased with 2 g/day ascorbic acid
Trust score:4/5

Urinary pH

1 evidences

Taking 2 g/day vitamin C increased urinary oxalate and calcium-oxalate saturation but did not change urine pH.

Trust comment: Controlled metabolic-diet crossover with 24 subjects and objective urinary measures, but small sample size limits generalizability.

Study Details

PMID:12853784
Participants:24
Impact:no change (≈6.02)
Trust score:4/5

Unpleasant taste (PEG-Asc)

1 evidences

PEG with ascorbic acid tasted worse and was more distressing but achieved similar completion rates and bowel-cleansing quality compared with SPS-Mg.

Trust comment: Single-blind RCT with 130 patients and blinded endoscopist assessment; outcomes are patient-reported taste and objective cleansing scores.

Study Details

PMID:25156179
Participants:130
Impact:higher: 37.9% vs 10.9% (absolute +27.0 percentage points)
Trust score:4/5

Distressing preparation (PEG-Asc)

1 evidences

PEG with ascorbic acid tasted worse and was more distressing but achieved similar completion rates and bowel-cleansing quality compared with SPS-Mg.

Trust comment: Single-blind RCT with 130 patients and blinded endoscopist assessment; outcomes are patient-reported taste and objective cleansing scores.

Study Details

PMID:25156179
Participants:130
Impact:higher: 15.1% vs 4.7%
Trust score:4/5

Completion rate / cleansing quality

1 evidences

PEG with ascorbic acid tasted worse and was more distressing but achieved similar completion rates and bowel-cleansing quality compared with SPS-Mg.

Trust comment: Single-blind RCT with 130 patients and blinded endoscopist assessment; outcomes are patient-reported taste and objective cleansing scores.

Study Details

PMID:25156179
Participants:130
Impact:no difference (completion 92.4% vs 93.8%; cleansing quality similar)
Trust score:4/5

Boston bowel preparation score (BBPS)

1 evidences

PEG with ascorbic acid and sodium phosphate tablets achieved similar bowel-cleaning quality and detection rates, but patient satisfaction and compliance favored sodium phosphate tablets.

Trust comment: Multicenter randomized trial with 189 patients and objective colon-cleansing scoring, though patient-reported measures vary.

Study Details

PMID:25603851
Participants:189
Impact:no difference (8.4 vs 8.3; p=0.441)
Trust score:4/5

Unable to take prescribed dose

1 evidences

PEG with ascorbic acid and sodium phosphate tablets achieved similar bowel-cleaning quality and detection rates, but patient satisfaction and compliance favored sodium phosphate tablets.

Trust comment: Multicenter randomized trial with 189 patients and objective colon-cleansing scoring, though patient-reported measures vary.

Study Details

PMID:25603851
Participants:189
Impact:more frequent with PEGA (8.6% vs 2.0%; p=0.045)
Trust score:4/5

Satisfactory bowel preparation

1 evidences

Compared bowel preparations including polyethylene glycol with ascorbic acid and found similar optimal preparation intervals and overall efficacy; tolerability depended on product type.

Trust comment: Large randomized, endoscopist-blinded multicentre trial providing objective bowel-prep outcomes; direct vitamin C role is as a component of a prep solution rather than a systemic health effect.

Study Details

PMID:29102524
Participants:612
Impact:Achieved with preparation length ≥8.4 h and time to colonoscopy ≤11.8 h; no difference between PEGA and PEG
Trust score:4/5

Optimum interval to colonoscopy

1 evidences

Compared bowel preparations including polyethylene glycol with ascorbic acid and found similar optimal preparation intervals and overall efficacy; tolerability depended on product type.

Trust comment: Large randomized, endoscopist-blinded multicentre trial providing objective bowel-prep outcomes; direct vitamin C role is as a component of a prep solution rather than a systemic health effect.

Study Details

PMID:29102524
Participants:612
Impact:≤11.8 h (PEG, PEGA) and ≤13.3 h (SPMC)
Trust score:4/5

Albumin-to-creatinine ratio (ACR)

1 evidences

In type 2 diabetic patients on metformin, adding 500 mg vitamin C daily for 12 months improved fasting glucose, HbA1c and albumin-to-creatinine ratio versus metformin alone.

Trust comment: Well-powered 12-month randomized multicenter trial with monthly monitoring and objective biochemical endpoints, though single-blind and lacking ITT/repeated-measures in final analysis.

Study Details

PMID:28807030
Participants:422
Impact:Decreased from 3.81 ±2.31 to 2.32 ±1.98 mg/mmol in ascorbic acid arm (−1.49 mg/mmol; P<0.001)
Trust score:4/5

Endothelium-dependent vasodilation (T1D)

1 evidences

Oral antioxidant combination including vitamin C (1,000 mg) improved endothelium-dependent vasodilation in type 1 but not type 2 diabetic patients after 6 months.

Trust comment: Randomized placebo-controlled study but small sample and intervention combined vitamin C with vitamin E, limiting attribution specifically to vitamin C.

Study Details

PMID:12881209
Participants:94
Impact:Increased by +3.4 ±1.4% (P=0.023)
Trust score:3/5

Endothelium-dependent vasodilation (T2D)

1 evidences

Oral antioxidant combination including vitamin C (1,000 mg) improved endothelium-dependent vasodilation in type 1 but not type 2 diabetic patients after 6 months.

Trust comment: Randomized placebo-controlled study but small sample and intervention combined vitamin C with vitamin E, limiting attribution specifically to vitamin C.

Study Details

PMID:12881209
Participants:94
Impact:No significant change (+0.5 ±0.4%, P=0.3)
Trust score:3/5

Withdrawal time

1 evidences

In patients undergoing colonoscopy, 2L-PEG/ascorbic acid and an oral sulfate solution had similar successful bowel cleansing rates; tolerability and adverse events were comparable.

Trust comment: Prospective randomized noninferiority trial with objective bowel-cleansing scoring; vitamin C present as part of a prep formulation rather than systemic therapy.

Study Details

PMID:30308546
Participants:187
Impact:Shorter with OSS: 11.8 ±5.2 vs 14.3 ±8.5 minutes (P=0.016)
Trust score:4/5

Mucosal adverse findings

1 evidences

In patients undergoing colonoscopy, 2L-PEG/ascorbic acid and an oral sulfate solution had similar successful bowel cleansing rates; tolerability and adverse events were comparable.

Trust comment: Prospective randomized noninferiority trial with objective bowel-cleansing scoring; vitamin C present as part of a prep formulation rather than systemic therapy.

Study Details

PMID:30308546
Participants:187
Impact:Mucosal erythema (4.3%) and aphthous lesions (2.1%) observed only in 2L-PEG/Asc group
Trust score:4/5

Intrinsic lymphocyte apoptosis (young)

1 evidences

Two-month randomized double-blind supplementation with multiple antioxidants (including ascorbic acid) reduced intrinsic and UV-induced lymphocyte apoptosis, especially in young and elderly adults.

Trust comment: Large randomized double-blind trial but used a multinutrient supplement, so effects cannot be attributed solely to vitamin C.

Study Details

PMID:22159782
Participants:274
Impact:Decreased by −1.7% vs control (p<0.001)
Trust score:3/5

Intrinsic lymphocyte apoptosis (elderly)

1 evidences

Two-month randomized double-blind supplementation with multiple antioxidants (including ascorbic acid) reduced intrinsic and UV-induced lymphocyte apoptosis, especially in young and elderly adults.

Trust comment: Large randomized double-blind trial but used a multinutrient supplement, so effects cannot be attributed solely to vitamin C.

Study Details

PMID:22159782
Participants:274
Impact:Decreased by −2.3% vs control (p<0.001)
Trust score:3/5

UV-induced lymphocyte apoptosis (children/young/elderly)

1 evidences

Two-month randomized double-blind supplementation with multiple antioxidants (including ascorbic acid) reduced intrinsic and UV-induced lymphocyte apoptosis, especially in young and elderly adults.

Trust comment: Large randomized double-blind trial but used a multinutrient supplement, so effects cannot be attributed solely to vitamin C.

Study Details

PMID:22159782
Participants:274
Impact:Decreased by −1.4% (children), −1.9% (young), and −3.1% (elderly) vs control (all p<0.001)
Trust score:3/5

Troponin-defined periprocedural myocardial injury (PMI)

1 evidences

Preprocedure intravenous 3 g vitamin C reduced the incidence of periprocedural myocardial injury in patients undergoing elective PCI.

Trust comment: Large randomized single-centre trial with objective biomarker endpoints showing lower PMI with preprocedure IV vitamin C; single-centre design limits generalizability.

Study Details

PMID:24365194
Participants:532
Impact:Reduced from 18.4% (control) to 10.9% (vit C) (absolute −7.5 percentage points; P=0.016)
Trust score:4/5

CK-MB-defined PMI

1 evidences

Preprocedure intravenous 3 g vitamin C reduced the incidence of periprocedural myocardial injury in patients undergoing elective PCI.

Trust comment: Large randomized single-centre trial with objective biomarker endpoints showing lower PMI with preprocedure IV vitamin C; single-centre design limits generalizability.

Study Details

PMID:24365194
Participants:532
Impact:Reduced from 8.6% (control) to 4.2% (vit C) (absolute −4.4 percentage points; P=0.035)
Trust score:4/5

MMP-1 expression

1 evidences

Topical antioxidant cocktail (including vitamin C) applied with sunscreen reduced IRA-induced MMP-1 in human skin versus sunscreen alone.

Trust comment: Double-blind randomized controlled trial in 30 volunteers showing significant reduction in MMP-1 with an antioxidant formulation that included vitamin C, but effect is from a cocktail not vitamin C alone.

Study Details

PMID:25349107
Participants:30
Impact:decreased (significant vs sunscreen alone)
Trust score:4/5

Nasal IL-6

1 evidences

In asthmatic children, daily supplementation with vitamins C and E prevented ozone-induced increases in nasal IL-6.

Trust comment: Randomized double-blind trial with 117 children showing protective nasal inflammatory effects, but vitamin C was given with vitamin E.

Study Details

PMID:15498043
Participants:117
Impact:prevented ozone-induced increase (difference vs placebo, P=0.02)
Trust score:4/5

Nasal IL-8

1 evidences

In asthmatic children, daily supplementation with vitamins C and E prevented ozone-induced increases in nasal IL-6.

Trust comment: Randomized double-blind trial with 117 children showing protective nasal inflammatory effects, but vitamin C was given with vitamin E.

Study Details

PMID:15498043
Participants:117
Impact:trend toward attenuation but no significant difference (P=0.12)
Trust score:4/5

Glutathione (GSx) in nasal lavage

1 evidences

In asthmatic children, daily supplementation with vitamins C and E prevented ozone-induced increases in nasal IL-6.

Trust comment: Randomized double-blind trial with 117 children showing protective nasal inflammatory effects, but vitamin C was given with vitamin E.

Study Details

PMID:15498043
Participants:117
Impact:decreased in both groups during follow-up
Trust score:4/5

Postprandial glucose iAUC

1 evidences

In people with type 2 diabetes, 4 months of 1 g/day ascorbic acid reduced post-meal and 24-hour glucose measures, lowered blood pressure, and reduced an oxidative stress marker.

Trust comment: Randomized cross-over RCT directly testing ascorbic acid with multiple clinically meaningful glycaemic and BP effects, but small sample (n=31).

Study Details

PMID:30394006
Participants:31
Impact:-36%
Trust score:4/5

Duration of day with hyperglycaemia

1 evidences

In people with type 2 diabetes, 4 months of 1 g/day ascorbic acid reduced post-meal and 24-hour glucose measures, lowered blood pressure, and reduced an oxidative stress marker.

Trust comment: Randomized cross-over RCT directly testing ascorbic acid with multiple clinically meaningful glycaemic and BP effects, but small sample (n=31).

Study Details

PMID:30394006
Participants:31
Impact:-2.8 h/day
Trust score:4/5

Postprandial hyperglycaemia duration

1 evidences

In people with type 2 diabetes, 4 months of 1 g/day ascorbic acid reduced post-meal and 24-hour glucose measures, lowered blood pressure, and reduced an oxidative stress marker.

Trust comment: Randomized cross-over RCT directly testing ascorbic acid with multiple clinically meaningful glycaemic and BP effects, but small sample (n=31).

Study Details

PMID:30394006
Participants:31
Impact:-1.7 h/day
Trust score:4/5

Average 24-hour glucose

1 evidences

In people with type 2 diabetes, 4 months of 1 g/day ascorbic acid reduced post-meal and 24-hour glucose measures, lowered blood pressure, and reduced an oxidative stress marker.

Trust comment: Randomized cross-over RCT directly testing ascorbic acid with multiple clinically meaningful glycaemic and BP effects, but small sample (n=31).

Study Details

PMID:30394006
Participants:31
Impact:-0.8 mmol/L
Trust score:4/5

Daily postprandial glucose concentration

1 evidences

In people with type 2 diabetes, 4 months of 1 g/day ascorbic acid reduced post-meal and 24-hour glucose measures, lowered blood pressure, and reduced an oxidative stress marker.

Trust comment: Randomized cross-over RCT directly testing ascorbic acid with multiple clinically meaningful glycaemic and BP effects, but small sample (n=31).

Study Details

PMID:30394006
Participants:31
Impact:-1.1 mmol/L
Trust score:4/5

VO2max (maximal aerobic capacity)

1 evidences

Acute and 30-day ascorbic acid increased plasma vitamin C and reduced oxidized LDL acutely, but did not change VO2max or maximal cardiac output in young or older adults.

Trust comment: Direct human infusion and oral study with clear null results for VO2max/Qmax but small sample limits precision.

Study Details

PMID:15501926
Participants:22
Impact:no change after acute or 30-day ascorbic acid administration
Trust score:3/5

Maximal cardiac output (Qmax)

1 evidences

Acute and 30-day ascorbic acid increased plasma vitamin C and reduced oxidized LDL acutely, but did not change VO2max or maximal cardiac output in young or older adults.

Trust comment: Direct human infusion and oral study with clear null results for VO2max/Qmax but small sample limits precision.

Study Details

PMID:15501926
Participants:22
Impact:no change after acute or 30-day ascorbic acid administration
Trust score:3/5

Oxidized LDL concentration

1 evidences

Acute and 30-day ascorbic acid increased plasma vitamin C and reduced oxidized LDL acutely, but did not change VO2max or maximal cardiac output in young or older adults.

Trust comment: Direct human infusion and oral study with clear null results for VO2max/Qmax but small sample limits precision.

Study Details

PMID:15501926
Participants:22
Impact:decreased acutely (~-6%) after infusion; no chronic effect
Trust score:3/5

ferritin

1 evidences

Randomized blind clinical study in preschool children testing water fortification with iron+ascorbic acid, ascorbic acid alone, or plain water over 3 months; hemoglobin rose in all groups, MCV improved with iron+ascorbic and with ascorbic alone, ferritin increased only with iron+ascorbic.

Trust comment: Randomized blinded clinical trial in children with clear hematologic outcomes and moderate sample size, although duration was short (3 months).

Study Details

PMID:23963460
Participants:153
Impact:increased in A (iron+ascorbic) only (A vs B or C significant)
Trust score:4/5

progression to advanced AMD (CFH risk alleles)

1 evidences

Genotype influences whether antioxidant and/or zinc supplements reduce progression to advanced AMD; different genotypes derive benefit from different supplement regimens.

Trust comment: Large genetic analysis of randomized AREDS trial data (n≈995) with long follow-up; secondary pharmacogenomic analysis but based on high-quality trial data.

Study Details

PMID:23972322
Participants:995
Impact:Antioxidants alone reduced progression in patients with 1–2 CFH risk alleles; adding zinc with antioxidants was associated with increased progression (RR=1.83 for 2 CFH risk alleles)
Trust score:4/5

progression to advanced AMD (ARMS2 risk alleles)

1 evidences

Genotype influences whether antioxidant and/or zinc supplements reduce progression to advanced AMD; different genotypes derive benefit from different supplement regimens.

Trust comment: Large genetic analysis of randomized AREDS trial data (n≈995) with long follow-up; secondary pharmacogenomic analysis but based on high-quality trial data.

Study Details

PMID:23972322
Participants:995
Impact:Patients with ARMS2 risk alleles derived benefit from zinc-containing regimens; antioxidants alone were associated with increased progression (RR=2.58 for 1 ARMS2 allele; RR=3.96 for 2 alleles)
Trust score:4/5

intradialytic vitamin C loss (RR%)

1 evidences

Re-infusive convective dialysis techniques (HFR and HFR-S) reduced intradialytic loss of vitamin C (~15% less loss vs ol-HDF) but did not produce a significant long-term increase in plasma vitamin C; overall oxidative markers improved.

Trust comment: Prospective multicenter crossover trial measuring vitamin C and oxidative markers directly but limited by small sample, dropouts, and some missing data.

Study Details

PMID:27566671
Participants:29
Impact:reduced by ~15% with HFR/HFR-S versus ol-HDF (less intradialytic loss)
Trust score:3/5

pre-dialysis plasma vitamin C

1 evidences

Re-infusive convective dialysis techniques (HFR and HFR-S) reduced intradialytic loss of vitamin C (~15% less loss vs ol-HDF) but did not produce a significant long-term increase in plasma vitamin C; overall oxidative markers improved.

Trust comment: Prospective multicenter crossover trial measuring vitamin C and oxidative markers directly but limited by small sample, dropouts, and some missing data.

Study Details

PMID:27566671
Participants:29
Impact:no significant long-term increase (approx. 20.0→21.5 μmol/L for HFR-S; 20.0 μmol/L for HFR)
Trust score:3/5

AOPP (oxidative stress)

1 evidences

Re-infusive convective dialysis techniques (HFR and HFR-S) reduced intradialytic loss of vitamin C (~15% less loss vs ol-HDF) but did not produce a significant long-term increase in plasma vitamin C; overall oxidative markers improved.

Trust comment: Prospective multicenter crossover trial measuring vitamin C and oxidative markers directly but limited by small sample, dropouts, and some missing data.

Study Details

PMID:27566671
Participants:29
Impact:decreased (example: 28.4 → 21.7 μmol/L with HFR-S; ≈-23.6%)
Trust score:3/5

vitamin C

1 evidences

Phlebotomy to reduce iron stores did not change CYP2E1 activity but was associated with lower LDL and vitamin E and a small but significant increase in plasma vitamin C.

Trust comment: Randomized trial (n=48) with clear biochemical endpoints; moderate sample size limits precision but findings on vitamin C are directly reported.

Study Details

PMID:17014579
Participants:48
Impact:mean change +0.5 vs −1.8 in control (P=0.03), i.e., modest increase with phlebotomy
Trust score:3/5

vitamin E

1 evidences

Phlebotomy to reduce iron stores did not change CYP2E1 activity but was associated with lower LDL and vitamin E and a small but significant increase in plasma vitamin C.

Trust comment: Randomized trial (n=48) with clear biochemical endpoints; moderate sample size limits precision but findings on vitamin C are directly reported.

Study Details

PMID:17014579
Participants:48
Impact:decreased (mean change −1.3 vs +2.3; P=0.03)
Trust score:3/5

urinary albumin excretion

1 evidences

In type 2 diabetic patients, combined mineral+vitamin supplementation (including zinc) improved urinary albumin and several metabolic and lipid markers, whereas mineral alone did not show clear benefit.

Trust comment: Randomized, double-blind, placebo-controlled trial but modest sample size (n=69); results for vitamin C reported both alone and in combination with minerals.

Study Details

PMID:16186280
Participants:69
Impact:-decreased (V group P=0.034; MV group P=0.005)
Trust score:4/5

urinary N-acetyl-beta-d-glucosaminidase (NAG) activity

1 evidences

In type 2 diabetic patients, combined mineral+vitamin supplementation (including zinc) improved urinary albumin and several metabolic and lipid markers, whereas mineral alone did not show clear benefit.

Trust comment: Randomized, double-blind, placebo-controlled trial but modest sample size (n=69); results for vitamin C reported both alone and in combination with minerals.

Study Details

PMID:16186280
Participants:69
Impact:no significant change
Trust score:4/5

blood pressure (systolic/diastolic/mean)

1 evidences

In type 2 diabetic patients, combined mineral+vitamin supplementation (including zinc) improved urinary albumin and several metabolic and lipid markers, whereas mineral alone did not show clear benefit.

Trust comment: Randomized, double-blind, placebo-controlled trial but modest sample size (n=69); results for vitamin C reported both alone and in combination with minerals.

Study Details

PMID:16186280
Participants:69
Impact:-significant decrease (MV group P=0.008, P=0.017, P=0.009 respectively)
Trust score:4/5

progression of coronary calcification

1 evidences

In this large randomized trial of combined atorvastatin plus vitamin C and E vs placebo, treatment did not alter progression of coronary calcification; possible non-significant reduction in ASCVD events was observed.

Trust comment: Large, double-blind randomized trial (n=1,005); multicomponent intervention (statin + vitamins) limits attribution of effects specifically to vitamin C.

Study Details

PMID:15992652
Participants:1005
Impact:no significant effect of treatment on calcification progression
Trust score:4/5

ASCVD events

1 evidences

In this large randomized trial of combined atorvastatin plus vitamin C and E vs placebo, treatment did not alter progression of coronary calcification; possible non-significant reduction in ASCVD events was observed.

Trust comment: Large, double-blind randomized trial (n=1,005); multicomponent intervention (statin + vitamins) limits attribution of effects specifically to vitamin C.

Study Details

PMID:15992652
Participants:1005
Impact:possible reduction in events (esp. calcium score >400) but did not reach conventional statistical significance
Trust score:4/5

alanine aminotransferase (ALT) normalization

1 evidences

In patients with fatty liver disease, 6 months of vitamin E (600 IU) plus vitamin C (500 mg) improved liver enzymes similarly to ursodeoxycholic acid; ALT normalized in ~63% vs 55% respectively.

Trust comment: Randomized but open-label with small sample (n=57); results suggest comparable enzyme improvements but limited power and lack of blinding reduce confidence.

Study Details

PMID:16245220
Participants:57
Impact:+ALT normalized in 17/27 (63%) vitamin-treated vs 16/29 (55%) ursodeoxycholic acid
Trust score:3/5

AST/ALT levels

1 evidences

In patients with fatty liver disease, 6 months of vitamin E (600 IU) plus vitamin C (500 mg) improved liver enzymes similarly to ursodeoxycholic acid; ALT normalized in ~63% vs 55% respectively.

Trust comment: Randomized but open-label with small sample (n=57); results suggest comparable enzyme improvements but limited power and lack of blinding reduce confidence.

Study Details

PMID:16245220
Participants:57
Impact:-significant decrease in both treatment groups after 6 months
Trust score:3/5

gamma-glutamyl transpeptidase (GGT)

1 evidences

In patients with fatty liver disease, 6 months of vitamin E (600 IU) plus vitamin C (500 mg) improved liver enzymes similarly to ursodeoxycholic acid; ALT normalized in ~63% vs 55% respectively.

Trust comment: Randomized but open-label with small sample (n=57); results suggest comparable enzyme improvements but limited power and lack of blinding reduce confidence.

Study Details

PMID:16245220
Participants:57
Impact:-decreased with ursodeoxycholic acid; no change with vitamin E+C
Trust score:3/5

ADMA

1 evidences

In middle-aged men with mildly high homocysteine, 8 weeks of B vitamins and/or antioxidants (including 150 mg ascorbic acid) did not change ADMA or CRP versus placebo.

Trust comment: Randomized, double-blind, placebo-controlled trial with moderate sample and clear negative results reported.

Study Details

PMID:20401662
Participants:101
Impact:no significant change vs placebo at 8 weeks
Trust score:4/5

CRP

1 evidences

In middle-aged men with mildly high homocysteine, 8 weeks of B vitamins and/or antioxidants (including 150 mg ascorbic acid) did not change ADMA or CRP versus placebo.

Trust comment: Randomized, double-blind, placebo-controlled trial with moderate sample and clear negative results reported.

Study Details

PMID:20401662
Participants:101
Impact:no significant change vs placebo at 8 weeks
Trust score:4/5

LDL resistance to oxidative stress

1 evidences

Critically ill patients receiving enteral formula enriched with vitamins A, C, and E showed increased plasma antioxidant vitamins and improved LDL resistance to oxidation, with no change in clinical outcomes.

Trust comment: Prospective randomized double-blind placebo-controlled ICU study with demonstrated biochemical effects but small completed sample and no clinical outcome differences.

Study Details

PMID:11153621
Participants:37
Impact:improved by 21 ± 4% (p<0.05)
Trust score:4/5

maximal voluntary contraction (MVCQ)

1 evidences

Daily supplementation (vitamin C + E + zinc + selenium) for 17 weeks improved quadriceps maximal voluntary contraction and endurance and altered antioxidant markers, but did not improve 2-minute walk distance.

Trust comment: Randomized double-blind placebo-controlled clinical trial with clear between-group biochemical and functional differences though modest sample size (pilot).

Study Details

PMID:25246239
Participants:53
Impact:significant increase in supplemented group vs placebo (MVCQD p=0.011; MVCQND p=0.004)
Trust score:4/5

endurance limit time (TlimQ)

1 evidences

Daily supplementation (vitamin C + E + zinc + selenium) for 17 weeks improved quadriceps maximal voluntary contraction and endurance and altered antioxidant markers, but did not improve 2-minute walk distance.

Trust comment: Randomized double-blind placebo-controlled clinical trial with clear between-group biochemical and functional differences though modest sample size (pilot).

Study Details

PMID:25246239
Participants:53
Impact:significant increase in supplemented group vs placebo (TlimQD p=0.028; TlimQND p=0.011)
Trust score:4/5

ischemic episodes (48 h)

1 evidences

Adding vitamins C+E to intensive statin therapy did not provide additional benefit on measures of myocardial ischemia.

Trust comment: Large (n=300), randomized double-blind placebo-controlled trial with objectively measured endpoints; credible but complex intervention (vitamins combined with statin).

Study Details

PMID:15809368
Participants:300
Impact:decreased 31–61% in all groups; no incremental effect of vitamins C+E versus atorvastatin alone
Trust score:4/5

duration of ischemia (48 h)

1 evidences

Adding vitamins C+E to intensive statin therapy did not provide additional benefit on measures of myocardial ischemia.

Trust comment: Large (n=300), randomized double-blind placebo-controlled trial with objectively measured endpoints; credible but complex intervention (vitamins combined with statin).

Study Details

PMID:15809368
Participants:300
Impact:decreased 26–62% in all groups; no incremental effect of vitamins C+E
Trust score:4/5

flow-mediated dilation

2 evidences

Adding vitamins C+E to intensive statin therapy did not provide additional benefit on measures of myocardial ischemia.

Trust comment: Large (n=300), randomized double-blind placebo-controlled trial with objectively measured endpoints; credible but complex intervention (vitamins combined with statin).

Study Details

PMID:15809368
Participants:300
Impact:no meaningful change with addition of vitamins C+E
Trust score:4/5

An acute antioxidant cocktail including vitamin C improved vascular function measures in COPD patients compared with placebo.

Trust comment: Randomized, placebo-controlled crossover with physiologic endpoints; sample size modest but design strong for acute effects.

Study Details

PMID:24324045
Participants:60
Impact:Improved with antioxidant cocktail versus placebo in COPD patients (P < 0.05)
Trust score:4/5

total endogenous antioxidant capacity (TEAC)

1 evidences

A perioperative antioxidant-containing drink raised plasma vitamin C and total antioxidant capacity shortly after surgery but did not reduce markers of systemic inflammation.

Trust comment: Double-blind RCT but small (n=36) and pilot in surgical patients, limiting power and generalizability.

Study Details

PMID:21890323
Participants:36
Impact:improved on POD 1, 3, and 7 in pONS group (P = 0.01)
Trust score:3/5

C-reactive protein (systemic inflammation)

1 evidences

A perioperative antioxidant-containing drink raised plasma vitamin C and total antioxidant capacity shortly after surgery but did not reduce markers of systemic inflammation.

Trust comment: Double-blind RCT but small (n=36) and pilot in surgical patients, limiting power and generalizability.

Study Details

PMID:21890323
Participants:36
Impact:no difference between groups after surgery
Trust score:3/5

nuclear opalescence (cataract progression)

1 evidences

Five-year randomized trial found that supplements including vitamin C, vitamin E and beta carotene did not slow cataract progression versus placebo.

Trust comment: Large (n=798), long (5-year), triple-masked randomized placebo-controlled field trial with high follow-up and compliance—high-quality evidence.

Study Details

PMID:16556618
Participants:798
Impact:no significant difference between antioxidant supplementation and placebo over 5 years
Trust score:5/5

secondary lens opacity measures / visual acuity

1 evidences

Five-year randomized trial found that supplements including vitamin C, vitamin E and beta carotene did not slow cataract progression versus placebo.

Trust comment: Large (n=798), long (5-year), triple-masked randomized placebo-controlled field trial with high follow-up and compliance—high-quality evidence.

Study Details

PMID:16556618
Participants:798
Impact:no significant difference between groups
Trust score:5/5

failure of treatment / myopic shift

1 evidences

Five-year randomized trial found that supplements including vitamin C, vitamin E and beta carotene did not slow cataract progression versus placebo.

Trust comment: Large (n=798), long (5-year), triple-masked randomized placebo-controlled field trial with high follow-up and compliance—high-quality evidence.

Study Details

PMID:16556618
Participants:798
Impact:no significant difference between groups
Trust score:5/5

aldosterone / DHEA

1 evidences

Intravenous ascorbic acid did not attenuate etomidate-induced suppression of adrenal steroid production in this small clinical study.

Trust comment: Controlled clinical setting but small sample (n=30) and limited power to detect modest effects.

Study Details

PMID:8842654
Participants:30
Impact:no evidence of attenuation by ascorbic acid
Trust score:3/5

15-F2t-isoprostane

1 evidences

In patients with prior nonmelanoma skin cancer, 60 days of antioxidant supplementation including zinc produced modest reductions in oxidative stress biomarkers (notably 15-F2t-isoprostane) but differences versus placebo were not statistically significant.

Trust comment: Double-blind, randomized, placebo-controlled design but small sample and short (60-day) supplementation limit power to detect effects.

Study Details

PMID:26509174
Participants:60
Impact:-10.5 pg/mL (87.3 → 76.8 pg/mL; not significant)
Trust score:3/5

TBARS

1 evidences

In patients with prior nonmelanoma skin cancer, 60 days of antioxidant supplementation including zinc produced modest reductions in oxidative stress biomarkers (notably 15-F2t-isoprostane) but differences versus placebo were not statistically significant.

Trust comment: Double-blind, randomized, placebo-controlled design but small sample and short (60-day) supplementation limit power to detect effects.

Study Details

PMID:26509174
Participants:60
Impact:-30 nmol/L (90.0 → 60.0 nmol/L; not significant)
Trust score:3/5

endothelium-independent (nitroglycerin) vasodilation

1 evidences

Antioxidant vitamins including vitamin C (500 mg twice daily) did not improve flow-mediated dilation or nitroglycerin-induced dilation in postmenopausal women with coronary artery disease.

Trust comment: Substudy of an RCT with objective vascular measures, but small sample size and limited power.

Study Details

PMID:15721027
Participants:61
Impact:no significant change
Trust score:3/5

new pressure ulcer occurrence

1 evidences

An enteral diet enriched with EPA, GLA and vitamins A, C and E reduced the occurrence of new pressure ulcers but did not affect healing of existing ulcers in critically ill patients.

Trust comment: Randomized prospective controlled design with 100 patients, but pressure ulcer outcomes were a secondary endpoint.

Study Details

PMID:17933438
Participants:100
Impact:decreased (significant, p<0.05)
Trust score:3/5

healing of existing pressure ulcers

1 evidences

An enteral diet enriched with EPA, GLA and vitamins A, C and E reduced the occurrence of new pressure ulcers but did not affect healing of existing ulcers in critically ill patients.

Trust comment: Randomized prospective controlled design with 100 patients, but pressure ulcer outcomes were a secondary endpoint.

Study Details

PMID:17933438
Participants:100
Impact:no difference
Trust score:3/5

acetylcholine-induced coronary artery vasodilation (endothelium-dependent)

1 evidences

Sequential intracoronary ascorbic acid infusions did not improve acetylcholine-induced coronary vasodilation or nitroglycerin responses in patients with coronary atherosclerosis.

Trust comment: Mechanistic human infusion study with objective angiographic and flow measures but small sample size limits generalizability.

Study Details

PMID:14732296
Participants:26
Impact:no effect versus placebo (no significant change in diameter response)
Trust score:3/5

coronary blood flow response

1 evidences

Sequential intracoronary ascorbic acid infusions did not improve acetylcholine-induced coronary vasodilation or nitroglycerin responses in patients with coronary atherosclerosis.

Trust comment: Mechanistic human infusion study with objective angiographic and flow measures but small sample size limits generalizability.

Study Details

PMID:14732296
Participants:26
Impact:no effect versus placebo (no significant change)
Trust score:3/5

total cancer incidence (overall)

1 evidences

Long-term low-dose antioxidant/multi-mineral supplementation (including 20 mg zinc) reduced total cancer incidence and all-cause mortality in men but not in women over ~7.5 years.

Trust comment: Large randomized double-blind placebo-controlled primary prevention trial with long follow-up, providing high-quality evidence.

Study Details

PMID:15557412
Participants:13017
Impact:no significant difference overall
Trust score:5/5

all-cause mortality (men)

1 evidences

Long-term low-dose antioxidant/multi-mineral supplementation (including 20 mg zinc) reduced total cancer incidence and all-cause mortality in men but not in women over ~7.5 years.

Trust comment: Large randomized double-blind placebo-controlled primary prevention trial with long follow-up, providing high-quality evidence.

Study Details

PMID:15557412
Participants:13017
Impact:decreased ~37% (RR 0.63, 95% CI 0.42–0.93)
Trust score:5/5

serum gamma-tocopherol

1 evidences

Analysis of factors linked to blood vitamin E levels in postmenopausal women; supplemental vitamin C was associated with higher alpha- and lower gamma-tocopherol.

Trust comment: Large, well-characterized observational cohort with confounder adjustment but cross-sectional associations limit causal inference.

Study Details

PMID:11164130
Participants:1047
Impact:decrease (associated with supplemental vitamin C)
Trust score:3/5

endothelium-dependent dilation (EDD)

1 evidences

Double-blind placebo-controlled human study of acute methionine-induced homocysteinemia testing high-dose antioxidant vitamins (2 g vitamin C + 800 IU vitamin E) vs placebo; vitamins reduced lipid peroxidation in hypertensives but did not prevent endothelial dysfunction or ET-1 elevation.

Trust comment: Randomized, placebo-controlled human trial with clearly measured vascular endpoints but modest sample size and acute experimental model.

Study Details

PMID:20160653
Participants:88
Impact:decreased after methionine loading in all groups; vitamins did not prevent the decrease
Trust score:4/5

plasma total lipid hydroperoxides (per-ox)

1 evidences

Double-blind placebo-controlled human study of acute methionine-induced homocysteinemia testing high-dose antioxidant vitamins (2 g vitamin C + 800 IU vitamin E) vs placebo; vitamins reduced lipid peroxidation in hypertensives but did not prevent endothelial dysfunction or ET-1 elevation.

Trust comment: Randomized, placebo-controlled human trial with clearly measured vascular endpoints but modest sample size and acute experimental model.

Study Details

PMID:20160653
Participants:88
Impact:reduced by vitamins in hypertensive group (P < 0.05)
Trust score:4/5

plasma endothelin-1 (ET-1) in hypertensives

1 evidences

Double-blind placebo-controlled human study of acute methionine-induced homocysteinemia testing high-dose antioxidant vitamins (2 g vitamin C + 800 IU vitamin E) vs placebo; vitamins reduced lipid peroxidation in hypertensives but did not prevent endothelial dysfunction or ET-1 elevation.

Trust comment: Randomized, placebo-controlled human trial with clearly measured vascular endpoints but modest sample size and acute experimental model.

Study Details

PMID:20160653
Participants:88
Impact:increased after methionine loading in hypertensives and not prevented by vitamins (P < 0.05)
Trust score:4/5

FEF25-75 (persistent asthmatics, low vitamin C)

1 evidences

Combined cohorts (one RCT supplementation subset) of asthmatic children examined longitudinally; low dietary vitamin C intake (≤105 mg/day) was associated with larger ozone-induced decrements in small-airway function (FEF25-75), especially in persistent asthmatics and genetically susceptible children.

Trust comment: Longitudinal cohort with repeated measures and genotype data; includes a randomized supplementation subset, but observational diet assessment and modest sample size limit causal inference.

Study Details

PMID:23379631
Participants:257
Impact:decrement −61.2 ml/s per 60 ppb ozone (p=0.02)
Trust score:4/5

FEF25-75 (persistent asthmatics, 4–6 risk alleles & low vitamin C)

1 evidences

Combined cohorts (one RCT supplementation subset) of asthmatic children examined longitudinally; low dietary vitamin C intake (≤105 mg/day) was associated with larger ozone-induced decrements in small-airway function (FEF25-75), especially in persistent asthmatics and genetically susceptible children.

Trust comment: Longitudinal cohort with repeated measures and genotype data; includes a randomized supplementation subset, but observational diet assessment and modest sample size limit causal inference.

Study Details

PMID:23379631
Participants:257
Impact:decrement −97.2 ml/s per 60 ppb ozone (p=0.03)
Trust score:4/5

FEF25-75 (overall sample)

1 evidences

Combined cohorts (one RCT supplementation subset) of asthmatic children examined longitudinally; low dietary vitamin C intake (≤105 mg/day) was associated with larger ozone-induced decrements in small-airway function (FEF25-75), especially in persistent asthmatics and genetically susceptible children.

Trust comment: Longitudinal cohort with repeated measures and genotype data; includes a randomized supplementation subset, but observational diet assessment and modest sample size limit causal inference.

Study Details

PMID:23379631
Participants:257
Impact:no significant ozone effect overall; protective effect observed with higher vitamin C intake (>105 mg/day)
Trust score:4/5

delayed-type hypersensitivity (DTH) response

1 evidences

Randomized placebo-controlled 2×2 factorial trial in healthy adults testing micronutrient mix (including vitamin C) and bovine colostrum over 10 weeks; micronutrient supplementation raised plasma vitamin C and other micronutrients and enhanced delayed-type hypersensitivity (DTH) responses, especially in older subjects; most other immune parameters unchanged.

Trust comment: Well-controlled randomized study with good compliance and relevant immune biomarkers, but effects were limited to DTH and concentrated in older subjects.

Study Details

PMID:17118191
Participants:131
Impact:number of positive indurations increased (micronutrient vs non-micronutrient, p=0.009), effect stronger in older subgroup
Trust score:4/5

vaccine-specific antibody responses and most ex vivo immune measures

1 evidences

Randomized placebo-controlled 2×2 factorial trial in healthy adults testing micronutrient mix (including vitamin C) and bovine colostrum over 10 weeks; micronutrient supplementation raised plasma vitamin C and other micronutrients and enhanced delayed-type hypersensitivity (DTH) responses, especially in older subjects; most other immune parameters unchanged.

Trust comment: Well-controlled randomized study with good compliance and relevant immune biomarkers, but effects were limited to DTH and concentrated in older subjects.

Study Details

PMID:17118191
Participants:131
Impact:no significant effect of micronutrients or colostrum on mean vaccine responses or most immune parameters
Trust score:4/5

total antioxidant capacity

2 evidences

Two weeks of a phenolic-rich dessert in institutionalised elderly produced no significant changes in antioxidant capacity, antioxidant vitamins (including vitamin C), LDL peroxidation or DNA damage.

Trust comment: Randomized short (2-week) intervention in 22 elderly subjects; limited duration and sample size reduce ability to detect changes.

Study Details

PMID:15182397
Participants:22
Impact:no significant change after 2 weeks
Trust score:3/5

In surgical patients on TPN, plasma vitamin C and other non-supplemented antioxidants fell during TPN despite alpha-tocopherol supplementation normalizing tocopherol levels in one group.

Trust comment: Randomized clinical setting but small sample and short duration; vitamin C was measured but not manipulated as the primary intervention.

Study Details

PMID:10895108
Participants:33
Impact:decreased during TPN (both groups)
Trust score:3/5

antioxidant vitamins (incl. vitamin C)

1 evidences

Two weeks of a phenolic-rich dessert in institutionalised elderly produced no significant changes in antioxidant capacity, antioxidant vitamins (including vitamin C), LDL peroxidation or DNA damage.

Trust comment: Randomized short (2-week) intervention in 22 elderly subjects; limited duration and sample size reduce ability to detect changes.

Study Details

PMID:15182397
Participants:22
Impact:no significant change after 2 weeks
Trust score:3/5

DNA damage (lymphocytes)

1 evidences

Two weeks of a phenolic-rich dessert in institutionalised elderly produced no significant changes in antioxidant capacity, antioxidant vitamins (including vitamin C), LDL peroxidation or DNA damage.

Trust comment: Randomized short (2-week) intervention in 22 elderly subjects; limited duration and sample size reduce ability to detect changes.

Study Details

PMID:15182397
Participants:22
Impact:no significant change after 2 weeks
Trust score:3/5

alpha-tocopherol

1 evidences

Controlled diet crossover: 30 g alcohol/day decreased alpha‑tocopherol modestly and marginally increased isoprostanes; vitamin C and selenium were not significantly changed.

Trust comment: Well-controlled randomized crossover diet study in 53 women with appropriate biomarkers, though some results were marginal.

Study Details

PMID:15367922
Participants:53
Impact:−4.6% with 30 g alcohol/day (P=0.02)
Trust score:4/5

isoprostanes (15-F2t-IsoP)

1 evidences

Controlled diet crossover: 30 g alcohol/day decreased alpha‑tocopherol modestly and marginally increased isoprostanes; vitamin C and selenium were not significantly changed.

Trust comment: Well-controlled randomized crossover diet study in 53 women with appropriate biomarkers, though some results were marginal.

Study Details

PMID:15367922
Participants:53
Impact:+4.9% with 30 g alcohol/day (marginal, P=0.07)
Trust score:4/5

vitamin C (plasma)

1 evidences

Controlled diet crossover: 30 g alcohol/day decreased alpha‑tocopherol modestly and marginally increased isoprostanes; vitamin C and selenium were not significantly changed.

Trust comment: Well-controlled randomized crossover diet study in 53 women with appropriate biomarkers, though some results were marginal.

Study Details

PMID:15367922
Participants:53
Impact:no significant change with alcohol treatments
Trust score:4/5

blood lead levels (BLL)

1 evidences

Combined succimer with calcium and ascorbic acid produced greater reductions in blood lead levels and higher rates of achieving BLL <10 μg/dL compared with nutritional intervention alone.

Trust comment: Randomized clinical study in 72 children showing significant benefits of combined therapy, though exact numeric magnitudes in the report summary are not provided.

Study Details

PMID:21787678
Participants:72
Impact:combined treatment produced significantly greater reduction vs nutritional intervention
Trust score:4/5

percentage with BLL <10 μg/dL

1 evidences

Combined succimer with calcium and ascorbic acid produced greater reductions in blood lead levels and higher rates of achieving BLL <10 μg/dL compared with nutritional intervention alone.

Trust comment: Randomized clinical study in 72 children showing significant benefits of combined therapy, though exact numeric magnitudes in the report summary are not provided.

Study Details

PMID:21787678
Participants:72
Impact:higher percentage at end of therapy and at 8 weeks in combined group (significant)
Trust score:4/5

blood ALAD activity

1 evidences

Combined succimer with calcium and ascorbic acid produced greater reductions in blood lead levels and higher rates of achieving BLL <10 μg/dL compared with nutritional intervention alone.

Trust comment: Randomized clinical study in 72 children showing significant benefits of combined therapy, though exact numeric magnitudes in the report summary are not provided.

Study Details

PMID:21787678
Participants:72
Impact:improvement reported in animal data; clinical effect implied but magnitude not detailed
Trust score:4/5

LDL oxidation lag time

1 evidences

In short-term supplementation in well-controlled type 2 diabetes, vitamin C (500 mg/day) did not meaningfully change LDL oxidation susceptibility, CRP, or adhesion molecules.

Trust comment: Randomized placebo-controlled trial in 57 patients; robust design but vitamin C arm showed no significant effects on the reported endpoints.

Study Details

PMID:10840987
Participants:57
Impact:no significant change with vitamin C
Trust score:4/5

Chromosomal damage (micronuclei frequency)

1 evidences

In cancer patients receiving cisplatin-based chemotherapy, a beverage containing antioxidants including vitamin C did not prevent chemotherapy-induced chromosomal damage.

Trust comment: Randomized small trial (n=27) in humans but used a mixed antioxidant beverage (vitamin C combined with others), limiting attribution to vitamin C alone.

Study Details

PMID:11673080
Participants:27
Impact:no significant change vs placebo
Trust score:3/5

HPRT mutant frequency

1 evidences

In cancer patients receiving cisplatin-based chemotherapy, a beverage containing antioxidants including vitamin C did not prevent chemotherapy-induced chromosomal damage.

Trust comment: Randomized small trial (n=27) in humans but used a mixed antioxidant beverage (vitamin C combined with others), limiting attribution to vitamin C alone.

Study Details

PMID:11673080
Participants:27
Impact:no significant change
Trust score:3/5

Nephrotoxicity (cisplatin-related renal function)

1 evidences

In cancer patients receiving cisplatin-based chemotherapy, a beverage containing antioxidants including vitamin C did not prevent chemotherapy-induced chromosomal damage.

Trust comment: Randomized small trial (n=27) in humans but used a mixed antioxidant beverage (vitamin C combined with others), limiting attribution to vitamin C alone.

Study Details

PMID:11673080
Participants:27
Impact:not prevented by antioxidant supplementation
Trust score:3/5

Bowel preparation quality (BBPS ≥6)

1 evidences

In inactive ulcerative colitis patients, bowel prep containing ascorbic acid (vitamin C) had similar cleansing efficacy and symptom flare risk but higher willingness to repeat.

Trust comment: Prospective randomized multicenter trial (n=109) directly comparing a regimen containing ascorbic acid; results are clinically applicable to UC surveillance patients.

Study Details

PMID:28639128
Participants:109
Impact:no significant difference
Trust score:4/5

Ulcerative colitis clinical activity (SCCAI)

1 evidences

In inactive ulcerative colitis patients, bowel prep containing ascorbic acid (vitamin C) had similar cleansing efficacy and symptom flare risk but higher willingness to repeat.

Trust comment: Prospective randomized multicenter trial (n=109) directly comparing a regimen containing ascorbic acid; results are clinically applicable to UC surveillance patients.

Study Details

PMID:28639128
Participants:109
Impact:no difference in post-procedure score increases
Trust score:4/5

Patient acceptability (willingness to repeat)

1 evidences

In inactive ulcerative colitis patients, bowel prep containing ascorbic acid (vitamin C) had similar cleansing efficacy and symptom flare risk but higher willingness to repeat.

Trust comment: Prospective randomized multicenter trial (n=109) directly comparing a regimen containing ascorbic acid; results are clinically applicable to UC surveillance patients.

Study Details

PMID:28639128
Participants:109
Impact:+17.9 percentage points (82.1% vs 64.2%) favoring 2L-PEG-Asc
Trust score:4/5

Diagnostic yield (P2 lesions)

1 evidences

Adding sodium ascorbate (vitamin C) to bowel purge did not improve capsule endoscopy diagnostic yield or small-bowel visualization and was less well tolerated than clear fluids alone.

Trust comment: Multicenter, blinded randomized controlled trial with 229 completers; sodium ascorbate was evaluated as part of the prep regimen, providing robust evidence.

Study Details

PMID:35843287
Participants:229
Impact:no significant difference
Trust score:4/5

Small-bowel visualization quality (Brotz score)

1 evidences

Adding sodium ascorbate (vitamin C) to bowel purge did not improve capsule endoscopy diagnostic yield or small-bowel visualization and was less well tolerated than clear fluids alone.

Trust comment: Multicenter, blinded randomized controlled trial with 229 completers; sodium ascorbate was evaluated as part of the prep regimen, providing robust evidence.

Study Details

PMID:35843287
Participants:229
Impact:no significant difference
Trust score:4/5

Patient tolerability (VAS)

1 evidences

Adding sodium ascorbate (vitamin C) to bowel purge did not improve capsule endoscopy diagnostic yield or small-bowel visualization and was less well tolerated than clear fluids alone.

Trust comment: Multicenter, blinded randomized controlled trial with 229 completers; sodium ascorbate was evaluated as part of the prep regimen, providing robust evidence.

Study Details

PMID:35843287
Participants:229
Impact:worse tolerability with purgative arms (arm C mean 2.6 vs clear fluids 1.5)
Trust score:4/5

Epoetin resistance index (rhuEPO dose/Hb)

1 evidences

In hemodialysis patients with iron overload, intravenous ascorbic acid did not increase iron mobilization but improved response to erythropoietin.

Trust comment: Randomized prospective trial but small (n=27); clear clinical endpoints though limited power for some outcomes.

Study Details

PMID:14733417
Participants:27
Impact:−21% in IV ascorbic acid group
Trust score:3/5

Iron mobilization / iron loss due to dialysis

1 evidences

In hemodialysis patients with iron overload, intravenous ascorbic acid did not increase iron mobilization but improved response to erythropoietin.

Trust comment: Randomized prospective trial but small (n=27); clear clinical endpoints though limited power for some outcomes.

Study Details

PMID:14733417
Participants:27
Impact:no increase with IV ascorbic acid
Trust score:3/5

Functional iron after stopping parenteral iron

1 evidences

In hemodialysis patients with iron overload, intravenous ascorbic acid did not increase iron mobilization but improved response to erythropoietin.

Trust comment: Randomized prospective trial but small (n=27); clear clinical endpoints though limited power for some outcomes.

Study Details

PMID:14733417
Participants:27
Impact:no drop with IV ascorbic acid (maintained)
Trust score:3/5

IL-6 mRNA expression

1 evidences

Giving vitamin C to brain-dead donors reduced IL-6 gene expression and improved early liver enzyme levels in transplant recipients.

Trust comment: Randomized donor study with molecular and clinical endpoints but modest sample size and specialized population.

Study Details

PMID:25780881
Participants:40
Impact:decrease (TP3 vs TP1, significant)
Trust score:4/5

TNF-α expression/levels

1 evidences

Giving vitamin C to brain-dead donors reduced IL-6 gene expression and improved early liver enzyme levels in transplant recipients.

Trust comment: Randomized donor study with molecular and clinical endpoints but modest sample size and specialized population.

Study Details

PMID:25780881
Participants:40
Impact:no significant change
Trust score:4/5

Recipient liver enzymes (AST/ALT)

1 evidences

Giving vitamin C to brain-dead donors reduced IL-6 gene expression and improved early liver enzyme levels in transplant recipients.

Trust comment: Randomized donor study with molecular and clinical endpoints but modest sample size and specialized population.

Study Details

PMID:25780881
Participants:40
Impact:decrease on day 3 vs day 1 (significant)
Trust score:4/5

Total cleansing solution volume

1 evidences

An ascorbic acid–enriched PEG solution prepared the bowel as well as standard PEG with a lower total drinking volume.

Trust comment: Phase III multicenter randomized non-inferiority trial with adequate sample and clear endpoints.

Study Details

PMID:37462794
Participants:173
Impact:decrease (1757.0 vs 1970.1 mL; −213.1 mL)
Trust score:5/5

Severe postoperative adverse events

1 evidences

An ascorbic acid–enriched PEG solution prepared the bowel as well as standard PEG with a lower total drinking volume.

Trust comment: Phase III multicenter randomized non-inferiority trial with adequate sample and clear endpoints.

Study Details

PMID:37462794
Participants:173
Impact:similar (2 vs 3 events)
Trust score:5/5

Plasma C-reactive protein (CRP)

2 evidences

Vitamin C 515 mg/day lowered plasma CRP by about 24% versus control over 2 months.

Trust comment: Randomized double-blind placebo-controlled trial with reasonable sample and statistically significant primary outcome.

Study Details

PMID:15047680
Participants:160
Impact:decrease (~24.0% vs control; 95% CI −38.9% to −5.5%, p=0.036)
Trust score:4/5

In short-term supplementation in well-controlled type 2 diabetes, vitamin C (500 mg/day) did not meaningfully change LDL oxidation susceptibility, CRP, or adhesion molecules.

Trust comment: Randomized placebo-controlled trial in 57 patients; robust design but vitamin C arm showed no significant effects on the reported endpoints.

Study Details

PMID:10840987
Participants:57
Impact:no significant change with vitamin C
Trust score:4/5

Incidence of nephrotoxicity (RIFLE)

1 evidences

Intravenous vitamin C did not reduce rates of colistin-associated nephrotoxicity in this small randomized trial.

Trust comment: Small randomized controlled clinical study with appropriate measures but limited power.

Study Details

PMID:25801556
Participants:28
Impact:no significant difference (53.8% vs 60.0%; P=0.956)
Trust score:3/5

Urinary renal injury markers (NGAL, NAG)

1 evidences

Intravenous vitamin C did not reduce rates of colistin-associated nephrotoxicity in this small randomized trial.

Trust comment: Small randomized controlled clinical study with appropriate measures but limited power.

Study Details

PMID:25801556
Participants:28
Impact:increased from baseline in both groups (no protective effect observed)
Trust score:3/5

Plasma colistin concentration

1 evidences

Intravenous vitamin C did not reduce rates of colistin-associated nephrotoxicity in this small randomized trial.

Trust comment: Small randomized controlled clinical study with appropriate measures but limited power.

Study Details

PMID:25801556
Participants:28
Impact:no significant difference between groups
Trust score:3/5

C-reactive protein

1 evidences

In a 6-month randomized trial subgroup, multivitamin use was associated with lower CRP levels compared with placebo.

Trust comment: Randomized controlled trial but effect is from a multivitamin (not vitamin C alone); post hoc subgroup analysis limits causal attribution to vitamin C.

Study Details

PMID:14693322
Participants:87
Impact:between-group difference -0.91 mg/L at 6 months (95% CI -1.52 to -0.30)
Trust score:3/5

dyspareunia

1 evidences

Adding vitamin C to standard antibiotic and topical therapy reduced pain with intercourse and vaginal discharge in women treated for chlamydial cervicitis.

Trust comment: Randomized double-blind RCT with clear clinical endpoints and n=80; good internal validity.

Study Details

PMID:19780738
Participants:80
Impact:decreased (P < 0.001)
Trust score:4/5

vaginal discharge

1 evidences

Adding vitamin C to standard antibiotic and topical therapy reduced pain with intercourse and vaginal discharge in women treated for chlamydial cervicitis.

Trust comment: Randomized double-blind RCT with clear clinical endpoints and n=80; good internal validity.

Study Details

PMID:19780738
Participants:80
Impact:decreased (P = 0.005)
Trust score:4/5

cervical severity score

1 evidences

Adding vitamin C to standard antibiotic and topical therapy reduced pain with intercourse and vaginal discharge in women treated for chlamydial cervicitis.

Trust comment: Randomized double-blind RCT with clear clinical endpoints and n=80; good internal validity.

Study Details

PMID:19780738
Participants:80
Impact:improved (significant)
Trust score:4/5

repigmentation (>75%)

1 evidences

Oral antioxidant pool given before and during NB-UVB phototherapy improved repigmentation and reduced oxidative stress in patients with nonsegmental vitiligo.

Trust comment: Randomized double-blind placebo-controlled multicentre trial but small completed sample (n=28).

Study Details

PMID:17953631
Participants:28
Impact:57% vs 18% in placebo (P < 0.05)
Trust score:4/5

catalase activity (PBMCs)

1 evidences

Oral antioxidant pool given before and during NB-UVB phototherapy improved repigmentation and reduced oxidative stress in patients with nonsegmental vitiligo.

Trust comment: Randomized double-blind placebo-controlled multicentre trial but small completed sample (n=28).

Study Details

PMID:17953631
Participants:28
Impact:increased to 114% of baseline (P < 0.05 vs placebo)
Trust score:4/5

reactive oxygen species (ROS) production (PBMCs)

1 evidences

Oral antioxidant pool given before and during NB-UVB phototherapy improved repigmentation and reduced oxidative stress in patients with nonsegmental vitiligo.

Trust comment: Randomized double-blind placebo-controlled multicentre trial but small completed sample (n=28).

Study Details

PMID:17953631
Participants:28
Impact:decreased to ~60% of baseline (P < 0.02 vs placebo)
Trust score:4/5

HDL-C

3 evidences

In CAD patients on simvastatin+niacin, adding antioxidant vitamins (including vitamin C) blunted the favorable increases in HDL metrics observed with lipid therapy alone.

Trust comment: Randomized 12-month trial of moderate size with clear lipid endpoints, but antioxidants were given as a combination so attribution to vitamin C alone is indirect.

Study Details

PMID:11498460
Participants:153
Impact:S-N: +25% vs S-N+A: +18% (increase blunted by antioxidants)
Trust score:4/5

Drinking 500 mL/day orange juice while doing aerobic training for 3 months was associated with better cholesterol and less muscle fatigue.

Trust comment: Controlled intervention in 26 women; orange juice raised vitamin C intake but contained multiple nutrients so attribution to vitamin C alone is uncertain (small sample).

Study Details

PMID:20729016
Participants:26
Impact:+18%
Trust score:3/5

Adding vitamin C to simvastatin did not provide lipid-profile benefits beyond simvastatin alone in patients with low HDL-C.

Trust comment: Randomized study but combined interventions and limited reporting on magnitude for vitamin C-specific effects.

Study Details

PMID:15590360
Participants:108
Impact:no additional increase with vitamin C vs simvastatin alone
Trust score:3/5

iron absorption (phytase + ascorbic acid + NaFeEDTA)

1 evidences

Adding ascorbic acid (vitamin C) together with phytase and NaFeEDTA markedly increased iron absorption from a maize meal.

Trust comment: Well-designed crossover isotope studies (n=101) with objective iron absorption measures.

Study Details

PMID:19106242
Participants:101
Impact:7.4% absorption
Trust score:4/5

iron absorption (FeSO4 without enhancers)

1 evidences

Adding ascorbic acid (vitamin C) together with phytase and NaFeEDTA markedly increased iron absorption from a maize meal.

Trust comment: Well-designed crossover isotope studies (n=101) with objective iron absorption measures.

Study Details

PMID:19106242
Participants:101
Impact:1.5% absorption (same-meal comparator; P < 0.001)
Trust score:4/5

ascorbic acid effect with NaFeEDTA

1 evidences

Adding ascorbic acid (vitamin C) together with phytase and NaFeEDTA markedly increased iron absorption from a maize meal.

Trust comment: Well-designed crossover isotope studies (n=101) with objective iron absorption measures.

Study Details

PMID:19106242
Participants:101
Impact:no significant additional increase from ascorbic acid alone with NaFeEDTA
Trust score:4/5

cognitive function

1 evidences

A 2-year RCT of combined antioxidants including vitamin C showed no improvement or stabilization of cognitive decline in individuals with Down syndrome and dementia.

Trust comment: Randomized double-blind placebo-controlled trial but used a combined antioxidant regimen, so vitamin C-specific effects cannot be isolated.

Study Details

PMID:21739598
Participants:53
Impact:no improvement or stabilization vs placebo
Trust score:4/5

complete response (CR)

1 evidences

In 48 myeloma patients undergoing stem-cell transplant, adding arsenic trioxide plus ascorbic acid to high-dose melphalan was safe and produced responses but showed no difference among arms.

Trust comment: Phase II randomized trial with clear endpoints but small sample and surrogate preparative-regimen setting limits generalizability.

Study Details

PMID:19041063
Participants:48
Impact:25% (12/48)
Trust score:3/5

overall response rate (ORR)

1 evidences

In 48 myeloma patients undergoing stem-cell transplant, adding arsenic trioxide plus ascorbic acid to high-dose melphalan was safe and produced responses but showed no difference among arms.

Trust comment: Phase II randomized trial with clear endpoints but small sample and surrogate preparative-regimen setting limits generalizability.

Study Details

PMID:19041063
Participants:48
Impact:85%
Trust score:3/5

progression-free survival (PFS)

1 evidences

In 48 myeloma patients undergoing stem-cell transplant, adding arsenic trioxide plus ascorbic acid to high-dose melphalan was safe and produced responses but showed no difference among arms.

Trust comment: Phase II randomized trial with clear endpoints but small sample and surrogate preparative-regimen setting limits generalizability.

Study Details

PMID:19041063
Participants:48
Impact:median 25 months
Trust score:3/5

ventilator- and vasopressor-free days

1 evidences

In 501 critically ill sepsis patients, IV vitamin C plus thiamine and hydrocortisone did not increase ventilator- and vasopressor-free days or reduce 30-day mortality compared with placebo.

Trust comment: Large multicenter randomized double-blind trial with rigorous design but stopped early for administrative reasons, which may reduce power.

Study Details

PMID:33620405
Participants:501
Impact:median 25 days (intervention) vs 26 days (placebo); median difference −1 day (95% CI −4 to 2); P = .85
Trust score:4/5

erythrocyte glutathione (GSH)

1 evidences

In adolescents with poorly controlled type 1 diabetes, improved glycemic control and 3–6 months of antioxidant supplementation (including vitamin C) did not restore erythrocyte glutathione or reduce markers of oxidative stress.

Trust comment: Randomized, controlled study with biochemical endpoints; small sample and short follow-up limit generalizability but results are direct and clear.

Study Details

PMID:37515943
Participants:41
Impact:No change after improved metabolic control or antioxidant supplementation
Trust score:4/5

albumin/creatinine ratio in urine

1 evidences

Perioperative multi-antioxidant treatment (including vitamin C) did not reduce albuminuria but was associated with higher creatinine clearance on day 2.

Trust comment: Randomized perioperative study in humans but used a multi-antioxidant cocktail and sample size was modest.

Study Details

PMID:12124559
Participants:44
Impact:no decrease
Trust score:3/5

24 hr creatinine clearance

1 evidences

Perioperative multi-antioxidant treatment (including vitamin C) did not reduce albuminuria but was associated with higher creatinine clearance on day 2.

Trust comment: Randomized perioperative study in humans but used a multi-antioxidant cocktail and sample size was modest.

Study Details

PMID:12124559
Participants:44
Impact:increased at day 2
Trust score:3/5

plasma ferritin

1 evidences

Daily guava juice (≈200 mg ascorbic acid) given with a meal modestly increased hemoglobin and had a smaller, non-significant increase in ferritin in mildly anemic children.

Trust comment: Randomized placebo-controlled trial with adequate sample size and clear ascorbic acid exposure, though ferritin change was not statistically significant.

Study Details

PMID:21896877
Participants:95
Impact:mean +2.47 ng/mL vs placebo (95% CI −1.04–5.98; p=0.12)
Trust score:4/5

flow-mediated dilation (brachial artery)

1 evidences

Vitamin C quickly and sustainably improved blood-vessel dilation in patients with coronary artery disease.

Trust comment: Randomized, double-blind, placebo-controlled human trial but relatively small sample (n=46).

Study Details

PMID:10385496
Participants:46
Impact:+3.5 percentage points (single-dose 2 g: 6.6% → 10.1%); +2.4 percentage points after 30 days (9.0%)
Trust score:4/5

chronic pelvic pain (everyday pain)

1 evidences

A combination of vitamins E and C reduced chronic pelvic pain and lowered inflammatory markers in women with endometriosis.

Trust comment: Randomized placebo-controlled trial in humans but vitamins E and C were combined, so effects cannot be attributed to vitamin C alone.

Study Details

PMID:22728166
Participants:59
Impact:43% of antioxidant-treated patients improved (P = 0.0055)
Trust score:3/5

dysmenorrhea and dyspareunia

1 evidences

A combination of vitamins E and C reduced chronic pelvic pain and lowered inflammatory markers in women with endometriosis.

Trust comment: Randomized placebo-controlled trial in humans but vitamins E and C were combined, so effects cannot be attributed to vitamin C alone.

Study Details

PMID:22728166
Participants:59
Impact:dysmenorrhea improved in 37%; dyspareunia improved in 24% (antioxidant group)
Trust score:3/5

peritoneal inflammatory markers (RANTES, IL-6, MCP-1)

1 evidences

A combination of vitamins E and C reduced chronic pelvic pain and lowered inflammatory markers in women with endometriosis.

Trust comment: Randomized placebo-controlled trial in humans but vitamins E and C were combined, so effects cannot be attributed to vitamin C alone.

Study Details

PMID:22728166
Participants:59
Impact:significant decreases (RANTES P ≤ 0.002; IL-6 P ≤ 0.056; MCP-1 P ≤ 0.016)
Trust score:3/5

oxidized DNA damage in lymphocytes

1 evidences

Children given multiple micronutrients including vitamin C had higher plasma antioxidant levels and less oxidized DNA damage in lymphocytes.

Trust comment: Randomized trial in children showing biochemical benefits but was a multinutrient supplement and details on blinding/completion are limited.

Study Details

PMID:15941534
Participants:82
Impact:significant decrease induced by H2O2 (P < 0.01)
Trust score:3/5

overall bowel-cleansing success

1 evidences

Adding ascorbic acid to a reduced-volume bowel prep gave the same cleansing success with better tolerability and fewer side effects.

Trust comment: Large, randomized, single-blind trial with clear clinical endpoints showing noninferiority in efficacy and improved tolerability.

Study Details

PMID:24955451
Participants:327
Impact:97.5% (2-L PEG+Asc) vs 98.8% (4-L PEG); mean difference = -1.3%
Trust score:4/5

patient compliance/acceptability/satisfaction

1 evidences

Adding ascorbic acid to a reduced-volume bowel prep gave the same cleansing success with better tolerability and fewer side effects.

Trust comment: Large, randomized, single-blind trial with clear clinical endpoints showing noninferiority in efficacy and improved tolerability.

Study Details

PMID:24955451
Participants:327
Impact:significantly better with 2-L PEG+Asc (P < 0.05)
Trust score:4/5

incidence of side effects

1 evidences

Adding ascorbic acid to a reduced-volume bowel prep gave the same cleansing success with better tolerability and fewer side effects.

Trust comment: Large, randomized, single-blind trial with clear clinical endpoints showing noninferiority in efficacy and improved tolerability.

Study Details

PMID:24955451
Participants:327
Impact:57.7% (2-L PEG+Asc) vs 73.2% (4-L PEG); absolute difference -15.5 percentage points
Trust score:4/5

Catalase (CAT)

1 evidences

Vitamin A+C given for 1 month produced mixed effects on oxidative-stress markers: some markers improved in HIV-only patients but worsened or did not improve in HIV-TB co-infected patients.

Trust comment: Moderate-quality non-blinded clinical supplementation study with short duration and mixed/contradictory biomarker results.

Study Details

PMID:29062324
Participants:90
Impact:↑ with supplementation in HIV mono-infected vs no-supplement; overall mixed changes in co-infected
Trust score:3/5

Antioxidant enzyme activities (SOD, CAT, GPX)

1 evidences

Patients with chronic bacterial prostatitis had lower plasma vitamin C and antioxidant enzymes and higher oxidative-damage markers than healthy controls.

Trust comment: Case-control biochemical study with adequate sample size but observational design limits causal inference.

Study Details

PMID:16625281
Participants:140
Impact:↓ in chronic bacterial prostatitis patients vs healthy volunteers
Trust score:3/5

Total spontaneous preterm birth

1 evidences

Large RCT found no reduction in overall spontaneous preterm birth with vitamins C+E, though births from preterm PROM before 32 weeks were less frequent with vitamins.

Trust comment: Large, double-masked, placebo-controlled randomized trial with robust sample size and follow-up.

Study Details

PMID:20733448
Participants:9968
Impact:No meaningful change (7.1% vitamin vs 6.9% placebo)
Trust score:5/5

Preterm PROM <32 weeks

1 evidences

Large RCT found no reduction in overall spontaneous preterm birth with vitamins C+E, though births from preterm PROM before 32 weeks were less frequent with vitamins.

Trust comment: Large, double-masked, placebo-controlled randomized trial with robust sample size and follow-up.

Study Details

PMID:20733448
Participants:9968
Impact:↓ (0.3% vitamin vs 0.6% placebo)
Trust score:5/5

Death or persistent organ dysfunction at day 28 (primary composite)

1 evidences

In ICU patients with sepsis on vasopressors, IV vitamin C increased the risk of death or persistent organ dysfunction at 28 days compared with placebo.

Trust comment: Large randomized, placebo-controlled ICU trial with clinically meaningful endpoints; high reliability.

Study Details

PMID:35704292
Participants:872
Impact:↑ (44.5% vitamin C vs 38.5% placebo; RR 1.21)
Trust score:5/5

pigmentation (melasma severity / MASI)

1 evidences

A cream containing hydroquinone, glycolic acid, vitamins C and E, and sunscreen reduced facial melasma pigmentation vs sunscreen alone over 12 weeks; irritation was more common but transient.

Trust comment: Randomized controlled trial in humans with objective measures but small sample and concomitant active agents (hydroquinone/glycolic acid) limit isolation of vitamin C effect.

Study Details

PMID:14636195
Participants:35
Impact:75% improved vs 13% (study vs sunscreen; P<0.0001)
Trust score:3/5

skin irritation

1 evidences

A cream containing hydroquinone, glycolic acid, vitamins C and E, and sunscreen reduced facial melasma pigmentation vs sunscreen alone over 12 weeks; irritation was more common but transient.

Trust comment: Randomized controlled trial in humans with objective measures but small sample and concomitant active agents (hydroquinone/glycolic acid) limit isolation of vitamin C effect.

Study Details

PMID:14636195
Participants:35
Impact:increased incidence with study cream (mostly transient, resolved with temporary cessation/moisturizers)
Trust score:3/5

incident type 2 diabetes risk

1 evidences

In this large prospective cohort of male smokers, dietary vitamin C intake was not associated with incidence of type 2 diabetes after multivariate adjustment.

Trust comment: Large prospective cohort with long follow-up increases confidence, though restricted to male smokers limits generalizability.

Study Details

PMID:21245884
Participants:25505
Impact:no association with dietary vitamin C (no decreased risk after multivariate adjustment)
Trust score:4/5

HIV disease progression or death

1 evidences

Large RCT in adults on HAART compared high- vs standard-dose multivitamins (including vitamin C); no benefit for disease progression or death but increased liver enzyme elevations with high-dose.

Trust comment: Large, randomized, double-blind controlled trial with clear endpoints and high sample size; high methodological quality though vitamin C was part of a multinutrient supplement.

Study Details

PMID:23073950
Participants:3418
Impact:no effect (72% vs 72%; RR 1.00)
Trust score:5/5

ALT (alanine transaminase) elevations

1 evidences

Large RCT in adults on HAART compared high- vs standard-dose multivitamins (including vitamin C); no benefit for disease progression or death but increased liver enzyme elevations with high-dose.

Trust comment: Large, randomized, double-blind controlled trial with clear endpoints and high sample size; high methodological quality though vitamin C was part of a multinutrient supplement.

Study Details

PMID:23073950
Participants:3418
Impact:increased risk (RR 1.44)
Trust score:5/5

CD4 count / viral load / BMI / hemoglobin

1 evidences

Large RCT in adults on HAART compared high- vs standard-dose multivitamins (including vitamin C); no benefit for disease progression or death but increased liver enzyme elevations with high-dose.

Trust comment: Large, randomized, double-blind controlled trial with clear endpoints and high sample size; high methodological quality though vitamin C was part of a multinutrient supplement.

Study Details

PMID:23073950
Participants:3418
Impact:no effect
Trust score:5/5

progression-free survival (overall cohort)

1 evidences

Phase 3 RCT found adding high‑dose IV vitamin C to first-line chemotherapy did not improve progression-free survival overall, but RAS‑mutant patients showed improved PFS in prespecified subgroup analysis.

Trust comment: Randomized, multicenter phase 3 trial with clear endpoints and adequate reporting; primary endpoint not met though a biologically plausible subgroup benefit was observed.

Study Details

PMID:35929990
Participants:442
Impact:no significant improvement (median 8.6 vs 8.3 months; HR 0.86; P = 0.1)
Trust score:5/5

progression-free survival (RAS-mutant subgroup)

1 evidences

Phase 3 RCT found adding high‑dose IV vitamin C to first-line chemotherapy did not improve progression-free survival overall, but RAS‑mutant patients showed improved PFS in prespecified subgroup analysis.

Trust comment: Randomized, multicenter phase 3 trial with clear endpoints and adequate reporting; primary endpoint not met though a biologically plausible subgroup benefit was observed.

Study Details

PMID:35929990
Participants:442
Impact:improved (9.2 vs 7.8 months; HR 0.67; P = 0.01)
Trust score:5/5

objective response rate / overall survival

1 evidences

Phase 3 RCT found adding high‑dose IV vitamin C to first-line chemotherapy did not improve progression-free survival overall, but RAS‑mutant patients showed improved PFS in prespecified subgroup analysis.

Trust comment: Randomized, multicenter phase 3 trial with clear endpoints and adequate reporting; primary endpoint not met though a biologically plausible subgroup benefit was observed.

Study Details

PMID:35929990
Participants:442
Impact:no meaningful difference
Trust score:5/5

fractional iron absorption (FIA) from WG wheat + lentils (with AA)

1 evidences

In a crossover stable‑isotope study of 30 Malawian infants, ascorbic acid–fortified cereals supported measurable iron absorption, with fractional iron absorption varying by cereal formulation.

Trust comment: Well-controlled single‑blind crossover isotope study in the target population with precise measurements but small sample size.

Study Details

PMID:34958374
Participants:30
Impact:15.8% (geometric mean)
Trust score:4/5

fractional iron absorption (FIA) from refined wheat reference (with AA)

1 evidences

In a crossover stable‑isotope study of 30 Malawian infants, ascorbic acid–fortified cereals supported measurable iron absorption, with fractional iron absorption varying by cereal formulation.

Trust comment: Well-controlled single‑blind crossover isotope study in the target population with precise measurements but small sample size.

Study Details

PMID:34958374
Participants:30
Impact:12.1% (geometric mean)
Trust score:4/5

fractional iron absorption (FIA) from WG-oat (with AA) and WG-oat with FeBG

1 evidences

In a crossover stable‑isotope study of 30 Malawian infants, ascorbic acid–fortified cereals supported measurable iron absorption, with fractional iron absorption varying by cereal formulation.

Trust comment: Well-controlled single‑blind crossover isotope study in the target population with precise measurements but small sample size.

Study Details

PMID:34958374
Participants:30
Impact:WG-oat Fefum 9.2%; WG-oat FeBG 7.4%
Trust score:4/5

(Na,K)-ATPase activity

1 evidences

In hypertensive men, 8 weeks of vitamins C (1 g/day) + E increased erythrocyte (Na,K)-ATPase activity, improved oxidative stress markers and reduced blood pressure versus placebo.

Trust comment: Double-blind randomized placebo-controlled trial in 120 men with direct biochemical and clinical measures; moderate-high quality but supplements were combined (C+E).

Study Details

PMID:23659494
Participants:120
Impact:increase with vitamins C+E supplementation
Trust score:4/5

Time to 50% symptom reduction

1 evidences

High‑dose zinc gluconate (50 mg nightly) did not significantly shorten time to 50% symptom reduction or other clinical endpoints in outpatients with COVID-19 compared with usual care.

Trust comment: Randomized multicenter clinical trial with objective symptom endpoints; stopped early for futility and was open-label without placebo.

Study Details

PMID:33576820
Participants:214
Impact:Ascorbic acid mean 5.5 d vs usual care 6.7 d (difference −1.18 d; not statistically significant, overall P=0.45)
Trust score:4/5

Time to complete symptom resolution (4-symptom score = 0)

1 evidences

High‑dose zinc gluconate (50 mg nightly) did not significantly shorten time to 50% symptom reduction or other clinical endpoints in outpatients with COVID-19 compared with usual care.

Trust comment: Randomized multicenter clinical trial with objective symptom endpoints; stopped early for futility and was open-label without placebo.

Study Details

PMID:33576820
Participants:214
Impact:Ascorbic acid 12.1 d vs usual care 9.9 d (difference +2.22 d; not significant)
Trust score:4/5

Adverse effects (gastrointestinal)

1 evidences

High‑dose zinc gluconate (50 mg nightly) did not significantly shorten time to 50% symptom reduction or other clinical endpoints in outpatients with COVID-19 compared with usual care.

Trust comment: Randomized multicenter clinical trial with objective symptom endpoints; stopped early for futility and was open-label without placebo.

Study Details

PMID:33576820
Participants:214
Impact:Higher proportion of nausea/diarrhea/stomach cramps in ascorbic acid groups (≤10% overall; more common with ascorbic acid)
Trust score:4/5

Plasma lipid peroxides

1 evidences

Preconditioning antioxidant supplementation (including 450 mg ascorbic acid) was associated with higher antioxidant levels and reduced markers of lipid peroxidation compared with no supplementation.

Trust comment: Small non-randomized groups but direct biochemical measures support effect on oxidative markers; limited sample size and mixed antioxidants limits attribution to vitamin C alone.

Study Details

PMID:9370141
Participants:36
Impact:Increased after conditioning in unsupplemented patients; supplementation attenuated this rise (reduced peroxidation)
Trust score:3/5

Plasma beta-carotene and alpha-tocopherol

1 evidences

Preconditioning antioxidant supplementation (including 450 mg ascorbic acid) was associated with higher antioxidant levels and reduced markers of lipid peroxidation compared with no supplementation.

Trust comment: Small non-randomized groups but direct biochemical measures support effect on oxidative markers; limited sample size and mixed antioxidants limits attribution to vitamin C alone.

Study Details

PMID:9370141
Participants:36
Impact:Significantly higher after supplementation vs unsupplemented patients (p<0.05 for beta-carotene; p<0.01 for alpha-tocopherol decreases in unsupplemented group)
Trust score:3/5

Antioxidant status overall

1 evidences

Preconditioning antioxidant supplementation (including 450 mg ascorbic acid) was associated with higher antioxidant levels and reduced markers of lipid peroxidation compared with no supplementation.

Trust comment: Small non-randomized groups but direct biochemical measures support effect on oxidative markers; limited sample size and mixed antioxidants limits attribution to vitamin C alone.

Study Details

PMID:9370141
Participants:36
Impact:Supplementation preserved/increased measured antioxidant concentrations during conditioning therapy
Trust score:3/5

Body weight

4 evidences

A 12-week water-soluble vitamin supplement improved some vitamin biomarkers, increased weight, and lowered homocysteine in elderly female residents; plasma vitamin C rose in both groups.

Trust comment: Single-blind randomized placebo-controlled trial with clear endpoints but modest sample size.

Study Details

PMID:7498103
Participants:42
Impact:increased (supplement group, significant)
Trust score:4/5

Adults with metabolic syndrome counseled on DASH diet plus low-sodium vegetable juice (a source of vitamin C) increased vitamin C intake and experienced modestly greater weight loss; oxidative stress markers did not change.

Trust comment: Randomized trial with objective measures but small sample, short duration and industry involvement which may affect bias.

Study Details

PMID:20178625
Participants:81
Impact:greater weight loss with juice vs no juice (e.g., completers: 8 oz group −2.25 kg at 12 weeks; aggregated models significant)
Trust score:3/5

Addition of L-ascorbic acid (with chitosan) for 8 weeks accentuated weight and BMI reduction compared with chitosan alone or placebo; BMI decrease was greater with ascorbic acid plus chitosan.

Trust comment: Moderate-sized controlled intervention with significant BMI differences, but short duration and combination with chitosan limit generalizability to vitamin C alone.

Study Details

PMID:25835230
Participants:80
Impact:Chitosan and chitosan+ascorbic acid groups showed significant weight loss vs control (p<0.05)
Trust score:3/5

A 6‑month lifestyle intervention led to weight loss and increased physical activity; measured vitamin C intake (marker of fruit/vegetable intake) showed no difference between groups.

Trust comment: Small randomized trial (n=45 randomized; ~38 completers) with meaningful clinical endpoints but limited power for nutrient intake differences.

Study Details

PMID:18243282
Participants:38
Impact:intervention group lost 3.5 kg at 12 months (vs +1.4 kg in control); mean difference -4.9 kg; p=0.018
Trust score:3/5

Fat mass / % body fat / circumferences

1 evidences

Addition of L-ascorbic acid (with chitosan) for 8 weeks accentuated weight and BMI reduction compared with chitosan alone or placebo; BMI decrease was greater with ascorbic acid plus chitosan.

Trust comment: Moderate-sized controlled intervention with significant BMI differences, but short duration and combination with chitosan limit generalizability to vitamin C alone.

Study Details

PMID:25835230
Participants:80
Impact:Decreased more in active groups vs control but differences between groups not statistically significant
Trust score:3/5

Infarct size (CK and CK-MB equivalents)

1 evidences

Combined antioxidant therapy including vitamin C (1,000 mg/day) given after suspected MI was associated with smaller mean infarct size and reduced oxidative markers and cardiac events versus placebo, but vitamins were given as a combination so effects cannot be attributed to vitamin C alone.

Trust comment: Randomized double-blind trial with positive clinical signals, but vitamins were administered as a multi-nutrient combination so individual contribution of vitamin C is uncertain.

Study Details

PMID:8607399
Participants:125
Impact:Mean infarct size significantly less in antioxidant group vs placebo (reported significant difference)
Trust score:3/5

Serum lipid peroxides / cardiac events

1 evidences

Combined antioxidant therapy including vitamin C (1,000 mg/day) given after suspected MI was associated with smaller mean infarct size and reduced oxidative markers and cardiac events versus placebo, but vitamins were given as a combination so effects cannot be attributed to vitamin C alone.

Trust comment: Randomized double-blind trial with positive clinical signals, but vitamins were administered as a multi-nutrient combination so individual contribution of vitamin C is uncertain.

Study Details

PMID:8607399
Participants:125
Impact:Lower serum lipid peroxides and fewer cardiac endpoints in antioxidant group (20.6% vs 30.6%)
Trust score:3/5

Blood lactate concentration (muscle fatigue)

1 evidences

Drinking 500 mL/day orange juice while doing aerobic training for 3 months was associated with better cholesterol and less muscle fatigue.

Trust comment: Controlled intervention in 26 women; orange juice raised vitamin C intake but contained multiple nutrients so attribution to vitamin C alone is uncertain (small sample).

Study Details

PMID:20729016
Participants:26
Impact:-27% (experimental) vs -17% (control)
Trust score:3/5

Cell adhesion molecules (VCAM-1, ICAM-1)

1 evidences

In short-term supplementation in well-controlled type 2 diabetes, vitamin C (500 mg/day) did not meaningfully change LDL oxidation susceptibility, CRP, or adhesion molecules.

Trust comment: Randomized placebo-controlled trial in 57 patients; robust design but vitamin C arm showed no significant effects on the reported endpoints.

Study Details

PMID:10840987
Participants:57
Impact:no significant change with vitamin C
Trust score:4/5

Red blood cell antioxidant resistance (functional test)

1 evidences

Low-dose vitamin supplementation (including 120 mg vitamin C) for 2 years increased nutrient levels and improved a red blood cell antioxidant resistance assay in elderly participants.

Trust comment: Double-blind, placebo-controlled trial with 57 completers showing increased serum vitamin C and improved an in vitro antioxidant defense test; hospitalized elderly population limits generalizability.

Study Details

PMID:9263186
Participants:57
Impact:increased (p=0.002; correlated with serum vitamin C, p<0.0001)
Trust score:4/5

contrast-induced nephropathy incidence (ascorbic acid + low‑dose NAC)

1 evidences

Adding ascorbic acid (with low-dose NAC) did not reduce contrast-induced kidney injury compared with hydration alone; high-dose NAC plus hydration was superior.

Trust comment: Randomized prospective placebo-controlled human trial but single-center and small group sizes; ascorbic acid was given with NAC (not isolated).

Study Details

PMID:26787567
Participants:105
Impact:16.7% incidence (Group B); no significant reduction vs hydration 17.8%; higher than high‑dose NAC 6.7%
Trust score:4/5

inflammatory markers (CRP, WBC, fibrinogen)

1 evidences

Short-term perioperative ascorbic acid did not reduce the postoperative rise in inflammatory markers after cardiothoracic surgery.

Trust comment: Randomized double-blind placebo-controlled human trial but very small sample (n=24), limiting precision.

Study Details

PMID:21856809
Participants:24
Impact:No attenuation of postoperative rise vs placebo (p > 0.05)
Trust score:3/5

systolic blood pressure reduction (CHH vs control)

1 evidences

A feeding trial comparing diets raised vitamin C intake and produced substantially greater systolic blood pressure reduction, but the study assessed a whole-diet intervention (not isolated vitamin C).

Trust comment: Randomized feeding trial with objective intake and BP outcomes, but vitamin C change is part of a multifactorial diet so causal attribution to vitamin C alone is limited.

Study Details

PMID:38445388
Participants:53
Impact:Incremental effect −10.95 mmHg (CHH −15.43 mmHg vs control −4.47 mmHg)
Trust score:4/5

postprandial oxidant markers (MDA, 4‑HNE, oxidized LDL)

1 evidences

Fifteen days of combined antioxidant therapy (NAC, vitamin E, vitamin C 250 mg/d) reduced postprandial oxidative stress and improved endothelial function markers across diabetes, IGT, and control groups.

Trust comment: Controlled clinical human study with adequate group sizes, but antioxidants were given as a combined regimen so vitamin C's isolated effect cannot be determined.

Study Details

PMID:16368447
Participants:138
Impact:Significant reductions after 15 days of antioxidant supplementation
Trust score:4/5

NO bioavailability

1 evidences

Fifteen days of combined antioxidant therapy (NAC, vitamin E, vitamin C 250 mg/d) reduced postprandial oxidative stress and improved endothelial function markers across diabetes, IGT, and control groups.

Trust comment: Controlled clinical human study with adequate group sizes, but antioxidants were given as a combined regimen so vitamin C's isolated effect cannot be determined.

Study Details

PMID:16368447
Participants:138
Impact:Increased after supplementation
Trust score:4/5

endothelial markers (vWF, VCAM-1)

1 evidences

Fifteen days of combined antioxidant therapy (NAC, vitamin E, vitamin C 250 mg/d) reduced postprandial oxidative stress and improved endothelial function markers across diabetes, IGT, and control groups.

Trust comment: Controlled clinical human study with adequate group sizes, but antioxidants were given as a combined regimen so vitamin C's isolated effect cannot be determined.

Study Details

PMID:16368447
Participants:138
Impact:Improved (reduced) after supplementation
Trust score:4/5

overall bowel cleansing (Aronchick score)

1 evidences

Low-volume PEG plus ascorbic acid provided bowel cleansing efficacy and tolerability comparable to high-volume PEG plus simethicon for colonoscopy prep.

Trust comment: Randomized single-blind clinical trial with reasonable sample size and clear endpoints; ascorbic acid used as part of bowel prep (not dietary supplementation).

Study Details

PMID:23751992
Participants:120
Impact:Adequate cleansing: 81.7% (PEG+Asc) vs 80.0% (PEG+Sim) — comparable
Trust score:4/5

patient tolerability and safety

1 evidences

Low-volume PEG plus ascorbic acid provided bowel cleansing efficacy and tolerability comparable to high-volume PEG plus simethicon for colonoscopy prep.

Trust comment: Randomized single-blind clinical trial with reasonable sample size and clear endpoints; ascorbic acid used as part of bowel prep (not dietary supplementation).

Study Details

PMID:23751992
Participants:120
Impact:Similar between preparations
Trust score:4/5

non-anemic proportion

1 evidences

Ferrous ascorbate raised hemoglobin and cured more children of anemia than colloidal iron over 12 weeks.

Trust comment: Randomized trial in children with a clear primary outcome (Hb) and significant results, moderate sample size.

Study Details

PMID:23180405
Participants:73
Impact:64.86% (ferrous ascorbate) vs 31.03% (colloidal iron) at 12 wk
Trust score:4/5

body weight change

1 evidences

Individualized nutrition support in malnourished hospital patients improved energy/protein intake, maintained weight, raised vitamin C levels, and reduced complications and readmissions.

Trust comment: Randomized controlled trial measuring biochemical vitamin C and clinical outcomes with moderate sample size.

Study Details

PMID:20937544
Participants:132
Impact:0.0 kg (intervention) vs -1.4 kg (control)
Trust score:4/5

complications / antibiotic therapies / readmissions

1 evidences

Individualized nutrition support in malnourished hospital patients improved energy/protein intake, maintained weight, raised vitamin C levels, and reduced complications and readmissions.

Trust comment: Randomized controlled trial measuring biochemical vitamin C and clinical outcomes with moderate sample size.

Study Details

PMID:20937544
Participants:132
Impact:complications 4/66 vs 13/66; antibiotic therapies 1/66 vs 8/66; readmissions 17/64 vs 28/61 (intervention vs control)
Trust score:4/5

AMD progression (antioxidants benefit group)

1 evidences

The effect of AREDS vitamins (including vitamin C) on progression to advanced AMD varied by CFH and ARMS2 genotype, with antioxidants beneficial in one genotype group but zinc harmful in others.

Trust comment: Large AREDS dataset with genotype-stratified analysis; credible but post-hoc subgrouping and multiple comparisons reduce certainty.

Study Details

PMID:25200399
Participants:989
Impact:Placebo 22.6% vs antioxidants 9.17% progression over 7 years; HR 0.38 (P = 0.034) in patients with 0 or 1 CFH risk alleles and no ARMS2 risk alleles
Trust score:4/5

AMD progression (zinc harm group)

1 evidences

The effect of AREDS vitamins (including vitamin C) on progression to advanced AMD varied by CFH and ARMS2 genotype, with antioxidants beneficial in one genotype group but zinc harmful in others.

Trust comment: Large AREDS dataset with genotype-stratified analysis; credible but post-hoc subgrouping and multiple comparisons reduce certainty.

Study Details

PMID:25200399
Participants:989
Impact:Placebo 17.0% vs zinc 43.2% progression over 7 years; HR 3.07 (P = 0.0196) in patients with 2 CFH risk alleles and no ARMS2 risk alleles
Trust score:4/5

colon cleansing (BBPS ≥6)

1 evidences

1-L PEG plus ascorbate was noninferior to 4-L PEG for colon cleansing, had higher patient compliance, and similar safety.

Trust comment: Large multicenter randomized phase IV trial with blinded assessment and adequate sample size.

Study Details

PMID:33940043
Participants:388
Impact:+4.9 percentage points (97.9% vs 93%; noninferior; superiority P = .027)
Trust score:4/5

safety (moderate/severe side effects)

1 evidences

1-L PEG plus ascorbate was noninferior to 4-L PEG for colon cleansing, had higher patient compliance, and similar safety.

Trust comment: Large multicenter randomized phase IV trial with blinded assessment and adequate sample size.

Study Details

PMID:33940043
Participants:388
Impact:no significant difference (20.8% vs 25.8%; P = .253)
Trust score:4/5

reactive hyperemia (RH%)

1 evidences

High-dose vitamin C (2 g/day for 4 weeks) improved forearm reactive hyperemia and reduced plasma vWF, tPA, and factor V in patients with type 2 diabetes and CAD.

Trust comment: Small clinical study with clear biochemical endpoints and significant effects but limited sample size.

Study Details

PMID:14514574
Participants:39
Impact:+20.7 percentage points (62.4% to 83.1%; P = 0.024)
Trust score:3/5

von Willebrand factor (vWF)

2 evidences

High-dose vitamin C (2 g/day for 4 weeks) improved forearm reactive hyperemia and reduced plasma vWF, tPA, and factor V in patients with type 2 diabetes and CAD.

Trust comment: Small clinical study with clear biochemical endpoints and significant effects but limited sample size.

Study Details

PMID:14514574
Participants:39
Impact:-24.0 percentage points (133.5% to 109.5%; P = 0.016)
Trust score:3/5

In healthy subjects and people with type 1 diabetes, hyperglycemic recovery from hypoglycemia worsened thrombosis and oxidative markers; intravenous vitamin C partially reversed these worsening effects.

Trust comment: Physiologic crossover‑style study with matched controls (n=43) and clear, consistent biomarker effects and demonstration of acute vitamin C benefit; limited by short‑term experimental setting.

Study Details

PMID:24094827
Participants:43
Impact:worsened by hyperglycemic recovery (p<0.01); partially counterbalanced by vitamin C (p<0.01 vs hyperglycemia alone)
Trust score:4/5

tissue plasminogen activator (tPA)

1 evidences

High-dose vitamin C (2 g/day for 4 weeks) improved forearm reactive hyperemia and reduced plasma vWF, tPA, and factor V in patients with type 2 diabetes and CAD.

Trust comment: Small clinical study with clear biochemical endpoints and significant effects but limited sample size.

Study Details

PMID:14514574
Participants:39
Impact:-3.9 ng/ml (12.3 to 8.40 ng/ml; P = 0.001)
Trust score:3/5

Monocyte Chemotactic Protein-1 (MCP-1)

1 evidences

Two formulations of encapsulated juice powder reduced several inflammatory chemokines and increased antioxidant enzyme activity and micronutrient levels (including vitamin C) versus placebo after 60 days.

Trust comment: Double-blind, placebo-controlled randomized trial with moderate sample size and clear biomarker outcomes.

Study Details

PMID:20425759
Participants:117
Impact:decreased (significant vs placebo)
Trust score:4/5

Macrophage Inflammatory Protein 1-β (MIP-1β)

1 evidences

Two formulations of encapsulated juice powder reduced several inflammatory chemokines and increased antioxidant enzyme activity and micronutrient levels (including vitamin C) versus placebo after 60 days.

Trust comment: Double-blind, placebo-controlled randomized trial with moderate sample size and clear biomarker outcomes.

Study Details

PMID:20425759
Participants:117
Impact:decreased (significant vs placebo)
Trust score:4/5

RANTES

1 evidences

Two formulations of encapsulated juice powder reduced several inflammatory chemokines and increased antioxidant enzyme activity and micronutrient levels (including vitamin C) versus placebo after 60 days.

Trust comment: Double-blind, placebo-controlled randomized trial with moderate sample size and clear biomarker outcomes.

Study Details

PMID:20425759
Participants:117
Impact:decreased (significant vs placebo)
Trust score:4/5

multiple organ failure

1 evidences

Early antioxidant supplementation including ascorbic acid in critically ill surgical patients reduced multiple organ failure (RR 0.43) and shortened mechanical ventilation and ICU stay; pulmonary morbidity reduction was not statistically significant.

Trust comment: Large randomized prospective trial with clinically relevant endpoints and significant reduction in organ failure.

Study Details

PMID:12454520
Participants:595
Impact:-57% relative risk (RR 0.43; 95% CI 0.19-0.96)
Trust score:4/5

pulmonary morbidity (ARDS or nosocomial pneumonia)

1 evidences

Early antioxidant supplementation including ascorbic acid in critically ill surgical patients reduced multiple organ failure (RR 0.43) and shortened mechanical ventilation and ICU stay; pulmonary morbidity reduction was not statistically significant.

Trust comment: Large randomized prospective trial with clinically relevant endpoints and significant reduction in organ failure.

Study Details

PMID:12454520
Participants:595
Impact:-19% relative risk (RR 0.81; 95% CI 0.60-1.1; not significant)
Trust score:4/5

duration of mechanical ventilation / ICU stay

1 evidences

Early antioxidant supplementation including ascorbic acid in critically ill surgical patients reduced multiple organ failure (RR 0.43) and shortened mechanical ventilation and ICU stay; pulmonary morbidity reduction was not statistically significant.

Trust comment: Large randomized prospective trial with clinically relevant endpoints and significant reduction in organ failure.

Study Details

PMID:12454520
Participants:595
Impact:decreased (no numeric values reported)
Trust score:4/5

Tender Point Index

1 evidences

Pilot randomized placebo-controlled trial of IV micronutrient therapy (includes vitamin C) in fibromyalgia showed within-group clinical improvements but no statistically significant differences versus placebo.

Trust comment: Small randomized double-blind pilot with high placebo response; safe but underpowered for definitive efficacy.

Study Details

PMID:19250003
Participants:34
Impact:improved within IVMT group (significant vs baseline) but no significant difference vs placebo
Trust score:3/5

global pain (VAS)

1 evidences

Pilot randomized placebo-controlled trial of IV micronutrient therapy (includes vitamin C) in fibromyalgia showed within-group clinical improvements but no statistically significant differences versus placebo.

Trust comment: Small randomized double-blind pilot with high placebo response; safe but underpowered for definitive efficacy.

Study Details

PMID:19250003
Participants:34
Impact:improved within IVMT group but no significant difference vs placebo
Trust score:3/5

quality of life / depression measures

1 evidences

Pilot randomized placebo-controlled trial of IV micronutrient therapy (includes vitamin C) in fibromyalgia showed within-group clinical improvements but no statistically significant differences versus placebo.

Trust comment: Small randomized double-blind pilot with high placebo response; safe but underpowered for definitive efficacy.

Study Details

PMID:19250003
Participants:34
Impact:improved within IVMT group (some sustained effect) but no significant difference vs placebo
Trust score:3/5

skin pigmentation (mexameter, left malar)

1 evidences

Oral procyanidin combined with vitamins A, C, and E reduced facial pigmentation in women with epidermal melasma over 8 weeks.

Trust comment: Randomized double-blind placebo-controlled trial with objective measurements but short duration (8 weeks) and modest sample size.

Study Details

PMID:19659873
Participants:56
Impact:-165.85 units (±70.91); P<0.0001
Trust score:4/5

skin pigmentation (mexameter, right malar)

1 evidences

Oral procyanidin combined with vitamins A, C, and E reduced facial pigmentation in women with epidermal melasma over 8 weeks.

Trust comment: Randomized double-blind placebo-controlled trial with objective measurements but short duration (8 weeks) and modest sample size.

Study Details

PMID:19659873
Participants:56
Impact:-161.33 units (±61.82); P<0.0001
Trust score:4/5

MASI score (melasma severity)

1 evidences

Oral procyanidin combined with vitamins A, C, and E reduced facial pigmentation in women with epidermal melasma over 8 weeks.

Trust comment: Randomized double-blind placebo-controlled trial with objective measurements but short duration (8 weeks) and modest sample size.

Study Details

PMID:19659873
Participants:56
Impact:left -2.4862 (±1.6782), right -1.8889 (±1.6711); P=0.001
Trust score:4/5

oxidative stress marker (RBC fatty acid ratio)

1 evidences

Patients with acute pancreatitis or colorectal cancer had lower serum vitamin C than healthy controls; antioxidant depletion accompanied increased oxidative stress markers.

Trust comment: Prospective descriptive clinical study with small groups; measurements appear reliable but limited sample size reduces generalizability.

Study Details

PMID:15723737
Participants:52
Impact:increased in acute pancreatitis and colorectal cancer patients vs controls (P<0.05)
Trust score:3/5

type 2 diabetes incidence (Vitamin C subgroup)

1 evidences

In this large trial, folic acid/B vitamins did not alter diabetes risk; randomization to vitamin C in the parent factorial trial did not meaningfully change diabetes incidence.

Trust comment: Large randomized trial with long follow-up and high adherence; the vitamin C-related result comes from factorial/subgroup analyses rather than as a primary outcome.

Study Details

PMID:19491213
Participants:4252
Impact:no significant effect in vitamin C active subgroup: 114/1,059 vs 119/1,059 (RR 0.95; 95% CI 0.74–1.23)
Trust score:4/5

adequate bowel cleansing (PEG-A vs 4 L PEG)

1 evidences

A low-volume PEG preparation containing ascorbate (PEG-A) provided noninferior bowel cleansing compared with standard 4 L PEG in screening colonoscopy.

Trust comment: Large randomized noninferiority trial with objective endpoints across screening centers; ascorbate was used as part of the bowel preparation formulation.

Study Details

PMID:26760605
Participants:2802
Impact:95.7% vs 93.7% (difference +1.9%; 95% CI -0.1 to 3.9) — noninferior
Trust score:4/5

ferritin (iron stores)

1 evidences

Iron-containing micronutrient supplements that included vitamin C improved hemoglobin and increased ferritin (iron stores); weekly 60 mg iron regimen was effective and better tolerated.

Trust comment: Randomized double-blind trial with objective hematologic outcomes; vitamin C was part of combination supplements, so effects cannot be isolated to vitamin C alone.

Study Details

PMID:9209187
Participants:273
Impact:+~27 µg/L (daily) and +14–15 µg/L (weekly) after 3 months
Trust score:4/5

Percent zinc absorption

1 evidences

Sprinkles provided measurable absorbed zinc (dose‑dependent total absorbed) and did not affect iron absorption in young children.

Trust comment: Randomized controlled trial using stable isotope tracers in 75 young children with direct bioavailability measures, but sample size is moderate.

Study Details

PMID:16549451
Participants:75
Impact:LoZn 6.4% vs HiZn 7.5% (no significant difference)
Trust score:4/5

Total zinc absorbed (mg)

1 evidences

Sprinkles provided measurable absorbed zinc (dose‑dependent total absorbed) and did not affect iron absorption in young children.

Trust comment: Randomized controlled trial using stable isotope tracers in 75 young children with direct bioavailability measures, but sample size is moderate.

Study Details

PMID:16549451
Participants:75
Impact:LoZn 0.31 mg vs HiZn 0.82 mg (difference +0.51 mg, P=0.0004)
Trust score:4/5

Percent iron absorption

1 evidences

Sprinkles provided measurable absorbed zinc (dose‑dependent total absorbed) and did not affect iron absorption in young children.

Trust comment: Randomized controlled trial using stable isotope tracers in 75 young children with direct bioavailability measures, but sample size is moderate.

Study Details

PMID:16549451
Participants:75
Impact:LoZn 5.9% vs HiZn 4.4% vs Control 5.0% (no significant differences; ascorbic acid had no effect)
Trust score:4/5

PPOX gene expression

1 evidences

In variegate porphyria patients, 6-month supplementation with vitamin E (50 mg) + vitamin C (150 mg) increased PPOX gene expression and raised antioxidant enzyme activities.

Trust comment: Randomized double-blind crossover study in 12 VP patients and 12 controls showing biochemical changes, but sample size is small.

Study Details

PMID:23601071
Participants:24
Impact:Increased with vitamin E + C supplementation in VP patients (no numeric value provided)
Trust score:3/5

Antioxidant enzyme activities (GRd, SOD)

1 evidences

In variegate porphyria patients, 6-month supplementation with vitamin E (50 mg) + vitamin C (150 mg) increased PPOX gene expression and raised antioxidant enzyme activities.

Trust comment: Randomized double-blind crossover study in 12 VP patients and 12 controls showing biochemical changes, but sample size is small.

Study Details

PMID:23601071
Participants:24
Impact:GRd and SOD activities were higher in the vitamin-treated groups (no numeric values provided)
Trust score:3/5

Weight change

1 evidences

Lifestyle intervention improved liver histology and lab markers in pediatric NAFLD; adding alpha-tocopherol + ascorbic acid did not provide additional benefit.

Trust comment: Randomized controlled trial with 24-month follow-up in 53 children; well-defined endpoints though sample size is modest.

Study Details

PMID:18537181
Participants:53
Impact:Placebo group -4.75 kg vs Antioxidant group -5.5 kg at 24 months (P=0.9; no significant difference)
Trust score:4/5

Liver histology / NAFLD activity score

1 evidences

Lifestyle intervention improved liver histology and lab markers in pediatric NAFLD; adding alpha-tocopherol + ascorbic acid did not provide additional benefit.

Trust comment: Randomized controlled trial with 24-month follow-up in 53 children; well-defined endpoints though sample size is modest.

Study Details

PMID:18537181
Participants:53
Impact:Improved in both groups with no significant difference between antioxidant and placebo
Trust score:4/5

Liver enzymes and metabolic markers

1 evidences

Lifestyle intervention improved liver histology and lab markers in pediatric NAFLD; adding alpha-tocopherol + ascorbic acid did not provide additional benefit.

Trust comment: Randomized controlled trial with 24-month follow-up in 53 children; well-defined endpoints though sample size is modest.

Study Details

PMID:18537181
Participants:53
Impact:Improved in both groups with no additional benefit from alpha-tocopherol + ascorbic acid
Trust score:4/5

HDL‑cholesterol

1 evidences

Eight-week randomized trial in 72 middle-aged subjects with cardiovascular risk factors: moderate berry consumption improved platelet function, raised HDL, and lowered systolic blood pressure in those with high baseline BP.

Trust comment: Randomized, placebo‑controlled trial (n=72) with objective platelet measures and clear between‑group differences; moderate sample size.

Study Details

PMID:18258621
Participants:72
Impact:+5.2% (berry) vs +0.6% (control); P=0.006
Trust score:4/5

thrombosis activation markers (F1+2, TAT, P‑selectin)

1 evidences

In healthy subjects and people with type 1 diabetes, hyperglycemic recovery from hypoglycemia worsened thrombosis and oxidative markers; intravenous vitamin C partially reversed these worsening effects.

Trust comment: Physiologic crossover‑style study with matched controls (n=43) and clear, consistent biomarker effects and demonstration of acute vitamin C benefit; limited by short‑term experimental setting.

Study Details

PMID:24094827
Participants:43
Impact:worsened by hyperglycemic recovery (p<0.01); partially counterbalanced by vitamin C (p<0.01)
Trust score:4/5

oxidative stress markers (nitrotyrosine, 8‑iso‑PGF2α)

1 evidences

In healthy subjects and people with type 1 diabetes, hyperglycemic recovery from hypoglycemia worsened thrombosis and oxidative markers; intravenous vitamin C partially reversed these worsening effects.

Trust comment: Physiologic crossover‑style study with matched controls (n=43) and clear, consistent biomarker effects and demonstration of acute vitamin C benefit; limited by short‑term experimental setting.

Study Details

PMID:24094827
Participants:43
Impact:worsened by hyperglycemic recovery (p<0.01); partially counterbalanced by vitamin C (p<0.01)
Trust score:4/5

reduced glutathione (GSH) in erythrocytes

1 evidences

In a randomized trial of 30 adults, supplementation with glutathione precursors (with or without polydatin) increased endogenous GSH and raised endogenous vitamin C, E and A levels; polydatin‑containing formula also reduced urinary neopterin.

Trust comment: Randomized human trial (n=30) with clear biochemical endpoints and complete follow‑up, but lacks a placebo arm and is small, limiting external validity.

Study Details

PMID:33105552
Participants:30
Impact:increased (GluReS +40% vs GluS +32%)
Trust score:3/5

endogenous vitamin C

1 evidences

In a randomized trial of 30 adults, supplementation with glutathione precursors (with or without polydatin) increased endogenous GSH and raised endogenous vitamin C, E and A levels; polydatin‑containing formula also reduced urinary neopterin.

Trust comment: Randomized human trial (n=30) with clear biochemical endpoints and complete follow‑up, but lacks a placebo arm and is small, limiting external validity.

Study Details

PMID:33105552
Participants:30
Impact:increased (significant; p≤0.01–0.0001)
Trust score:3/5

neopterin (urine)

1 evidences

In a randomized trial of 30 adults, supplementation with glutathione precursors (with or without polydatin) increased endogenous GSH and raised endogenous vitamin C, E and A levels; polydatin‑containing formula also reduced urinary neopterin.

Trust comment: Randomized human trial (n=30) with clear biochemical endpoints and complete follow‑up, but lacks a placebo arm and is small, limiting external validity.

Study Details

PMID:33105552
Participants:30
Impact:decreased −30% (GluReS group)
Trust score:3/5

skeletal muscle HSP72 mRNA

1 evidences

Young men took vitamin C (500 mg) together with different vitamin E forms; exercise normally raised muscle and serum HSP72 but this increase was fully prevented only when gamma-tocopherol was included, and lipid-peroxidation marker rise was reduced with alpha-tocopherol + vitamin C.

Trust comment: Small randomized human trial (n=21) with muscle biopsies and blood measures; limited sample size but direct human data.

Study Details

PMID:16384840
Participants:21
Impact:Control: +150% (2.5-fold) post-exercise; CEalphagamma: exercise-induced increase completely blunted
Trust score:3/5

serum HSP72 protein

1 evidences

Young men took vitamin C (500 mg) together with different vitamin E forms; exercise normally raised muscle and serum HSP72 but this increase was fully prevented only when gamma-tocopherol was included, and lipid-peroxidation marker rise was reduced with alpha-tocopherol + vitamin C.

Trust comment: Small randomized human trial (n=21) with muscle biopsies and blood measures; limited sample size but direct human data.

Study Details

PMID:16384840
Participants:21
Impact:Control: +300% (4-fold) post-exercise; CEalphagamma: increase completely blunted
Trust score:3/5

8-iso-prostaglandin-F2alpha (lipid peroxidation marker)

1 evidences

Young men took vitamin C (500 mg) together with different vitamin E forms; exercise normally raised muscle and serum HSP72 but this increase was fully prevented only when gamma-tocopherol was included, and lipid-peroxidation marker rise was reduced with alpha-tocopherol + vitamin C.

Trust comment: Small randomized human trial (n=21) with muscle biopsies and blood measures; limited sample size but direct human data.

Study Details

PMID:16384840
Participants:21
Impact:Increased from 0 to 3 h in all groups; CEalpha showed a markedly smaller increase (P<0.05)
Trust score:3/5

iron absorption (MDFP in wheat-based meal)

1 evidences

In young women, adding ascorbic acid (4:1 molar ratio to iron) to fortified cereal markedly increased iron absorption from ferric pyrophosphate and ferrous sulfate; food matrix and iron status strongly modified absorption.

Trust comment: Well-controlled crossover human isotope study (n=26) with direct absorption measurements; moderate sample but robust methods.

Study Details

PMID:16522911
Participants:26
Impact:Without AA: 2.0% → With AA: 5.8% (absolute +3.8 percentage points)
Trust score:4/5

iron absorption (ferrous sulfate in wheat-based meal)

1 evidences

In young women, adding ascorbic acid (4:1 molar ratio to iron) to fortified cereal markedly increased iron absorption from ferric pyrophosphate and ferrous sulfate; food matrix and iron status strongly modified absorption.

Trust comment: Well-controlled crossover human isotope study (n=26) with direct absorption measurements; moderate sample but robust methods.

Study Details

PMID:16522911
Participants:26
Impact:Without AA: 3.2% → With AA: 14.8% (absolute +11.6 percentage points)
Trust score:4/5

food matrix effect on iron absorption

1 evidences

In young women, adding ascorbic acid (4:1 molar ratio to iron) to fortified cereal markedly increased iron absorption from ferric pyrophosphate and ferrous sulfate; food matrix and iron status strongly modified absorption.

Trust comment: Well-controlled crossover human isotope study (n=26) with direct absorption measurements; moderate sample but robust methods.

Study Details

PMID:16522911
Participants:26
Impact:RBV varied markedly by meal (e.g., MDFP 1.7% in rice vs 3.0% extruded), and iron status strongly predicted RBV (P<0.001)
Trust score:4/5

ALT (liver enzyme)

1 evidences

In a randomized trial of T2DM patients, combined vitamin C (500 mg) and chromium (200 µg) for the treatment group (n=30) improved glycemic control (HbA1c), lipid profile, liver enzymes and BMI versus placebo.

Trust comment: Small randomized controlled trial (n=60) testing a combined supplement (vitamin C + chromium) so effects cannot be attributed to vitamin C alone; limited methodological detail reported.

Study Details

PMID:38747270
Participants:60
Impact:ALT 34.7 ± 9.1 U/L, significantly lower versus control (P<0.001)
Trust score:3/5

fatigue (Fisk scale)

1 evidences

In patients with primary biliary cirrhosis, a mixed oral antioxidant supplement including vitamin C did not improve fatigue or other liver-related symptoms compared with placebo.

Trust comment: Multicentre, randomized double-blind crossover trial with completed-data available (n=44), moderate quality though sample modest.

Study Details

PMID:12492743
Participants:44
Impact:median change active +1 (P=0.61); placebo +4 (P=0.03) — no benefit from active treatment
Trust score:4/5

other liver-related symptoms

1 evidences

In patients with primary biliary cirrhosis, a mixed oral antioxidant supplement including vitamin C did not improve fatigue or other liver-related symptoms compared with placebo.

Trust comment: Multicentre, randomized double-blind crossover trial with completed-data available (n=44), moderate quality though sample modest.

Study Details

PMID:12492743
Participants:44
Impact:no improvement with active treatment (no quantitative change reported)
Trust score:4/5

circulating antioxidant levels (β-carotene, α-tocopherol)

1 evidences

Short-term high-dose combination antioxidants including vitamin C lowered systolic blood pressure (significantly in treated hypertensives) and increased circulating antioxidant levels.

Trust comment: Randomized double-blind crossover trial but small sample (n=38 completers) and multi-antioxidant intervention limits attribution to vitamin C alone.

Study Details

PMID:9176034
Participants:38
Impact:increased (P<0.01)
Trust score:3/5

urine nitrite (marker of NO availability)

1 evidences

Short-term high-dose combination antioxidants including vitamin C lowered systolic blood pressure (significantly in treated hypertensives) and increased circulating antioxidant levels.

Trust comment: Randomized double-blind crossover trial but small sample (n=38 completers) and multi-antioxidant intervention limits attribution to vitamin C alone.

Study Details

PMID:9176034
Participants:38
Impact:increased in hypertensive patients (P<0.05)
Trust score:3/5

percentage oxalate absorption

1 evidences

High-dose vitamin C (1000 mg twice daily) increased urinary oxalate and stone-risk markers in a subset of participants.

Trust comment: Randomized crossover, controlled metabolic-unit study with measured dietary control and objective urinary endpoints.

Study Details

PMID:15987848
Participants:48
Impact:increase 31% (8.0% → 10.5%)
Trust score:4/5

endogenous oxalate synthesis

1 evidences

High-dose vitamin C (1000 mg twice daily) increased urinary oxalate and stone-risk markers in a subset of participants.

Trust comment: Randomized crossover, controlled metabolic-unit study with measured dietary control and objective urinary endpoints.

Study Details

PMID:15987848
Participants:48
Impact:increase 39% (391 → 544 μmol/day)
Trust score:4/5

plasma nitric oxide (NO)

2 evidences

Children conceived by ART given vitamins C (1 g) and E (400 IU) for 4 weeks showed improved NO levels, better brachial FMD and lower pulmonary artery pressure versus placebo (effects seen in ART children only).

Trust comment: Randomized double‑blind placebo‑controlled RCT in 42 children with significant, physiologically relevant endpoints—moderate sample size but solid design.

Study Details

PMID:24817695
Participants:42
Impact:21.7 ± 7.9 → 26.9 ± 7.6 µM in ART children (p = 0.04) (~+24%)
Trust score:4/5

Patients with IgA nephropathy had more oxidative damage and lower antioxidant levels including vitamin C than healthy volunteers.

Trust comment: Moderate-quality comparative study with clear measurements but observational design limits causal inference about vitamin C effects.

Study Details

PMID:15593395
Participants:144
Impact:increased (significantly vs controls, P<0.0001)
Trust score:3/5

iron stores (transferrin receptor / proportion normal)

1 evidences

Anemic children given iron/folate improved hemoglobin; adding vitamins A and C helped restore iron stores faster.

Trust comment: Randomized, double-blind trial with moderate-to-large sample and clinically relevant hematologic endpoints.

Study Details

PMID:11442213
Participants:215
Impact:improved iron stores with vitamins A+C plus SP versus SP alone (greater proportion normal TfR; P=0.012)
Trust score:4/5

plasma/urinary vitamin C biomarkers

1 evidences

Increasing fruit and vegetable intake raised dietary and biomarker vitamin C levels in adults at increased CVD risk.

Trust comment: Randomized dietary intervention with objective biomarker verification and reasonable sample size.

Study Details

PMID:22476876
Participants:174
Impact:increase (verified by biomarker analysis)
Trust score:4/5

TNF-alpha

1 evidences

A 4-month RCT of an antioxidant cocktail including 1 g vitamin C reduced inflammatory and oxidative biomarkers (notably TNF-α and cystine) in colorectal adenoma patients.

Trust comment: Randomized double-blind trial with significant biomarker changes but small pilot sample and multinutrient intervention limits attribution to vitamin C alone.

Study Details

PMID:20200432
Participants:47
Impact:-37% (P = 0.002)
Trust score:3/5

vitamin C (plasma level)

3 evidences

Resistance training with whey increased some antioxidant markers (including vitamin C) and improved some lipid/HDL measures in overweight young men.

Trust comment: Small randomized study (n=30) with objective measures but limited sample size and short duration.

Study Details

PMID:22889987
Participants:30
Impact:significant change (reported increase; exact values not specified)
Trust score:3/5

Yoga and sham-yoga produced similar improvements in many markers in T2DM; only reduced glutathione improved more with yoga, and vitamin C changed within groups but not between groups.

Trust comment: Single-blind pilot RCT with active control and small sample size; measured vitamin C but between-group differences were absent except for GSH.

Study Details

PMID:31283365
Participants:40
Impact:within-group changes in both groups; no significant between-group difference
Trust score:3/5

Three months of community yoga lowered oxidative stress (MDA) and improved BMI, waist, systolic BP and fasting glucose but did not change vitamin C levels.

Trust comment: Small RCT with objective oxidative stress measures; vitamin C was measured as an antioxidant but showed no effect.

Study Details

PMID:24280463
Participants:29
Impact:no significant change
Trust score:3/5

lipid measures (LDL/triglycerides/HDL)

1 evidences

Resistance training with whey increased some antioxidant markers (including vitamin C) and improved some lipid/HDL measures in overweight young men.

Trust comment: Small randomized study (n=30) with objective measures but limited sample size and short duration.

Study Details

PMID:22889987
Participants:30
Impact:significant changes noted (HDL ↑ in RW vs control; LDL/triglyceride changes reported but exact directions/values not specified)
Trust score:3/5

soluble transferrin receptor

1 evidences

Randomized 16-week trial showing that eating vitamin C–rich gold kiwifruit with iron-fortified cereal improves iron status in women with low iron stores.

Trust comment: Randomized controlled dietary trial with clear biomarker changes, moderate sample size (final n=69).

Study Details

PMID:20727238
Participants:69
Impact:median change −0.5 mg/L (kiwifruit) vs 0.0 mg/L (banana)
Trust score:4/5

5-pyridoxal phosphate (vitamin B6 active form)

1 evidences

Omega-3 or vitamins E+C during 3 months of strength training changed concentrations of some B-vitamins and redox aminothiols in older men.

Trust comment: Randomized with clearly reported group sizes but small total sample and combined E+C supplement limits attribution to Vitamin C alone.

Study Details

PMID:26848570
Participants:50
Impact:decreased in vitamins E+C group (p=0.01)
Trust score:3/5

reduced aminothiols (redox status)

1 evidences

Omega-3 or vitamins E+C during 3 months of strength training changed concentrations of some B-vitamins and redox aminothiols in older men.

Trust comment: Randomized with clearly reported group sizes but small total sample and combined E+C supplement limits attribution to Vitamin C alone.

Study Details

PMID:26848570
Participants:50
Impact:increased in vitamins E+C group (p<0.001)
Trust score:3/5

primary composite maternal/perinatal outcome

1 evidences

Large multicenter randomized trial showing no reduction in preeclampsia or related adverse outcomes with high-dose vitamin C + E started early in pregnancy.

Trust comment: Large, multicenter, double-blind randomized controlled trial with high participant numbers and minimal risk of bias.

Study Details

PMID:20375405
Participants:9969
Impact:no significant difference (6.1% vitamin group vs 5.7% placebo; RR 1.07)
Trust score:5/5

preeclampsia rate

1 evidences

Large multicenter randomized trial showing no reduction in preeclampsia or related adverse outcomes with high-dose vitamin C + E started early in pregnancy.

Trust comment: Large, multicenter, double-blind randomized controlled trial with high participant numbers and minimal risk of bias.

Study Details

PMID:20375405
Participants:9969
Impact:no significant difference (7.2% vitamin group vs 6.7% placebo; RR 1.07)
Trust score:5/5

periodontal inflamed surface area (PISA)

1 evidences

In patients receiving non-surgical periodontal therapy, a 4‑week free-sugar avoidance led to greater reductions in bleeding on probing and periodontal inflamed surface area and increased dietary vitamin C intake compared with control.

Trust comment: Single-blinded randomized controlled exploratory trial with objective clinical endpoints but very small sample (n=22) and dietary change (not isolated vitamin C supplementation).

Study Details

PMID:39185702
Participants:22
Impact:−858.7 mm² (SAG T1–T3) vs −815.5 mm² (CG T1–T3)
Trust score:3/5

iron absorption (ferrous fumarate)

1 evidences

Randomized crossover in children: orange juice (25 mg ascorbic acid) increased absorption of ferrous fumarate compared with apple juice (no ascorbic acid).

Trust comment: Small randomized crossover in children directly testing ascorbic acid (in orange juice) effect on iron absorption; well controlled though limited sample size.

Study Details

PMID:20639713
Participants:21
Impact:Increased from 5.5% ± 0.7% (apple) to 8.2% ± 1.2% (orange with 25 mg ascorbic acid)
Trust score:4/5

age effect on absorption

1 evidences

Randomized crossover in children: orange juice (25 mg ascorbic acid) increased absorption of ferrous fumarate compared with apple juice (no ascorbic acid).

Trust comment: Small randomized crossover in children directly testing ascorbic acid (in orange juice) effect on iron absorption; well controlled though limited sample size.

Study Details

PMID:20639713
Participants:21
Impact:Children >6 years had nearly a 2-fold increase in iron absorption with orange juice
Trust score:4/5

bladder cancer risk

1 evidences

Prospective cohort of male smokers found no association between dietary or supplemental vitamin C intake and bladder cancer risk over median 11-year follow-up.

Trust comment: Large prospective cohort with validated dietary assessment and long follow-up; observational design but high quality for exposure-disease association.

Study Details

PMID:12434284
Participants:27111
Impact:No association with dietary or total (diet + supplements) vitamin C intake (null results)
Trust score:4/5

incidence (cases)

1 evidences

Prospective cohort of male smokers found no association between dietary or supplemental vitamin C intake and bladder cancer risk over median 11-year follow-up.

Trust comment: Large prospective cohort with validated dietary assessment and long follow-up; observational design but high quality for exposure-disease association.

Study Details

PMID:12434284
Participants:27111
Impact:344 bladder cancer cases over median 11 years among 27,111 men
Trust score:4/5

urinary deoxypyridinoline (bone resorption)

1 evidences

Randomized double-blind 4-week trial comparing isoflavones, vitamins C+E, and placebo; vitamin C+E did not change bone resorption marker.

Trust comment: Small randomized double-blind human trial but short duration (4 weeks) and vitamins were given as a combined C+E pill, limiting attribution to vitamin C alone.

Study Details

PMID:15649287
Participants:67
Impact:no significant change (vitamin C+E vs baseline/placebo)
Trust score:3/5

serum BGP (bone formation)

1 evidences

Randomized double-blind 4-week trial comparing isoflavones, vitamins C+E, and placebo; vitamin C+E did not change bone resorption marker.

Trust comment: Small randomized double-blind human trial but short duration (4 weeks) and vitamins were given as a combined C+E pill, limiting attribution to vitamin C alone.

Study Details

PMID:15649287
Participants:67
Impact:no significant change
Trust score:3/5

presumptive clinical malaria (symptomatic)

1 evidences

Large randomized double-blind trial: multivitamins including vitamin C reduced presumptive clinical malaria but increased any malaria parasitemia.

Trust comment: Large randomized double-blind factorial trial with robust follow-up; however vitamin C was given as part of a multivitamin so effects reflect the combined supplement.

Study Details

PMID:25436815
Participants:1050
Impact:−22% risk (95% CI: 8% to 33% lower) with multivitamins
Trust score:4/5

any malaria parasitemia (asymptomatic or symptomatic)

1 evidences

Large randomized double-blind trial: multivitamins including vitamin C reduced presumptive clinical malaria but increased any malaria parasitemia.

Trust comment: Large randomized double-blind factorial trial with robust follow-up; however vitamin C was given as part of a multivitamin so effects reflect the combined supplement.

Study Details

PMID:25436815
Participants:1050
Impact:+24% risk (95% CI: 2% to 50% higher) with multivitamins
Trust score:4/5

adenoma growth (overall)

1 evidences

3-year placebo-controlled intervention with calcium plus antioxidants (including vitamin C) showed no overall effect on adenoma growth but suggested reduced new adenoma formation in some subgroups.

Trust comment: Long randomized intervention with reasonable follow-up, but vitamin C was one component of a multi-nutrient regimen so causal attribution to vitamin C is uncertain.

Study Details

PMID:9586828
Participants:116
Impact:no significant overall effect
Trust score:3/5

new adenoma formation (selected subgroups)

1 evidences

3-year placebo-controlled intervention with calcium plus antioxidants (including vitamin C) showed no overall effect on adenoma growth but suggested reduced new adenoma formation in some subgroups.

Trust comment: Long randomized intervention with reasonable follow-up, but vitamin C was one component of a multi-nutrient regimen so causal attribution to vitamin C is uncertain.

Study Details

PMID:9586828
Participants:116
Impact:reduced in some subgroups; e.g., mean difference in adenoma growth in <60 yrs: 2.3 mm (95% CI 0.26–4.36)
Trust score:3/5

CK-MB, troponin I, LDH (myocardial injury markers)

1 evidences

Double-blind randomized trial giving high-dose IV and cardioplegia vitamin C in CABG patients found no change in cardiac enzymes but improved ejection fraction and shorter ICU stay.

Trust comment: Randomized double-blind surgical trial with clear vitamin C dosing but small sample size and single-center design limit generalizability.

Study Details

PMID:31719005
Participants:50
Impact:no significant difference between vitamin C and control
Trust score:3/5

left ventricular ejection fraction (EF)

1 evidences

Double-blind randomized trial giving high-dose IV and cardioplegia vitamin C in CABG patients found no change in cardiac enzymes but improved ejection fraction and shorter ICU stay.

Trust comment: Randomized double-blind surgical trial with clear vitamin C dosing but small sample size and single-center design limit generalizability.

Study Details

PMID:31719005
Participants:50
Impact:EF change +0.8% (vitamin C) vs −4.2% (control); significant improvement with vitamin C
Trust score:3/5

wound closure

1 evidences

In patients with non-healing diabetic foot ulcers, adding oral vitamins E and C to PRP-FG dressing increased wound closures and reduced oxidative/inflammatory markers over 8 weeks.

Trust comment: Randomized double-blind trial but very small (n=25) and vitamin C was given combined with vitamin E and PRP-FG, limiting attribution to vitamin C alone.

Study Details

PMID:33646060
Participants:25
Impact:6 vs 2 wounds completely closed (intervention vs control) at 8 weeks
Trust score:3/5

wound size

1 evidences

In patients with non-healing diabetic foot ulcers, adding oral vitamins E and C to PRP-FG dressing increased wound closures and reduced oxidative/inflammatory markers over 8 weeks.

Trust comment: Randomized double-blind trial but very small (n=25) and vitamin C was given combined with vitamin E and PRP-FG, limiting attribution to vitamin C alone.

Study Details

PMID:33646060
Participants:25
Impact:significant reduction in both groups (p=0.019) — greater closure in intervention
Trust score:3/5

oxidative/inflammatory markers (PAB, ESR, hs-CRP)

1 evidences

In patients with non-healing diabetic foot ulcers, adding oral vitamins E and C to PRP-FG dressing increased wound closures and reduced oxidative/inflammatory markers over 8 weeks.

Trust comment: Randomized double-blind trial but very small (n=25) and vitamin C was given combined with vitamin E and PRP-FG, limiting attribution to vitamin C alone.

Study Details

PMID:33646060
Participants:25
Impact:significant decrease in intervention vs control (p<0.05)
Trust score:3/5

ACTH

1 evidences

Preoperative ascorbic acid did not prevent the surgical stress hormone changes; some hormones transiently rose after surgery.

Trust comment: Small randomized study with repeated hormone measures but limited sample size and short follow-up, and no clear protective effect of ascorbic acid.

Study Details

PMID:15587771
Participants:22
Impact:increased at 2 and 6 hours (statistically significant) vs baseline/control
Trust score:3/5

cortisol

1 evidences

Preoperative ascorbic acid did not prevent the surgical stress hormone changes; some hormones transiently rose after surgery.

Trust comment: Small randomized study with repeated hormone measures but limited sample size and short follow-up, and no clear protective effect of ascorbic acid.

Study Details

PMID:15587771
Participants:22
Impact:higher in AA group at 6 hours (within normal limits) vs control
Trust score:3/5

osteocalcin

1 evidences

Preoperative ascorbic acid did not prevent the surgical stress hormone changes; some hormones transiently rose after surgery.

Trust comment: Small randomized study with repeated hormone measures but limited sample size and short follow-up, and no clear protective effect of ascorbic acid.

Study Details

PMID:15587771
Participants:22
Impact:no decrease observed with AA (no protective effect)
Trust score:3/5

blood vitamin C

3 evidences

Changing cows' diet to alter cheese fat composition raised blood vitamins C and E and lowered oxidized LDL and myristic acid in healthy volunteers after 4 weeks.

Trust comment: Small crossover pilot (n=30) with biochemical endpoints; vitamin C was an outcome (increased) not the intervention, limiting causal inference about vitamin C effects.

Study Details

PMID:21591986
Participants:30
Impact:increased after experimental cheese consumption
Trust score:3/5

New parenteral nutrition with multivitamins increased blood vitamin C and was safely tolerated in healthy volunteers.

Trust comment: Phase I randomized active-controlled trial in healthy volunteers with small sample size and open-label elements limiting generalizability.

Study Details

PMID:35871950
Participants:46
Impact:increased in OPF-105 group (observed in multiple-dose Step 4)
Trust score:3/5

A 6-month randomized dietary intervention (Mediterranean Diet) in breast cancer survivors increased blood vitamin C and improved body composition and glycemic measures compared with control.

Trust comment: Randomized intervention with 70 participants and reported biochemical outcomes; moderate-high quality though dietary intervention (not isolated vitamin C) limits attribution to vitamin C alone.

Study Details

PMID:28634625
Participants:70
Impact:increase (statistically significant)
Trust score:4/5

oxidized LDL

1 evidences

Changing cows' diet to alter cheese fat composition raised blood vitamins C and E and lowered oxidized LDL and myristic acid in healthy volunteers after 4 weeks.

Trust comment: Small crossover pilot (n=30) with biochemical endpoints; vitamin C was an outcome (increased) not the intervention, limiting causal inference about vitamin C effects.

Study Details

PMID:21591986
Participants:30
Impact:significantly decreased with experimental cheese
Trust score:3/5

myristic acid (blood)

1 evidences

Changing cows' diet to alter cheese fat composition raised blood vitamins C and E and lowered oxidized LDL and myristic acid in healthy volunteers after 4 weeks.

Trust comment: Small crossover pilot (n=30) with biochemical endpoints; vitamin C was an outcome (increased) not the intervention, limiting causal inference about vitamin C effects.

Study Details

PMID:21591986
Participants:30
Impact:significantly decreased with experimental cheese
Trust score:3/5

successful bowel preparation (Aronchick)

1 evidences

In this randomized phase II trial, combinations including 2-L PEG with ascorbic acid (split-dose) achieved high rates of successful bowel cleansing for colonoscopy.

Trust comment: Large randomized phase II trial (229 analyzed) with blinded endoscopists and objective bowel-prep scoring; ascorbic acid was part of the PEG regimen but not isolated.

Study Details

PMID:26886637
Participants:229
Impact:PMC-PEG-SD 100% success; PMC-NaP-SD 100%; PMC-PEG-DP 82.5%; PMC-NaP-DP 64.4%
Trust score:4/5

Ottawa preparation score

1 evidences

In this randomized phase II trial, combinations including 2-L PEG with ascorbic acid (split-dose) achieved high rates of successful bowel cleansing for colonoscopy.

Trust comment: Large randomized phase II trial (229 analyzed) with blinded endoscopists and objective bowel-prep scoring; ascorbic acid was part of the PEG regimen but not isolated.

Study Details

PMID:26886637
Participants:229
Impact:split-dose PMC-PEG and PMC-NaP had significantly lower (better) scores (p<0.0001)
Trust score:4/5

tolerability/adverse GI symptoms

1 evidences

In this randomized phase II trial, combinations including 2-L PEG with ascorbic acid (split-dose) achieved high rates of successful bowel cleansing for colonoscopy.

Trust comment: Large randomized phase II trial (229 analyzed) with blinded endoscopists and objective bowel-prep scoring; ascorbic acid was part of the PEG regimen but not isolated.

Study Details

PMID:26886637
Participants:229
Impact:adverse GI symptoms mild overall; completion ~99% with high willingness to reuse
Trust score:4/5

H. pylori eradication rate (standard + ascorbic acid)

1 evidences

Randomized study testing ascorbic acid, beta carotene, and allicin with/without standard therapy for H. pylori eradication; ascorbic acid showed no benefit.

Trust comment: Randomized clinical design with clear outcome measures but small group sizes (n≈30 per arm) and limited reporting on allocation/concealment.

Study Details

PMID:11811084
Participants:210
Impact:-16.6 percentage points (50.0% vs 66.6% for standard alone)
Trust score:3/5

H. pylori eradication rate (ascorbic acid alone)

1 evidences

Randomized study testing ascorbic acid, beta carotene, and allicin with/without standard therapy for H. pylori eradication; ascorbic acid showed no benefit.

Trust comment: Randomized clinical design with clear outcome measures but small group sizes (n≈30 per arm) and limited reporting on allocation/concealment.

Study Details

PMID:11811084
Participants:210
Impact:10.0% eradication
Trust score:3/5

Chromosomal aberration frequency

1 evidences

Workers exposed to solvents received an antioxidant vitamin mix (A, C, E, selenium); cytogenetic markers improved after 1 month of supplementation.

Trust comment: Human controlled trial but used a vitamin mixture (including C) so effects cannot be attributed to vitamin C alone and sample size is modest.

Study Details

PMID:23625906
Participants:78
Impact:Statistically significant decrease after antioxidant supplementation (exact % not reported)
Trust score:3/5

Sister chromatid exchanges (SCEs)

1 evidences

Workers exposed to solvents received an antioxidant vitamin mix (A, C, E, selenium); cytogenetic markers improved after 1 month of supplementation.

Trust comment: Human controlled trial but used a vitamin mixture (including C) so effects cannot be attributed to vitamin C alone and sample size is modest.

Study Details

PMID:23625906
Participants:78
Impact:88% of previously abnormal SCE levels returned to normal after supplementation
Trust score:3/5

Gut permeability (lactulose/rhamnose test)

1 evidences

Perioperative multi-antioxidant regimen (including vitamin C) did not change gut permeability after lower torso ischemia compared with standard care.

Trust comment: Randomized prospective study but small sample size and combined antioxidant regimen limits attribution to vitamin C specifically.

Study Details

PMID:12145556
Participants:42
Impact:No significant difference between antioxidant and control groups (p=0.93 at 6 h; p=0.97 at 24 h)
Trust score:3/5

Association of plasma ascorbic acid with 90-day mortality

1 evidences

In septic shock patients, baseline plasma ascorbic acid levels did not predict hydrocortisone treatment effect or 90-day mortality.

Trust comment: Large, multicenter nested cohort with standardized measurements; observational association analysis limits causal claims but data quality is high.

Study Details

PMID:32396775
Participants:529
Impact:No significant association (OR ~1.11 for treated vs OR ~1.05 for placebo; interaction P=0.70)
Trust score:4/5

Association of plasma ascorbic acid with shock resolution

1 evidences

In septic shock patients, baseline plasma ascorbic acid levels did not predict hydrocortisone treatment effect or 90-day mortality.

Trust comment: Large, multicenter nested cohort with standardized measurements; observational association analysis limits causal claims but data quality is high.

Study Details

PMID:32396775
Participants:529
Impact:No significant interaction with hydrocortisone treatment (no heterogeneity observed)
Trust score:4/5

Maintenance of hemoglobin >105 g/L

1 evidences

Young children received cereal fortified with iron and ascorbic acid (3:1 molar ratio); no difference between iron compounds in maintaining hemoglobin >105 g/L.

Trust comment: Randomized double-blind trial with adequate sample for the question, but vitamin C was present across formulations and its isolated effect cannot be determined.

Study Details

PMID:19403640
Participants:235
Impact:No significant difference between groups (P = 0.508)
Trust score:3/5

gastric cancer incidence

3 evidences

Large randomized placebo-controlled trial in a high-risk Chinese population; long-term (7.3 years) vitamin supplementation (included 250 mg vitamin C with vitamin E and selenium) reduced gastric cancer incidence and gastric cancer mortality over 22.3 years.

Trust comment: Large randomized, placebo-controlled factorial trial with excellent compliance and 22-year follow-up; vitamin arm included vitamin C as a component.

Study Details

PMID:31511230
Participants:3365
Impact:reduced (odds ratio 0.64; ~36% reduction, fully adjusted)
Trust score:5/5

Long-term combined vitamin supplement (including vitamin C) vs placebo had no beneficial effect on precancerous gastric lesions or gastric cancer incidence.

Trust comment: Large, long-term randomized trial with objective outcomes, but vitamin C was given as part of a multi-nutrient supplement (not isolated).

Study Details

PMID:16849680
Participants:3365
Impact:no significant effect
Trust score:4/5

Long-term follow-up of a randomized, placebo-controlled trial: combined vitamin treatment (vitamins C and E plus selenium) did not reduce overall gastric cancer incidence but was associated with fewer gastric or esophageal cancer deaths.

Trust comment: Large randomized, masked factorial placebo-controlled trial with long follow-up; attribution to vitamin C alone limited because treatment was combined with other antioxidants.

Study Details

PMID:22271764
Participants:3365
Impact:non-significant decrease
Trust score:4/5

gastric cancer mortality

2 evidences

Long-term follow-up of a randomized, placebo-controlled trial: combined vitamin treatment (vitamins C and E plus selenium) did not reduce overall gastric cancer incidence but was associated with fewer gastric or esophageal cancer deaths.

Trust comment: Large randomized, masked factorial placebo-controlled trial with long follow-up; attribution to vitamin C alone limited because treatment was combined with other antioxidants.

Study Details

PMID:22271764
Participants:3365
Impact:non-significant decrease
Trust score:4/5

Large randomized placebo-controlled trial in a high-risk Chinese population; long-term (7.3 years) vitamin supplementation (included 250 mg vitamin C with vitamin E and selenium) reduced gastric cancer incidence and gastric cancer mortality over 22.3 years.

Trust comment: Large randomized, placebo-controlled factorial trial with excellent compliance and 22-year follow-up; vitamin arm included vitamin C as a component.

Study Details

PMID:31511230
Participants:3365
Impact:reduced (hazard ratio 0.48; ~52% reduction, fully adjusted)
Trust score:5/5

death from gastric or esophageal cancer (secondary)

1 evidences

Long-term follow-up of a randomized, placebo-controlled trial: combined vitamin treatment (vitamins C and E plus selenium) did not reduce overall gastric cancer incidence but was associated with fewer gastric or esophageal cancer deaths.

Trust comment: Large randomized, masked factorial placebo-controlled trial with long follow-up; attribution to vitamin C alone limited because treatment was combined with other antioxidants.

Study Details

PMID:22271764
Participants:3365
Impact:-49% (HR 0.51, 95% CI 0.30–0.87, P=0.014)
Trust score:4/5

flow-mediated vasodilation

1 evidences

Two small controlled studies in adults ≥70 showed statins lowered LDL but adding antioxidant vitamins (including vitamin C in one arm) did not improve brachial artery flow-mediated or nitroglycerin-mediated vasodilation.

Trust comment: Controlled, double-blind studies but small sample sizes and combined interventions limit ability to isolate vitamin C effects.

Study Details

PMID:11738278
Participants:54
Impact:no change (baseline ~2.2%, no improvement after statins or vitamins)
Trust score:3/5

nitroglycerin-mediated vasodilation

1 evidences

Two small controlled studies in adults ≥70 showed statins lowered LDL but adding antioxidant vitamins (including vitamin C in one arm) did not improve brachial artery flow-mediated or nitroglycerin-mediated vasodilation.

Trust comment: Controlled, double-blind studies but small sample sizes and combined interventions limit ability to isolate vitamin C effects.

Study Details

PMID:11738278
Participants:54
Impact:no change (baseline ~10.7%, no improvement)
Trust score:3/5

linoleic acid (18:2n-6) levels

1 evidences

Randomized placebo-controlled trial of micronutrient sprinkles (including vitamins A,C,D3, zinc, iron, folic acid) in Cambodian infants; outcomes on fatty acid status reported but vitamin D effect not isolated.

Trust comment: Large randomized double-blind placebo-controlled trial with good sample retention, but vitamin C was part of a multi-micronutrient supplement so individual contribution is unclear.

Study Details

PMID:17204967
Participants:204
Impact:increased in MMN group vs placebo (approached Italian reference levels)
Trust score:4/5

alpha-linolenic acid (18:3n-3) levels

1 evidences

Randomized placebo-controlled trial of micronutrient sprinkles (including vitamins A,C,D3, zinc, iron, folic acid) in Cambodian infants; outcomes on fatty acid status reported but vitamin D effect not isolated.

Trust comment: Large randomized double-blind placebo-controlled trial with good sample retention, but vitamin C was part of a multi-micronutrient supplement so individual contribution is unclear.

Study Details

PMID:17204967
Participants:204
Impact:increased in MMN group vs placebo
Trust score:4/5

long-chain derivatives (20:4n-6, 22:6n-3)

1 evidences

Randomized placebo-controlled trial of micronutrient sprinkles (including vitamins A,C,D3, zinc, iron, folic acid) in Cambodian infants; outcomes on fatty acid status reported but vitamin D effect not isolated.

Trust comment: Large randomized double-blind placebo-controlled trial with good sample retention, but vitamin C was part of a multi-micronutrient supplement so individual contribution is unclear.

Study Details

PMID:17204967
Participants:204
Impact:no significant change vs placebo
Trust score:4/5

progression to advanced AMD

1 evidences

High-dose antioxidant formulation including vitamin C plus zinc reduced progression to advanced AMD and reduced risk of moderate vision loss compared with placebo.

Trust comment: Large multicenter randomized double-masked trial with long follow-up and low loss to follow-up, but vitamin C was given in combination with other antioxidants and zinc.

Study Details

PMID:11594942
Participants:3640
Impact:antioxidants + zinc OR 0.72 (99% CI 0.52–0.98) vs placebo (statistically significant)
Trust score:5/5

at least moderate visual acuity loss

1 evidences

High-dose antioxidant formulation including vitamin C plus zinc reduced progression to advanced AMD and reduced risk of moderate vision loss compared with placebo.

Trust comment: Large multicenter randomized double-masked trial with long follow-up and low loss to follow-up, but vitamin C was given in combination with other antioxidants and zinc.

Study Details

PMID:11594942
Participants:3640
Impact:antioxidants + zinc OR 0.73 (99% CI 0.54–0.99) vs placebo (statistically significant)
Trust score:5/5

plasma ascorbate (vitamin C)

1 evidences

A 4-month high-antioxidant diet (designed to raise vitamins A, C and E) increased plasma and leukocyte vitamin C, boosted antioxidant enzyme activities, and lowered lipid oxidative markers in women with endometriosis.

Trust comment: Randomized diet intervention with objective biochemical endpoints and moderate completion rates, but unblinded and with some dropouts.

Study Details

PMID:19476631
Participants:72
Impact:+40% (from second month)
Trust score:3/5

HDL2-C

1 evidences

In CAD patients on simvastatin+niacin, adding antioxidant vitamins (including vitamin C) blunted the favorable increases in HDL metrics observed with lipid therapy alone.

Trust comment: Randomized 12-month trial of moderate size with clear lipid endpoints, but antioxidants were given as a combination so attribution to vitamin C alone is indirect.

Study Details

PMID:11498460
Participants:153
Impact:S-N: +42% vs S-N+A: 0% (antioxidants blocked HDL2-C increase)
Trust score:4/5

Lp(A-I) apo A-I / HDL particle size

1 evidences

In CAD patients on simvastatin+niacin, adding antioxidant vitamins (including vitamin C) blunted the favorable increases in HDL metrics observed with lipid therapy alone.

Trust comment: Randomized 12-month trial of moderate size with clear lipid endpoints, but antioxidants were given as a combination so attribution to vitamin C alone is indirect.

Study Details

PMID:11498460
Participants:153
Impact:S-N: +64% in apo A-I-containing HDL vs S-N+A: no selective increase (blunted)
Trust score:4/5

progression rate of gastric precancerous lesions

1 evidences

Three-year supplementation with vitamin C (750 mg/day) plus vitamin E and beta-carotene did not significantly change progression or regression rates of precancerous gastric lesions compared with placebo.

Trust comment: Large, double-blind randomized trial with objective histologic outcomes and appropriate statistical analysis.

Study Details

PMID:17227997
Participants:1980
Impact:74.3 → 67.8 per 100 person-years (−8.7%); rate ratio 0.92 (95% CI 0.74–1.15), not significant
Trust score:5/5

regression rate of gastric precancerous lesions

1 evidences

Three-year supplementation with vitamin C (750 mg/day) plus vitamin E and beta-carotene did not significantly change progression or regression rates of precancerous gastric lesions compared with placebo.

Trust comment: Large, double-blind randomized trial with objective histologic outcomes and appropriate statistical analysis.

Study Details

PMID:17227997
Participants:1980
Impact:109.4 → 116.5 per 100 person-years (+6.5%); rate ratio 1.09 (95% CI 0.90–1.33), not significant
Trust score:5/5

central retinal function (N1-P1 RAD, R1-R2)

1 evidences

In nonadvanced AMD patients, one-year supplementation including vitamin C and carotenoids improved central retinal electrophysiologic responses compared with no supplementation.

Trust comment: Randomized study but small sample size and multi-nutrient supplement means effect cannot be attributed to vitamin C alone.

Study Details

PMID:17716735
Participants:27
Impact:significant increase after 6 and 12 months in treated group (magnitude not specified)
Trust score:3/5

28-day all-cause mortality

1 evidences

An enteral diet enriched with EPA, GLA, and elevated antioxidants lowered 28-day mortality and improved ventilator- and ICU-free days in mechanically ventilated severe sepsis/septic shock patients.

Trust comment: Prospective double-blind randomized trial with clinically meaningful endpoints, but the intervention combined multiple components so attribution to vitamin C alone is indirect.

Study Details

PMID:16850002
Participants:165
Impact:absolute reduction −19.4% (p = 0.037)
Trust score:4/5

ventilator-free days

1 evidences

An enteral diet enriched with EPA, GLA, and elevated antioxidants lowered 28-day mortality and improved ventilator- and ICU-free days in mechanically ventilated severe sepsis/septic shock patients.

Trust comment: Prospective double-blind randomized trial with clinically meaningful endpoints, but the intervention combined multiple components so attribution to vitamin C alone is indirect.

Study Details

PMID:16850002
Participants:165
Impact:+7.6 days (13.4 ±1.2 vs 5.8 ±1.0, p < .001)
Trust score:4/5

ICU-free days

1 evidences

An enteral diet enriched with EPA, GLA, and elevated antioxidants lowered 28-day mortality and improved ventilator- and ICU-free days in mechanically ventilated severe sepsis/septic shock patients.

Trust comment: Prospective double-blind randomized trial with clinically meaningful endpoints, but the intervention combined multiple components so attribution to vitamin C alone is indirect.

Study Details

PMID:16850002
Participants:165
Impact:+6.2 days (10.8 ±1.1 vs 4.6 ±0.9, p < .001)
Trust score:4/5

minimum luminal diameter (MLD) change, Hp1-1

1 evidences

In postmenopausal women, vitamins C and E altered angiographic progression of coronary atherosclerosis in a manner dependent on haptoglobin genotype — beneficial in Hp1-1 (especially diabetics) and possibly harmful in Hp2-2 diabetics.

Trust comment: Randomized angiographic study with genotype-stratified findings, but subgroup analyses and moderate sample size limit certainty.

Study Details

PMID:15047650
Participants:299
Impact:+0.079 mm annualized (vitamin therapy vs placebo, 0.079 ±0.040 mm, P = 0.049)
Trust score:3/5

MLD change, Hp1-1 diabetics

1 evidences

In postmenopausal women, vitamins C and E altered angiographic progression of coronary atherosclerosis in a manner dependent on haptoglobin genotype — beneficial in Hp1-1 (especially diabetics) and possibly harmful in Hp2-2 diabetics.

Trust comment: Randomized angiographic study with genotype-stratified findings, but subgroup analyses and moderate sample size limit certainty.

Study Details

PMID:15047650
Participants:299
Impact:+0.149 mm annualized (0.149 ±0.064 mm, P = 0.021)
Trust score:3/5

MLD change, Hp2-2 diabetics

1 evidences

In postmenopausal women, vitamins C and E altered angiographic progression of coronary atherosclerosis in a manner dependent on haptoglobin genotype — beneficial in Hp1-1 (especially diabetics) and possibly harmful in Hp2-2 diabetics.

Trust comment: Randomized angiographic study with genotype-stratified findings, but subgroup analyses and moderate sample size limit certainty.

Study Details

PMID:15047650
Participants:299
Impact:−0.128 mm annualized (0.128 ±0.057 mm, P = 0.027) — trend toward harm
Trust score:3/5

serum malondialdehyde (MDA)

1 evidences

Giving oral antioxidant capsules around ESWL reduced markers of oxidative stress and short-term kidney injury compared with no antioxidants.

Trust comment: Randomized clinical trial with 120 patients and objective biochemical endpoints, but antioxidants were a multi-component product so Vitamin C–specific effects are not isolated.

Study Details

PMID:18064446
Participants:120
Impact:significant decrease at 24 h in antioxidant groups (P<0.001)
Trust score:4/5

urinary albumin and beta2-microglobulin (renal tubular injury markers)

1 evidences

Giving oral antioxidant capsules around ESWL reduced markers of oxidative stress and short-term kidney injury compared with no antioxidants.

Trust comment: Randomized clinical trial with 120 patients and objective biochemical endpoints, but antioxidants were a multi-component product so Vitamin C–specific effects are not isolated.

Study Details

PMID:18064446
Participants:120
Impact:significant decrease in antioxidant groups versus control
Trust score:4/5

handgrip and quadriceps strength

1 evidences

Perioperative micronutrient supplementation (including vitamin C) had little effect on muscle strength but preserved self-rated physical function compared with placebo.

Trust comment: Randomized double-blind placebo-controlled design but small sample (n=36) and multi-nutrient intervention limits attribution to Vitamin C alone.

Study Details

PMID:12135593
Participants:36
Impact:decreased after surgery with no significant difference between supplemented and placebo groups
Trust score:3/5

self-rated physical function

1 evidences

Perioperative micronutrient supplementation (including vitamin C) had little effect on muscle strength but preserved self-rated physical function compared with placebo.

Trust comment: Randomized double-blind placebo-controlled design but small sample (n=36) and multi-nutrient intervention limits attribution to Vitamin C alone.

Study Details

PMID:12135593
Participants:36
Impact:decreased in placebo group but preserved in supplemented group
Trust score:3/5

adequate bowel cleansing (BBPS ≥2 per segment)

1 evidences

In patients with prior poor preparation, 4-L split-dose PEG cleansing was superior to 2-L PEG plus ascorbic acid; adding ascorbic acid made the lower-volume prep less effective.

Trust comment: Randomized controlled study with adequate sample size and objective scale showing ascorbic acid-containing low-volume prep was inferior in this population.

Study Details

PMID:28291237
Participants:256
Impact:4-L PEG 81.1% vs 2-L PEG+Asc 67.4% (intention-to-treat); difference significant favoring 4-L PEG
Trust score:4/5

all-cause mortality (zinc)

1 evidences

Large randomized trial of high-dose antioxidants and zinc in older adults; zinc assignment was associated with lower mortality but no clear mortality benefit reported for antioxidant treatment.

Trust comment: Large randomized AREDS trial with long follow-up and clear reporting; antioxidant composition not fully specified in this text so attribution to vitamin C alone is uncertain.

Study Details

PMID:15136320
Participants:4753
Impact:-27% (RR 0.73; 95% CI 0.61–0.89) lower mortality in participants assigned to zinc
Trust score:4/5

advanced AMD and mortality

1 evidences

Large randomized trial of high-dose antioxidants and zinc in older adults; zinc assignment was associated with lower mortality but no clear mortality benefit reported for antioxidant treatment.

Trust comment: Large randomized AREDS trial with long follow-up and clear reporting; antioxidant composition not fully specified in this text so attribution to vitamin C alone is uncertain.

Study Details

PMID:15136320
Participants:4753
Impact:+41% (RR 1.41; 95% CI 1.08–1.86) increased mortality associated with advanced AMD (observational association)
Trust score:4/5

antioxidant supplementation on mortality

1 evidences

Large randomized trial of high-dose antioxidants and zinc in older adults; zinc assignment was associated with lower mortality but no clear mortality benefit reported for antioxidant treatment.

Trust comment: Large randomized AREDS trial with long follow-up and clear reporting; antioxidant composition not fully specified in this text so attribution to vitamin C alone is uncertain.

Study Details

PMID:15136320
Participants:4753
Impact:no mortality benefit for antioxidants reported (no significant effect reported in text)
Trust score:4/5

dietary iron absorption (normal-weight, +AA)

1 evidences

Crossover test-meal study in nonanemic women showing added ascorbic acid (31.4 mg) increases iron absorption, but the enhancing effect is smaller in overweight/obese women.

Trust comment: Well-measured controlled feeding test-meal study with stable isotopes and objective outcomes; moderate sample size but appropriate methods.

Study Details

PMID:26561622
Participants:62
Impact:increased from 19.0% to 29.5% (median +56% relative increase)
Trust score:4/5

dietary iron absorption (overweight/obese, +AA)

1 evidences

Crossover test-meal study in nonanemic women showing added ascorbic acid (31.4 mg) increases iron absorption, but the enhancing effect is smaller in overweight/obese women.

Trust comment: Well-measured controlled feeding test-meal study with stable isotopes and objective outcomes; moderate sample size but appropriate methods.

Study Details

PMID:26561622
Participants:62
Impact:increased from 12.9% to 16.6% (median +28% relative increase)
Trust score:4/5

iron absorption comparing groups

1 evidences

Crossover test-meal study in nonanemic women showing added ascorbic acid (31.4 mg) increases iron absorption, but the enhancing effect is smaller in overweight/obese women.

Trust comment: Well-measured controlled feeding test-meal study with stable isotopes and objective outcomes; moderate sample size but appropriate methods.

Study Details

PMID:26561622
Participants:62
Impact:absolute absorption with +AA: NW 29.5% vs OW/OB 16.6% (P=0.004); enhancing effect of ascorbic acid ~half in OW/OB vs NW
Trust score:4/5

low birth weight incidence

1 evidences

Large double-blind RCT of daily multivitamins in pregnant HIV-negative women showed reduced low birth weight and small-for-gestational-age births; vitamin C was part of the multivitamin regimen but not isolated.

Trust comment: Large, double-blind randomized trial with robust sample size and clear outcomes; multivitamin composition prevents attribution of effects to vitamin C alone.

Study Details

PMID:17409323
Participants:8468
Impact:7.8% (multivitamin) vs 9.4% (placebo); RR 0.82 (95% CI 0.70–0.95)
Trust score:5/5

mean birth weight

2 evidences

In HIV-infected pregnant women, multivitamin supplements (including vitamin C) at single versus multiple RDA doses produced similar pregnancy outcomes.

Trust comment: Large, double-blind randomized trial with clear endpoints, but vitamin C was one component of multivitamins so effects cannot be isolated to vitamin C.

Study Details

PMID:19939985
Participants:1129
Impact:3045 ± 549 g vs 3052 ± 534 g; P=0.83 (no significant difference)
Trust score:4/5

Large double-blind RCT of daily multivitamins in pregnant HIV-negative women showed reduced low birth weight and small-for-gestational-age births; vitamin C was part of the multivitamin regimen but not isolated.

Trust comment: Large, double-blind randomized trial with robust sample size and clear outcomes; multivitamin composition prevents attribution of effects to vitamin C alone.

Study Details

PMID:17409323
Participants:8468
Impact:+67 g (P<0.001) higher in multivitamin group
Trust score:5/5

small-for-gestational-age births

1 evidences

Large double-blind RCT of daily multivitamins in pregnant HIV-negative women showed reduced low birth weight and small-for-gestational-age births; vitamin C was part of the multivitamin regimen but not isolated.

Trust comment: Large, double-blind randomized trial with robust sample size and clear outcomes; multivitamin composition prevents attribution of effects to vitamin C alone.

Study Details

PMID:17409323
Participants:8468
Impact:10.7% (multivitamin) vs 13.6% (placebo); RR 0.77 (95% CI 0.68–0.87)
Trust score:5/5

insulin sensitivity

1 evidences

In healthy volunteers, a 1-month high-heat-treated diet reduced insulin sensitivity and lowered plasma vitamins (including vitamin C) while increasing blood lipids.

Trust comment: Randomized crossover diet intervention with objective biochemical measures; moderate sample size limits precision.

Study Details

PMID:20335546
Participants:62
Impact:-17% (vs steamed diet)
Trust score:4/5

plasma triglycerides

1 evidences

In healthy volunteers, a 1-month high-heat-treated diet reduced insulin sensitivity and lowered plasma vitamins (including vitamin C) while increasing blood lipids.

Trust comment: Randomized crossover diet intervention with objective biochemical measures; moderate sample size limits precision.

Study Details

PMID:20335546
Participants:62
Impact:+9% (vs steamed diet)
Trust score:4/5

verbal memory

1 evidences

In this 13-year cohort study, higher vitamin C intake was positively associated with verbal memory performance but study design is observational.

Trust comment: Large prospective cohort with long follow-up showing associations, but observational design limits causal inference and residual confounding is possible.

Study Details

PMID:21955649
Participants:2533
Impact:positive association with vitamin C intake (P-trend = 0.005)
Trust score:3/5

GA proximity progression toward central macula

1 evidences

Pooled post-hoc analysis of AREDS and AREDS2 found that antioxidant-containing formulations (including 500 mg vitamin C) slowed GA progression toward the central macula but did not change GA area.

Trust comment: Large randomized multicenter trials (AREDS/AREDS2) with robust imaging outcomes; high-quality evidence.

Study Details

PMID:39025435
Participants:1209
Impact:reduced from 72.9 to 50.7 μm/yr in AREDS noncentral GA (-22.2 μm/yr)
Trust score:5/5

GA proximity progression with lutein/zeaxanthin (AREDS2)

1 evidences

Pooled post-hoc analysis of AREDS and AREDS2 found that antioxidant-containing formulations (including 500 mg vitamin C) slowed GA progression toward the central macula but did not change GA area.

Trust comment: Large randomized multicenter trials (AREDS/AREDS2) with robust imaging outcomes; high-quality evidence.

Study Details

PMID:39025435
Participants:1209
Impact:reduced from 114.4 to 80.1 μm/yr (-34.3 μm/yr)
Trust score:5/5

GA area-based progression

1 evidences

Pooled post-hoc analysis of AREDS and AREDS2 found that antioxidant-containing formulations (including 500 mg vitamin C) slowed GA progression toward the central macula but did not change GA area.

Trust comment: Large randomized multicenter trials (AREDS/AREDS2) with robust imaging outcomes; high-quality evidence.

Study Details

PMID:39025435
Participants:1209
Impact:no significant difference
Trust score:5/5

risk of advanced AMD

1 evidences

In a large randomized trial and follow-up, the AREDS antioxidant/zinc formulation (including vitamin C) reduced risk of progression to advanced and neovascular AMD and lowered risk of moderate vision loss over 10 years.

Trust comment: Large randomized controlled trial with long-term follow-up and clinically meaningful endpoints; high trustworthiness.

Study Details

PMID:23582353
Participants:4757
Impact:OR 0.66 (~34% risk reduction vs placebo)
Trust score:5/5

risk of neovascular (NV) AMD

1 evidences

In a large randomized trial and follow-up, the AREDS antioxidant/zinc formulation (including vitamin C) reduced risk of progression to advanced and neovascular AMD and lowered risk of moderate vision loss over 10 years.

Trust comment: Large randomized controlled trial with long-term follow-up and clinically meaningful endpoints; high trustworthiness.

Study Details

PMID:23582353
Participants:4757
Impact:OR 0.60 (~40% risk reduction vs placebo)
Trust score:5/5

risk of moderate vision loss (≥15 letters)

1 evidences

In a large randomized trial and follow-up, the AREDS antioxidant/zinc formulation (including vitamin C) reduced risk of progression to advanced and neovascular AMD and lowered risk of moderate vision loss over 10 years.

Trust comment: Large randomized controlled trial with long-term follow-up and clinically meaningful endpoints; high trustworthiness.

Study Details

PMID:23582353
Participants:4757
Impact:OR 0.71 (~29% risk reduction vs placebo)
Trust score:5/5

pulmonary artery pressure

1 evidences

Children conceived by ART given vitamins C (1 g) and E (400 IU) for 4 weeks showed improved NO levels, better brachial FMD and lower pulmonary artery pressure versus placebo (effects seen in ART children only).

Trust comment: Randomized double‑blind placebo‑controlled RCT in 42 children with significant, physiologically relevant endpoints—moderate sample size but solid design.

Study Details

PMID:24817695
Participants:42
Impact:33 ± 8 → 28 ± 6 mm Hg in ART children (p = 0.028) (-5 mm Hg)
Trust score:4/5

prevalence of advanced precancerous gastric lesions

1 evidences

Long-term combined vitamin supplement (including vitamin C) vs placebo had no beneficial effect on precancerous gastric lesions or gastric cancer incidence.

Trust comment: Large, long-term randomized trial with objective outcomes, but vitamin C was given as part of a multi-nutrient supplement (not isolated).

Study Details

PMID:16849680
Participants:3365
Impact:no significant effect
Trust score:4/5

histopathologic severity of gastric lesions

1 evidences

Long-term combined vitamin supplement (including vitamin C) vs placebo had no beneficial effect on precancerous gastric lesions or gastric cancer incidence.

Trust comment: Large, long-term randomized trial with objective outcomes, but vitamin C was given as part of a multi-nutrient supplement (not isolated).

Study Details

PMID:16849680
Participants:3365
Impact:no significant effect
Trust score:4/5

cystine (CySS)

1 evidences

A 4-month RCT of an antioxidant cocktail including 1 g vitamin C reduced inflammatory and oxidative biomarkers (notably TNF-α and cystine) in colorectal adenoma patients.

Trust comment: Randomized double-blind trial with significant biomarker changes but small pilot sample and multinutrient intervention limits attribution to vitamin C alone.

Study Details

PMID:20200432
Participants:47
Impact:-19% (P = 0.03)
Trust score:3/5

IL-6 / F2-isoprostanes (by smoking status)

1 evidences

A 4-month RCT of an antioxidant cocktail including 1 g vitamin C reduced inflammatory and oxidative biomarkers (notably TNF-α and cystine) in colorectal adenoma patients.

Trust comment: Randomized double-blind trial with significant biomarker changes but small pilot sample and multinutrient intervention limits attribution to vitamin C alone.

Study Details

PMID:20200432
Participants:47
Impact:decreased in nonsmokers, increased in smokers (not significant)
Trust score:3/5

atrial glutathione peroxidase activity (>60 years)

1 evidences

Perioperative supplementation with n-3 PUFAs plus vitamins C and E reduced postoperative atrial fibrillation more in older patients and increased atrial glutathione peroxidase activity in those >60 years.

Trust comment: Randomized double-blind design and moderate size, but vitamin C was combined with other agents (n-3 PUFAs and vitamin E), so isolated vitamin C effects cannot be determined.

Study Details

PMID:22561296
Participants:152
Impact:increased (supplemented vs control)
Trust score:3/5

number of RAS episodes

1 evidences

Daily multivitamin at 100% RDI (including vitamin D among others) did not reduce number or duration of recurrent mouth ulcers compared with placebo over up to 365 days.

Trust comment: Well-conducted randomized double-masked placebo-controlled RCT, but intervention was a broad multivitamin (not vitamin C–specific), limiting attribution to vitamin C.

Study Details

PMID:22467697
Participants:160
Impact:no significant change (multivitamin 4.19 vs placebo 4.60; P=0.69)
Trust score:3/5

duration of RAS episodes

1 evidences

Daily multivitamin at 100% RDI (including vitamin D among others) did not reduce number or duration of recurrent mouth ulcers compared with placebo over up to 365 days.

Trust comment: Well-conducted randomized double-masked placebo-controlled RCT, but intervention was a broad multivitamin (not vitamin C–specific), limiting attribution to vitamin C.

Study Details

PMID:22467697
Participants:160
Impact:no significant change (8.66 vs 8.99 days; P=0.60)
Trust score:3/5

mouth pain

1 evidences

Daily multivitamin at 100% RDI (including vitamin D among others) did not reduce number or duration of recurrent mouth ulcers compared with placebo over up to 365 days.

Trust comment: Well-conducted randomized double-masked placebo-controlled RCT, but intervention was a broad multivitamin (not vitamin C–specific), limiting attribution to vitamin C.

Study Details

PMID:22467697
Participants:160
Impact:no difference between groups
Trust score:3/5

iron absorption from sorghum meals

1 evidences

Ascorbic acid (vitamin C) added to fortified sorghum meals substantially increased iron absorption in young women, overcoming polyphenol inhibition.

Trust comment: Well-controlled iron absorption studies using stable isotopes in 50 women showing a large, statistically significant ascorbic acid effect.

Study Details

PMID:23962728
Participants:50
Impact:increased to 13.6% with ascorbic acid (P<0.001) versus 4.6% (NaFeEDTA) and 2.7% (FeSO4) in high-PP meals
Trust score:4/5

effect of polyphenol concentration

1 evidences

Ascorbic acid (vitamin C) added to fortified sorghum meals substantially increased iron absorption in young women, overcoming polyphenol inhibition.

Trust comment: Well-controlled iron absorption studies using stable isotopes in 50 women showing a large, statistically significant ascorbic acid effect.

Study Details

PMID:23962728
Participants:50
Impact:meals with low PP (17 mg) had higher absorption than meals with 73 or 167 mg PP (P<0.001)
Trust score:4/5

NaFeEDTA vs FeSO4 in high-PP meals

1 evidences

Ascorbic acid (vitamin C) added to fortified sorghum meals substantially increased iron absorption in young women, overcoming polyphenol inhibition.

Trust comment: Well-controlled iron absorption studies using stable isotopes in 50 women showing a large, statistically significant ascorbic acid effect.

Study Details

PMID:23962728
Participants:50
Impact:NaFeEDTA 4.6% vs FeSO4 2.7% (P<0.001)
Trust score:4/5

insulin resistance (HOMA)

1 evidences

8-week antioxidant supplement (including vitamin C) reduced insulin resistance and some inflammation and oxidative stress in overweight young adults.

Trust comment: Randomized double-blind trial but small sample and intervention combined several antioxidants so vitamin C effect cannot be isolated.

Study Details

PMID:19154960
Participants:48
Impact:-15% (overweight AOX group at week 8)
Trust score:3/5

endothelial adhesion molecules (sICAM-1, ELAM-1)

1 evidences

8-week antioxidant supplement (including vitamin C) reduced insulin resistance and some inflammation and oxidative stress in overweight young adults.

Trust comment: Randomized double-blind trial but small sample and intervention combined several antioxidants so vitamin C effect cannot be isolated.

Study Details

PMID:19154960
Participants:48
Impact:sICAM-1 -6%, ELAM-1 -13% (overweight AOX-treated groups)
Trust score:3/5

oxidative stress (plasma lipid hydroperoxides)

1 evidences

8-week antioxidant supplement (including vitamin C) reduced insulin resistance and some inflammation and oxidative stress in overweight young adults.

Trust comment: Randomized double-blind trial but small sample and intervention combined several antioxidants so vitamin C effect cannot be isolated.

Study Details

PMID:19154960
Participants:48
Impact:reduction: -0.31 nmol/mL (normal-weight), -0.70 nmol/mL (overweight) by week 8
Trust score:3/5

platelet CD40L

1 evidences

Giving IV vitamin C during coronary stenting reduced markers of oxidative stress and lowered platelet and soluble CD40L compared with placebo.

Trust comment: Randomized controlled trial in humans with clear measurements and reported significant differences, but small sample size limits precision.

Study Details

PMID:20629665
Participants:56
Impact:decrease vs placebo (significant; lower at 60 and 120 min)
Trust score:4/5

soluble CD40L

1 evidences

Giving IV vitamin C during coronary stenting reduced markers of oxidative stress and lowered platelet and soluble CD40L compared with placebo.

Trust comment: Randomized controlled trial in humans with clear measurements and reported significant differences, but small sample size limits precision.

Study Details

PMID:20629665
Participants:56
Impact:decrease vs placebo (significant; lower at 60 and 120 min)
Trust score:4/5

8-hydroxy-2'-deoxyguanosine (oxidative stress marker)

1 evidences

Giving IV vitamin C during coronary stenting reduced markers of oxidative stress and lowered platelet and soluble CD40L compared with placebo.

Trust comment: Randomized controlled trial in humans with clear measurements and reported significant differences, but small sample size limits precision.

Study Details

PMID:20629665
Participants:56
Impact:decrease (significant)
Trust score:4/5

overall mortality (factor D: Se + vitamin E + beta-carotene)

1 evidences

Large randomized population trial of multiple vitamin/mineral regimens found some regimens reduced overall or cancer mortality; vitamin C (with molybdenum) was associated with decreased stroke mortality.

Trust comment: Very large randomized trial with long follow-up, but supplements were combined in regimens so attribution to vitamin C alone is limited.

Study Details

PMID:19318634
Participants:29584
Impact:HR=0.95; cumulative mortality reduced from 33.62% to 32.19% (10-year follow-up)
Trust score:4/5

gastric cancer mortality (factor D)

1 evidences

Large randomized population trial of multiple vitamin/mineral regimens found some regimens reduced overall or cancer mortality; vitamin C (with molybdenum) was associated with decreased stroke mortality.

Trust comment: Very large randomized trial with long follow-up, but supplements were combined in regimens so attribution to vitamin C alone is limited.

Study Details

PMID:19318634
Participants:29584
Impact:HR=0.89; cumulative gastric cancer mortality 4.28%→3.84% (significant)
Trust score:4/5

stroke mortality (vitamin C + molybdenum)

1 evidences

Large randomized population trial of multiple vitamin/mineral regimens found some regimens reduced overall or cancer mortality; vitamin C (with molybdenum) was associated with decreased stroke mortality.

Trust comment: Very large randomized trial with long follow-up, but supplements were combined in regimens so attribution to vitamin C alone is limited.

Study Details

PMID:19318634
Participants:29584
Impact:decrease (reported association; exact HR not provided in text)
Trust score:4/5

Weight-for-age Z-score

2 evidences

Giving HIV-infected mothers multivitamins (including B12) during pregnancy and postpartum improved their children's weight at 24 months.

Trust comment: Large randomized placebo-controlled trial (886 pairs) showing improved child weight; vitamin C was part of a multivitamin so effects of vitamin C alone are not isolated.

Study Details

PMID:15817867
Participants:886
Impact:+0.42 z at 24 mo
Trust score:4/5

Daily low-dose MNP containing bioavailable iron and 2.5 mg zinc reduced iron and zinc deficiencies and modestly improved weight-for-age over 23 weeks.

Trust comment: Randomized double-blind trial (n=200) with clear effects on iron/zinc status, but vitamin C was a component of a combined formula so its isolated effect is not determined.

Study Details

PMID:21178093
Participants:200
Impact:Increased (P < 0.05)
Trust score:3/5

Prevalence of iron deficiency

1 evidences

Daily low-dose MNP containing bioavailable iron and 2.5 mg zinc reduced iron and zinc deficiencies and modestly improved weight-for-age over 23 weeks.

Trust comment: Randomized double-blind trial (n=200) with clear effects on iron/zinc status, but vitamin C was a component of a combined formula so its isolated effect is not determined.

Study Details

PMID:21178093
Participants:200
Impact:Decreased by 30.6% (P < 0.01)
Trust score:3/5

Prevalence of zinc deficiency

1 evidences

Daily low-dose MNP containing bioavailable iron and 2.5 mg zinc reduced iron and zinc deficiencies and modestly improved weight-for-age over 23 weeks.

Trust comment: Randomized double-blind trial (n=200) with clear effects on iron/zinc status, but vitamin C was a component of a combined formula so its isolated effect is not determined.

Study Details

PMID:21178093
Participants:200
Impact:Decreased by 11.8% (P < 0.05)
Trust score:3/5

CSF F2-isoprostane (oxidative stress)

1 evidences

In mild–moderate Alzheimer patients, combined antioxidant treatment including vitamin C lowered a CSF oxidative stress marker but was associated with faster cognitive decline over 16 weeks.

Trust comment: Randomized, double-blind trial directly included vitamin C but given in combination with other antioxidants, limiting attribution to vitamin C alone.

Study Details

PMID:22431837
Participants:66
Impact:decreased by ~19% (E/C/ALA group)
Trust score:3/5

cognitive function (MMSE)

1 evidences

In mild–moderate Alzheimer patients, combined antioxidant treatment including vitamin C lowered a CSF oxidative stress marker but was associated with faster cognitive decline over 16 weeks.

Trust comment: Randomized, double-blind trial directly included vitamin C but given in combination with other antioxidants, limiting attribution to vitamin C alone.

Study Details

PMID:22431837
Participants:66
Impact:accelerated decline in E/C/ALA group (worse cognitive change vs others)
Trust score:3/5

CSF Aβ42/tau biomarkers

1 evidences

In mild–moderate Alzheimer patients, combined antioxidant treatment including vitamin C lowered a CSF oxidative stress marker but was associated with faster cognitive decline over 16 weeks.

Trust comment: Randomized, double-blind trial directly included vitamin C but given in combination with other antioxidants, limiting attribution to vitamin C alone.

Study Details

PMID:22431837
Participants:66
Impact:no significant change
Trust score:3/5

peroxide generation in PN (in vitro)

1 evidences

In extremely preterm infants, complete photoprotection of PN reduced peroxide contamination and preserved ascorbic acid in PN, lowering urinary peroxide levels in the first week.

Trust comment: Randomized pilot trial directly measured ascorbic acid degradation and oxidative markers in preterm infants, but small sample size limits generalizability.

Study Details

PMID:39866008
Participants:28
Impact:decreased by ~44% (photoprotection)
Trust score:4/5

ascorbic acid degradation in PN (in vitro)

1 evidences

In extremely preterm infants, complete photoprotection of PN reduced peroxide contamination and preserved ascorbic acid in PN, lowering urinary peroxide levels in the first week.

Trust comment: Randomized pilot trial directly measured ascorbic acid degradation and oxidative markers in preterm infants, but small sample size limits generalizability.

Study Details

PMID:39866008
Participants:28
Impact:reduced by ~50% (photoprotection)
Trust score:4/5

urinary peroxide levels (infants)

1 evidences

In extremely preterm infants, complete photoprotection of PN reduced peroxide contamination and preserved ascorbic acid in PN, lowering urinary peroxide levels in the first week.

Trust comment: Randomized pilot trial directly measured ascorbic acid degradation and oxidative markers in preterm infants, but small sample size limits generalizability.

Study Details

PMID:39866008
Participants:28
Impact:decreased over first week (significant)
Trust score:4/5

retinol (vitamin A) concentration

1 evidences

Weekly or daily micronutrient supplements including zinc raised hemoglobin, serum zinc, and retinol versus placebo; growth improved only in children who were stunted at baseline.

Trust comment: Checklist: Vitamin C present in both supplementation regimens (not isolated); key outcomes (Hb, retinol, zinc) identified; participant count confirmed—well-conducted randomized placebo-controlled trial.

Study Details

PMID:9925127
Participants:163
Impact:increase vs placebo (P<0.001)
Trust score:4/5

zinc concentration

1 evidences

Weekly or daily micronutrient supplements including zinc raised hemoglobin, serum zinc, and retinol versus placebo; growth improved only in children who were stunted at baseline.

Trust comment: Checklist: Vitamin C present in both supplementation regimens (not isolated); key outcomes (Hb, retinol, zinc) identified; participant count confirmed—well-conducted randomized placebo-controlled trial.

Study Details

PMID:9925127
Participants:163
Impact:increase vs placebo (P<0.001)
Trust score:4/5

wound fluid type I procollagen propeptide (CICP)

1 evidences

Small randomized trial in men undergoing hernia repair found perioperative supplementation (arginine, glutamine, vitamin C, zinc) increased markers of collagen synthesis in wound fluid during the first 1–2 days after surgery.

Trust comment: Checklist: Vitamin C included in multinutrient supplement; key collagen markers identified; participant count confirmed—small randomized exploratory trial with limited power but biologically plausible signals.

Study Details

PMID:31897483
Participants:21
Impact:increased from day 1 to 2 in supplement group; ~+49% vs control on day 2 (P=0.10)
Trust score:3/5

serum PRO-C5 (type V procollagen propeptide)

1 evidences

Small randomized trial in men undergoing hernia repair found perioperative supplementation (arginine, glutamine, vitamin C, zinc) increased markers of collagen synthesis in wound fluid during the first 1–2 days after surgery.

Trust comment: Checklist: Vitamin C included in multinutrient supplement; key collagen markers identified; participant count confirmed—small randomized exploratory trial with limited power but biologically plausible signals.

Study Details

PMID:31897483
Participants:21
Impact:decreased postoperatively in control but not in supplement group (control decrease P<0.05; supplement prevented decrease)
Trust score:3/5

safety parameters (hematology/chemistry/vitals)

1 evidences

Randomized 4-arm safety/tolerability trial (40 completers) testing daily consumption (0–3 stick packs/day for 4 weeks) of an allulose–amino acid–electrolyte powder; product was generally well tolerated with no clinically meaningful adverse changes in labs over 4 weeks.

Trust comment: Checklist: product contained vitamin C but study assessed overall safety/tolerability rather than Vitamin C efficacy; participant count confirmed—small randomized trial adequate for safety screening but underpowered for rare events.

Study Details

PMID:38892699
Participants:40
Impact:no clinically meaningful adverse changes over 4 weeks (no significant safety signals)
Trust score:3/5

gastrointestinal tolerability

1 evidences

Randomized 4-arm safety/tolerability trial (40 completers) testing daily consumption (0–3 stick packs/day for 4 weeks) of an allulose–amino acid–electrolyte powder; product was generally well tolerated with no clinically meaningful adverse changes in labs over 4 weeks.

Trust comment: Checklist: product contained vitamin C but study assessed overall safety/tolerability rather than Vitamin C efficacy; participant count confirmed—small randomized trial adequate for safety screening but underpowered for rare events.

Study Details

PMID:38892699
Participants:40
Impact:minor increases in some GI symptoms (bloating, cramping) in some groups; overall well tolerated
Trust score:3/5

thyroxine (T4) and electrolytes

1 evidences

Randomized 4-arm safety/tolerability trial (40 completers) testing daily consumption (0–3 stick packs/day for 4 weeks) of an allulose–amino acid–electrolyte powder; product was generally well tolerated with no clinically meaningful adverse changes in labs over 4 weeks.

Trust comment: Checklist: product contained vitamin C but study assessed overall safety/tolerability rather than Vitamin C efficacy; participant count confirmed—small randomized trial adequate for safety screening but underpowered for rare events.

Study Details

PMID:38892699
Participants:40
Impact:small, transient between-group differences noted for thyroxine and select electrolytes but within normal ranges
Trust score:3/5

probing pocket depth

1 evidences

In patients with stage III/IV periodontitis, a 2-month multinutrient supplement (including vitamin C) given with scaling/root planing produced some additional improvement in pocket depth and bleeding compared with placebo.

Trust comment: Double-blind RCT but small sample and intervention was a multinutrient combination so vitamin C–specific effects cannot be isolated.

Study Details

PMID:37439597
Participants:42
Impact:improved (additional benefit vs placebo)
Trust score:3/5

bleeding on probing

1 evidences

In patients with stage III/IV periodontitis, a 2-month multinutrient supplement (including vitamin C) given with scaling/root planing produced some additional improvement in pocket depth and bleeding compared with placebo.

Trust comment: Double-blind RCT but small sample and intervention was a multinutrient combination so vitamin C–specific effects cannot be isolated.

Study Details

PMID:37439597
Participants:42
Impact:reduced (additional benefit vs placebo)
Trust score:3/5

mononuclear leukocyte DNA damage (comet assay, 8-OHdG)

1 evidences

Four-week antioxidant regimens including ascorbic acid increased plasma ascorbic acid but did not change measures of mononuclear leukocyte DNA damage in smokers or nonsmokers.

Trust comment: Randomized double-blind placebo-controlled design but very small groups (n=9 smokers, n=12 nonsmokers) limit power to detect effects.

Study Details

PMID:10578484
Participants:21
Impact:no significant change with ascorbic acid supplementation
Trust score:3/5

bowel cleansing quality

1 evidences

A 2-L PEG solution plus ascorbic acid cleaned the colon as well as 4-L PEG, with better taste and higher patient compliance.

Trust comment: Large randomized trial with blinded endoscopists and complete outcome reporting for cleansing, tolerability, and compliance.

Study Details

PMID:21900786
Participants:461
Impact:noninferior to 4-L PEG for rectosigmoid and whole colon (2-L PEG+ascorbic acid vs 4-L PEG)
Trust score:4/5

taste

1 evidences

A 2-L PEG solution plus ascorbic acid cleaned the colon as well as 4-L PEG, with better taste and higher patient compliance.

Trust comment: Large randomized trial with blinded endoscopists and complete outcome reporting for cleansing, tolerability, and compliance.

Study Details

PMID:21900786
Participants:461
Impact:rated better for 2-L PEG+ascorbic acid
Trust score:4/5

plasma ascorbic acid (vitamin C) level

1 evidences

Supplementation with a fruit-and-vegetable concentrate increased plasma vitamin C and folate and modestly lowered homocysteine in men.

Trust comment: Randomized double-blind crossover (n=32) with biochemical endpoints; small sample but well controlled.

Study Details

PMID:12840177
Participants:32
Impact:increased by +12.0 µmol/L (72.1 → 84.1 µmol/L; P<0.002)
Trust score:4/5

ascorbic acid potentiation of endothelium-dependent relaxation

1 evidences

Ascorbic acid acutely potentiated acetylcholine-induced vasodilation at baseline, but after aliskiren treatment ascorbic acid no longer enhanced endothelium-dependent relaxation.

Trust comment: Randomized, open-label with blinded endpoints (n=50); ascorbic acid used acutely as a probe for endothelial oxidative status—appropriate but indirect for vitamin C effects long-term.

Study Details

PMID:22450428
Participants:50
Impact:present at baseline (potentiated acetylcholine response); abolished after 12 weeks of aliskiren treatment
Trust score:4/5

dosing schedule effect (split vs same-day)

1 evidences

Low-volume PEG with ascorbic acid cleans as well as standard PEG, tastes better, and split dosing gives the best cleansing.

Trust comment: Large randomized, single-blind multicenter trial with objective endpoints and good sample size, though not double-blind.

Study Details

PMID:20561621
Participants:868
Impact:Split-dosage markedly better: good/excellent 75.2% vs 43.0% (P = 0.00001).
Trust score:4/5

episodic memory

1 evidences

Long-term combined antioxidant supplementation including 120 mg vitamin C showed a small improvement in episodic/verbal memory, especially in nonsmokers or those with low baseline vitamin C.

Trust comment: Large double-blind randomized trial with long follow-up, but current results are from a post-hoc analysis and concern a multi-nutrient supplement rather than vitamin C alone.

Study Details

PMID:21775560
Participants:4447
Impact:Improved: mean difference +0.61 (95% CI 0.02, 1.20).
Trust score:4/5

verbal memory (subgroup)

1 evidences

Long-term combined antioxidant supplementation including 120 mg vitamin C showed a small improvement in episodic/verbal memory, especially in nonsmokers or those with low baseline vitamin C.

Trust comment: Large double-blind randomized trial with long follow-up, but current results are from a post-hoc analysis and concern a multi-nutrient supplement rather than vitamin C alone.

Study Details

PMID:21775560
Participants:4447
Impact:Improved in nonsmokers or participants with low baseline serum vitamin C (post-hoc subgroup).
Trust score:4/5

executive functioning (PCA factor)

1 evidences

Long-term combined antioxidant supplementation including 120 mg vitamin C showed a small improvement in episodic/verbal memory, especially in nonsmokers or those with low baseline vitamin C.

Trust comment: Large double-blind randomized trial with long follow-up, but current results are from a post-hoc analysis and concern a multi-nutrient supplement rather than vitamin C alone.

Study Details

PMID:21775560
Participants:4447
Impact:No consistent overall effect reported (factor identified but benefit mainly in verbal memory subgroup).
Trust score:4/5

taste rating

1 evidences

PEG with ascorbate components (2 L) produced substantially higher successful bowel cleansing than sodium phosphate and was well tolerated.

Trust comment: Randomized controlled trial with blinded expert panel assessment and clear, large differences in primary outcome.

Study Details

PMID:25180609
Participants:356
Impact:Better for PEG+Asc (mean VAS 31.2) vs NaP (mean VAS 38.1) (p = 0.0111).
Trust score:4/5

willingness to reuse preparation

1 evidences

PEG with ascorbate components (2 L) produced substantially higher successful bowel cleansing than sodium phosphate and was well tolerated.

Trust comment: Randomized controlled trial with blinded expert panel assessment and clear, large differences in primary outcome.

Study Details

PMID:25180609
Participants:356
Impact:Higher for PEG+Asc 88.4% vs NaP 78.1% (p < 0.0001).
Trust score:4/5

erythrocyte membrane fluidity (EMF; polarisation ρ and microviscosity η)

1 evidences

Daily antioxidant supplement (included ascorbic acid) given to children, young and elderly improved oxidative markers and erythrocyte membrane fluidity in young/elderly but not children.

Trust comment: Randomized human groups and clear biomarker changes, but Vitamin C was given as part of a multi-nutrient mix so effects cannot be attributed to Vitamin C alone.

Study Details

PMID:21736780
Participants:255
Impact:increased (young & elderly; significant)
Trust score:3/5

VO2 AUC (resting energy expenditure)

1 evidences

Acute ingestion of the pre-workout supplement (contains 70 mg methylcobalamin) increased short-term metabolism and improved cognitive scores and perceived energy with minimal safety signals in young trained adults.

Trust comment: Well-controlled crossover trial but small N and vitamin C was one of many active ingredients, so effects cannot be ascribed to vitamin C specifically.

Study Details

PMID:28096758
Participants:25
Impact:increased (PWS+S 1,034 vs PLA 684 ml/min AUC; p=0.015)
Trust score:3/5

VCO2 and RER AUC (substrate oxidation)

1 evidences

Acute ingestion of the pre-workout supplement (contains 70 mg methylcobalamin) increased short-term metabolism and improved cognitive scores and perceived energy with minimal safety signals in young trained adults.

Trust comment: Well-controlled crossover trial but small N and vitamin C was one of many active ingredients, so effects cannot be ascribed to vitamin C specifically.

Study Details

PMID:28096758
Participants:25
Impact:increased (PWS and PWS+S vs PLA; p<0.001)
Trust score:3/5

cognitive performance (Stroop scores) and perceived vigor/energy

1 evidences

Acute ingestion of the pre-workout supplement (contains 70 mg methylcobalamin) increased short-term metabolism and improved cognitive scores and perceived energy with minimal safety signals in young trained adults.

Trust comment: Well-controlled crossover trial but small N and vitamin C was one of many active ingredients, so effects cannot be ascribed to vitamin C specifically.

Study Details

PMID:28096758
Participants:25
Impact:improved (PWS and PWS+S > PLA at several time points)
Trust score:3/5

Stroop cognitive scores

1 evidences

Eight-week randomized, double-blind trial (supplement contains 70 mg methylcobalamin) found some within-group gains in cognition and strength with PWS, but no consistent between-group advantages in body composition or most performance outcomes; supplements were well tolerated.

Trust comment: Large, randomized double-blind placebo-controlled trial with good adherence; vitamin C present but not isolated—results reflect whole-formula effects.

Study Details

PMID:28096757
Participants:80
Impact:greater increases early (4 weeks) in PWS and PWS+S groups vs placebo; by 8 weeks all groups improved
Trust score:4/5

1RM strength (bench and leg press)

1 evidences

Eight-week randomized, double-blind trial (supplement contains 70 mg methylcobalamin) found some within-group gains in cognition and strength with PWS, but no consistent between-group advantages in body composition or most performance outcomes; supplements were well tolerated.

Trust comment: Large, randomized double-blind placebo-controlled trial with good adherence; vitamin C present but not isolated—results reflect whole-formula effects.

Study Details

PMID:28096757
Participants:80
Impact:increased over time in all groups; some greater early gains at 4 weeks in PWS/PWS+S but no clear between-group differences at 8 weeks
Trust score:4/5

safety markers (hemodynamics and blood chemistries)

1 evidences

Eight-week randomized, double-blind trial (supplement contains 70 mg methylcobalamin) found some within-group gains in cognition and strength with PWS, but no consistent between-group advantages in body composition or most performance outcomes; supplements were well tolerated.

Trust comment: Large, randomized double-blind placebo-controlled trial with good adherence; vitamin C present but not isolated—results reflect whole-formula effects.

Study Details

PMID:28096757
Participants:80
Impact:no clinically relevant adverse changes attributable to supplementation
Trust score:4/5

fruit and vegetable intake (portions/day)

1 evidences

Brief behavioural counselling increased fruit and vegetable intake versus nutrition education; plasma beta-carotene and alpha-tocopherol rose but plasma ascorbic acid (vitamin C) did not change.

Trust comment: Adequately powered randomized trial with objective biomarkers; directly measured plasma ascorbic acid though no change observed.

Study Details

PMID:12702620
Participants:271
Impact:behavioral +1.5 vs nutrition +0.9 (mean difference 0.6 portions/day; 95% CI 0.1 to 1.1)
Trust score:4/5

plasma ascorbic acid (vitamin C) concentration

2 evidences

Brief behavioural counselling increased fruit and vegetable intake versus nutrition education; plasma beta-carotene and alpha-tocopherol rose but plasma ascorbic acid (vitamin C) did not change.

Trust comment: Adequately powered randomized trial with objective biomarkers; directly measured plasma ascorbic acid though no change observed.

Study Details

PMID:12702620
Participants:271
Impact:no change
Trust score:4/5

Lutein or lutein plus green tea supplements raised plasma lutein and ascorbic acid concentrations but did not change overall antioxidant activity or lipid peroxidation markers.

Trust comment: Randomized groups (n=20 each) with clear biochemical measurements, but participants were already adequately nourished and sample size is moderate.

Study Details

PMID:19447020
Participants:40
Impact:significantly increased at 4 weeks and throughout 16 weeks
Trust score:3/5

ascorbic acid transmyocardial consumption

1 evidences

Warm blood cardioplegia reduced oxidative-stress markers and improved post-ischemic heart function; cold cardioplegia showed increased myocardial consumption of ascorbic acid.

Trust comment: Randomized clinical trial with direct biochemical measures but small sample (n=30); vitamin C measured as a biomarker rather than as an intervention.

Study Details

PMID:7715228
Participants:30
Impact:increased (cold cardioplegia vs warm)
Trust score:3/5

lipid peroxidation (fluorescent products)

1 evidences

Warm blood cardioplegia reduced oxidative-stress markers and improved post-ischemic heart function; cold cardioplegia showed increased myocardial consumption of ascorbic acid.

Trust comment: Randomized clinical trial with direct biochemical measures but small sample (n=30); vitamin C measured as a biomarker rather than as an intervention.

Study Details

PMID:7715228
Participants:30
Impact:increased (cold cardioplegia)
Trust score:3/5

left ventricular stroke work index

1 evidences

Warm blood cardioplegia reduced oxidative-stress markers and improved post-ischemic heart function; cold cardioplegia showed increased myocardial consumption of ascorbic acid.

Trust comment: Randomized clinical trial with direct biochemical measures but small sample (n=30); vitamin C measured as a biomarker rather than as an intervention.

Study Details

PMID:7715228
Participants:30
Impact:improved (warm cardioplegia > cold)
Trust score:3/5

H2O2-induced oxidative DNA damage

1 evidences

A 4-week blueberry/apple juice (providing 16 mg ascorbic acid/day) raised plasma antioxidants and reduced some oxidative DNA damage but increased another DNA adduct type; effects varied by genotype.

Trust comment: Intervention in 168 volunteers with biomarker endpoints and reported p-values; moderate quality though not clearly randomized in excerpt.

Study Details

PMID:17602170
Participants:168
Impact:-20% (protection, P<0.01)
Trust score:4/5

BPDE-induced DNA adducts

1 evidences

A 4-week blueberry/apple juice (providing 16 mg ascorbic acid/day) raised plasma antioxidants and reduced some oxidative DNA damage but increased another DNA adduct type; effects varied by genotype.

Trust comment: Intervention in 168 volunteers with biomarker endpoints and reported p-values; moderate quality though not clearly randomized in excerpt.

Study Details

PMID:17602170
Participants:168
Impact:+28% (P<0.01)
Trust score:4/5

ascorbic acid intake

1 evidences

Nutrition education classes reduced fat intake and increased fiber and ascorbic acid (vitamin C) intake among postmenopausal women, especially in those motivated to change.

Trust comment: Large behavioral trial with clear group sizes and repeated measures, but dietary intake measured by FFQ and effect sizes not provided in excerpt.

Study Details

PMID:15020177
Participants:866
Impact:increased (magnitude not reported)
Trust score:3/5

fiber intake

2 evidences

An 18‑week worksite plant‑based dietary intervention increased reported vitamin C intake and other micronutrients among completers.

Trust comment: Large multicenter randomized cluster trial with objective design and adequate sample (183 completers) though nutrient intakes were self‑reported, limiting precision.

Study Details

PMID:23942177
Participants:183
Impact:increased (significant in intervention group)
Trust score:4/5

Nutrition education classes reduced fat intake and increased fiber and ascorbic acid (vitamin C) intake among postmenopausal women, especially in those motivated to change.

Trust comment: Large behavioral trial with clear group sizes and repeated measures, but dietary intake measured by FFQ and effect sizes not provided in excerpt.

Study Details

PMID:15020177
Participants:866
Impact:increased (magnitude not reported)
Trust score:3/5

influenza vaccine antibody titers

1 evidences

In institutionalized elderly, daily low‑dose supplements (including ascorbic acid in the vitamin arm) corrected deficiencies but vitamins did not improve cell‑mediated immunity and the vitamin arm had lower influenza antibody titers; trace elements improved antibody response.

Trust comment: Large randomized double-blind placebo-controlled trial in 725 elderly patients with clinical and immunologic endpoints, high-quality evidence for the reported outcomes.

Study Details

PMID:10218756
Participants:725
Impact:increased with trace elements (alone or with vitamins); decreased in vitamin-only group (P<0.05)
Trust score:4/5

delayed-type hypersensitivity skin response

1 evidences

In institutionalized elderly, daily low‑dose supplements (including ascorbic acid in the vitamin arm) corrected deficiencies but vitamins did not improve cell‑mediated immunity and the vitamin arm had lower influenza antibody titers; trace elements improved antibody response.

Trust comment: Large randomized double-blind placebo-controlled trial in 725 elderly patients with clinical and immunologic endpoints, high-quality evidence for the reported outcomes.

Study Details

PMID:10218756
Participants:725
Impact:no effect during first year
Trust score:4/5

respiratory tract infections (patients without infections)

1 evidences

In institutionalized elderly, daily low‑dose supplements (including ascorbic acid in the vitamin arm) corrected deficiencies but vitamins did not improve cell‑mediated immunity and the vitamin arm had lower influenza antibody titers; trace elements improved antibody response.

Trust comment: Large randomized double-blind placebo-controlled trial in 725 elderly patients with clinical and immunologic endpoints, high-quality evidence for the reported outcomes.

Study Details

PMID:10218756
Participants:725
Impact:more patients without infections in trace element groups (trend, P=0.06)
Trust score:4/5

top-quality bowel cleansing (A scores)

1 evidences

Moviprep (PEG + ascorbic acid) produced a higher rate of top-quality bowel cleansing and less vomiting than Phosphoral, with similar overall acceptable cleansing rates.

Trust comment: Randomized single-blind trial with 250 completed colonoscopies; intervention contains ascorbic acid as part of formulation but not isolated vitamin C testing.

Study Details

PMID:25038914
Participants:250
Impact:higher with Moviprep (p=0.028)
Trust score:3/5

vomiting during cleansing

1 evidences

Moviprep (PEG + ascorbic acid) produced a higher rate of top-quality bowel cleansing and less vomiting than Phosphoral, with similar overall acceptable cleansing rates.

Trust comment: Randomized single-blind trial with 250 completed colonoscopies; intervention contains ascorbic acid as part of formulation but not isolated vitamin C testing.

Study Details

PMID:25038914
Participants:250
Impact:less frequent with Moviprep (Phosphoral had more vomiting, p=0.002)
Trust score:3/5

acceptable bowel cleansing rate

1 evidences

Moviprep (PEG + ascorbic acid) produced a higher rate of top-quality bowel cleansing and less vomiting than Phosphoral, with similar overall acceptable cleansing rates.

Trust comment: Randomized single-blind trial with 250 completed colonoscopies; intervention contains ascorbic acid as part of formulation but not isolated vitamin C testing.

Study Details

PMID:25038914
Participants:250
Impact:no difference (~90% acceptable in both groups)
Trust score:3/5

gingival bleeding on probing

1 evidences

A 6-month randomized placebo-controlled pilot trial found the micronutrient mix (including vitamin C) reduced gum bleeding and more patients met the defined improvement criteria than placebo.

Trust comment: Randomized, double-blind, placebo-controlled pilot with small sample (n=32); design is strong but limited power.

Study Details

PMID:20225703
Participants:32
Impact:significantly more reduced vs placebo at 6 months
Trust score:4/5

evident clinical improvement (≥40% reduction in bleeding or summated pocket depth)

1 evidences

A 6-month randomized placebo-controlled pilot trial found the micronutrient mix (including vitamin C) reduced gum bleeding and more patients met the defined improvement criteria than placebo.

Trust comment: Randomized, double-blind, placebo-controlled pilot with small sample (n=32); design is strong but limited power.

Study Details

PMID:20225703
Participants:32
Impact:significantly more frequent in treatment vs placebo
Trust score:4/5

oxidative stress markers (LPO, breath pentane, 8-OHdG)

1 evidences

In Marines completing 24 days of cold-weather training, oxidative stress markers rose in all subjects and the antioxidant mix (including vitamin C) did not significantly reduce stress for the group as a whole.

Trust comment: Randomized placebo-controlled field trial with objective biomarkers but modest sample and challenging field conditions limit generalizability.

Study Details

PMID:12092978
Participants:40
Impact:increased after 24 days in both groups; no significant difference between supplement and placebo
Trust score:3/5

antioxidant capacity (ORAC) in low-baseline individuals

1 evidences

In Marines completing 24 days of cold-weather training, oxidative stress markers rose in all subjects and the antioxidant mix (including vitamin C) did not significantly reduce stress for the group as a whole.

Trust comment: Randomized placebo-controlled field trial with objective biomarkers but modest sample and challenging field conditions limit generalizability.

Study Details

PMID:12092978
Participants:40
Impact:possible reduction in oxidative stress for some with low baseline ORAC (subgroup indication)
Trust score:3/5

biomarkers of antioxidant activity / lipid peroxidation

1 evidences

Lutein or lutein plus green tea supplements raised plasma lutein and ascorbic acid concentrations but did not change overall antioxidant activity or lipid peroxidation markers.

Trust comment: Randomized groups (n=20 each) with clear biochemical measurements, but participants were already adequately nourished and sample size is moderate.

Study Details

PMID:19447020
Participants:40
Impact:no significant change
Trust score:3/5

overall colon cleansing efficacy

1 evidences

In 299 children, a low-volume PEG with ascorbic acid (PEG-Asc) provided bowel cleansing that was noninferior to high-volume PEG and was among effective low-volume options.

Trust comment: Large randomized, investigator-blinded pediatric RCT (299 patients) directly tested an ascorbic-acid–containing prep with clear noninferiority results.

Study Details

PMID:25002661
Participants:299
Impact:PEG-Asc noninferior to PEG-ELS (no significant difference)
Trust score:4/5

tolerability/acceptability/compliance

1 evidences

In 299 children, a low-volume PEG with ascorbic acid (PEG-Asc) provided bowel cleansing that was noninferior to high-volume PEG and was among effective low-volume options.

Trust comment: Large randomized, investigator-blinded pediatric RCT (299 patients) directly tested an ascorbic-acid–containing prep with clear noninferiority results.

Study Details

PMID:25002661
Participants:299
Impact:highest in NaPico+MgCit (NaPico+MgCit rated better than others)
Trust score:4/5

brachial artery flow-mediated dilation (FMD_BA)

1 evidences

In ~54 completers with CKD, lanthanum carbonate lowered urinary phosphate excretion but did not improve endothelial function or reduce oxidative stress; supraphysiologic ascorbic acid infusion acutely increased FMD during testing but lanthanum had no effect on oxidative markers.

Trust comment: Well-conducted randomized, placebo-controlled mechanistic trial in humans with clear methodology and moderate sample size; vitamin C was used acutely as an experimental antioxidant infusion.

Study Details

PMID:38781013
Participants:54
Impact:no improvement with lanthanum vs placebo (lanthanum: 13% reduction; placebo: 17% reduction; intergroup P=0.67)
Trust score:4/5

carotid-to-femoral pulse-wave velocity (cfPWV)

1 evidences

In ~54 completers with CKD, lanthanum carbonate lowered urinary phosphate excretion but did not improve endothelial function or reduce oxidative stress; supraphysiologic ascorbic acid infusion acutely increased FMD during testing but lanthanum had no effect on oxidative markers.

Trust comment: Well-conducted randomized, placebo-controlled mechanistic trial in humans with clear methodology and moderate sample size; vitamin C was used acutely as an experimental antioxidant infusion.

Study Details

PMID:38781013
Participants:54
Impact:no change with lanthanum vs placebo (no significant intergroup difference)
Trust score:4/5

FMD response during high-dose ascorbic acid infusion

1 evidences

In ~54 completers with CKD, lanthanum carbonate lowered urinary phosphate excretion but did not improve endothelial function or reduce oxidative stress; supraphysiologic ascorbic acid infusion acutely increased FMD during testing but lanthanum had no effect on oxidative markers.

Trust comment: Well-conducted randomized, placebo-controlled mechanistic trial in humans with clear methodology and moderate sample size; vitamin C was used acutely as an experimental antioxidant infusion.

Study Details

PMID:38781013
Participants:54
Impact:FMD increased during ascorbic acid infusion from baseline to 12 weeks in both groups (no intergroup difference)
Trust score:4/5

ascorbic acid intake (dietary)

1 evidences

Dietary counselling in pregnant women increased reported vitamin C (ascorbic acid) intake by about 20 mg/day compared with controls.

Trust comment: Randomized prospective intervention with self-reported dietary intake; moderate quality but not blinded and relies on food records.

Study Details

PMID:17181885
Participants:209
Impact:+19.8 mg/day (95% CI 3.5 to 36.0 mg)
Trust score:3/5

PUFA intake (% energy)

1 evidences

Dietary counselling in pregnant women increased reported vitamin C (ascorbic acid) intake by about 20 mg/day compared with controls.

Trust comment: Randomized prospective intervention with self-reported dietary intake; moderate quality but not blinded and relies on food records.

Study Details

PMID:17181885
Participants:209
Impact:+0.5% energy (95% CI 0.1 to 0.8)
Trust score:3/5

SFA intake (% energy)

1 evidences

Dietary counselling in pregnant women increased reported vitamin C (ascorbic acid) intake by about 20 mg/day compared with controls.

Trust comment: Randomized prospective intervention with self-reported dietary intake; moderate quality but not blinded and relies on food records.

Study Details

PMID:17181885
Participants:209
Impact:−0.8% energy (95% CI −1.4 to −0.4)
Trust score:3/5

colon cleanliness (Chicago BPS)

1 evidences

In 1000 outpatients, a bowel preparation containing ascorbic acid cleaned colons as effectively as other split-dose regimens, with no clear tolerability advantage.

Trust comment: Large randomized investigator-blinded trial (n=1000); ascorbic acid was included in one prep but not isolated as a single-variable intervention.

Study Details

PMID:27433812
Participants:1000
Impact:no significant difference among preparations; overall 98.5% adequately cleansed
Trust score:4/5

Chicago BPS fluid and total scores

1 evidences

In 1000 outpatients, a bowel preparation containing ascorbic acid cleaned colons as effectively as other split-dose regimens, with no clear tolerability advantage.

Trust comment: Large randomized investigator-blinded trial (n=1000); ascorbic acid was included in one prep but not isolated as a single-variable intervention.

Study Details

PMID:27433812
Participants:1000
Impact:Gatorade+357 g PEG (day-prior) had lower (drier) fluid and total scores vs split-dose arms
Trust score:4/5

tolerability / patient acceptance

1 evidences

In 1000 outpatients, a bowel preparation containing ascorbic acid cleaned colons as effectively as other split-dose regimens, with no clear tolerability advantage.

Trust comment: Large randomized investigator-blinded trial (n=1000); ascorbic acid was included in one prep but not isolated as a single-variable intervention.

Study Details

PMID:27433812
Participants:1000
Impact:Gatorade+PEG better tolerated; many patients unwilling to use split-dose preparations
Trust score:4/5

symptom regression (venous lymphatic insufficiency)

2 evidences

The Cyclo 3 Fort product containing ascorbic acid reduced symptoms and leg size more than rutoside and was safe.

Trust comment: Duplicate/related report to pmid 10811525; open-label design and subjective outcomes limit confidence.

Study Details

PMID:10917578
Participants:80
Impact:more rapid and more complete vs rutoside (p<0.01)
Trust score:3/5

A combination product containing ascorbic acid improved symptoms and reduced leg size more than rutoside and was well tolerated.

Trust comment: Randomized multicenter design is a strength, but open-label and subjective symptom ratings reduce confidence.

Study Details

PMID:10811525
Participants:80
Impact:more rapid and more complete vs rutoside (p<0.01)
Trust score:3/5

affected limb size

2 evidences

A combination product containing ascorbic acid improved symptoms and reduced leg size more than rutoside and was well tolerated.

Trust comment: Randomized multicenter design is a strength, but open-label and subjective symptom ratings reduce confidence.

Study Details

PMID:10811525
Participants:80
Impact:reduced in both groups; reduction persisted at 90 days only in Cyclo 3 Fort group (p<0.01)
Trust score:3/5

The Cyclo 3 Fort product containing ascorbic acid reduced symptoms and leg size more than rutoside and was safe.

Trust comment: Duplicate/related report to pmid 10811525; open-label design and subjective outcomes limit confidence.

Study Details

PMID:10917578
Participants:80
Impact:reduced in both groups; reduction persisted at 90 days only in Cyclo 3 Fort group (p<0.01)
Trust score:3/5

safety

2 evidences

A combination product containing ascorbic acid improved symptoms and reduced leg size more than rutoside and was well tolerated.

Trust comment: Randomized multicenter design is a strength, but open-label and subjective symptom ratings reduce confidence.

Study Details

PMID:10811525
Participants:80
Impact:no major adverse effects reported
Trust score:3/5

The Cyclo 3 Fort product containing ascorbic acid reduced symptoms and leg size more than rutoside and was safe.

Trust comment: Duplicate/related report to pmid 10811525; open-label design and subjective outcomes limit confidence.

Study Details

PMID:10917578
Participants:80
Impact:no major adverse effects reported
Trust score:3/5

colon cleansing quality

1 evidences

Bowel prep containing ascorbic acid cleaned the colon better and led to more adenomas being detected, with similar tolerability.

Trust comment: Randomized single-blind trial with validated outcomes and objective adenoma detection; reasonable quality.

Study Details

PMID:20626383
Participants:107
Impact:better with PEG+Asc (mean score 1.40 vs 1.75, P<0.003; 69% excellent/good vs 38%, P=0.01)
Trust score:4/5

tolerability/safety

1 evidences

Bowel prep containing ascorbic acid cleaned the colon better and led to more adenomas being detected, with similar tolerability.

Trust comment: Randomized single-blind trial with validated outcomes and objective adenoma detection; reasonable quality.

Study Details

PMID:20626383
Participants:107
Impact:similar between groups
Trust score:4/5

LDL oxidation lag time (resistance to oxidation)

1 evidences

In a double-blind randomized factorial trial, antioxidant vitamins including 150 mg ascorbic acid increased LDL resistance to ex vivo oxidation over 8 weeks compared with placebo; B-group vitamins did not have this antioxidant effect.

Trust comment: Well-designed double-blind randomized trial with adequate sample completing intervention (101) showing clear biochemical effect of antioxidant regimen containing vitamin C.

Study Details

PMID:10407503
Participants:101
Impact:Increased in antioxidant groups: antioxidants alone +8.51 ±1.77 min; antioxidants + B-vitamins +6.88 ±1.65 min vs placebo −2.03 ±1.50 (between-group contrast P<0.001)
Trust score:4/5

ascorbic acid (vitamin C) infusion effect on FMD

1 evidences

In postmenopausal women, estrogen treatment enabled exercise to improve endothelial function; intravenous ascorbic acid infusion increased endothelial function in certain groups.

Trust comment: Randomized, controlled design with clear measurements (FMD) and a direct ascorbic acid infusion substudy; moderate sample size for subgroup analyses.

Study Details

PMID:24092827
Participants:36
Impact:ascorbic acid infusion acutely increased FMD at baseline in sedentary women and in endurance-trained controls, and after training in placebo-treated but not estrogen-treated women
Trust score:4/5

endothelial function response to exercise

1 evidences

In postmenopausal women, estrogen treatment enabled exercise to improve endothelial function; intravenous ascorbic acid infusion increased endothelial function in certain groups.

Trust comment: Randomized, controlled design with clear measurements (FMD) and a direct ascorbic acid infusion substudy; moderate sample size for subgroup analyses.

Study Details

PMID:24092827
Participants:36
Impact:improved only in estrogen-treated women after endurance training
Trust score:4/5

vibriocidal antibody titer (serologic response)

1 evidences

Using buffers (one containing ascorbic acid) with the oral cholera vaccine increased serologic responses compared with saline; the CeraVacx buffer produced the largest rises.

Trust comment: Double-masked outpatient volunteer study directly testing ascorbic acid–containing buffer vs alternatives with clear serologic outcomes; moderate sample size.

Study Details

PMID:9169739
Participants:39
Impact:significant rise in all 30 volunteers given vaccine with a buffer; 4/9 in saline group showed smaller rises
Trust score:4/5

magnitude of vibriocidal response

1 evidences

Using buffers (one containing ascorbic acid) with the oral cholera vaccine increased serologic responses compared with saline; the CeraVacx buffer produced the largest rises.

Trust comment: Double-masked outpatient volunteer study directly testing ascorbic acid–containing buffer vs alternatives with clear serologic outcomes; moderate sample size.

Study Details

PMID:9169739
Participants:39
Impact:greater with CeraVacx buffer than with bicarbonate-ascorbic acid or Alka-Seltzer buffers
Trust score:4/5

vaccine strain excretion

1 evidences

Using buffers (one containing ascorbic acid) with the oral cholera vaccine increased serologic responses compared with saline; the CeraVacx buffer produced the largest rises.

Trust comment: Double-masked outpatient volunteer study directly testing ascorbic acid–containing buffer vs alternatives with clear serologic outcomes; moderate sample size.

Study Details

PMID:9169739
Participants:39
Impact:similar across buffer groups and not associated with titer magnitude
Trust score:4/5

total cancer incidence (postintervention, all participants)

1 evidences

Large randomized trial where a combined antioxidant supplement (including 120 mg ascorbic acid daily) showed decreased cancer incidence and mortality in men during intervention, but these benefits were no longer evident after 5 years off supplementation.

Trust comment: Large randomized, double-blind, placebo-controlled trial with long follow-up, but Vitamin C was given as part of a multinutrient combination so effects cannot be attributed to Vitamin C alone.

Study Details

PMID:20104528
Participants:12741
Impact:RR 0.98 (95% CI 0.75–1.27) — no significant difference during 5-year postintervention follow-up
Trust score:4/5

total mortality (postintervention, men)

1 evidences

Large randomized trial where a combined antioxidant supplement (including 120 mg ascorbic acid daily) showed decreased cancer incidence and mortality in men during intervention, but these benefits were no longer evident after 5 years off supplementation.

Trust comment: Large randomized, double-blind, placebo-controlled trial with long follow-up, but Vitamin C was given as part of a multinutrient combination so effects cannot be attributed to Vitamin C alone.

Study Details

PMID:20104528
Participants:12741
Impact:RR 0.98 (95% CI 0.75–1.26) — no significant difference during 5-year postintervention follow-up
Trust score:4/5

ischemic cardiovascular disease incidence (postintervention)

1 evidences

Large randomized trial where a combined antioxidant supplement (including 120 mg ascorbic acid daily) showed decreased cancer incidence and mortality in men during intervention, but these benefits were no longer evident after 5 years off supplementation.

Trust comment: Large randomized, double-blind, placebo-controlled trial with long follow-up, but Vitamin C was given as part of a multinutrient combination so effects cannot be attributed to Vitamin C alone.

Study Details

PMID:20104528
Participants:12741
Impact:no late effect observed (no significant difference)
Trust score:4/5

serum ferritin (week 28)

1 evidences

Pregnant women receiving L. plantarum 299v capsules (which included low-dose iron, 12 mg ascorbic acid and folic acid) had smaller decreases in ferritin and hemoglobin and lower prevalence of iron deficiency and iron-deficiency anemia in late pregnancy compared with placebo.

Trust comment: Well-powered, randomized double-blind multicenter RCT showing clinically relevant iron-status benefits; however ascorbic acid was included at low dose within a combination product, so effects are for the combination.

Study Details

PMID:33880752
Participants:340
Impact:ferritin decrease −44 µg/L (Lp) vs −49 µg/L (placebo); week 28 means 17.3 vs 15.5 µg/L (p=0.003); smaller decline with active product
Trust score:4/5

prevalence of iron deficiency (week 35)

1 evidences

Pregnant women receiving L. plantarum 299v capsules (which included low-dose iron, 12 mg ascorbic acid and folic acid) had smaller decreases in ferritin and hemoglobin and lower prevalence of iron deficiency and iron-deficiency anemia in late pregnancy compared with placebo.

Trust comment: Well-powered, randomized double-blind multicenter RCT showing clinically relevant iron-status benefits; however ascorbic acid was included at low dose within a combination product, so effects are for the combination.

Study Details

PMID:33880752
Participants:340
Impact:59% (Lp) vs 78% (placebo), p=0.017 (lower prevalence with active product)
Trust score:4/5

prevalence of anemia / hemoglobin decrease

1 evidences

Pregnant women receiving L. plantarum 299v capsules (which included low-dose iron, 12 mg ascorbic acid and folic acid) had smaller decreases in ferritin and hemoglobin and lower prevalence of iron deficiency and iron-deficiency anemia in late pregnancy compared with placebo.

Trust comment: Well-powered, randomized double-blind multicenter RCT showing clinically relevant iron-status benefits; however ascorbic acid was included at low dose within a combination product, so effects are for the combination.

Study Details

PMID:33880752
Participants:340
Impact:anemia prevalence week 28: 14% vs 26% (p=0.050); week 35: 7.4% vs 21% (p=0.023); smaller Hb decrease with active product
Trust score:4/5

hemoglobin concentration (Hb change)

1 evidences

Various iron delivery strategies (including a fortified water containing iron, zinc and ascorbic acid) all increased hemoglobin in anemic children over 4 months; supplements (iron ± other micronutrients) produced larger Hb increases than fortified complementary food.

Trust comment: Randomized field trial with reasonable sample and outcomes, but some unblinded arms, varying iron doses across arms, and dropout reduce certainty about Vitamin C-specific effects (it was included only in some interventions).

Study Details

PMID:20863398
Participants:217
Impact:All treatments increased Hb; FW (fortified water with ascorbic acid) change +1.07 g/dL (95% CI 0.77–1.36); IS/IFS/MMS had larger increases (e.g., IS +1.49 g/dL)
Trust score:3/5

post-treatment anemia prevalence (reduction)

1 evidences

Various iron delivery strategies (including a fortified water containing iron, zinc and ascorbic acid) all increased hemoglobin in anemic children over 4 months; supplements (iron ± other micronutrients) produced larger Hb increases than fortified complementary food.

Trust comment: Randomized field trial with reasonable sample and outcomes, but some unblinded arms, varying iron doses across arms, and dropout reduce certainty about Vitamin C-specific effects (it was included only in some interventions).

Study Details

PMID:20863398
Participants:217
Impact:Prevalence reductions: MMS 72%, IFS 69%, IS 58%, FW 52%, FCF 45% (unadjusted)
Trust score:3/5

ferritin concentration (change)

1 evidences

Various iron delivery strategies (including a fortified water containing iron, zinc and ascorbic acid) all increased hemoglobin in anemic children over 4 months; supplements (iron ± other micronutrients) produced larger Hb increases than fortified complementary food.

Trust comment: Randomized field trial with reasonable sample and outcomes, but some unblinded arms, varying iron doses across arms, and dropout reduce certainty about Vitamin C-specific effects (it was included only in some interventions).

Study Details

PMID:20863398
Participants:217
Impact:No consistent increases across groups for ferritin with adjusted analyses; FW ferritin change −12.77 µg/dL (unadjusted) and varied by group
Trust score:3/5

lung cancer mortality

1 evidences

Large randomized trial tested four supplement combinations (one included ascorbic acid + molybdenum) versus placebo for 5.25 years and found no reduction in lung cancer mortality.

Trust comment: Large randomized double-blind trial with long follow-up; vitamin C was given as part of a combination so effects are indirect but study quality is high.

Study Details

PMID:16896051
Participants:29584
Impact:no significant reduction with supplementation including ascorbic acid (no effect)
Trust score:4/5

skin cancer incidence (women)

1 evidences

Post-trial follow-up of SU.VI.MAX participants who had taken daily antioxidant supplements (including 120 mg ascorbic acid) found that supplementation increased skin cancer risk in women during the supplementation period but no residual increased risk was evident in the 5 years after stopping.

Trust comment: Large randomized, placebo-controlled trial with long supplementation and follow-up; vitamin C was part of a multinutrient supplement so effects are from the combination.

Study Details

PMID:20605091
Participants:12741
Impact:increased during supplementation period (no numeric RR provided here)
Trust score:4/5

skin cancer incidence (post-supplementation)

1 evidences

Post-trial follow-up of SU.VI.MAX participants who had taken daily antioxidant supplements (including 120 mg ascorbic acid) found that supplementation increased skin cancer risk in women during the supplementation period but no residual increased risk was evident in the 5 years after stopping.

Trust comment: Large randomized, placebo-controlled trial with long supplementation and follow-up; vitamin C was part of a multinutrient supplement so effects are from the combination.

Study Details

PMID:20605091
Participants:12741
Impact:no delayed or residual increase in either gender during 5-year follow-up
Trust score:4/5

C-reactive protein (CRP) — inflammation marker

1 evidences

In hemodialysis patients, an antioxidant cocktail that included vitamin B12 did not change markers of oxidative stress or inflammation over 8 weeks.

Trust comment: Randomized placebo-controlled design but small sample and use of a multi-vitamin cocktail prevents attribution of effects specifically to vitamin C.

Study Details

PMID:19397224
Participants:37
Impact:no change
Trust score:3/5

primary liver cancer mortality (overall)

1 evidences

Large randomized trial tested four vitamin/mineral factor combinations (one factor included ascorbic acid + molybdenum) versus placebo for ~5 years and found no overall reduction in primary liver cancer mortality, though some subgroup effects were noted.

Trust comment: Large randomized, double-blind trial with long follow-up; factor C included ascorbic acid but was combined with molybdenum, limiting attribution to Vitamin C alone.

Study Details

PMID:17686823
Participants:29450
Impact:No statistically significant difference with factor C (ascorbic acid + molybdenum) versus no factor
Trust score:5/5

male subgroup — factor C effect

1 evidences

Large randomized trial tested four vitamin/mineral factor combinations (one factor included ascorbic acid + molybdenum) versus placebo for ~5 years and found no overall reduction in primary liver cancer mortality, though some subgroup effects were noted.

Trust comment: Large randomized, double-blind trial with long follow-up; factor C included ascorbic acid but was combined with molybdenum, limiting attribution to Vitamin C alone.

Study Details

PMID:17686823
Participants:29450
Impact:Borderline reduction in males: HR=0.70 (95% CI 0.47–1.02)
Trust score:5/5

spatial working memory response speed

1 evidences

Double-blind controlled trial in overweight older men compared 5 weeks of Enzogenol+vitamin C versus vitamin C alone; cognitive response speed improved with Enzogenol+vitamin C while vitamin C alone produced no improvements.

Trust comment: Randomized, double-blind controlled study but small (n=42); vitamin C was given to all participants as part of both arms, and vitamin C alone showed no cognitive benefit in this trial.

Study Details

PMID:18683195
Participants:42
Impact:No improvement with vitamin C alone; improved with Enzogenol+vitamin C
Trust score:3/5

immediate recognition response speed

1 evidences

Double-blind controlled trial in overweight older men compared 5 weeks of Enzogenol+vitamin C versus vitamin C alone; cognitive response speed improved with Enzogenol+vitamin C while vitamin C alone produced no improvements.

Trust comment: Randomized, double-blind controlled study but small (n=42); vitamin C was given to all participants as part of both arms, and vitamin C alone showed no cognitive benefit in this trial.

Study Details

PMID:18683195
Participants:42
Impact:No improvement with vitamin C alone; improved with Enzogenol+vitamin C
Trust score:3/5

Protein carbonyl concentration

1 evidences

In 40 septic shock patients, 3 days of high‑dose IV vitamin C raised blood vitamin C but did not reduce increases in protein oxidative damage.

Trust comment: Small randomized controlled trial in critically ill humans with objective biochemical endpoints but limited sample size (n=40).

Study Details

PMID:34818575
Participants:40
Impact:+2.2-fold overall (169 → 369 pmol/mg); vitamin C did not attenuate the increase
Trust score:3/5

Laboratory-confirmed SARS-CoV-2 infection

1 evidences

Among 619 men randomized to the vitamin C arm (500 mg/day), 70% had laboratory-confirmed SARS-CoV-2 infection; vitamin C served as the comparator and did not protect against infection in this setting.

Trust comment: Large cluster-randomized pragmatic trial with laboratory-confirmed outcomes; vitamin C was the comparator (open-label and cluster design limit blinding and some generalizability).

Study Details

PMID:33864917
Participants:619
Impact:433/619 (70.0%) infected in the vitamin C arm
Trust score:4/5

Acute respiratory symptoms

1 evidences

Among 619 men randomized to the vitamin C arm (500 mg/day), 70% had laboratory-confirmed SARS-CoV-2 infection; vitamin C served as the comparator and did not protect against infection in this setting.

Trust comment: Large cluster-randomized pragmatic trial with laboratory-confirmed outcomes; vitamin C was the comparator (open-label and cluster design limit blinding and some generalizability).

Study Details

PMID:33864917
Participants:619
Impact:69/619 (11.1%) reported acute respiratory symptoms in the vitamin C arm
Trust score:4/5

Interleukin-1β (IL-1β)

1 evidences

In 91 power-plant workers, 1000 mg/day vitamin C for 3 months reduced several proinflammatory cytokines compared with control.

Trust comment: Double-blind randomized controlled trial with reasonable sample size and clear biochemical outcomes, though groups were modest in size and exposure-specific population limits generalizability.

Study Details

PMID:32931612
Participants:91
Impact:decreased in vitamin C and combined vitamin groups (effect size ~0.71)
Trust score:4/5

TNF-α

1 evidences

In 91 power-plant workers, 1000 mg/day vitamin C for 3 months reduced several proinflammatory cytokines compared with control.

Trust comment: Double-blind randomized controlled trial with reasonable sample size and clear biochemical outcomes, though groups were modest in size and exposure-specific population limits generalizability.

Study Details

PMID:32931612
Participants:91
Impact:decreased in the vitamin C group (effect size ~0.2)
Trust score:4/5

cumulative cold days

1 evidences

In children 4–12 years, the vitamin C control group had more cold days, more respiratory infections and more antibiotic use than the Echinacea group over 4 months.

Trust comment: Randomized, blinded, multicenter pediatric RCT with objective outcomes and adequate sample size, though vitamin C was used as an active control rather than placebo.

Study Details

PMID:33832544
Participants:187
Impact:+47% (602 vs 429 total cold days; VC had 47% more symptom days than EFJ)
Trust score:4/5

RTI incidence (cold episodes)

1 evidences

In children 4–12 years, the vitamin C control group had more cold days, more respiratory infections and more antibiotic use than the Echinacea group over 4 months.

Trust comment: Randomized, blinded, multicenter pediatric RCT with objective outcomes and adequate sample size, though vitamin C was used as an active control rather than placebo.

Study Details

PMID:33832544
Participants:187
Impact:+16.3 percentage points (55.1% VC vs 38.8% EFJ)
Trust score:4/5

antibiotic prescriptions and days

1 evidences

In children 4–12 years, the vitamin C control group had more cold days, more respiratory infections and more antibiotic use than the Echinacea group over 4 months.

Trust comment: Randomized, blinded, multicenter pediatric RCT with objective outcomes and adequate sample size, though vitamin C was used as an active control rather than placebo.

Study Details

PMID:33832544
Participants:187
Impact:+9.5 percentage points prescriptions (15.3% VC vs 5.8% EFJ); +171 antibiotic days in VC vs EFJ (sample of 103 children)
Trust score:4/5

cutaneous vasodilation (%CVCmax)

1 evidences

In healthy adults a high-salt diet reduced skin microvascular vasodilation; the study tested local infusions including ascorbic acid but ascorbic-acid–specific results are not fully reported in the excerpt.

Trust comment: Controlled feeding human study with small sample and direct use of ascorbic acid locally, but the excerpt lacks clear ascorbic-acid–specific outcome data.

Study Details

PMID:31074652
Participants:29
Impact:−6.2 %CVCmax on high-sodium vs low-sodium diet (LS 93.0 ±2.2 vs HS 86.8 ±2.0 %CVCmax)
Trust score:3/5

total plasma antioxidant capacity

1 evidences

A 4-week antioxidant-containing drink (included vitamin C) increased plasma antioxidant capacity and serum selenium and increased faecal Lactobacillus plantarum counts.

Trust comment: Randomized, double-blind parallel trial with 98 subjects and measurable biochemical endpoints, though short duration (4 weeks).

Study Details

PMID:12850889
Participants:98
Impact:+7% (FRAP method, P<0.05 vs placebo)
Trust score:4/5

serum selenium / selenoprotein P

1 evidences

A 4-week antioxidant-containing drink (included vitamin C) increased plasma antioxidant capacity and serum selenium and increased faecal Lactobacillus plantarum counts.

Trust comment: Randomized, double-blind parallel trial with 98 subjects and measurable biochemical endpoints, though short duration (4 weeks).

Study Details

PMID:12850889
Participants:98
Impact:+16–17% (P<0.001 vs placebo)
Trust score:4/5

faecal Lactobacillus plantarum 299v

1 evidences

A 4-week antioxidant-containing drink (included vitamin C) increased plasma antioxidant capacity and serum selenium and increased faecal Lactobacillus plantarum counts.

Trust comment: Randomized, double-blind parallel trial with 98 subjects and measurable biochemical endpoints, though short duration (4 weeks).

Study Details

PMID:12850889
Participants:98
Impact:significant increase after 4 weeks (supplement contained L. plantarum 299v)
Trust score:4/5

association with disease activity

1 evidences

In RA patients, shifting to a Mediterranean diet increased reported vitamin C intake but plasma vitamin C levels were unchanged at 12 weeks; baseline vitamin C correlated inversely with inflammation markers.

Trust comment: Randomized dietary intervention in RA with objective biochemical measures but modest sample size and potential dietary-report limitations.

Study Details

PMID:12952549
Participants:51
Impact:inverse correlation between vitamin C and ESR (r = -0.33, P<0.05) and HAQ (r = -0.34, P<0.05)
Trust score:3/5

pre-exercise plasma vitamin C

1 evidences

Six weeks of mixed antioxidant (primarily vitamins C & E) supplementation raised plasma vitamin C but did not improve muscle function recovery after damaging exercise and had mixed effects on oxidative/inflammatory markers.

Trust comment: Double-blind randomized trial with objective functional and biochemical endpoints, moderate sample size; results clearly reported.

Study Details

PMID:21069377
Participants:38
Impact:increased to 93 ± 8 μmol·L⁻¹ (P<0.001 vs baseline and placebo)
Trust score:4/5

recovery of muscle function (peak isometric torque)

1 evidences

Six weeks of mixed antioxidant (primarily vitamins C & E) supplementation raised plasma vitamin C but did not improve muscle function recovery after damaging exercise and had mixed effects on oxidative/inflammatory markers.

Trust comment: Double-blind randomized trial with objective functional and biochemical endpoints, moderate sample size; results clearly reported.

Study Details

PMID:21069377
Participants:38
Impact:no improvement (same post-exercise deficit and recovery time as placebo)
Trust score:4/5

urinary F2-isoprostanes and inflammatory markers

1 evidences

Six weeks of mixed antioxidant (primarily vitamins C & E) supplementation raised plasma vitamin C but did not improve muscle function recovery after damaging exercise and had mixed effects on oxidative/inflammatory markers.

Trust comment: Double-blind randomized trial with objective functional and biochemical endpoints, moderate sample size; results clearly reported.

Study Details

PMID:21069377
Participants:38
Impact:tendency to higher F2-isoprostanes at 48 h (6.2 ± 6.1 vs 3.7 ± 3.4 ng·ml⁻¹); attenuated serum cortisol rise and higher IL-6 at 1 h in supplemented group
Trust score:4/5

delivery before 37 weeks (high-risk multigravidae)

1 evidences

In a large RCT where women with BV received either metronidazole or oral vitamin C, vitamin C recipients did not show increased preterm delivery and in one high-risk subgroup had lower preterm rates than the metronidazole group.

Trust comment: Large randomized trial but short vitamin C regimen and older study; some outcomes significant in subgroup analyses and interpretation limited by design details.

Study Details

PMID:12040953
Participants:955
Impact:24% in vitamin C group vs 29% in BV-negative and 43% in metronidazole group (differences significant between metronidazole and others)
Trust score:3/5

birth weight (high-risk multigravidae)

1 evidences

In a large RCT where women with BV received either metronidazole or oral vitamin C, vitamin C recipients did not show increased preterm delivery and in one high-risk subgroup had lower preterm rates than the metronidazole group.

Trust comment: Large randomized trial but short vitamin C regimen and older study; some outcomes significant in subgroup analyses and interpretation limited by design details.

Study Details

PMID:12040953
Participants:955
Impact:mean birth weight higher in vitamin C group (2,759 g) than metronidazole group (2,475 g); metronidazole group significantly lower vs BV-negative (P=0.0109)
Trust score:3/5

body weight/body fat/waist circumference

1 evidences

A 6-month randomized dietary intervention (Mediterranean Diet) in breast cancer survivors increased blood vitamin C and improved body composition and glycemic measures compared with control.

Trust comment: Randomized intervention with 70 participants and reported biochemical outcomes; moderate-high quality though dietary intervention (not isolated vitamin C) limits attribution to vitamin C alone.

Study Details

PMID:28634625
Participants:70
Impact:decrease (statistically significant)
Trust score:4/5

glycemic profile (blood glucose)

1 evidences

A 6-month randomized dietary intervention (Mediterranean Diet) in breast cancer survivors increased blood vitamin C and improved body composition and glycemic measures compared with control.

Trust comment: Randomized intervention with 70 participants and reported biochemical outcomes; moderate-high quality though dietary intervention (not isolated vitamin C) limits attribution to vitamin C alone.

Study Details

PMID:28634625
Participants:70
Impact:improved (between-group difference; statistically significant)
Trust score:4/5

shock time / duration of vasopressor use

1 evidences

In septic shock patients, adding vitamin C and thiamine to hydrocortisone did not significantly reduce 28-day mortality but shortened shock duration and vasopressor use and reduced some adverse renal and fever outcomes.

Trust comment: Randomised clinical trial in ICU patients with clear clinical endpoints, but vitamin C was given as part of a combined regimen so its isolated effect is uncertain.

Study Details

PMID:34003568
Participants:94
Impact:decrease (median 4.0 vs 5.0 days; P=0.01)
Trust score:3/5

serum creatinine (SCr) change

1 evidences

In septic shock patients, adding vitamin C and thiamine to hydrocortisone did not significantly reduce 28-day mortality but shortened shock duration and vasopressor use and reduced some adverse renal and fever outcomes.

Trust comment: Randomised clinical trial in ICU patients with clear clinical endpoints, but vitamin C was given as part of a combined regimen so its isolated effect is uncertain.

Study Details

PMID:34003568
Participants:94
Impact:control group +0.59 greater SCr vs intervention (P<0.05)
Trust score:3/5

neutrophil function / whole blood killing / ROS / phagocytosis

1 evidences

12-week double-blind RCT of an MVM (including vitamin D) increased vitamin C and zinc levels and reduced reported illness duration/severity, but did not change 25(OH) vitamin D or measured neutrophil functional assays.

Trust comment: Well-designed double-blind RCT with objective nutrient measures but small sample (n=42); multinutrient formulation prevents attribution to vitamin C alone.

Study Details

PMID:32823974
Participants:42
Impact:no significant change
Trust score:4/5

self-reported illness duration

1 evidences

12-week double-blind RCT of an MVM (including vitamin D) increased vitamin C and zinc levels and reduced reported illness duration/severity, but did not change 25(OH) vitamin D or measured neutrophil functional assays.

Trust comment: Well-designed double-blind RCT with objective nutrient measures but small sample (n=42); multinutrient formulation prevents attribution to vitamin C alone.

Study Details

PMID:32823974
Participants:42
Impact:decrease (~70%; 6.43 to 2.29 days; P=0.02)
Trust score:4/5

plasma protein carbonyls (protein oxidation)

1 evidences

In a 4-week randomized study, adding mandarin juice (rich in vitamin C and other antioxidants) to a low-calorie diet in obese children reduced oxidative stress markers and greatly increased plasma vitamin C.

Trust comment: Randomized controlled dietary intervention in children with consistent biomarker changes but short duration and small sample limit long-term inference.

Study Details

PMID:20528796
Participants:40
Impact:−36.1% (P=0.006)
Trust score:3/5

lymphocyte number

1 evidences

A multi-component nutraceutical (includes vitamin D among other ingredients) reduced lymphocyte counts, IL-6, and CRP and improved self-reported wellness in hospitalized elderly compared with untreated elderly controls.

Trust comment: Adequately sized study with randomized elderly treatment groups but multi-ingredient supplement and hospitalized sample make isolating vitamin C effects and generalizability limited.

Study Details

PMID:36079732
Participants:120
Impact:decrease (statistically significant in treated groups)
Trust score:3/5

Buccal mucosa cell (BMC) vitamin C

1 evidences

Obese participants on a 3-month low-calorie, DRI-covering formula diet showed declines in cellular and serum vitamin C but an increase in leukocyte vitamin C; some vitamin C deficiency cases increased after the diet.

Trust comment: Human pilot study with well-described methods and intracellular measures but small subgroup sample sizes (serum n=14) limit precision.

Study Details

PMID:22657586
Participants:32
Impact:−55% (6.62 → 2.95 pmol/μg DNA; p<0.001)
Trust score:3/5

RPF response to vitamin C infusion

1 evidences

In a double‑blind randomized cross‑over trial of folic acid vs placebo, the renal plasma flow (RPF) response to an acute vitamin C infusion (+93 to +94 ml/min·m²) did not differ between treatment phases, indicating folic acid did not modify the vitamin C–sensitive component of renal oxidant stress.

Trust comment: Randomized double‑blind cross‑over in patients with objective RPF measures; moderate sample size and direct vitamin C infusion make results reliable for the tested endpoints.

Study Details

PMID:24724807
Participants:28
Impact:ΔRPF to vitamin C: +93 ±118 ml/min·m² (placebo) vs +94 ±108 ml/min·m² (folic acid); no difference (P=0.70)
Trust score:4/5

Plasma vitamin C change

1 evidences

In newly diagnosed type 2 diabetes patients, plasma vitamin C (biomarker of fruit/vegetable intake) rose modestly (+2.0 μmol/L) over 1 year and increases in plasma vitamin C were associated with small improvements in BMI, waist, HbA1c and modelled 10‑year CVD risk.

Trust comment: Large prospective cohort with validated biomarker (plasma vitamin C) and multivariable adjustment; observational design limits causal inference but findings are robustly measured.

Study Details

PMID:24102972
Participants:736
Impact:Mean increase +2.0 μmol/L over 1 year
Trust score:4/5

Association with BMI

1 evidences

In newly diagnosed type 2 diabetes patients, plasma vitamin C (biomarker of fruit/vegetable intake) rose modestly (+2.0 μmol/L) over 1 year and increases in plasma vitamin C were associated with small improvements in BMI, waist, HbA1c and modelled 10‑year CVD risk.

Trust comment: Large prospective cohort with validated biomarker (plasma vitamin C) and multivariable adjustment; observational design limits causal inference but findings are robustly measured.

Study Details

PMID:24102972
Participants:736
Impact:ΔBMI −0.028 kg/m² per μmol increase in plasma vitamin C (95% CI −0.048 to −0.007)
Trust score:4/5

Association with waist circumference

1 evidences

In newly diagnosed type 2 diabetes patients, plasma vitamin C (biomarker of fruit/vegetable intake) rose modestly (+2.0 μmol/L) over 1 year and increases in plasma vitamin C were associated with small improvements in BMI, waist, HbA1c and modelled 10‑year CVD risk.

Trust comment: Large prospective cohort with validated biomarker (plasma vitamin C) and multivariable adjustment; observational design limits causal inference but findings are robustly measured.

Study Details

PMID:24102972
Participants:736
Impact:ΔWaist −0.102 cm per μmol increase in plasma vitamin C (95% CI −0.151 to −0.054)
Trust score:4/5

Association with HbA1c and modelled CVD risk

1 evidences

In newly diagnosed type 2 diabetes patients, plasma vitamin C (biomarker of fruit/vegetable intake) rose modestly (+2.0 μmol/L) over 1 year and increases in plasma vitamin C were associated with small improvements in BMI, waist, HbA1c and modelled 10‑year CVD risk.

Trust comment: Large prospective cohort with validated biomarker (plasma vitamin C) and multivariable adjustment; observational design limits causal inference but findings are robustly measured.

Study Details

PMID:24102972
Participants:736
Impact:Small inverse associations (HbA1c −0.004 mmol/mol per μmol; modelled CVD risk −0.001 % per μmol)
Trust score:4/5

LDL TBARS

1 evidences

Cross‑sectional study found vegetarians had higher plasma antioxidant status and higher plasma vitamin C (statistically significant) and lower LDL TBARS compared with nonvegetarians.

Trust comment: Small cross‑sectional human study (n=38) with clear biochemical measures; associations are plausible but limited by sample size and observational design.

Study Details

PMID:9895420
Participants:38
Impact:Lower TBARS in native and oxidized LDL in vegetarians (statistically significant)
Trust score:3/5

DNA strand breaks (background and total)

1 evidences

9-week randomized placebo-controlled trial comparing anthocyanin-rich juice vs a placebo beverage that was high in vitamin C; both drinks reduced DNA strand breaks and improved some lipid markers, likely due in part to high vitamin C content.

Trust comment: Randomized, placebo-controlled 9-week intervention (n=57) with objective biomarkers; placebo contained high vitamin C so vitamin C likely contributed to observed antioxidant and lipid effects.

Study Details

PMID:31088176
Participants:57
Impact:significant reduction in both groups (24 h and 8 weeks)
Trust score:4/5

LDL and total cholesterol

1 evidences

9-week randomized placebo-controlled trial comparing anthocyanin-rich juice vs a placebo beverage that was high in vitamin C; both drinks reduced DNA strand breaks and improved some lipid markers, likely due in part to high vitamin C content.

Trust comment: Randomized, placebo-controlled 9-week intervention (n=57) with objective biomarkers; placebo contained high vitamin C so vitamin C likely contributed to observed antioxidant and lipid effects.

Study Details

PMID:31088176
Participants:57
Impact:decrease in both groups within first week
Trust score:4/5

SOD activity

1 evidences

9-week randomized placebo-controlled trial comparing anthocyanin-rich juice vs a placebo beverage that was high in vitamin C; both drinks reduced DNA strand breaks and improved some lipid markers, likely due in part to high vitamin C content.

Trust comment: Randomized, placebo-controlled 9-week intervention (n=57) with objective biomarkers; placebo contained high vitamin C so vitamin C likely contributed to observed antioxidant and lipid effects.

Study Details

PMID:31088176
Participants:57
Impact:increase (anthocyanin group only)
Trust score:4/5

vitality

1 evidences

Two-week RCT increasing fruit & vegetable intake; participants given fresh FV (FVI) showed improved vitality, flourishing and motivation; vitamin C measured rose modestly but did not mediate psychological changes.

Trust comment: Well-powered, preregistered three-arm RCT (n=171) with objective blood biomarkers (vitamin C) though mediation analyses found vitamin C did not explain effects.

Study Details

PMID:28158239
Participants:171
Impact:increase in FVI group (improvement; FVI explained ~8.7% variance)
Trust score:4/5

flourishing

1 evidences

Two-week RCT increasing fruit & vegetable intake; participants given fresh FV (FVI) showed improved vitality, flourishing and motivation; vitamin C measured rose modestly but did not mediate psychological changes.

Trust comment: Well-powered, preregistered three-arm RCT (n=171) with objective blood biomarkers (vitamin C) though mediation analyses found vitamin C did not explain effects.

Study Details

PMID:28158239
Participants:171
Impact:increase in FVI group (improvement; ~10.5% variance)
Trust score:4/5

flourishing behaviors / motivation

1 evidences

Two-week RCT increasing fruit & vegetable intake; participants given fresh FV (FVI) showed improved vitality, flourishing and motivation; vitamin C measured rose modestly but did not mediate psychological changes.

Trust comment: Well-powered, preregistered three-arm RCT (n=171) with objective blood biomarkers (vitamin C) though mediation analyses found vitamin C did not explain effects.

Study Details

PMID:28158239
Participants:171
Impact:increase in FVI group (improvement; flourishing behaviors ~18.4% variance)
Trust score:4/5

recurrence rate of parotitis

1 evidences

Randomized controlled study in children comparing massage+oral vitamin C, traditional Chinese medicines (huangqi + bear bile), and combination; TCM groups had larger decreases in recurrence and higher recovery rates than the vitamin C/massage group.

Trust comment: Prospective randomized study (n=151) in children reporting clinical benefit for TCM; vitamin C was used in the control/massage arm but study was not designed to isolate vitamin C effects.

Study Details

PMID:23463769
Participants:151
Impact:decreased in all groups, significantly greater decrease in Groups B (TCM) and C (TCM+vitamin C) vs Group A (massage+vitamin C)
Trust score:3/5

recovery rate

1 evidences

Randomized controlled study in children comparing massage+oral vitamin C, traditional Chinese medicines (huangqi + bear bile), and combination; TCM groups had larger decreases in recurrence and higher recovery rates than the vitamin C/massage group.

Trust comment: Prospective randomized study (n=151) in children reporting clinical benefit for TCM; vitamin C was used in the control/massage arm but study was not designed to isolate vitamin C effects.

Study Details

PMID:23463769
Participants:151
Impact:Group B recovery 63% (significantly higher than other groups)
Trust score:3/5

plasma vitamin C concentration at 2 h

1 evidences

In 34 healthy adults, a liposomal multivitamin altered how some minerals and vitamins appeared in blood; serum calcium rose at 2 h after the liposomal MVM and some calcium PK markers (Tmax, absorption rate) differed; no side effects reported.

Trust comment: Double-blind randomized crossover PK trial (n=34 completers) with validated assays and detailed PK analysis; sample size modest but methods robust for PK endpoints.

Study Details

PMID:37447400
Participants:34
Impact:NL +23.3% vs L +2.8% (difference significant, p=0.013)
Trust score:4/5

plasma vitamin C at 4–6 h

1 evidences

In 34 healthy adults, a liposomal multivitamin altered how some minerals and vitamins appeared in blood; serum calcium rose at 2 h after the liposomal MVM and some calcium PK markers (Tmax, absorption rate) differed; no side effects reported.

Trust comment: Double-blind randomized crossover PK trial (n=34 completers) with validated assays and detailed PK analysis; sample size modest but methods robust for PK endpoints.

Study Details

PMID:37447400
Participants:34
Impact:both treatments increased significantly (no difference at 4–6 h)
Trust score:4/5

vitamin C pharmacokinetics (distribution/absorption slope & rate)

1 evidences

In 34 healthy adults, a liposomal multivitamin altered how some minerals and vitamins appeared in blood; serum calcium rose at 2 h after the liposomal MVM and some calcium PK markers (Tmax, absorption rate) differed; no side effects reported.

Trust comment: Double-blind randomized crossover PK trial (n=34 completers) with validated assays and detailed PK analysis; sample size modest but methods robust for PK endpoints.

Study Details

PMID:37447400
Participants:34
Impact:trend toward higher distribution/absorption slope/rate with liposomal formulation (PK differences)
Trust score:4/5

energy intake

1 evidences

An 18‑week worksite plant‑based dietary intervention increased reported vitamin C intake and other micronutrients among completers.

Trust comment: Large multicenter randomized cluster trial with objective design and adequate sample (183 completers) though nutrient intakes were self‑reported, limiting precision.

Study Details

PMID:23942177
Participants:183
Impact:decreased (reported overall fall in both groups)
Trust score:4/5

NEWS2 clinical score

1 evidences

A randomized, double‑blind phase II trial of ArtemiC oral spray (contains vitamin C plus other actives) in hospitalized COVID‑19 patients showed improved clinical scores (NEWS2) versus placebo.

Trust comment: Randomized double‑blind placebo‑controlled phase II trial but small (n=50) and the effect cannot be attributed to vitamin C alone because it was given in a multi‑component preparation.

Study Details

PMID:35587574
Participants:50
Impact:mean last‑observed 0.52 vs 2.23 (p=0.042) — improved with ArtemiC
Trust score:3/5

requirement for supplemental oxygen

1 evidences

A randomized, double‑blind phase II trial of ArtemiC oral spray (contains vitamin C plus other actives) in hospitalized COVID‑19 patients showed improved clinical scores (NEWS2) versus placebo.

Trust comment: Randomized double‑blind placebo‑controlled phase II trial but small (n=50) and the effect cannot be attributed to vitamin C alone because it was given in a multi‑component preparation.

Study Details

PMID:35587574
Participants:50
Impact:fewer patients required oxygen at end of study (0 vs 4) / shorter mean duration (2.3±1.4 vs 7.6±4.6 days, p=0.171)
Trust score:3/5

abnormal SpO2 duration

1 evidences

A randomized, double‑blind phase II trial of ArtemiC oral spray (contains vitamin C plus other actives) in hospitalized COVID‑19 patients showed improved clinical scores (NEWS2) versus placebo.

Trust comment: Randomized double‑blind placebo‑controlled phase II trial but small (n=50) and the effect cannot be attributed to vitamin C alone because it was given in a multi‑component preparation.

Study Details

PMID:35587574
Participants:50
Impact:shortened in active arm (fewer patients with prolonged abnormal SpO2)
Trust score:3/5

platelet function

1 evidences

Eight-week randomized trial in 72 middle-aged subjects with cardiovascular risk factors: moderate berry consumption improved platelet function, raised HDL, and lowered systolic blood pressure in those with high baseline BP.

Trust comment: Randomized, placebo‑controlled trial (n=72) with objective platelet measures and clear between‑group differences; moderate sample size.

Study Details

PMID:18258621
Participants:72
Impact:improved: 11% inhibition (berry) vs -1.4% (control); P=0.018
Trust score:4/5

physical activity (LSI)

1 evidences

A 6‑month lifestyle intervention led to weight loss and increased physical activity; measured vitamin C intake (marker of fruit/vegetable intake) showed no difference between groups.

Trust comment: Small randomized trial (n=45 randomized; ~38 completers) with meaningful clinical endpoints but limited power for nutrient intake differences.

Study Details

PMID:18243282
Participants:38
Impact:increase: +16.4 in intervention vs -1.3 in control; mean difference +17.8; p=0.002
Trust score:3/5

γδ T cell number

1 evidences

Drinking Concord grape juice daily for 9 weeks increased serum vitamin C, improved antioxidant measures, and increased certain immune cell measures versus placebo.

Trust comment: Randomized double-blind placebo-controlled trial (n=85) with objective immunologic and biochemical endpoints, but grape juice contains multiple bioactives so vitamin C-specific effects are not isolated.

Study Details

PMID:21138361
Participants:85
Impact:increase (significant, P<0.05)
Trust score:4/5

antioxidant capacity

1 evidences

Drinking Concord grape juice daily for 9 weeks increased serum vitamin C, improved antioxidant measures, and increased certain immune cell measures versus placebo.

Trust comment: Randomized double-blind placebo-controlled trial (n=85) with objective immunologic and biochemical endpoints, but grape juice contains multiple bioactives so vitamin C-specific effects are not isolated.

Study Details

PMID:21138361
Participants:85
Impact:increase / protection vs placebo (significant)
Trust score:4/5

common cold symptom score (CCS / ACCS)

1 evidences

A double-blind RCT of a micronutrient combination including vitamin D3 modestly improved common cold symptom scores and reduced the decline in 25(OH)D3 vs placebo.

Trust comment: Large double-blind randomized multicenter trial (n=192) with clinical and biochemical endpoints, but used a multi-nutrient preparation so vitamin C-specific causal effects cannot be isolated.

Study Details

PMID:22184801
Participants:192
Impact:greater improvement in active group (ACCS −6.9 ± 4.8) vs placebo (−5.4 ± 4.5); p=0.034 (subset with ≥2 symptoms)
Trust score:4/5

work absence during cold episodes (<45 years subgroup)

1 evidences

A double-blind RCT of a micronutrient combination including vitamin D3 modestly improved common cold symptom scores and reduced the decline in 25(OH)D3 vs placebo.

Trust comment: Large double-blind randomized multicenter trial (n=192) with clinical and biochemical endpoints, but used a multi-nutrient preparation so vitamin C-specific causal effects cannot be isolated.

Study Details

PMID:22184801
Participants:192
Impact:fewer absences in active group (14.3% vs 47.8%, p=0.038)
Trust score:4/5

plasma antioxidant capacity (TEAC/HORAC/FRAP)

1 evidences

Giving low consumers ~480 g/day fruit/veg + up to 300 ml juice for 12 weeks raised blood vitamin C and other nutrients but did not change measures of plasma antioxidant capacity or vascular risk markers.

Trust comment: Randomised controlled trial with objective biomarkers and good compliance; not blinded and modest sample size limits generalizability.

Study Details

PMID:28560503
Participants:45
Impact:no significant change
Trust score:4/5

RBC folate

1 evidences

An 8-week double-blind RCT of a multivitamin/multimineral/phytonutrient product increased vitamin C and folate status and reduced homocysteine in adults with low fruit/veg intake.

Trust comment: Well-designed double-blind, placebo-controlled RCT with 120 completers and measured biomarkers; short duration limits clinical outcome inference.

Study Details

PMID:29370120
Participants:120
Impact:+3.20 µg/L (VMP) vs −0.23 µg/L (PLA) at Day 56
Trust score:4/5

serum homocysteine

3 evidences

A 12-week water-soluble vitamin supplement improved some vitamin biomarkers, increased weight, and lowered homocysteine in elderly female residents; plasma vitamin C rose in both groups.

Trust comment: Single-blind randomized placebo-controlled trial with clear endpoints but modest sample size.

Study Details

PMID:7498103
Participants:42
Impact:decreased (supplement group, significant)
Trust score:4/5

In a large 7.3‑year randomized trial (n=3411), garlic increased serum folate and a vitamin+selenium supplement increased glutathione, but neither intervention changed serum vitamin B12 or homocysteine.

Trust comment: Large randomized, double-blind, placebo-controlled trial with long duration; this result comes from a planned subset analysis of sera.

Study Details

PMID:19056661
Participants:3411
Impact:no significant change with vitamin+selenium supplementation
Trust score:4/5

An 8-week double-blind RCT of a multivitamin/multimineral/phytonutrient product increased vitamin C and folate status and reduced homocysteine in adults with low fruit/veg intake.

Trust comment: Well-designed double-blind, placebo-controlled RCT with 120 completers and measured biomarkers; short duration limits clinical outcome inference.

Study Details

PMID:29370120
Participants:120
Impact:−3.97 µmol/L (VMP) vs −0.82 µmol/L (PLA) at Day 56
Trust score:4/5

symptom severity (modified Jackson score)

1 evidences

Feasibility RCT comparing high‑flow heated humidified air (rhinothermy) versus low‑dose vitamin C (250 mg/day) as control; rhinothermy reduced cold symptom scores faster than the vitamin C control.

Trust comment: Small, randomized but open‑label feasibility RCT with complete follow‑up; vitamin C used as an active control (low dose) and not expected to be therapeutic, limiting inference about vitamin C efficacy.

Study Details

PMID:29593018
Participants:30
Impact:Vitamin C control had worse symptom scores vs rhinothermy: differences rhinothermy minus control −4.11 (day2), −5.18 (day3), −6.37 (day4), −5.29 (day5), −4.61 (day6) — i.e. control ≈ +4–6 points higher (worse) during days 2–6.
Trust score:3/5

time to feeling 'a lot better'

1 evidences

Feasibility RCT comparing high‑flow heated humidified air (rhinothermy) versus low‑dose vitamin C (250 mg/day) as control; rhinothermy reduced cold symptom scores faster than the vitamin C control.

Trust comment: Small, randomized but open‑label feasibility RCT with complete follow‑up; vitamin C used as an active control (low dose) and not expected to be therapeutic, limiting inference about vitamin C efficacy.

Study Details

PMID:29593018
Participants:30
Impact:Fewer vitamin C participants reported resolution by day10 (2/10 resolved) vs rhinothermy (10/19); hazard ratio for feeling a lot better 1.33 (95% CI 0.60–2.98) favoring rhinothermy (non‑significant).
Trust score:3/5

anemia prevalence (vitamin C-only group)

1 evidences

Double-masked, placebo-controlled 100-day trial in 100 anemic schoolchildren comparing a multi‑fortified juice (including zinc) vs non‑fortified juice; supervised administration and deworming were done.

Trust comment: Randomized, double-masked, placebo-controlled trial with supervised dosing and objective biomarkers, but intervention combined multiple nutrients in one arm.

Study Details

PMID:22094838
Participants:100
Impact:-60 percentage points (100% to 40%)
Trust score:4/5

plasma zinc (multi‑fortified group)

1 evidences

Double-masked, placebo-controlled 100-day trial in 100 anemic schoolchildren comparing a multi‑fortified juice (including zinc) vs non‑fortified juice; supervised administration and deworming were done.

Trust comment: Randomized, double-masked, placebo-controlled trial with supervised dosing and objective biomarkers, but intervention combined multiple nutrients in one arm.

Study Details

PMID:22094838
Participants:100
Impact:+20 μg/dL (83.9 to 103.9 μg/dL)
Trust score:4/5

fruit drink selection (parent choice)

1 evidences

In a large online randomized experiment, a "100% Vitamin C" claim on fruit drinks increased parents' selection of fruit drinks over 100% juice or water.

Trust comment: Large randomized experiment with clear behavioral outcome and adequate sample size; simulated shopping may differ from real-world behavior.

Study Details

PMID:35040866
Participants:2219
Impact:+19 percentage points (51% vs 32% choosing fruit drink with "100% Vitamin C" vs no claim)
Trust score:4/5

baseline forearm blood flow

1 evidences

In 75 men with CAD, vitamin C co‑infusion increased baseline forearm blood flow and acetylcholine‑stimulated responses in patients with elevated CRP, indicating improved NO bioavailability.

Trust comment: Well-characterized patient cohort with physiological measures and statistically significant results, though subgroup effect limited to high‑CRP patients.

Study Details

PMID:15321699
Participants:75
Impact:Increased from 2.0 to 2.5 mL/min/100 mL (+0.5 mL/min/100 mL) in high‑CRP patients
Trust score:4/5

acetylcholine-stimulated FBF response

1 evidences

In 75 men with CAD, vitamin C co‑infusion increased baseline forearm blood flow and acetylcholine‑stimulated responses in patients with elevated CRP, indicating improved NO bioavailability.

Trust comment: Well-characterized patient cohort with physiological measures and statistically significant results, though subgroup effect limited to high‑CRP patients.

Study Details

PMID:15321699
Participants:75
Impact:Significantly increased with vitamin C in patients with elevated CRP (AUC improved; exact AUC change not provided)
Trust score:4/5

retinal arterial diameter response to 100% O2

1 evidences

A 14-day antioxidant supplement including vitamin C largely restored retinal blood-flow responses blunted by low-dose endotoxin in healthy volunteers.

Trust comment: Randomized, double-masked, placebo-controlled human trial with objective hemodynamic measures though moderate sample size.

Study Details

PMID:25525163
Participants:43
Impact:restored O2-induced decrease after LPS (significant; P=0.03 vs placebo)
Trust score:4/5

retinal RBC velocity

1 evidences

A 14-day antioxidant supplement including vitamin C largely restored retinal blood-flow responses blunted by low-dose endotoxin in healthy volunteers.

Trust comment: Randomized, double-masked, placebo-controlled human trial with objective hemodynamic measures though moderate sample size.

Study Details

PMID:25525163
Participants:43
Impact:restored O2-induced decrease after LPS (significant; P<0.01 vs placebo)
Trust score:4/5

retinal blood flow

1 evidences

A 14-day antioxidant supplement including vitamin C largely restored retinal blood-flow responses blunted by low-dose endotoxin in healthy volunteers.

Trust comment: Randomized, double-masked, placebo-controlled human trial with objective hemodynamic measures though moderate sample size.

Study Details

PMID:25525163
Participants:43
Impact:restored O2-induced decrease after LPS (significant; P<0.01 vs placebo)
Trust score:4/5

vitamin C level in serum and follicular fluid

1 evidences

Multivitamin/mineral supplements given to women undergoing IVF were associated with decreased oxidative stress markers and higher antioxidant vitamin levels in serum and follicular fluid.

Trust comment: Moderate-sized human study with biological measures but unclear blinding/controls and combined multivitamin intervention limits attribution to vitamin C alone.

Study Details

PMID:20226443
Participants:69
Impact:increased
Trust score:3/5

adenoid size (adenoid grade)

1 evidences

Children treated with a PPI or with low-dose vitamin C both showed reduced adenoid size, with no difference between groups.

Trust comment: Randomized, double-blinded pediatric RCT but small sample and control used vitamin C (not placebo), limiting interpretation of vitamin C effect.

Study Details

PMID:22496101
Participants:40
Impact:decreased in vitamin C control group (significant within-group); no difference versus PPI
Trust score:3/5

vitamin C intake correlation with CRP

1 evidences

Increasing fruit and vegetable intake after surgery reduced CRP more than usual diet, with a correlation between vitamin C intake and CRP reduction.

Trust comment: Prospective controlled dietary intervention with objective CRP outcome but short duration and modest sample size limit generalizability.

Study Details

PMID:21336433
Participants:60
Impact:negative correlation (higher vitamin C associated with lower CRP; P=0.014)
Trust score:3/5

nitric oxide (NO)

1 evidences

Following the DASH diet (which raised serum vitamin C) reduced some oxidative stress markers and improved migraine scores versus usual diet.

Trust comment: Well-conducted RCT with serum vitamin C measured for compliance, but DASH is a multicomponent diet so effects cannot be attributed to vitamin C alone.

Study Details

PMID:34269164
Participants:102
Impact:−5.75 vs +4.18 (P = 0.025)
Trust score:3/5

acetylcholine-mediated endothelial vasodilation

1 evidences

In healthy men, coinfusion of vitamin C acutely restored endothelial (acetylcholine) responses that were impaired by continuous nitroglycerin.

Trust comment: Randomized human study with objective vascular measures; modest sample size but clear acute physiological effects of vitamin C coinfusion.

Study Details

PMID:21185507
Participants:36
Impact:completely restored by vitamin C coinfusion (in GTN+placebo group)
Trust score:4/5

blood pressure response to sublingual GTN

1 evidences

In healthy men, coinfusion of vitamin C acutely restored endothelial (acetylcholine) responses that were impaired by continuous nitroglycerin.

Trust comment: Randomized human study with objective vascular measures; modest sample size but clear acute physiological effects of vitamin C coinfusion.

Study Details

PMID:21185507
Participants:36
Impact:blunted in GTN+placebo group (no reported restoration by vitamin C)
Trust score:4/5

SOFA (organ failure) score

1 evidences

Critically ill septic patients receiving an enteral supplement (including vitamin C) had faster improvement in organ dysfunction and serum vitamin C rose to normal range by day 3.

Trust comment: Randomized, double-blind clinical trial in humans, but vitamin C was part of a multi-nutrient supplement so specific attribution is limited.

Study Details

PMID:18007263
Participants:55
Impact:faster decline (regression slope difference: −0.32 vs −0.14)
Trust score:4/5

time to symptom resolution

1 evidences

Non-hospitalized adults with COVID-19/covid-like illness received melatonin, zinc and multivitamins (including vitamin D) or placebo; the supplement arm had faster symptom resolution by days 5 and 10.

Trust comment: Well-conducted multicenter double-blind RCT with adequate sample size, but intervention is multi-component so effects cannot be attributed to vitamin C alone.

Study Details

PMID:37419768
Participants:163
Impact:49.4% vs 32.9% symptom-free at day 5 (treatment vs placebo); 80.5% vs 67.1% symptom-free at day 10
Trust score:3/5

hospitalization / ventilation requirement

1 evidences

Non-hospitalized adults with COVID-19/covid-like illness received melatonin, zinc and multivitamins (including vitamin D) or placebo; the supplement arm had faster symptom resolution by days 5 and 10.

Trust comment: Well-conducted multicenter double-blind RCT with adequate sample size, but intervention is multi-component so effects cannot be attributed to vitamin C alone.

Study Details

PMID:37419768
Participants:163
Impact:no patients required hospitalization or ventilation in either group
Trust score:3/5

collagen structure (confocal VAS)

1 evidences

12-week triple-blind randomized placebo-controlled trial in women showed that a drinkable supplement containing collagen peptides and dermonutrients improved dermal collagen structure and subjective skin measures without adverse events.

Trust comment: Randomized, triple-blind trial with objective and subjective endpoints but the product contained multiple active nutrients including collagen peptides, so vitamin C's individual contribution is unclear.

Study Details

PMID:32017646
Participants:60
Impact:significant improvement with active product vs placebo (positive VAS change)
Trust score:3/5

skin moisture / suppleness / softness (subjective)

1 evidences

12-week triple-blind randomized placebo-controlled trial in women showed that a drinkable supplement containing collagen peptides and dermonutrients improved dermal collagen structure and subjective skin measures without adverse events.

Trust comment: Randomized, triple-blind trial with objective and subjective endpoints but the product contained multiple active nutrients including collagen peptides, so vitamin C's individual contribution is unclear.

Study Details

PMID:32017646
Participants:60
Impact:participants reported greater moisture, suppleness and softness with active product
Trust score:3/5

daily micturitions

1 evidences

A multi-ingredient CAM (including vitamin D) reduced urinary frequency, nocturia, and urge incontinence and was reported more effective and better tolerated than solifenacin in this small RCT.

Trust comment: Randomized controlled design but small sample and CAM contains multiple ingredients (including vitamin C), preventing isolation of vitamin C effects.

Study Details

PMID:29473382
Participants:90
Impact:reduction with both treatments; greater reduction with CAM vs solifenacin
Trust score:3/5

nocturia and episodes of urge incontinence

1 evidences

A multi-ingredient CAM (including vitamin D) reduced urinary frequency, nocturia, and urge incontinence and was reported more effective and better tolerated than solifenacin in this small RCT.

Trust comment: Randomized controlled design but small sample and CAM contains multiple ingredients (including vitamin C), preventing isolation of vitamin C effects.

Study Details

PMID:29473382
Participants:90
Impact:reductions in both; CAM more effective than solifenacin
Trust score:3/5

patient-reported improvement / quality scores (PPIUS, OAB-q SF, PGI-I)

1 evidences

A multi-ingredient CAM (including vitamin D) reduced urinary frequency, nocturia, and urge incontinence and was reported more effective and better tolerated than solifenacin in this small RCT.

Trust comment: Randomized controlled design but small sample and CAM contains multiple ingredients (including vitamin C), preventing isolation of vitamin C effects.

Study Details

PMID:29473382
Participants:90
Impact:improvements in both groups with greater efficacy and satisfaction for CAM
Trust score:3/5

attained weight

1 evidences

Giving HIV-infected mothers multivitamins (including B12) during pregnancy and postpartum improved their children's weight at 24 months.

Trust comment: Large randomized placebo-controlled trial (886 pairs) showing improved child weight; vitamin C was part of a multivitamin so effects of vitamin C alone are not isolated.

Study Details

PMID:15817867
Participants:886
Impact:+459 g at 24 mo
Trust score:4/5

weight-for-length z-score

1 evidences

Giving HIV-infected mothers multivitamins (including B12) during pregnancy and postpartum improved their children's weight at 24 months.

Trust comment: Large randomized placebo-controlled trial (886 pairs) showing improved child weight; vitamin C was part of a multivitamin so effects of vitamin C alone are not isolated.

Study Details

PMID:15817867
Participants:886
Impact:+0.38 z at 24 mo
Trust score:4/5

cutaneous microvascular response

1 evidences

A 4-week polyphenol beverage that contained vitamin C did not improve vascular function but was associated with an increase in IL-6 compared with placebo.

Trust comment: Randomized pilot RCT (n=39) but small sample and intervention combined polyphenols with vitamin C, so vitamin C–specific effects cannot be isolated.

Study Details

PMID:26797134
Participants:39
Impact:no significant difference (logΔ AUC group differences non-significant)
Trust score:3/5

gastric noncardia cancer incidence

1 evidences

In this prospective cohort of male smokers, higher dietary vitamin C intake was associated with lower risk of gastric noncardia cancer.

Trust comment: Large prospective cohort (n=29,133) with long follow-up; observational so subject to confounding but association is robust and statistically significant.

Study Details

PMID:16172214
Participants:29133
Impact:reduced risk with higher vitamin C intake (HR 0.60; 95% CI 0.41–0.86)
Trust score:4/5

salivary total antioxidant status (TAS)

1 evidences

In dental students under exam stress, a daily micronutrient supplement including vitamin C modestly raised plasma vitamin C and showed small non-significant improvements in inflammatory and antioxidant markers.

Trust comment: Small randomized pilot study (40 completers) with objective lab measures but limited power and mostly non-significant differences.

Study Details

PMID:22027646
Participants:40
Impact:smaller, non-significant decrease in TAS in supplement group (p=0.43)
Trust score:3/5

skin elasticity (R2)

1 evidences

Randomized placebo‑controlled 12‑week trial in 72 women: daily drinkable collagen peptides + dermonutrients improved objective measures of skin appearance versus placebo.

Trust comment: Randomized, placebo-controlled trial with objective measurements and complete follow-up (n=72); single-blind and combination supplement limits attribution solely to vitamin C.

Study Details

PMID:31627309
Participants:72
Impact:R2 increased from ~0.69 to ~0.81 in verum vs smaller increase in placebo (between-group p<0.0004)
Trust score:4/5

skin roughness

1 evidences

Randomized placebo‑controlled 12‑week trial in 72 women: daily drinkable collagen peptides + dermonutrients improved objective measures of skin appearance versus placebo.

Trust comment: Randomized, placebo-controlled trial with objective measurements and complete follow-up (n=72); single-blind and combination supplement limits attribution solely to vitamin C.

Study Details

PMID:31627309
Participants:72
Impact:−26.8% (verum T12 vs baseline) vs −6.4% placebo (p<0.0004)
Trust score:4/5

skin density (epidermal thickness)

1 evidences

Randomized placebo‑controlled 12‑week trial in 72 women: daily drinkable collagen peptides + dermonutrients improved objective measures of skin appearance versus placebo.

Trust comment: Randomized, placebo-controlled trial with objective measurements and complete follow-up (n=72); single-blind and combination supplement limits attribution solely to vitamin C.

Study Details

PMID:31627309
Participants:72
Impact:+24.8% (verum T12 vs baseline; p<0.0001)
Trust score:4/5

heel estimated bone mineral density (QUS)

1 evidences

Osteopenic postmenopausal women receiving antioxidant supplement mix (including vitamin C) plus calcium/vitamin D had a small but borderline-significant better heel BMD after 12 months versus calcium/vitamin D alone.

Trust comment: Randomized trial but small sample and borderline statistical significance (44 completers), and supplement was a combination so vitamin C effect not isolated.

Study Details

PMID:23444750
Participants:44
Impact:0.401 vs 0.388 g/cm2 (difference +0.013 g/cm2) favoring antioxidant group (p=0.048)
Trust score:3/5

nitrate tolerance occurrence

1 evidences

In patients on isosorbide dinitrate, adding vitamin C (ISD+vitamin C) reduced occurrence of nitrate tolerance and improved endothelial-dependent vasodilation and eNOS expression compared with ISD alone over a 10-day course.

Trust comment: Randomized clinical groups with molecular and functional endpoints, but short treatment (10 days), unclear blinding and CSI performed better than vitamin C, limiting attribution solely to vitamin C.

Study Details

PMID:15719745
Participants:84
Impact:reduced to 35.7% with ISD+vitamin C vs 64.29% with ISD alone
Trust score:3/5

endothelial-dependent vasodilation (EDD)

1 evidences

In patients on isosorbide dinitrate, adding vitamin C (ISD+vitamin C) reduced occurrence of nitrate tolerance and improved endothelial-dependent vasodilation and eNOS expression compared with ISD alone over a 10-day course.

Trust comment: Randomized clinical groups with molecular and functional endpoints, but short treatment (10 days), unclear blinding and CSI performed better than vitamin C, limiting attribution solely to vitamin C.

Study Details

PMID:15719745
Participants:84
Impact:increased in ISD+vitamin C group (P<0.05)
Trust score:3/5

eNOS mRNA expression

1 evidences

In patients on isosorbide dinitrate, adding vitamin C (ISD+vitamin C) reduced occurrence of nitrate tolerance and improved endothelial-dependent vasodilation and eNOS expression compared with ISD alone over a 10-day course.

Trust comment: Randomized clinical groups with molecular and functional endpoints, but short treatment (10 days), unclear blinding and CSI performed better than vitamin C, limiting attribution solely to vitamin C.

Study Details

PMID:15719745
Participants:84
Impact:increased in ISD+vitamin C group vs baseline and vs ISD alone (P<0.05)
Trust score:3/5

Se-dependent glutathione peroxidase (Se-GPx)

1 evidences

In institutionalized elderly, daily vitamin supplementation (including 120 mg vitamin C) raised plasma vitamin levels (including vitamin C) and some antioxidant enzyme activity over 6–12 months, with limited effects on most immune markers.

Trust comment: Large randomized double-blind trial in institutionalized elderly with biochemical endpoints and long follow-up, supporting reliable changes in vitamin status though clinical benefits limited.

Study Details

PMID:9433680
Participants:756
Impact:increased in groups receiving trace elements (± vitamins)
Trust score:4/5

IL-1 production

1 evidences

In institutionalized elderly, daily vitamin supplementation (including 120 mg vitamin C) raised plasma vitamin levels (including vitamin C) and some antioxidant enzyme activity over 6–12 months, with limited effects on most immune markers.

Trust comment: Large randomized double-blind trial in institutionalized elderly with biochemical endpoints and long follow-up, supporting reliable changes in vitamin status though clinical benefits limited.

Study Details

PMID:9433680
Participants:756
Impact:increased after 6 months in vitamin groups
Trust score:4/5

Gait speed

1 evidences

Daily fortified yogurt containing HMB, 1000 IU vitamin D, and vitamin C improved handgrip strength, gait speed, vitamin D and IGF-1 levels, and reduced inflammation markers versus control in sarcopenic older adults.

Trust comment: Well-conducted double-blind RCT (n=66) with clear benefits, but vitamin C was given in combination with HMB and vitamin D so effects cannot be attributed to vitamin C alone.

Study Details

PMID:33067129
Participants:66
Impact:intervention mean change 0.10 vs control 0.01 (mean difference ≈ +0.09 m/s; P<0.001)
Trust score:4/5

fruit and vegetable intake

1 evidences

A school nutrition intervention increased fruit and vegetable intake by 47% in 7-9-year-olds and produced a borderline increase in vitamin C intake.

Trust comment: Controlled school intervention with weighed dietary records and paired baseline/follow-up data (n=106), though some nutrient changes were only borderline significant.

Study Details

PMID:20409359
Participants:106
Impact:+47% (mean change +61.3 g/day)
Trust score:4/5

executive function

1 evidences

In this 13-year cohort study, higher vitamin C intake was positively associated with verbal memory performance but study design is observational.

Trust comment: Large prospective cohort with long follow-up showing associations, but observational design limits causal inference and residual confounding is possible.

Study Details

PMID:21955649
Participants:2533
Impact:some negative associations observed with specific fruit/vegetable groups (e.g., vegetables) for executive function tests
Trust score:3/5

biomarkers of oxidative damage (lipids, proteins, DNA)

1 evidences

A 3-week fruit/vegetable concentrate raised blood vitamin C and some antioxidants but did not change markers of oxidative damage in male smokers.

Trust comment: Randomized crossover trial directly measured serum vitamin C with clear outcomes but had a small sample and used a complex concentrate, limiting attribution solely to vitamin C.

Study Details

PMID:11385058
Participants:22
Impact:no change
Trust score:3/5

biomarkers of inflammation and oxidative stress

1 evidences

In pregnant women with obesity, adding a supplement (includes 90 mg vitamin C plus other nutrients) raised some micronutrients but did not change vitamin C levels or markers of inflammation/oxidative stress.

Trust comment: Double-blind RCT in humans with adequate randomization and clinical outcomes, but vitamin C was given in a multinutrient supplement and vitamin C concentrations did not differ between groups.

Study Details

PMID:38396126
Participants:98
Impact:no change with supplementation
Trust score:4/5

exercise-induced lipid peroxidation (CDmax, Rmax, POOL, MDA)

1 evidences

In athletes, adding an antioxidant mixture (includes 60 mg vitamin C) to n-3 supplementation reduced markers of exercise-induced lipid peroxidation but did not prevent increased resting oxidative stress from n-3 alone.

Trust comment: Randomized study in humans with objective biochemical endpoints but vitamin C was part of a multi-antioxidant mixture, so effects cannot be isolated to vitamin C.

Study Details

PMID:21222131
Participants:36
Impact:reduced after training when antioxidants were added (decreases reported vs n-3 alone)
Trust score:3/5

resting oxidative stress

1 evidences

In athletes, adding an antioxidant mixture (includes 60 mg vitamin C) to n-3 supplementation reduced markers of exercise-induced lipid peroxidation but did not prevent increased resting oxidative stress from n-3 alone.

Trust comment: Randomized study in humans with objective biochemical endpoints but vitamin C was part of a multi-antioxidant mixture, so effects cannot be isolated to vitamin C.

Study Details

PMID:21222131
Participants:36
Impact:n-3 LCPUFA increased resting oxidative stress and antioxidants did not prevent this increase
Trust score:3/5

CH3SH (methyl mercaptan) levels

1 evidences

A single 30-s bedtime rinse with a chlorhexidine + vitamin C mouthwash reduced some volatile sulfur compounds in morning breath versus placebo, though organoleptic scores did not differ.

Trust comment: Randomized double-blind crossover clinical trial with objective GC measurements but small sample size (n=32) limits generalizability.

Study Details

PMID:36385592
Participants:32
Impact:decrease (significant; p=0.0081)
Trust score:4/5

(CH3)2S (dimethyl sulfide) levels

1 evidences

A single 30-s bedtime rinse with a chlorhexidine + vitamin C mouthwash reduced some volatile sulfur compounds in morning breath versus placebo, though organoleptic scores did not differ.

Trust comment: Randomized double-blind crossover clinical trial with objective GC measurements but small sample size (n=32) limits generalizability.

Study Details

PMID:36385592
Participants:32
Impact:decrease (significant; p=0.0003)
Trust score:4/5

organoleptic score (Rosenberg)

1 evidences

A single 30-s bedtime rinse with a chlorhexidine + vitamin C mouthwash reduced some volatile sulfur compounds in morning breath versus placebo, though organoleptic scores did not differ.

Trust comment: Randomized double-blind crossover clinical trial with objective GC measurements but small sample size (n=32) limits generalizability.

Study Details

PMID:36385592
Participants:32
Impact:no significant change vs placebo
Trust score:4/5

urine total phenolics

1 evidences

A 12-week randomized trial of a multi-ingredient flavonoid chewable (which included vitamin C) increased urine total phenolics and certain gut-derived phenolic metabolites but did not change common inflammation or oxidative stress markers.

Trust comment: Well-powered randomized human trial but used a multi-ingredient supplement, so effects cannot be attributed to vitamin C specifically.

Study Details

PMID:28631923
Participants:103
Impact:+24% at 4 weeks vs placebo (interaction p=0.041)
Trust score:4/5

gut-derived phenolic metabolites

1 evidences

A 12-week randomized trial of a multi-ingredient flavonoid chewable (which included vitamin C) increased urine total phenolics and certain gut-derived phenolic metabolites but did not change common inflammation or oxidative stress markers.

Trust comment: Well-powered randomized human trial but used a multi-ingredient supplement, so effects cannot be attributed to vitamin C specifically.

Study Details

PMID:28631923
Participants:103
Impact:increased (significant fold-changes for several metabolites; p≤0.050)
Trust score:4/5

inflammation and oxidative stress markers (IL-6, MCP-1, CRP, oxLDL, FRAP)

1 evidences

A 12-week randomized trial of a multi-ingredient flavonoid chewable (which included vitamin C) increased urine total phenolics and certain gut-derived phenolic metabolites but did not change common inflammation or oxidative stress markers.

Trust comment: Well-powered randomized human trial but used a multi-ingredient supplement, so effects cannot be attributed to vitamin C specifically.

Study Details

PMID:28631923
Participants:103
Impact:no significant change vs placebo
Trust score:4/5

ER/PR status, nodal status, tumor size

1 evidences

In this observational analysis, higher premorbid vitamin C intake was not linked to tumor ER/PR status or size but was associated with a lower risk of dying from breast cancer.

Trust comment: Large cohort analysis with dietary data and survival outcomes, but observational design allows residual confounding and cannot prove causation.

Study Details

PMID:9116317
Participants:676
Impact:no significant association with higher vitamin C intake
Trust score:3/5

breast cancer mortality (risk of dying)

1 evidences

In this observational analysis, higher premorbid vitamin C intake was not linked to tumor ER/PR status or size but was associated with a lower risk of dying from breast cancer.

Trust comment: Large cohort analysis with dietary data and survival outcomes, but observational design allows residual confounding and cannot prove causation.

Study Details

PMID:9116317
Participants:676
Impact:lower risk associated with higher vitamin C intake (statistically significant association)
Trust score:3/5

FEV1 decrement due to ozone exposure

1 evidences

In healthy adults placed on a low-ascorbate diet, 2-week antioxidant supplementation including 250 mg vitamin C reduced ozone-induced declines in lung function but did not affect airway inflammatory markers.

Trust comment: Randomized human exposure study with objective lung function and BAL measures but small sample (n=31) and combined antioxidant intervention.

Study Details

PMID:11549539
Participants:31
Impact:30% smaller in supplemented group vs placebo
Trust score:4/5

FVC decrement due to ozone exposure

1 evidences

In healthy adults placed on a low-ascorbate diet, 2-week antioxidant supplementation including 250 mg vitamin C reduced ozone-induced declines in lung function but did not affect airway inflammatory markers.

Trust comment: Randomized human exposure study with objective lung function and BAL measures but small sample (n=31) and combined antioxidant intervention.

Study Details

PMID:11549539
Participants:31
Impact:24% smaller in supplemented group vs placebo
Trust score:4/5

airway inflammation (BAL % neutrophils, IL-6)

1 evidences

In healthy adults placed on a low-ascorbate diet, 2-week antioxidant supplementation including 250 mg vitamin C reduced ozone-induced declines in lung function but did not affect airway inflammatory markers.

Trust comment: Randomized human exposure study with objective lung function and BAL measures but small sample (n=31) and combined antioxidant intervention.

Study Details

PMID:11549539
Participants:31
Impact:no significant difference vs placebo
Trust score:4/5

forced vital capacity (FVC) ozone-response

1 evidences

Cyclists taking a daily antioxidant supplement (including vitamin C) showed protection of lung function against ozone exposure compared with non-supplemented cyclists.

Trust comment: Small human study with objective spirometry measures but used a combined antioxidant supplement (vitamin C plus others), limiting attribution to vitamin C alone.

Study Details

PMID:9536157
Participants:26
Impact:+2.08 ml/µg/m3 (difference in regression coefficient vs control)
Trust score:3/5

forced expiratory volume in 1 s (FEV1) ozone-response

1 evidences

Cyclists taking a daily antioxidant supplement (including vitamin C) showed protection of lung function against ozone exposure compared with non-supplemented cyclists.

Trust comment: Small human study with objective spirometry measures but used a combined antioxidant supplement (vitamin C plus others), limiting attribution to vitamin C alone.

Study Details

PMID:9536157
Participants:26
Impact:+1.66 ml/µg/m3 (difference in regression coefficient vs control)
Trust score:3/5

peak expiratory flow (PEF) ozone-response

1 evidences

Cyclists taking a daily antioxidant supplement (including vitamin C) showed protection of lung function against ozone exposure compared with non-supplemented cyclists.

Trust comment: Small human study with objective spirometry measures but used a combined antioxidant supplement (vitamin C plus others), limiting attribution to vitamin C alone.

Study Details

PMID:9536157
Participants:26
Impact:+6.83 ml/µg/m3 (difference in regression coefficient vs control)
Trust score:3/5

visual discomfort (Floater Disturbance Questionnaire)

1 evidences

People with symptomatic eye floaters who took a 6-month micronutrient supplement (including vitamin C) reported less discomfort and had smaller measured floater areas than before treatment.

Trust comment: Randomized, double-blind, placebo-controlled trial with objective imaging and validated analyses, but small sample and multi-nutrient formulation prevents isolating vitamin C effects.

Study Details

PMID:34647961
Participants:56
Impact:mean score −1.80 points (from 3.90 to 2.10; P < 0.001)
Trust score:4/5

vitreous opacity area

1 evidences

People with symptomatic eye floaters who took a 6-month micronutrient supplement (including vitamin C) reported less discomfort and had smaller measured floater areas than before treatment.

Trust comment: Randomized, double-blind, placebo-controlled trial with objective imaging and validated analyses, but small sample and multi-nutrient formulation prevents isolating vitamin C effects.

Study Details

PMID:34647961
Participants:56
Impact:−21.53 cm² (from 121.31 to 99.78 cm²; P < 0.001)
Trust score:4/5

photopic functional contrast sensitivity (positive polarity)

1 evidences

People with symptomatic eye floaters who took a 6-month micronutrient supplement (including vitamin C) reported less discomfort and had smaller measured floater areas than before treatment.

Trust comment: Randomized, double-blind, placebo-controlled trial with objective imaging and validated analyses, but small sample and multi-nutrient formulation prevents isolating vitamin C effects.

Study Details

PMID:34647961
Participants:56
Impact:+0.06 log units (improvement; P = 0.047)
Trust score:4/5

total antioxidant status

1 evidences

Physically active men who practiced yoga for 3 months had improvements in antioxidant markers (including higher vitamin C) and some metabolic measures versus controls.

Trust comment: Controlled human study with objective biochemical endpoints, but non-blinded, lifestyle intervention and results reported without detailed effect sizes in the abstract.

Study Details

PMID:24834493
Participants:64
Impact:increased (statistically significant)
Trust score:3/5

resting metabolism (CO2 elimination and peripheral O2 saturation)

1 evidences

Physically active men who practiced yoga for 3 months had improvements in antioxidant markers (including higher vitamin C) and some metabolic measures versus controls.

Trust comment: Controlled human study with objective biochemical endpoints, but non-blinded, lifestyle intervention and results reported without detailed effect sizes in the abstract.

Study Details

PMID:24834493
Participants:64
Impact:CO2 elimination and SpO2 increased (statistically significant)
Trust score:3/5

vitamin C probability of adequacy (PA)

1 evidences

A cluster RCT of an agriculture-plus-nutrition program increased the probability that preschool children met recommended intakes of several micronutrients, including vitamin C.

Trust comment: Large cluster-randomized trial with low loss to follow-up and adjusted DID estimates, providing robust evidence for improved vitamin C intake probability though intervention targeted multiple behaviors.

Study Details

PMID:31616933
Participants:1248
Impact:+14 percentage points (DID; SE 3 pp)
Trust score:4/5

vitamin A probability of adequacy (PA)

1 evidences

A cluster RCT of an agriculture-plus-nutrition program increased the probability that preschool children met recommended intakes of several micronutrients, including vitamin C.

Trust comment: Large cluster-randomized trial with low loss to follow-up and adjusted DID estimates, providing robust evidence for improved vitamin C intake probability though intervention targeted multiple behaviors.

Study Details

PMID:31616933
Participants:1248
Impact:+9 percentage points (DID; SE 3 pp)
Trust score:4/5

mean probability of adequacy (MPA) for 11 nutrients

1 evidences

A cluster RCT of an agriculture-plus-nutrition program increased the probability that preschool children met recommended intakes of several micronutrients, including vitamin C.

Trust comment: Large cluster-randomized trial with low loss to follow-up and adjusted DID estimates, providing robust evidence for improved vitamin C intake probability though intervention targeted multiple behaviors.

Study Details

PMID:31616933
Participants:1248
Impact:+5 percentage points (DID; SE 1 pp)
Trust score:4/5

low-density lipoprotein cholesterol (LDL-C)

1 evidences

A combined nutraceutical containing bergamot extract and phytosterols improved triglycerides, LDL-C, and insulin resistance markers versus placebo in overweight dyslipidemic subjects.

Trust comment: Well-designed double-blind placebo-controlled RCT but the intervention was a multi-ingredient nutraceutical (including vitamin C), so individual contribution of vitamin C is not isolated.

Study Details

PMID:31225673
Participants:90
Impact:decrease — significant vs baseline and placebo
Trust score:4/5

leptin

1 evidences

In women, interpersonal stressors were associated with higher ghrelin, lower leptin, and small/marginal increases in several dietary components including vitamin C intake.

Trust comment: Small observational study (n=50) with repeated measures linking stressors to hormones and diet; vitamin C appears only as part of dietary associations.

Study Details

PMID:25032903
Participants:50
Impact:lower levels associated with more interpersonal stressors
Trust score:3/5

ischemic vascular disease incidence

1 evidences

Long-term low-dose antioxidant supplementation (including 120 mg vitamin C) did not affect vascular disease but lowered total cancer incidence in men.

Trust comment: Large, long-duration double-blind RCT offering high-quality evidence for the combination, but multiple nutrients were given so effects cannot be ascribed to vitamin C alone.

Study Details

PMID:17119469
Participants:12741
Impact:no significant change
Trust score:4/5

total cancer incidence (women)

1 evidences

Long-term low-dose antioxidant supplementation (including 120 mg vitamin C) did not affect vascular disease but lowered total cancer incidence in men.

Trust comment: Large, long-duration double-blind RCT offering high-quality evidence for the combination, but multiple nutrients were given so effects cannot be ascribed to vitamin C alone.

Study Details

PMID:17119469
Participants:12741
Impact:no significant change
Trust score:4/5

triglycerides (TG)

1 evidences

A combined nutraceutical containing bergamot extract and phytosterols improved triglycerides, LDL-C, and insulin resistance markers versus placebo in overweight dyslipidemic subjects.

Trust comment: Well-designed double-blind placebo-controlled RCT but the intervention was a multi-ingredient nutraceutical (including vitamin C), so individual contribution of vitamin C is not isolated.

Study Details

PMID:31225673
Participants:90
Impact:decrease — significant vs placebo and baseline
Trust score:4/5

lumen loss

1 evidences

Subgroup analysis of an RCT (MVP Trial) where one arm received multivitamins (including vitamin C 500 mg) ± probucol; outcomes were lumen loss and restenosis at 6 months.

Trust comment: Randomized trial subgroup with objective angiographic outcomes, but vitamin C was given as part of a multivitamin combination so effects cannot be attributed to vitamin C alone.

Study Details

PMID:9490236
Participants:189
Impact:Vitamins arm: 0.35±0.56 mm vs placebo 0.38±0.51 mm (probucol arm showed greater reduction)
Trust score:3/5

restenosis rate

1 evidences

Subgroup analysis of an RCT (MVP Trial) where one arm received multivitamins (including vitamin C 500 mg) ± probucol; outcomes were lumen loss and restenosis at 6 months.

Trust comment: Randomized trial subgroup with objective angiographic outcomes, but vitamin C was given as part of a multivitamin combination so effects cannot be attributed to vitamin C alone.

Study Details

PMID:9490236
Participants:189
Impact:Vitamins arm: 45.1% vs placebo 37.3% per segment (vitamins did not reduce restenosis in this subgroup)
Trust score:3/5

flow-mediated dilation (FMD) after ischemia-reperfusion

1 evidences

In healthy volunteers, IV vitamin C (2 g) given with nitroglycerin removed nitroglycerin's protective effect on blood-vessel dilation after ischemia-reperfusion.

Trust comment: Randomized double-blind human mechanistic study (n=66) with clear physiological endpoints; effect of vitamin C assessed as a co-intervention.

Study Details

PMID:17324239
Participants:66
Impact:-3.2 percentage points (GTN alone 5.3% vs GTN+vitamin C 2.1%)
Trust score:4/5

plasma adiponectin

1 evidences

A 5-week multi-ingredient supplement (including vitamin C) modestly increased adiponectin and produced subtle omics-signals of reduced inflammation and oxidative stress in overweight men; CRP unchanged.

Trust comment: Well-controlled double-blind crossover but small sample (n=36) and effects cannot be attributed to vitamin C alone because of the multi-ingredient formulation.

Study Details

PMID:20181810
Participants:36
Impact:+7%
Trust score:3/5

oxidative stress / inflammation markers (omics)

1 evidences

A 5-week multi-ingredient supplement (including vitamin C) modestly increased adiponectin and produced subtle omics-signals of reduced inflammation and oxidative stress in overweight men; CRP unchanged.

Trust comment: Well-controlled double-blind crossover but small sample (n=36) and effects cannot be attributed to vitamin C alone because of the multi-ingredient formulation.

Study Details

PMID:20181810
Participants:36
Impact:subtle/modest improvement (qualitative)
Trust score:3/5

fruit and vegetable consumption (self-reported)

1 evidences

In low-income adults, fruit-and-vegetable vouchers increased short-term consumption but did not change blood vitamin C levels at 3 months.

Trust comment: Randomized 12-month trial with objective vitamin measurements, but high loss-to-follow-up limited long-term analysis.

Study Details

PMID:21989324
Participants:302
Impact:increase at 3 months (advice: +0.62 times/day; vouchers: +0.74 times/day)
Trust score:3/5

hemoglobin / hematocrit / red cell count

1 evidences

In 7–11-year-old schoolchildren, one year of a multiple-micronutrient food supplement (including B12) improved hemoglobin/red cell indices and several memory and attention test scores compared with controls.

Trust comment: Pre-post design with non-randomized control (residential vs day scholars) and multiple nutrients combined, so attribution to vitamin C alone is uncertain.

Study Details

PMID:18716734
Participants:123
Impact:significant increase in experimental group (P<0.05) vs decline in controls
Trust score:3/5

memory and attention test scores

1 evidences

In 7–11-year-old schoolchildren, one year of a multiple-micronutrient food supplement (including B12) improved hemoglobin/red cell indices and several memory and attention test scores compared with controls.

Trust comment: Pre-post design with non-randomized control (residential vs day scholars) and multiple nutrients combined, so attribution to vitamin C alone is uncertain.

Study Details

PMID:18716734
Participants:123
Impact:improvement in 5 of 7 memory tests and attention test (P<0.05)
Trust score:3/5

days with severe illnesses

1 evidences

Randomized trial in children 1–3 y: milk fortified with multiple micronutrients (including vitamin C) reduced diarrhoea, lower respiratory infections and days with severe illness.

Trust comment: Large, community-based randomized double-masked trial with good sample size and clear outcomes, but effect is of a multi-micronutrient product (not vitamin C alone).

Study Details

PMID:17132678
Participants:633
Impact:-15% (reduced odds; 95% CI 5% to 24%)
Trust score:4/5

diarrhoea incidence

1 evidences

Randomized trial in children 1–3 y: milk fortified with multiple micronutrients (including vitamin C) reduced diarrhoea, lower respiratory infections and days with severe illness.

Trust comment: Large, community-based randomized double-masked trial with good sample size and clear outcomes, but effect is of a multi-micronutrient product (not vitamin C alone).

Study Details

PMID:17132678
Participants:633
Impact:-18% (95% CI 7% to 27%)
Trust score:4/5

acute lower respiratory illness incidence

1 evidences

Randomized trial in children 1–3 y: milk fortified with multiple micronutrients (including vitamin C) reduced diarrhoea, lower respiratory infections and days with severe illness.

Trust comment: Large, community-based randomized double-masked trial with good sample size and clear outcomes, but effect is of a multi-micronutrient product (not vitamin C alone).

Study Details

PMID:17132678
Participants:633
Impact:-26% (95% CI 3% to 43%)
Trust score:4/5

sP-selectin and sE-selectin

1 evidences

Two-month Mediterranean-style diet (which increased dietary vitamin C intake) showed within-group decreases in some inflammation markers but no significant between-group changes for most adhesion molecules.

Trust comment: Randomized dietary intervention in humans with modest sample size; vitamin C intake changed as part of a broader diet, and between-group differences were generally not significant.

Study Details

PMID:28361746
Participants:90
Impact:decreased within intervention group (between-group change not statistically significant)
Trust score:3/5

sICAM-1 / IL-6

1 evidences

Two-month Mediterranean-style diet (which increased dietary vitamin C intake) showed within-group decreases in some inflammation markers but no significant between-group changes for most adhesion molecules.

Trust comment: Randomized dietary intervention in humans with modest sample size; vitamin C intake changed as part of a broader diet, and between-group differences were generally not significant.

Study Details

PMID:28361746
Participants:90
Impact:no significant change
Trust score:3/5

all skin cancer incidence (women)

1 evidences

Large randomized placebo-controlled trial of combined antioxidant supplements (including 120 mg vitamin C) found higher skin cancer incidence in women assigned to antioxidants, with no effect in men.

Trust comment: Large randomized, double-blind, placebo-controlled trial with long follow-up, but supplements were a combined antioxidant formulation (vitamin C not tested alone).

Study Details

PMID:17709449
Participants:13017
Impact:+68% (adjusted HR = 1.68; P = 0.03)
Trust score:4/5

melanoma incidence (women)

1 evidences

Large randomized placebo-controlled trial of combined antioxidant supplements (including 120 mg vitamin C) found higher skin cancer incidence in women assigned to antioxidants, with no effect in men.

Trust comment: Large randomized, double-blind, placebo-controlled trial with long follow-up, but supplements were a combined antioxidant formulation (vitamin C not tested alone).

Study Details

PMID:17709449
Participants:13017
Impact:+331% (adjusted HR = 4.31; P = 0.02)
Trust score:4/5

nonmelanoma skin cancer incidence

1 evidences

Large randomized placebo-controlled trial of combined antioxidant supplements (including 120 mg vitamin C) found higher skin cancer incidence in women assigned to antioxidants, with no effect in men.

Trust comment: Large randomized, double-blind, placebo-controlled trial with long follow-up, but supplements were a combined antioxidant formulation (vitamin C not tested alone).

Study Details

PMID:17709449
Participants:13017
Impact:no significant difference
Trust score:4/5

macular drusen >63 μm

1 evidences

Cross-sectional analysis relating dietary vitamins (including vitamin C) to early AMD signs; higher vitamin A (not vitamin C) intake associated with larger drusen in certain genotypes.

Trust comment: Well-sized cross-sectional human study; vitamin C was assessed but no clear association with early AMD was reported.

Study Details

PMID:27502478
Participants:848
Impact:increased risk associated with higher vitamin A intake (no significant association reported for vitamin C)
Trust score:3/5

numerous small hard macular drusen

1 evidences

Cross-sectional analysis relating dietary vitamins (including vitamin C) to early AMD signs; higher vitamin A (not vitamin C) intake associated with larger drusen in certain genotypes.

Trust comment: Well-sized cross-sectional human study; vitamin C was assessed but no clear association with early AMD was reported.

Study Details

PMID:27502478
Participants:848
Impact:analyzed but no vitamin C effect reported
Trust score:3/5

myocardial injury (hs-troponin AUC over 3 days)

1 evidences

Large randomized, blinded trial gave IV antioxidants (3 g vitamin C + NAC) perioperatively and found no reduction in postoperative myocardial injury compared with placebo.

Trust comment: Large, multicenter, blinded randomized trial with low risk of bias demonstrating no cardiovascular benefit from perioperative IV vitamin C + NAC.

Study Details

PMID:35120193
Participants:576
Impact:no significant change with antioxidants vs placebo (median difference -0.5 ng·day/l; P = 0.228)
Trust score:4/5

lipoperoxide (LPO) - plasma/erythrocytes

1 evidences

Patients with IgA nephropathy had more oxidative damage and lower antioxidant levels including vitamin C than healthy volunteers.

Trust comment: Moderate-quality comparative study with clear measurements but observational design limits causal inference about vitamin C effects.

Study Details

PMID:15593395
Participants:144
Impact:increased (significantly vs controls, P<0.0001)
Trust score:3/5

maternal plasma vitamin C

1 evidences

Randomized double-blind trial in pregnant women: micronutrient supplement raised maternal vitamin levels, was associated with 10% higher birth weights and fewer low-birth-weight infants; maternal plasma zinc correlated with newborn height.

Trust comment: Double-blind RCT but substantial attrition (100 recruited → 65 completed) which reduces confidence in effect estimates.

Study Details

PMID:14679367
Participants:65
Impact:increased in supplemented group vs placebo
Trust score:3/5

low birth weight frequency (<2700 g)

1 evidences

Randomized double-blind trial in pregnant women: micronutrient supplement raised maternal vitamin levels, was associated with 10% higher birth weights and fewer low-birth-weight infants; maternal plasma zinc correlated with newborn height.

Trust comment: Double-blind RCT but substantial attrition (100 recruited → 65 completed) which reduces confidence in effect estimates.

Study Details

PMID:14679367
Participants:65
Impact:decreased in supplemented group (significant)
Trust score:3/5

plasma lipid hydroperoxides (LPOs)

1 evidences

A multi-antioxidant supplement (including 500 mg vitamin C) prevented the rise in plasma lipid hydroperoxides seen in placebo but urine oxidative markers rose in both groups, showing mixed effects.

Trust comment: Randomized field study with small sample and combined antioxidant formulation, making it hard to isolate vitamin C-specific effects; markers showed inconsistent patterns.

Study Details

PMID:10442154
Participants:30
Impact:placebo: +30% between t0 and t2 (p<0.05); supplement: no increase (prevented the 30% rise)
Trust score:3/5

urine TBARS / HNE / 8-OHdG

1 evidences

A multi-antioxidant supplement (including 500 mg vitamin C) prevented the rise in plasma lipid hydroperoxides seen in placebo but urine oxidative markers rose in both groups, showing mixed effects.

Trust comment: Randomized field study with small sample and combined antioxidant formulation, making it hard to isolate vitamin C-specific effects; markers showed inconsistent patterns.

Study Details

PMID:10442154
Participants:30
Impact:increased by t2 in both groups (greater early increase in supplement group)
Trust score:3/5

plasma total peroxyl radical trapping potential (TRAP)

1 evidences

A multi-antioxidant supplement (including 500 mg vitamin C) prevented the rise in plasma lipid hydroperoxides seen in placebo but urine oxidative markers rose in both groups, showing mixed effects.

Trust comment: Randomized field study with small sample and combined antioxidant formulation, making it hard to isolate vitamin C-specific effects; markers showed inconsistent patterns.

Study Details

PMID:10442154
Participants:30
Impact:not clearly protective across urine and plasma markers (conflicting results)
Trust score:3/5

flow-mediated dilation (FMD) after ischemia–reperfusion

1 evidences

GTN and PETN prevented IR-induced endothelial dysfunction; ISMN did not; vitamin C blocked GTN protection but did not alter PETN's protective effect.

Trust comment: Randomized mechanistic human trial with small vitamin C subgroup (n=8)—direct test of vitamin C's effect on nitrate-mediated endothelial responses but limited by small sample size.

Study Details

PMID:17641250
Participants:37
Impact:PETN and GTN prevented IR-induced FMD impairment (PETN after IR 8.1%); ISMN no effect (3.6%)
Trust score:3/5

effect of vitamin C on GTN and PETN preconditioning

1 evidences

GTN and PETN prevented IR-induced endothelial dysfunction; ISMN did not; vitamin C blocked GTN protection but did not alter PETN's protective effect.

Trust comment: Randomized mechanistic human trial with small vitamin C subgroup (n=8)—direct test of vitamin C's effect on nitrate-mediated endothelial responses but limited by small sample size.

Study Details

PMID:17641250
Participants:37
Impact:Vitamin C blocked GTN protection but did not modify PETN preconditioning (vitamin C group FMD after IR ~6.3%)
Trust score:3/5

gingival index (bleeding)

1 evidences

A 4-week anti-inflammatory diet (which included vitamin C among many components) reduced gum bleeding in people with gingivitis.

Trust comment: Randomized trial but vitamin C was one of many dietary changes (small sample), so effects cannot be attributed to vitamin C alone.

Study Details

PMID:30941800
Participants:30
Impact:GI 1.04 → 0.61 (absolute −0.43), p < 0.05
Trust score:3/5

serum vitamin D

1 evidences

A 4-week anti-inflammatory diet (which included vitamin C among many components) reduced gum bleeding in people with gingivitis.

Trust comment: Randomized trial but vitamin C was one of many dietary changes (small sample), so effects cannot be attributed to vitamin C alone.

Study Details

PMID:30941800
Participants:30
Impact:significant increase (no value reported)
Trust score:3/5

left ventricular (LV) volumes

1 evidences

In elderly patients with chronic heart failure, long-term high-dose multiple micronutrient supplementation (including vitamin D) improved left ventricular volumes, increased LVEF and improved quality-of-life versus placebo.

Trust comment: Randomized double-blind trial with objective cardiac outcomes, but multiple nutrients were given so vitamin C–specific effects cannot be isolated.

Study Details

PMID:16081469
Participants:28
Impact:−13.1% in intervention vs +3.8% in placebo (P < 0.05)
Trust score:3/5

quality-of-life (QoL) score

1 evidences

In elderly patients with chronic heart failure, long-term high-dose multiple micronutrient supplementation (including vitamin D) improved left ventricular volumes, increased LVEF and improved quality-of-life versus placebo.

Trust comment: Randomized double-blind trial with objective cardiac outcomes, but multiple nutrients were given so vitamin C–specific effects cannot be isolated.

Study Details

PMID:16081469
Participants:28
Impact:+9.5% in intervention vs −1.1% in placebo (P < 0.05)
Trust score:3/5

total oxidative status (TOS)

1 evidences

Following the DASH diet (which raised serum vitamin C) reduced some oxidative stress markers and improved migraine scores versus usual diet.

Trust comment: Well-conducted RCT with serum vitamin C measured for compliance, but DASH is a multicomponent diet so effects cannot be attributed to vitamin C alone.

Study Details

PMID:34269164
Participants:102
Impact:−1.55 vs +0.71 (P = 0.034)
Trust score:3/5

migraine index (MI)

1 evidences

Following the DASH diet (which raised serum vitamin C) reduced some oxidative stress markers and improved migraine scores versus usual diet.

Trust comment: Well-conducted RCT with serum vitamin C measured for compliance, but DASH is a multicomponent diet so effects cannot be attributed to vitamin C alone.

Study Details

PMID:34269164
Participants:102
Impact:−31.33 vs −15.09 (between-group difference)
Trust score:3/5

Flow‑mediated dilation (FMD) — noise effect

1 evidences

Randomized crossover field study (75 analyzed); night aircraft noise impaired endothelial function and raised adrenaline; an acute oral Vitamin C challenge (2 g) in a small subgroup (n=5) improved flow‑mediated dilation.

Trust comment: Well‑designed randomized crossover with 75 subjects for noise effects; Vitamin C evidence is from an acute challenge in only 5 subjects, limiting robustness.

Study Details

PMID:23821397
Participants:75
Impact:decreased (control 10.4% → Noise60 9.5%; −0.9 percentage points; dose–response p=0.020)
Trust score:3/5

Adrenaline (catecholamines)

1 evidences

Randomized crossover field study (75 analyzed); night aircraft noise impaired endothelial function and raised adrenaline; an acute oral Vitamin C challenge (2 g) in a small subgroup (n=5) improved flow‑mediated dilation.

Trust comment: Well‑designed randomized crossover with 75 subjects for noise effects; Vitamin C evidence is from an acute challenge in only 5 subjects, limiting robustness.

Study Details

PMID:23821397
Participants:75
Impact:increased (control 28.3 ng/L → Noise30 33.2 ng/L and Noise60 34.1 ng/L; ≈+5–6 ng/L; p≈0.01)
Trust score:3/5

Flow‑mediated dilation (Vitamin C challenge)

1 evidences

Randomized crossover field study (75 analyzed); night aircraft noise impaired endothelial function and raised adrenaline; an acute oral Vitamin C challenge (2 g) in a small subgroup (n=5) improved flow‑mediated dilation.

Trust comment: Well‑designed randomized crossover with 75 subjects for noise effects; Vitamin C evidence is from an acute challenge in only 5 subjects, limiting robustness.

Study Details

PMID:23821397
Participants:75
Impact:acute oral Vitamin C (2 g) markedly improved FMD in 5 subjects (significant, p=0.017)
Trust score:3/5

Vitamin C concentration

1 evidences

Randomized trial found a high-polyphenol diet increased vitamin C biomarkers and improved endothelium-dependent vasodilation in hypertensive participants.

Trust comment: Randomized controlled trial with objective biochemical and vascular function measures showing consistent changes.

Study Details

PMID:27164919
Participants:92
Impact:significant increase in the high-polyphenol group versus low-polyphenol (between-group p < 0.001)
Trust score:4/5

Vitamin C intake adequacy

1 evidences

Oral nutritional supplements plus dietary counseling increased energy and micronutrient intakes (including calcium), and improved appetite versus counseling alone in picky-eating children over 90 days.

Trust comment: Large randomized, double‑blind trial with complete dietary assessment showing robust increases in vitamin C intake from the supplements, but effects are for multi‑nutrient ONS rather than isolated Vitamin C.

Study Details

PMID:37299491
Participants:321
Impact:increased from ~40% at baseline to >90% at Day 90 in supplemented groups (≈+50 percentage points; p<0.001)
Trust score:3/5

Nutrient adequacy (overall)

1 evidences

Oral nutritional supplements plus dietary counseling increased energy and micronutrient intakes (including calcium), and improved appetite versus counseling alone in picky-eating children over 90 days.

Trust comment: Large randomized, double‑blind trial with complete dietary assessment showing robust increases in vitamin C intake from the supplements, but effects are for multi‑nutrient ONS rather than isolated Vitamin C.

Study Details

PMID:37299491
Participants:321
Impact:higher percentages of children met EARs for multiple nutrients (energy, iron, thiamin, vitamin C, calcium) in supplemented groups vs control at Day 90
Trust score:3/5

Ferritin (FER, adjusted)

1 evidences

Daily baobab fruit pulp (rich in vitamin C) given with a school meal for 83 days produced a small increase in hemoglobin and smaller declines in ferritin versus control, but differences were not statistically significant.

Trust comment: Randomized, single-blind trial with appropriate biochemical outcomes but small, underpowered sample and variable vitamin C content limit confidence.

Study Details

PMID:33355689
Participants:58
Impact:Intervention: -17.3% (geometric mean); Control: -26.0% (geometric mean)
Trust score:3/5

Soluble transferrin receptor (sTfR)

1 evidences

Daily baobab fruit pulp (rich in vitamin C) given with a school meal for 83 days produced a small increase in hemoglobin and smaller declines in ferritin versus control, but differences were not statistically significant.

Trust comment: Randomized, single-blind trial with appropriate biochemical outcomes but small, underpowered sample and variable vitamin C content limit confidence.

Study Details

PMID:33355689
Participants:58
Impact:Intervention: +0.7% (geometric mean); Control: +2.7% (geometric mean)
Trust score:3/5

Overall diet quality / micronutrient intake

1 evidences

6-month randomized weight-loss program (partial meal replacements + exercise) in older obese adults improved diet quality and increased intake of key micronutrients despite reduced calories.

Trust comment: Randomized intervention with dietary records and objective weight outcomes; micronutrient increases reported but blood nutrient status not all measured.

Study Details

PMID:20617289
Participants:71
Impact:Key micronutrients (calcium, iron, vitamin D, vitamin E, vitamin C) higher in WL vs WS at 6 months
Trust score:4/5

Markers of oxidative stress (3-nitrotyrosine, F2-isoprostane, 8-OHdG)

1 evidences

In adolescents with poorly controlled type 1 diabetes, improved glycemic control and 3–6 months of antioxidant supplementation (including vitamin C) did not restore erythrocyte glutathione or reduce markers of oxidative stress.

Trust comment: Randomized, controlled study with biochemical endpoints; small sample and short follow-up limit generalizability but results are direct and clear.

Study Details

PMID:37515943
Participants:41
Impact:No change after improved metabolic control or antioxidant supplementation
Trust score:4/5

Hemoglobin (g/dL)

1 evidences

A mobile-technology education program (MyPinkMom) for anemic pregnant women increased dietary vitamin C intake substantially and improved hemoglobin versus routine counseling.

Trust comment: Cluster RCT with adequate sample size and clear, significant changes in dietary vitamin C intake and hemoglobin, though biochemical iron markers were not measured.

Study Details

PMID:36473006
Participants:104
Impact:+0.66 g/dL (mean difference intervention vs control at week 6; p<0.001)
Trust score:4/5

Neuropathy symptom score (MNSI questionnaire)

1 evidences

Type 2 diabetic patients given micronutrient formulas (one including B-vitamins) reported reduced neuropathy symptom scores, but objective measures did not differ between groups.

Trust comment: Randomized, double-blind trial but small sample and intervention was a multi-nutrient mix so vitamin C–specific effects cannot be isolated.

Study Details

PMID:21496936
Participants:67
Impact:MVB: 3.45 → 0.64 (−2.81); MV: 3.96 → 1.00 (−2.96); Placebo: 2.54 → 1.95 (−0.59); within-group p=0.001 for supplemented groups
Trust score:3/5

Objective neuropathy examinations / electrophysiology

1 evidences

Type 2 diabetic patients given micronutrient formulas (one including B-vitamins) reported reduced neuropathy symptom scores, but objective measures did not differ between groups.

Trust comment: Randomized, double-blind trial but small sample and intervention was a multi-nutrient mix so vitamin C–specific effects cannot be isolated.

Study Details

PMID:21496936
Participants:67
Impact:No significant between-group differences after 4 months
Trust score:3/5

Serum folate

1 evidences

Double-blind RCT of a multivitamin/mineral vs placebo in older adults on certain medications; MVMS increased folate and vitamin C status but did not significantly change serum calcium.

Trust comment: Double-blind, placebo-controlled RCT with direct biochemical measurement showing a small but significant increase in plasma vitamin C; small sample size limits precision.

Study Details

PMID:33078646
Participants:54
Impact:+7.5 ng/mL in MVMS vs −1.6 ng/mL in placebo (p=0.007)
Trust score:4/5

adenoma recurrence

1 evidences

In post-polypectomy patients, long-term daily antioxidant supplementation that included zinc (30 mg) reduced adenoma recurrence over follow-up (~39% reduced risk; adjusted HR=0.61, 95% CI 0.41–0.92).

Trust comment: Well-conducted randomized double-blind trial with long follow-up showing reduced adenoma recurrence, but the intervention combined multiple antioxidants so effects cannot be attributed solely to vitamin C.

Study Details

PMID:23065023
Participants:330
Impact:-39% risk (adjusted HR = 0.61; 95% CI 0.41–0.92); 15-year cumulative incidence 48.3% vs 64.5% (intervention vs placebo)
Trust score:3/5

endothelium-dependent vasodilation (ACh response)

1 evidences

Randomized trial found a high-polyphenol diet increased vitamin C biomarkers and improved endothelium-dependent vasodilation in hypertensive participants.

Trust comment: Randomized controlled trial with objective biochemical and vascular function measures showing consistent changes.

Study Details

PMID:27164919
Participants:92
Impact:significant improvement in maximum % response to acetylcholine (p = 0.02)
Trust score:4/5

serum vitamin B1/B6/folic acid levels

1 evidences

A revised parenteral nutrition formula restored vitamin C and other vitamin levels to normal ranges after gastrointestinal surgery.

Trust comment: Randomized multicenter phase III trial with objective biochemical outcomes; open-label design reduces blinding.

Study Details

PMID:30799392
Participants:110
Impact:Higher on POD5 and POD8 versus previous formula
Trust score:4/5

serum vitamin K level

1 evidences

A revised parenteral nutrition formula restored vitamin C and other vitamin levels to normal ranges after gastrointestinal surgery.

Trust comment: Randomized multicenter phase III trial with objective biochemical outcomes; open-label design reduces blinding.

Study Details

PMID:30799392
Participants:110
Impact:Maintained within standard ranges (lower than ELN group which exceeded upper limit)
Trust score:4/5

leukocyte DNA damage (comet assay)

1 evidences

Antioxidant supplementation (1000 mg vitamin C + vitamin E) reduced exercise-induced leukocyte DNA damage in women but not in men after a 50 km ultramarathon.

Trust comment: Randomized small trial with clear gender-specific effects; limited sample size reduces generalizability.

Study Details

PMID:15059637
Participants:21
Impact:Women: 62% less DNA damage 1 day postrace with antioxidants versus placebo; men: no significant effect
Trust score:3/5

major vascular events (MI/stroke/vascular death)

1 evidences

A high-dose antioxidant combination including 250 mg vitamin C showed no benefit in reducing major vascular events in PAD patients over 2 years.

Trust comment: Large randomized, double-blind, placebo-controlled trial with robust design; vitamin C was part of the tested combination.

Study Details

PMID:17305650
Participants:210
Impact:No benefit for antioxidant vitamins (16/185 events in antioxidant group vs 11/181 in placebo)
Trust score:5/5

pulse wave velocity

1 evidences

An acute antioxidant cocktail including vitamin C improved vascular function measures in COPD patients compared with placebo.

Trust comment: Randomized, placebo-controlled crossover with physiologic endpoints; sample size modest but design strong for acute effects.

Study Details

PMID:24324045
Participants:60
Impact:Improved from 14±1 to 11±1 m·s⁻¹ with antioxidant versus placebo (P < 0.05)
Trust score:4/5

endothelial markers (sTM, vWF, E-selectin, VCAM-1, tPAag, P-selectin)

1 evidences

In smokers with hyperlipidaemia, antioxidant supplementation including 150 mg vitamin C had no effect on measured endothelial cell markers over 6 weeks.

Trust comment: Randomized factorial trial with small sample; endpoints measured are relevant but study is limited by size.

Study Details

PMID:9767357
Participants:41
Impact:No significant changes with antioxidant supplementation versus placebo
Trust score:3/5

protein oxidative stress (plasma free carbonyls / carbonyl:protein ratio)

1 evidences

Women with cervical cancer received an antioxidant mix (including vitamin C) during radiotherapy; supplementation reduced protein oxidative stress and improved quality of life.

Trust comment: Randomized, blinded clinical trial in 103 patients with relevant biochemical and QoL outcomes; moderate sample but appropriate design.

Study Details

PMID:22470030
Participants:103
Impact:decreased (statistically significant, p<0.009)
Trust score:4/5

global quality of life

1 evidences

Women with cervical cancer received an antioxidant mix (including vitamin C) during radiotherapy; supplementation reduced protein oxidative stress and improved quality of life.

Trust comment: Randomized, blinded clinical trial in 103 patients with relevant biochemical and QoL outcomes; moderate sample but appropriate design.

Study Details

PMID:22470030
Participants:103
Impact:improved (statistically significant, p<0.025)
Trust score:4/5

weight velocity

1 evidences

Preschool children consumed milk fortified with multiple micronutrients (including vitamin C) for 1 year; fortified milk improved growth and iron status and reduced anemia.

Trust comment: Large double-masked RCT with high adherence and clinically meaningful, statistically robust outcomes.

Study Details

PMID:20730057
Participants:633
Impact:+0.21 kg/yr vs control (difference 0.21; 95% CI 0.12–0.31; p<0.001)
Trust score:5/5

height velocity

1 evidences

Preschool children consumed milk fortified with multiple micronutrients (including vitamin C) for 1 year; fortified milk improved growth and iron status and reduced anemia.

Trust comment: Large double-masked RCT with high adherence and clinically meaningful, statistically robust outcomes.

Study Details

PMID:20730057
Participants:633
Impact:+0.51 cm/yr vs control (difference 0.51; 95% CI 0.27–0.75; p<0.001)
Trust score:5/5

oxidative stress markers (TRAP, TBARS)

1 evidences

Adults with metabolic syndrome counseled on DASH diet plus low-sodium vegetable juice (a source of vitamin C) increased vitamin C intake and experienced modestly greater weight loss; oxidative stress markers did not change.

Trust comment: Randomized trial with objective measures but small sample, short duration and industry involvement which may affect bias.

Study Details

PMID:20178625
Participants:81
Impact:no significant change
Trust score:3/5

24 h ambulatory blood pressure

1 evidences

Crossover RCT increasing potassium intake from fruit/veg or supplements in early hypertensives; plasma vitamin C was measured and remained unchanged and blood pressure did not improve.

Trust comment: Well-designed crossover RCT with biochemical verification and reasonable completion (48 completers), but modest sample size.

Study Details

PMID:20673378
Participants:48
Impact:no significant change versus control
Trust score:4/5

hypertension risk

1 evidences

A large randomized trial found that low-dose antioxidant supplementation (including vitamin C) did not reduce 6.5-year risk of high blood pressure; baseline beta-carotene in men and higher vitamin C in women showed observational associations with lower risk.

Trust comment: Large randomized trial with long follow-up, but intervention was a multi-antioxidant combination so vitamin C-specific effects are unclear.

Study Details

PMID:16208143
Participants:5086
Impact:no effect (OR 1.04 in men; OR 1.10 in women over 6.5 years)
Trust score:3/5

baseline vitamin C level association (women)

1 evidences

A large randomized trial found that low-dose antioxidant supplementation (including vitamin C) did not reduce 6.5-year risk of high blood pressure; baseline beta-carotene in men and higher vitamin C in women showed observational associations with lower risk.

Trust comment: Large randomized trial with long follow-up, but intervention was a multi-antioxidant combination so vitamin C-specific effects are unclear.

Study Details

PMID:16208143
Participants:5086
Impact:observational decreasing trend with risk (not quantified)
Trust score:3/5

baseline beta-carotene (men)

1 evidences

A large randomized trial found that low-dose antioxidant supplementation (including vitamin C) did not reduce 6.5-year risk of high blood pressure; baseline beta-carotene in men and higher vitamin C in women showed observational associations with lower risk.

Trust comment: Large randomized trial with long follow-up, but intervention was a multi-antioxidant combination so vitamin C-specific effects are unclear.

Study Details

PMID:16208143
Participants:5086
Impact:lower risk in higher tertiles (placebo ORs 0.70 and 0.53)
Trust score:3/5

fibroadenoma risk

1 evidences

A case-control study found no association between circulating vitamin C and risk of benign breast fibroadenomas.

Trust comment: Moderately sized observational study with appropriate controls, but cannot establish causality and vitamin C showed null association.

Study Details

PMID:20484550
Participants:1293
Impact:no association with circulating vitamin C
Trust score:3/5

isoflavone levels

1 evidences

A case-control study found no association between circulating vitamin C and risk of benign breast fibroadenomas.

Trust comment: Moderately sized observational study with appropriate controls, but cannot establish causality and vitamin C showed null association.

Study Details

PMID:20484550
Participants:1293
Impact:higher levels associated with lower risk (e.g., daidzein OR 0.36 highest vs lowest quartile)
Trust score:3/5

prostate cancer diagnoses

1 evidences

In a large randomized trial, high-dose zinc supplementation increased hospital admissions for genitourinary problems, including UTIs and urinary retention/stone events.

Trust comment: Large randomized trial with robust data, but the antioxidant formulation combined multiple agents (including vitamin C), and the prostate cancer finding was a secondary/subgroup observation.

Study Details

PMID:17222649
Participants:3640
Impact:−40% (RR 0.6 antioxidant arm vs placebo)
Trust score:3/5

genitourinary hospital admissions (zinc effect)

1 evidences

In a large randomized trial, high-dose zinc supplementation increased hospital admissions for genitourinary problems, including UTIs and urinary retention/stone events.

Trust comment: Large randomized trial with robust data, but the antioxidant formulation combined multiple agents (including vitamin C), and the prostate cancer finding was a secondary/subgroup observation.

Study Details

PMID:17222649
Participants:3640
Impact:increased with zinc vs non-zinc (11.1% vs 7.6%)
Trust score:3/5

antiviral / interferon-related gene expression

1 evidences

A 10-week mixed flavonoid–fish oil supplement (which included 250 mg vitamin C/day) upregulated antiviral/interferon-related gene expression but did not change standard inflammatory or oxidative-stress biomarkers.

Trust comment: Randomized, double-blind RCT (n=48) with robust transcriptomic analysis showing consistent gene-expression changes though traditional biomarkers were unchanged.

Study Details

PMID:27187447
Participants:48
Impact:+ (upregulation; several IFN pathway genes increased)
Trust score:4/5

EPA

1 evidences

A 10-week mixed flavonoid–fish oil supplement (which included 250 mg vitamin C/day) upregulated antiviral/interferon-related gene expression but did not change standard inflammatory or oxidative-stress biomarkers.

Trust comment: Randomized, double-blind RCT (n=48) with robust transcriptomic analysis showing consistent gene-expression changes though traditional biomarkers were unchanged.

Study Details

PMID:27187447
Participants:48
Impact:+80% (vs placebo at 10 weeks, p<0.001)
Trust score:4/5

DHA

1 evidences

A 10-week mixed flavonoid–fish oil supplement (which included 250 mg vitamin C/day) upregulated antiviral/interferon-related gene expression but did not change standard inflammatory or oxidative-stress biomarkers.

Trust comment: Randomized, double-blind RCT (n=48) with robust transcriptomic analysis showing consistent gene-expression changes though traditional biomarkers were unchanged.

Study Details

PMID:27187447
Participants:48
Impact:+4% (vs placebo at 10 weeks, p<0.001)
Trust score:4/5

inflammatory biomarkers (CRP, IL-6)

1 evidences

A 10-week mixed flavonoid–fish oil supplement (which included 250 mg vitamin C/day) upregulated antiviral/interferon-related gene expression but did not change standard inflammatory or oxidative-stress biomarkers.

Trust comment: Randomized, double-blind RCT (n=48) with robust transcriptomic analysis showing consistent gene-expression changes though traditional biomarkers were unchanged.

Study Details

PMID:27187447
Participants:48
Impact:no change (no significant difference vs placebo)
Trust score:4/5

clinic-reported pain score

1 evidences

Daily antioxidant tablets (including vitamin C) raised blood antioxidant levels but did not reduce pain or improve quality of life compared with placebo in chronic pancreatitis patients.

Trust comment: Well-conducted double-blind RCT (n=70) with intention-to-treat analysis; biochemical changes observed but no clinical benefit.

Study Details

PMID:22683257
Participants:70
Impact:−0.36 difference vs placebo (not significant; 95% CI -1.44 to 0.72)
Trust score:4/5

diary average daily pain

1 evidences

Daily antioxidant tablets (including vitamin C) raised blood antioxidant levels but did not reduce pain or improve quality of life compared with placebo in chronic pancreatitis patients.

Trust comment: Well-conducted double-blind RCT (n=70) with intention-to-treat analysis; biochemical changes observed but no clinical benefit.

Study Details

PMID:22683257
Participants:70
Impact:no significant difference (antioxidant 2.93 vs placebo 3.05)
Trust score:4/5

blood vitamin C (and other antioxidants)

1 evidences

Daily antioxidant tablets (including vitamin C) raised blood antioxidant levels but did not reduce pain or improve quality of life compared with placebo in chronic pancreatitis patients.

Trust comment: Well-conducted double-blind RCT (n=70) with intention-to-treat analysis; biochemical changes observed but no clinical benefit.

Study Details

PMID:22683257
Participants:70
Impact:significant increase (sustained rise in blood antioxidant levels)
Trust score:4/5

oxidised DNA lesions (FPG-sensitive sites)

1 evidences

Ten days of steamed broccoli (which contains vitamin C among other antioxidants) reduced oxidized DNA lesions and increased resistance to oxidative DNA damage in young smokers.

Trust comment: Crossover dietary intervention in 27 smokers with clear pre/post differences in oxidative-DNA endpoints; vitamin C was a component of broccoli but not isolated.

Study Details

PMID:20713433
Participants:27
Impact:−41% (95% CI 10% to 72%)
Trust score:4/5

resistance to H2O2-induced DNA strand breaks

1 evidences

Ten days of steamed broccoli (which contains vitamin C among other antioxidants) reduced oxidized DNA lesions and increased resistance to oxidative DNA damage in young smokers.

Trust comment: Crossover dietary intervention in 27 smokers with clear pre/post differences in oxidative-DNA endpoints; vitamin C was a component of broccoli but not isolated.

Study Details

PMID:20713433
Participants:27
Impact:+23% (95% CI 13% to 34%)
Trust score:4/5

DNA repair enzyme expression/activity (OGG1, NUDT1, HO-1)

1 evidences

Ten days of steamed broccoli (which contains vitamin C among other antioxidants) reduced oxidized DNA lesions and increased resistance to oxidative DNA damage in young smokers.

Trust comment: Crossover dietary intervention in 27 smokers with clear pre/post differences in oxidative-DNA endpoints; vitamin C was a component of broccoli but not isolated.

Study Details

PMID:20713433
Participants:27
Impact:no change
Trust score:4/5

lipid hydroperoxides (LPH)

1 evidences

A 4-month high-antioxidant diet (designed to raise vitamins A, C and E) increased plasma and leukocyte vitamin C, boosted antioxidant enzyme activities, and lowered lipid oxidative markers in women with endometriosis.

Trust comment: Randomized diet intervention with objective biochemical endpoints and moderate completion rates, but unblinded and with some dropouts.

Study Details

PMID:19476631
Participants:72
Impact:−20% (at 3 months)
Trust score:3/5

central retinal function (mfERG R1 RAD)

1 evidences

Randomized double-blind trial of Macuprev (multi-ingredient supplement including vitamin D3 800 IU) vs placebo in 30 patients with intermediate AMD (28 completed): after 6 months the active supplement increased central mfERG amplitudes (R1 and R2) without OCT structural changes.

Trust comment: Well-designed double-blind randomized trial with good compliance, but the supplement is multi-component so effects cannot be attributed to vitamin C alone.

Study Details

PMID:31243641
Participants:28
Impact:+23.5 nV/degree^2 (61.52 → 85.02; significant)
Trust score:4/5

central retinal function (mfERG R2 RAD)

1 evidences

Randomized double-blind trial of Macuprev (multi-ingredient supplement including vitamin D3 800 IU) vs placebo in 30 patients with intermediate AMD (28 completed): after 6 months the active supplement increased central mfERG amplitudes (R1 and R2) without OCT structural changes.

Trust comment: Well-designed double-blind randomized trial with good compliance, but the supplement is multi-component so effects cannot be attributed to vitamin C alone.

Study Details

PMID:31243641
Participants:28
Impact:+8.13 nV/degree^2 (26.65 → 34.78; significant)
Trust score:4/5

macular structure (SD-OCT)

1 evidences

Randomized double-blind trial of Macuprev (multi-ingredient supplement including vitamin D3 800 IU) vs placebo in 30 patients with intermediate AMD (28 completed): after 6 months the active supplement increased central mfERG amplitudes (R1 and R2) without OCT structural changes.

Trust comment: Well-designed double-blind randomized trial with good compliance, but the supplement is multi-component so effects cannot be attributed to vitamin C alone.

Study Details

PMID:31243641
Participants:28
Impact:no significant change
Trust score:4/5

consumption / compliance rate

1 evidences

Kindergarten children received Sprinkles (contain vitamin C among other micronutrients) daily or weekly for 13 weeks; high consumption and no evidence of iron overload were observed.

Trust comment: Cluster-randomized trial with objective safety outcomes; vitamin C was included in the mix but not isolated, so effects cannot be attributed to vitamin C alone.

Study Details

PMID:16684385
Participants:415
Impact:daily 86% ±12% and weekly 87% ±16% mean sachet consumption per child
Trust score:3/5

prostate cancer incidence (overall)

1 evidences

A large randomized trial of a multivitamin/mineral supplement (including zinc) vs placebo in men showed no significant overall reduction in prostate cancer, but a significant reduction in men with normal baseline PSA; PSA and IGF levels were unchanged.

Trust comment: Large randomized trial with long follow-up, but vitamin C was given in combination with other antioxidants and minerals, preventing attribution to vitamin C alone.

Study Details

PMID:15800922
Participants:5141
Impact:HR 0.88 (nonsignificant) — ~12% reduction
Trust score:3/5

prostate cancer incidence (baseline PSA <3 µg/L)

1 evidences

A large randomized trial of a multivitamin/mineral supplement (including zinc) vs placebo in men showed no significant overall reduction in prostate cancer, but a significant reduction in men with normal baseline PSA; PSA and IGF levels were unchanged.

Trust comment: Large randomized trial with long follow-up, but vitamin C was given in combination with other antioxidants and minerals, preventing attribution to vitamin C alone.

Study Details

PMID:15800922
Participants:5141
Impact:HR 1.54 (54% increase, borderline significance)
Trust score:3/5

ozone-associated FVC decline

1 evidences

Daily antioxidant supplementation (including high-dose vitamin C) attenuated ozone-associated declines in lung function among exposed workers compared with placebo.

Trust comment: Randomized crossover trial in humans with small sample; supplement contained high-dose vitamin C but also other antioxidants so effects cannot be solely attributed to vitamin C.

Study Details

PMID:9655734
Participants:47
Impact:attenuated; placebo association β = -1.60 ml/ppb, no decrement in supplement group (p<0.01)
Trust score:3/5

ozone-associated FEV1 decline

1 evidences

Daily antioxidant supplementation (including high-dose vitamin C) attenuated ozone-associated declines in lung function among exposed workers compared with placebo.

Trust comment: Randomized crossover trial in humans with small sample; supplement contained high-dose vitamin C but also other antioxidants so effects cannot be solely attributed to vitamin C.

Study Details

PMID:9655734
Participants:47
Impact:attenuated; placebo association β = -2.11 ml/ppb, no decrement in supplement group (p<0.01)
Trust score:3/5

ozone-associated FEF25-75 decline

1 evidences

Daily antioxidant supplementation (including high-dose vitamin C) attenuated ozone-associated declines in lung function among exposed workers compared with placebo.

Trust comment: Randomized crossover trial in humans with small sample; supplement contained high-dose vitamin C but also other antioxidants so effects cannot be solely attributed to vitamin C.

Study Details

PMID:9655734
Participants:47
Impact:attenuated; placebo association β = -4.92 ml/ppb, no decrement in supplement group (p<0.01)
Trust score:3/5

breast-milk cell-free HIV viral load (detectable proportion)

1 evidences

In HIV-infected breastfeeding women, a multivitamin (which included vitamin C) had no effect on HIV levels in breast milk, whereas β-carotene/preformed vitamin A increased detectable viral load.

Trust comment: Large randomized trial with repeated measures and clear reporting; direct effects of vitamin C (as part of multivitamin) were null.

Study Details

PMID:20739426
Participants:594
Impact:No change with multivitamin (includes vitamin C); VA/BC increased detectable proportion from 44.8% to 51.3% (P=0.02)
Trust score:4/5

breast-milk proviral (cell-associated) HIV load

1 evidences

In HIV-infected breastfeeding women, a multivitamin (which included vitamin C) had no effect on HIV levels in breast milk, whereas β-carotene/preformed vitamin A increased detectable viral load.

Trust comment: Large randomized trial with repeated measures and clear reporting; direct effects of vitamin C (as part of multivitamin) were null.

Study Details

PMID:20739426
Participants:594
Impact:No change with multivitamin or VA/BC
Trust score:4/5

brachial artery flow-mediated dilation (FMDBA)

1 evidences

Acute vitamin C infusion improved brachial artery flow-mediated dilation in older men with low testosterone but had no effect in young men or older men with higher testosterone.

Trust comment: Small, cross-sectional study with acute infusion intervention and clear physiological measures; modest sample size limits generalizability.

Study Details

PMID:34597384
Participants:58
Impact:Increase from 3.7% ±2.0% to 5.3% ±1.6% in middle-aged/older men with low testosterone (+~1.6 percentage points); no effect in other groups
Trust score:3/5

markers of oxidative stress/inflammation (IL-6, CRP, oxidized LDL, total antioxidant status)

1 evidences

Acute vitamin C infusion improved brachial artery flow-mediated dilation in older men with low testosterone but had no effect in young men or older men with higher testosterone.

Trust comment: Small, cross-sectional study with acute infusion intervention and clear physiological measures; modest sample size limits generalizability.

Study Details

PMID:34597384
Participants:58
Impact:Correlated with FMDBA but direct acute changes with vitamin C not reported
Trust score:3/5

anthropometric indices

1 evidences

Children given improved gruel with or without a multi-micronutrient mix (including iodine) both showed Hb increases; the micronutrient mix added no significant benefit.

Trust comment: Randomized community trial with modest sample size and clear outcomes; multi-nutrient composition limits attribution to vitamin C alone.

Study Details

PMID:20529401
Participants:131
Impact:No difference between groups
Trust score:3/5

placental nitrotyrosine immunostaining

1 evidences

In placentas from type 1 diabetic pregnancies, maternal vitamin C+E supplementation did not alter nitrotyrosine staining or activities of p38-MAPKα, ERK, or JNK.

Trust comment: Sub-cohort analysis from an RCT with small group sizes; negative results reported but limited power for subgroup comparisons.

Study Details

PMID:23558107
Participants:57
Impact:No significant change with vitamin C+E supplementation
Trust score:3/5

placental MAPK activities (p38-MAPKα, ERK, JNK)

1 evidences

In placentas from type 1 diabetic pregnancies, maternal vitamin C+E supplementation did not alter nitrotyrosine staining or activities of p38-MAPKα, ERK, or JNK.

Trust comment: Sub-cohort analysis from an RCT with small group sizes; negative results reported but limited power for subgroup comparisons.

Study Details

PMID:23558107
Participants:57
Impact:No significant change with vitamin C+E supplementation
Trust score:3/5

hemoglobin and transferrin saturation (%TS)

1 evidences

Increasing consumption of citrus fruit/juice (rich in vitamin C) after meals improved serum ferritin in iron-depleted preschool children over three months.

Trust comment: Randomized pilot study with small sample; results suggest association between increased vitamin-C-rich intake and ferritin but limited size and duration.

Study Details

PMID:15580808
Participants:62
Impact:No significant change between groups over three months
Trust score:3/5

urinary εdA excretion (DNA damage marker)

1 evidences

A 1-year dietary consultation aimed to reduce salt and increase vitamin C/carotene; urinary DNA-damage marker (εdA) tended to decrease in the intervention group but changes were not statistically significant.

Trust comment: Human dietary intervention with small sample and non-significant primary biomarker changes; vitamin C change part of multicomponent dietary advice.

Study Details

PMID:12115589
Participants:59
Impact:Intervention: 61 → 44 pmol (−17 pmol, ≈−28%; p=0.14); Control: 58 → 75 pmol (+17 pmol, p=0.24)
Trust score:3/5

proportion with decreased εdA

1 evidences

A 1-year dietary consultation aimed to reduce salt and increase vitamin C/carotene; urinary DNA-damage marker (εdA) tended to decrease in the intervention group but changes were not statistically significant.

Trust comment: Human dietary intervention with small sample and non-significant primary biomarker changes; vitamin C change part of multicomponent dietary advice.

Study Details

PMID:12115589
Participants:59
Impact:62% in intervention vs 38% in control (18/29 vs 10/26; p=0.08)
Trust score:3/5

pulmonary endothelium-dependent vasodilation

1 evidences

Perioperative antioxidant treatment (vitamin C plus other antioxidants) better preserved pulmonary endothelium-dependent vasodilation after cardiopulmonary bypass than placebo.

Trust comment: Small randomized double-blind human trial but used a combination antioxidant regimen so effects cannot be attributed to vitamin C alone.

Study Details

PMID:12827578
Participants:22
Impact:Better maintained in antioxidant group post-op (post-op decrease 20% vs 8% in placebo; between-group p=0.048)
Trust score:3/5

glutathione (oxidative status)

1 evidences

Perioperative antioxidant treatment (vitamin C plus other antioxidants) better preserved pulmonary endothelium-dependent vasodilation after cardiopulmonary bypass than placebo.

Trust comment: Small randomized double-blind human trial but used a combination antioxidant regimen so effects cannot be attributed to vitamin C alone.

Study Details

PMID:12827578
Participants:22
Impact:Glutathione and oxidized glutathione increased after CPB in treatment group
Trust score:3/5

prednisone requirement

1 evidences

In patients with mild–moderate ulcerative colitis, a multi-ingredient supplement (including vitamin C) did not change disease activity more than placebo but allowed a greater reduction in prednisone use over 6 months.

Trust comment: Randomized controlled trial with reasonable size but multi-ingredient formula and some baseline imbalance; effect is steroid-sparing rather than a clear vitamin C–specific effect.

Study Details

PMID:15822041
Participants:86
Impact:Significantly greater rate of decrease in prednisone dose in supplement group over 6 months (p < 0.001)
Trust score:3/5

disease activity index (DAI)

1 evidences

In patients with mild–moderate ulcerative colitis, a multi-ingredient supplement (including vitamin C) did not change disease activity more than placebo but allowed a greater reduction in prednisone use over 6 months.

Trust comment: Randomized controlled trial with reasonable size but multi-ingredient formula and some baseline imbalance; effect is steroid-sparing rather than a clear vitamin C–specific effect.

Study Details

PMID:15822041
Participants:86
Impact:Both groups improved similarly at 6 months (−2.5 supplement vs −2.8 placebo; no between-group difference)
Trust score:3/5

intervertebral disc (IVD) 3D volume

1 evidences

Randomized double-blind trial of a multi-nutrient supplement (including collagen type II) vs placebo for lumbar osteochondrosis; no differences in patient-reported outcomes, but supplement group showed significant increases in 3D-measured intervertebral disc (IVD) volumes.

Trust comment: Randomized double-blind RCT but small sample and multi-ingredient intervention limits attribution to vitamin C alone; MRI volume outcome significant but clinical PROMs were not.

Study Details

PMID:39203831
Participants:45
Impact:Supplement: +740.3 ± 796.1 mm³ vs Placebo: −417.2 ± 875.0 mm³ (between-group p < 0.001)
Trust score:3/5

Oswestry Disability Index (ODI)

1 evidences

Randomized double-blind trial of a multi-nutrient supplement (including collagen type II) vs placebo for lumbar osteochondrosis; no differences in patient-reported outcomes, but supplement group showed significant increases in 3D-measured intervertebral disc (IVD) volumes.

Trust comment: Randomized double-blind RCT but small sample and multi-ingredient intervention limits attribution to vitamin C alone; MRI volume outcome significant but clinical PROMs were not.

Study Details

PMID:39203831
Participants:45
Impact:No significant between-group difference in ODI (no clear clinical improvement)
Trust score:3/5

fasting insulin

1 evidences

Eating two kiwifruit daily increased vitamin C intake and lowered systolic blood pressure by ~2.7 mmHg over 7 weeks, without changing fasting insulin or other metabolic markers.

Trust comment: Randomized controlled trial with objective measures and documented vitamin C intake increase; modest sample size and short duration limit generalizability.

Study Details

PMID:35807858
Participants:43
Impact:No statistically significant change between groups
Trust score:4/5

bone mass

1 evidences

Daily consumption of a dairy product enriched with calcium, vitamin D and other bone‑supporting nutrients for 24 weeks improved bone mass and bone turnover markers and mitigated BMD loss in menopausal women at risk of osteoporosis.

Trust comment: Randomized double-blind RCT with moderate sample size but tests a multi-nutrient product so effects cannot be attributed to vitamin C alone.

Study Details

PMID:32722015
Participants:65
Impact:+0.01 kg (EG) vs −0.01 kg (CG); p < 0.05
Trust score:4/5

bone mineral density (BMD)

1 evidences

Daily consumption of a dairy product enriched with calcium, vitamin D and other bone‑supporting nutrients for 24 weeks improved bone mass and bone turnover markers and mitigated BMD loss in menopausal women at risk of osteoporosis.

Trust comment: Randomized double-blind RCT with moderate sample size but tests a multi-nutrient product so effects cannot be attributed to vitamin C alone.

Study Details

PMID:32722015
Participants:65
Impact:EG stable vs CG decline (EG: no change; CG: −0.01 kg/cm²); p < 0.05
Trust score:4/5

bone turnover markers (P1NP, CTx)

1 evidences

Daily consumption of a dairy product enriched with calcium, vitamin D and other bone‑supporting nutrients for 24 weeks improved bone mass and bone turnover markers and mitigated BMD loss in menopausal women at risk of osteoporosis.

Trust comment: Randomized double-blind RCT with moderate sample size but tests a multi-nutrient product so effects cannot be attributed to vitamin C alone.

Study Details

PMID:32722015
Participants:65
Impact:P1NP +13.19 ± 25.17 ng/mL (EG) vs −4.21 ± 15.62 (CG); CTx −0.05 ± 0.19 ng/mL (EG) vs 0.04 ± 0.14 (CG); p < 0.05
Trust score:4/5

parathyroid hormone (PTH)

1 evidences

Daily consumption of a dairy product enriched with calcium, vitamin D and other bone‑supporting nutrients for 24 weeks improved bone mass and bone turnover markers and mitigated BMD loss in menopausal women at risk of osteoporosis.

Trust comment: Randomized double-blind RCT with moderate sample size but tests a multi-nutrient product so effects cannot be attributed to vitamin C alone.

Study Details

PMID:32722015
Participants:65
Impact:decrease 4.49 ± 13.94 vs 1.93 ± 6.60 ng/mL (EG vs CG); p < 0.05
Trust score:4/5

developmental quotient (Griffiths)

1 evidences

Daily antioxidant (including 50 mg vitamin C) and/or folinic acid given in infancy produced no measurable benefit in development or language at 18 months.

Trust comment: Large, well-conducted randomized controlled trial in infants showing null results for antioxidant supplementation including vitamin C.

Study Details

PMID:18296460
Participants:156
Impact:mean 57.3 vs 56.1 (antioxidants vs none); adjusted mean difference 1.2 points (95% CI −2.2 to 4.6); no significant effect
Trust score:5/5

expressive vocabulary (words said/signed)

1 evidences

Daily antioxidant (including 50 mg vitamin C) and/or folinic acid given in infancy produced no measurable benefit in development or language at 18 months.

Trust comment: Large, well-conducted randomized controlled trial in infants showing null results for antioxidant supplementation including vitamin C.

Study Details

PMID:18296460
Participants:156
Impact:no significant difference (antioxidants ratio of means 0.85, 95% CI 0.6 to 1.2)
Trust score:5/5

biochemical markers

1 evidences

Daily antioxidant (including 50 mg vitamin C) and/or folinic acid given in infancy produced no measurable benefit in development or language at 18 months.

Trust comment: Large, well-conducted randomized controlled trial in infants showing null results for antioxidant supplementation including vitamin C.

Study Details

PMID:18296460
Participants:156
Impact:no significant between-group differences at 12 months
Trust score:5/5

adherence

1 evidences

Home fortification micronutrient powder (contains vitamin C among others) was at least as effective as iron–folic acid tablets in maintaining hemoglobin during pregnancy, though adherence was lower.

Trust comment: Large cluster-randomized noninferiority trial with pragmatic design, but intervention is a multi-nutrient powder so effects cannot be isolated to vitamin C.

Study Details

PMID:22908696
Participants:478
Impact:powder 57.5% ± 22.5 vs tablets 76.0% ± 13.7 (difference −18.5 pp approx.)
Trust score:4/5

augmentation index (AIx) and blood pressure

1 evidences

In healthy young adults a single antioxidant cocktail (including vitamin C) taken before a high-sodium meal did not change endothelial function or arterial stiffness compared with placebo.

Trust comment: Randomized, crossover design in humans but small, acute study using a combined antioxidant cocktail so isolating vitamin C effects is not possible.

Study Details

PMID:32610254
Participants:41
Impact:no difference between antioxidant and placebo across time
Trust score:4/5

sequential organ failure assessment (SOFA) score

1 evidences

Five-day IV antioxidant regimen (including high-dose vitamin C) did not improve early organ dysfunction (SOFA) or AKI overall, but reduced CRP (blunted inflammation) and showed some shorter hospital stay in trauma subgroup.

Trust comment: Well-designed randomized double-blind trial in critically ill patients with sufficient size, but single-center with protocol violations and multi-nutrient intervention limits attribution to vitamin C alone.

Study Details

PMID:18687132
Participants:200
Impact:no significant difference between AOX and placebo over first 5 days
Trust score:4/5

acute kidney injury (AKI)

1 evidences

Five-day IV antioxidant regimen (including high-dose vitamin C) did not improve early organ dysfunction (SOFA) or AKI overall, but reduced CRP (blunted inflammation) and showed some shorter hospital stay in trauma subgroup.

Trust comment: Well-designed randomized double-blind trial in critically ill patients with sufficient size, but single-center with protocol violations and multi-nutrient intervention limits attribution to vitamin C alone.

Study Details

PMID:18687132
Participants:200
Impact:no significant difference in incidence (AOX 29% vs placebo 37%; P = 0.11)
Trust score:4/5

fatigue severity (FSS)

1 evidences

Adults with mild-to-moderate prolonged fatigue who took a pomegranate extract plus water-soluble vitamins (including 200 mg vitamin C) for 2 months reported reduced fatigue severity versus placebo; biomarkers showed no clear treatment-specific changes.

Trust comment: Randomized double-blind placebo-controlled study showing symptom benefit but small single-center sample and combined supplement mean effects cannot be ascribed solely to vitamin C.

Study Details

PMID:37447210
Participants:58
Impact:treatment group FSS lower at 56 days: difference −0.86 ± 0.18 (p < 0.001) and at follow-up −1.55 ± 0.18 (p < 0.001) vs placebo
Trust score:4/5

quality of life (SF-12)

1 evidences

Adults with mild-to-moderate prolonged fatigue who took a pomegranate extract plus water-soluble vitamins (including 200 mg vitamin C) for 2 months reported reduced fatigue severity versus placebo; biomarkers showed no clear treatment-specific changes.

Trust comment: Randomized double-blind placebo-controlled study showing symptom benefit but small single-center sample and combined supplement mean effects cannot be ascribed solely to vitamin C.

Study Details

PMID:37447210
Participants:58
Impact:no significant between-group change (trend toward improvement in supplement group; p = 0.91)
Trust score:4/5

inflammatory marker IL-6

1 evidences

Adults with mild-to-moderate prolonged fatigue who took a pomegranate extract plus water-soluble vitamins (including 200 mg vitamin C) for 2 months reported reduced fatigue severity versus placebo; biomarkers showed no clear treatment-specific changes.

Trust comment: Randomized double-blind placebo-controlled study showing symptom benefit but small single-center sample and combined supplement mean effects cannot be ascribed solely to vitamin C.

Study Details

PMID:37447210
Participants:58
Impact:higher overall in supplement group (difference 0.48 ± 0.24; p = 0.050) though no treatment × time interaction
Trust score:4/5

serum alpha-tocopherol

1 evidences

Analysis of factors linked to blood vitamin E levels in postmenopausal women; supplemental vitamin C was associated with higher alpha- and lower gamma-tocopherol.

Trust comment: Large, well-characterized observational cohort with confounder adjustment but cross-sectional associations limit causal inference.

Study Details

PMID:11164130
Participants:1047
Impact:increase (associated with supplemental vitamin C)
Trust score:3/5

total serum cholesterol/triglycerides (covariate)

1 evidences

Analysis of factors linked to blood vitamin E levels in postmenopausal women; supplemental vitamin C was associated with higher alpha- and lower gamma-tocopherol.

Trust comment: Large, well-characterized observational cohort with confounder adjustment but cross-sectional associations limit causal inference.

Study Details

PMID:11164130
Participants:1047
Impact:controlled for in analyses
Trust score:3/5

f-2 isoprostane (oxidative stress marker)

1 evidences

In hemodialysis patients, an antioxidant cocktail that included vitamin B12 did not change markers of oxidative stress or inflammation over 8 weeks.

Trust comment: Randomized placebo-controlled design but small sample and use of a multi-vitamin cocktail prevents attribution of effects specifically to vitamin C.

Study Details

PMID:19397224
Participants:37
Impact:no change
Trust score:3/5

IL-6 (inflammation marker)

1 evidences

In hemodialysis patients, an antioxidant cocktail that included vitamin B12 did not change markers of oxidative stress or inflammation over 8 weeks.

Trust comment: Randomized placebo-controlled design but small sample and use of a multi-vitamin cocktail prevents attribution of effects specifically to vitamin C.

Study Details

PMID:19397224
Participants:37
Impact:no change
Trust score:3/5

baseline serum antioxidant concentrations

1 evidences

Large prospective cohort of male smokers found no link between dietary or serum antioxidant vitamins (including vitamin C) and colorectal cancer risk.

Trust comment: Large prospective cohort with adjustment for major confounders; high sample size supports reliability.

Study Details

PMID:12080400
Participants:26951
Impact:no association with colorectal cancer risk
Trust score:4/5

basal metabolic rate

1 evidences

Randomized 8-week trial: adding fruit or nuts raised serum vitamin C in both groups; no change in hepatic fat; basal metabolic rate increased in the nut group.

Trust comment: Randomized human trial with objective biochemical and MRI outcomes but small sample size limits precision.

Study Details

PMID:26788923
Participants:30
Impact:Nut group: 1931 → 2031 kcal/24h (+100 kcal, p=0.028); Fruit group: no significant change
Trust score:4/5

hepatic fat content

1 evidences

Randomized 8-week trial: adding fruit or nuts raised serum vitamin C in both groups; no change in hepatic fat; basal metabolic rate increased in the nut group.

Trust comment: Randomized human trial with objective biochemical and MRI outcomes but small sample size limits precision.

Study Details

PMID:26788923
Participants:30
Impact:no significant change in either group (p>0.4)
Trust score:4/5

Low birth weight

1 evidences

In HIV-infected pregnant women, multivitamin supplements (including vitamin C) at single versus multiple RDA doses produced similar pregnancy outcomes.

Trust comment: Large, double-blind randomized trial with clear endpoints, but vitamin C was one component of multivitamins so effects cannot be isolated to vitamin C.

Study Details

PMID:19939985
Participants:1129
Impact:11.6% (multiple RDA) vs 10.2% (single RDA); P=0.75 (no significant difference)
Trust score:4/5

Preterm birth

1 evidences

In HIV-infected pregnant women, multivitamin supplements (including vitamin C) at single versus multiple RDA doses produced similar pregnancy outcomes.

Trust comment: Large, double-blind randomized trial with clear endpoints, but vitamin C was one component of multivitamins so effects cannot be isolated to vitamin C.

Study Details

PMID:19939985
Participants:1129
Impact:19.3% vs 18.4%; P=0.73 (no significant difference)
Trust score:4/5

pain score

1 evidences

In children undergoing outpatient pin removal, acetaminophen or ibuprofen did not reduce pain compared with placebo (vitamin C used as placebo).

Trust comment: Large randomized controlled trial (n=240) with clear outcomes and no effect of the vitamin C placebo on pain or heart rate.

Study Details

PMID:24695927
Participants:240
Impact:no significant difference vs vitamin C placebo
Trust score:4/5

insulin sensitivity (metabolic clearance rate of glucose)

1 evidences

In patients with type 2 diabetes, a calorie-restricted vegetarian diet (± exercise) improved insulin sensitivity, reduced visceral fat, and increased plasma vitamin C versus a conventional diet.

Trust comment: Randomized, parallel, metabolically controlled 24-week trial (n=74) with objective clamp and imaging outcomes; moderate sample size but robust measures.

Study Details

PMID:21480966
Participants:74
Impact:increased by 30% in vegetarian group vs 20% in control (group × time P = 0.04)
Trust score:4/5

visceral fat volume

1 evidences

In patients with type 2 diabetes, a calorie-restricted vegetarian diet (± exercise) improved insulin sensitivity, reduced visceral fat, and increased plasma vitamin C versus a conventional diet.

Trust comment: Randomized, parallel, metabolically controlled 24-week trial (n=74) with objective clamp and imaging outcomes; moderate sample size but robust measures.

Study Details

PMID:21480966
Participants:74
Impact:further decrease (~4% after added exercise) in vegetarian group vs no change in control (group × time P = 0.007)
Trust score:4/5

vitamin C intake (FFQ-derived)

1 evidences

The FAVVA brief index correlates moderately-strongly with total daily vegetable/fruit intake and with multiple nutrient intakes (including calcium) and plasma carotenoids.

Trust comment: Validation study with moderate sample (n=99) showing strong correlation between brief index and estimated vitamin C intake, but not an interventional trial on vitamin C effects.

Study Details

PMID:30661686
Participants:99
Impact:strong correlation with FAVVA (r = 0.71, p < 0.01)
Trust score:3/5

plasma total carotenoids

1 evidences

The FAVVA brief index correlates moderately-strongly with total daily vegetable/fruit intake and with multiple nutrient intakes (including calcium) and plasma carotenoids.

Trust comment: Validation study with moderate sample (n=99) showing strong correlation between brief index and estimated vitamin C intake, but not an interventional trial on vitamin C effects.

Study Details

PMID:30661686
Participants:99
Impact:moderate correlation with FAVVA (r = 0.18–0.26, p ≤ 0.05)
Trust score:3/5

LF/HF ratio (autonomic balance)

1 evidences

Hemodialysis patients received a multi-nutrient drink (includes 30 µg B12) or placebo for 12 weeks; the supplement improved some objective autonomic and immune markers but not subjective fatigue versus placebo.

Trust comment: Large randomized double-blind multicenter RCT (n=202) with objective autonomic and virological measures, but intervention combined multiple nutrients so individual vitamin C effect unclear.

Study Details

PMID:25746727
Participants:174
Impact:increase in changes (0–12 weeks) in nutritional drink vs placebo (significant)
Trust score:4/5

HHV7 reactivation (saliva DNA copies)

1 evidences

Hemodialysis patients received a multi-nutrient drink (includes 30 µg B12) or placebo for 12 weeks; the supplement improved some objective autonomic and immune markers but not subjective fatigue versus placebo.

Trust comment: Large randomized double-blind multicenter RCT (n=202) with objective autonomic and virological measures, but intervention combined multiple nutrients so individual vitamin C effect unclear.

Study Details

PMID:25746727
Participants:174
Impact:significant decrease with nutritional supplementation (P = 0.016)
Trust score:4/5

fatigue scores (subjective)

1 evidences

Hemodialysis patients received a multi-nutrient drink (includes 30 µg B12) or placebo for 12 weeks; the supplement improved some objective autonomic and immune markers but not subjective fatigue versus placebo.

Trust comment: Large randomized double-blind multicenter RCT (n=202) with objective autonomic and virological measures, but intervention combined multiple nutrients so individual vitamin C effect unclear.

Study Details

PMID:25746727
Participants:174
Impact:no significant difference vs placebo (placebo effect observed)
Trust score:4/5

ghrelin

1 evidences

In women, interpersonal stressors were associated with higher ghrelin, lower leptin, and small/marginal increases in several dietary components including vitamin C intake.

Trust comment: Small observational study (n=50) with repeated measures linking stressors to hormones and diet; vitamin C appears only as part of dietary associations.

Study Details

PMID:25032903
Participants:50
Impact:higher levels associated with more interpersonal stressors
Trust score:3/5

Overall fetal loss / early infant mortality (multiple micronutrients including vitamin C)

1 evidences

Maternal multiple micronutrient supplements (which included 10 µg vitamin D) did not reduce overall fetal loss or early infant mortality; effects of vitamin D alone were not separable.

Trust comment: Large, double-blind cluster-RCT with high sample size; vitamin C was included only as part of a multiple micronutrient supplement so effects cannot be attributed to vitamin C alone.

Study Details

PMID:14668283
Participants:4926
Impact:No reduction compared with control (vitamin A only)
Trust score:4/5

3-month mortality in preterm infants

1 evidences

Maternal multiple micronutrient supplements (which included 10 µg vitamin D) did not reduce overall fetal loss or early infant mortality; effects of vitamin D alone were not separable.

Trust comment: Large, double-blind cluster-RCT with high sample size; vitamin C was included only as part of a multiple micronutrient supplement so effects cannot be attributed to vitamin C alone.

Study Details

PMID:14668283
Participants:4926
Impact:Reduced with folic acid alone (RR 0.36, 95% CI 0.18–0.75) and with folic acid+iron (RR 0.53, 95% CI 0.30–0.92); no benefit seen with multiple micronutrients
Trust score:4/5

3-month mortality in term infants (multiple micronutrients including vitamin C)

1 evidences

Maternal multiple micronutrient supplements (which included 10 µg vitamin D) did not reduce overall fetal loss or early infant mortality; effects of vitamin D alone were not separable.

Trust comment: Large, double-blind cluster-RCT with high sample size; vitamin C was included only as part of a multiple micronutrient supplement so effects cannot be attributed to vitamin C alone.

Study Details

PMID:14668283
Participants:4926
Impact:Increased risk reported with multiple micronutrients (RR 1.74, 95% CI 1.00–3.04)
Trust score:4/5

blood triglycerides

1 evidences

New parenteral nutrition with multivitamins increased blood vitamin C and was safely tolerated in healthy volunteers.

Trust comment: Phase I randomized active-controlled trial in healthy volunteers with small sample size and open-label elements limiting generalizability.

Study Details

PMID:35871950
Participants:46
Impact:transient increase after OPF-105 administration that returned to baseline
Trust score:3/5

blood urea nitrogen (BUN)

1 evidences

New parenteral nutrition with multivitamins increased blood vitamin C and was safely tolerated in healthy volunteers.

Trust comment: Phase I randomized active-controlled trial in healthy volunteers with small sample size and open-label elements limiting generalizability.

Study Details

PMID:35871950
Participants:46
Impact:gradual increase in BFI group but not in OPF-105 group (suggesting less protein breakdown in OPF)
Trust score:3/5

protein intake

1 evidences

Randomized trial comparing GUMLi formula vs cows' milk in toddlers; reports nutrient intake differences including higher vitamin D intake in the GUMLi group.

Trust comment: Multi-centre, double-blind RCT with repeated dietary assessments and adequate sample size.

Study Details

PMID:30912737
Participants:160
Impact:lower in GUMLi group at 2 years
Trust score:4/5

vitamin B12 intake

1 evidences

Randomized trial comparing GUMLi formula vs cows' milk in toddlers; reports nutrient intake differences including higher vitamin D intake in the GUMLi group.

Trust comment: Multi-centre, double-blind RCT with repeated dietary assessments and adequate sample size.

Study Details

PMID:30912737
Participants:160
Impact:lower in GUMLi group at 2 years
Trust score:4/5

serum glutathione

1 evidences

In a large 7.3‑year randomized trial (n=3411), garlic increased serum folate and a vitamin+selenium supplement increased glutathione, but neither intervention changed serum vitamin B12 or homocysteine.

Trust comment: Large randomized, double-blind, placebo-controlled trial with long duration; this result comes from a planned subset analysis of sera.

Study Details

PMID:19056661
Participants:3411
Impact:increased by 13.4% after 7.3 years of vitamin and selenium supplementation
Trust score:4/5

serum vitamin B-12

1 evidences

In a large 7.3‑year randomized trial (n=3411), garlic increased serum folate and a vitamin+selenium supplement increased glutathione, but neither intervention changed serum vitamin B12 or homocysteine.

Trust comment: Large randomized, double-blind, placebo-controlled trial with long duration; this result comes from a planned subset analysis of sera.

Study Details

PMID:19056661
Participants:3411
Impact:no significant change with vitamin+selenium supplementation
Trust score:4/5

interaction of nitrate exposure with vitamin C intake

1 evidences

In this cohort, vitamin C intake did not modify associations between nitrate exposure and pancreatic cancer risk.

Trust comment: Large prospective cohort with long follow-up but observational design and potential residual confounding limit causal inference.

Study Details

PMID:28921575
Participants:34242
Impact:no interaction detected (vitamin C did not modify nitrate–pancreatic cancer relationship)
Trust score:3/5

dietary nitrite from processed meat

1 evidences

In this cohort, vitamin C intake did not modify associations between nitrate exposure and pancreatic cancer risk.

Trust comment: Large prospective cohort with long follow-up but observational design and potential residual confounding limit causal inference.

Study Details

PMID:28921575
Participants:34242
Impact:suggested positive association with pancreatic cancer (HR ~1.66 highest vs lowest intake)
Trust score:3/5

Heart rate variability

1 evidences

Controlled exposure to fine particulates (± ozone) increased diastolic blood pressure and, in one location, impaired endothelial function; high-dose vitamin C (2 g) pretreatment did not prevent the BP rise or endothelial impairment.

Trust comment: Randomized, double-blind, crossover human exposure study with objective vascular and BP measures; moderate sample size and clear negative finding for high-dose vitamin C as a mitigator.

Study Details

PMID:19620518
Participants:81
Impact:Reductions associated with particle-containing exposures (vitamin C pretreatment did not prevent BP response)
Trust score:4/5

cardiovascular disease risk

1 evidences

Among 867 newly diagnosed type 2 diabetes patients, adopting multiple healthy behaviors within 1 year was linked to lower cardiovascular disease risk over ~5 years (plasma vitamin C was used as a diet marker).

Trust comment: Large population-based prospective cohort with objective (plasma vitamin C) and clinical outcomes but observational design limits causal inference.

Study Details

PMID:24658389
Participants:867
Impact:RR 4.17 higher in individuals who made no health behavior changes versus those who adopted 3–4 changes (implies ~76% lower risk in adopters)
Trust score:3/5

plasma vitamin C (diet marker)

1 evidences

Among 867 newly diagnosed type 2 diabetes patients, adopting multiple healthy behaviors within 1 year was linked to lower cardiovascular disease risk over ~5 years (plasma vitamin C was used as a diet marker).

Trust comment: Large population-based prospective cohort with objective (plasma vitamin C) and clinical outcomes but observational design limits causal inference.

Study Details

PMID:24658389
Participants:867
Impact:measured at baseline and 1 year as part of diet assessment; no specific effect size on outcomes reported
Trust score:3/5

number of healthy behavior changes

1 evidences

Among 867 newly diagnosed type 2 diabetes patients, adopting multiple healthy behaviors within 1 year was linked to lower cardiovascular disease risk over ~5 years (plasma vitamin C was used as a diet marker).

Trust comment: Large population-based prospective cohort with objective (plasma vitamin C) and clinical outcomes but observational design limits causal inference.

Study Details

PMID:24658389
Participants:867
Impact:inverse association with CVD risk (P for trend = 0.005)
Trust score:3/5

progression to late age-related macular degeneration (late AMD)

2 evidences

In 1,237 genotyped AREDS participants, response to AREDS supplement components (including vitamin C) reduced progression to late AMD across genotype groups with no significant genotype-by-treatment interaction.

Trust comment: Secondary analysis of a large randomized, placebo-controlled trial (AREDS) with long follow-up; robust dataset though analysis is retrospective.

Study Details

PMID:24974817
Participants:1237
Impact:AREDS supplements (antioxidants including vitamin C) reduced progression across genotypes; 385/1237 (31.1%) developed late AMD over mean 6.6 years; no significant genotype interaction with treatment response
Trust score:4/5

Pooled post-hoc analysis of AREDS and AREDS2 cohorts (8,242 participants) found higher dietary intake of multiple nutrients, including vitamin C (top quintiles), was associated with decreased risk of progression to late AMD over ~10 years.

Trust comment: Large observational/post-hoc analysis with long follow-up and dietary data but subject to confounding and measurement error inherent to FFQs and observational design.

Study Details

PMID:32858063
Participants:8242
Impact:higher dietary vitamin C intake (quintiles 4–5 vs 1) associated with decreased risk of late AMD (significant at P≤0.0005 as part of multiple nutrient associations)
Trust score:3/5

supplement effect consistency across genotypes

1 evidences

In 1,237 genotyped AREDS participants, response to AREDS supplement components (including vitamin C) reduced progression to late AMD across genotype groups with no significant genotype-by-treatment interaction.

Trust comment: Secondary analysis of a large randomized, placebo-controlled trial (AREDS) with long follow-up; robust dataset though analysis is retrospective.

Study Details

PMID:24974817
Participants:1237
Impact:no evidence that CFH or ARMS2 genotypes altered relative benefit of AREDS components (interaction P values not significant)
Trust score:4/5

high-molecular-weight (HMW) adiponectin

1 evidences

In a randomized crossover trial of overweight/obese adolescents (58 completers), an anti-inflammatory supplement containing vitamin C maintained high-molecular-weight adiponectin but did not change insulin resistance overall; a subgroup (n=23) showed ≥10% improvement in HOMA-IR.

Trust comment: Randomized, double-blind, placebo-controlled crossover with biologic measures and compliance data, though sample size is modest and supplement was multi-nutrient (vitamin C not isolated).

Study Details

PMID:29665620
Participants:58
Impact:maintained by the AINS versus decrease with placebo (intervention p=0.004)
Trust score:4/5

adiponectin receptor mRNA (ADIPOR1/2) in PBMC

1 evidences

In a randomized crossover trial of overweight/obese adolescents (58 completers), an anti-inflammatory supplement containing vitamin C maintained high-molecular-weight adiponectin but did not change insulin resistance overall; a subgroup (n=23) showed ≥10% improvement in HOMA-IR.

Trust comment: Randomized, double-blind, placebo-controlled crossover with biologic measures and compliance data, though sample size is modest and supplement was multi-nutrient (vitamin C not isolated).

Study Details

PMID:29665620
Participants:58
Impact:increased expression after AINS relative to placebo (reported as significant)
Trust score:4/5

antioxidant/oxidative stress markers

1 evidences

Pilot randomized trial in 44 critically ill adults found enteral or parenteral alanyl-glutamine did not change plasma vitamin C, glutathione, markers of oxidative stress, lymphocyte subsets, gut permeability, or nitrogen balance compared to control by day 9.

Trust comment: Double-blind pilot RCT with direct biochemical measures but small sample and limited duration reduces confidence in null findings.

Study Details

PMID:18258342
Participants:44
Impact:no between-group differences for glutathione, MDA, or overall antioxidant indices
Trust score:3/5

urinary 11-dehydro-TXB2 / 2,3-dinor-6-keto-PGF1α ratio (platelet activation marker)

1 evidences

In 186 generally healthy volunteers randomized to low-dose multi-antioxidant supplementation (including vitamin C) or placebo for two years, the supplemented group had a lower urinary thromboxane/prostacyclin metabolite ratio, suggesting reduced platelet activation.

Trust comment: Randomized, double-blind, placebo-controlled trial with clinically relevant biomarker outcome and moderate size, but supplement was a multi-antioxidant formulation so vitamin C-specific effects are not isolated.

Study Details

PMID:17914127
Participants:186
Impact:median ratio lower in supplement group (2.78) versus placebo (3.4); p=0.015
Trust score:3/5

blood vitamin C concentration

1 evidences

In 186 generally healthy volunteers randomized to low-dose multi-antioxidant supplementation (including vitamin C) or placebo for two years, the supplemented group had a lower urinary thromboxane/prostacyclin metabolite ratio, suggesting reduced platelet activation.

Trust comment: Randomized, double-blind, placebo-controlled trial with clinically relevant biomarker outcome and moderate size, but supplement was a multi-antioxidant formulation so vitamin C-specific effects are not isolated.

Study Details

PMID:17914127
Participants:186
Impact:measured but not reported as significantly increased (study reports significant increases for zinc, selenium, and beta-carotene)
Trust score:3/5

sperm concentration (change at 3 months)

1 evidences

A randomized, double-blind trial of a multi-ingredient antioxidant (including 500 mg vitamin C) found no improvement in semen parameters, sperm DNA fragmentation, or live-birth rates versus placebo.

Trust comment: Well-conducted multicenter double-blind RCT, but intervention was a multi-ingredient antioxidant formulation so vitamin C–specific effects cannot be isolated; sample size limited for live-birth outcome.

Study Details

PMID:32111479
Participants:174
Impact:Antioxidant median −4.0 million/mL vs placebo +2.4 million/mL
Trust score:4/5

sperm motility / morphology / DNA fragmentation

1 evidences

A randomized, double-blind trial of a multi-ingredient antioxidant (including 500 mg vitamin C) found no improvement in semen parameters, sperm DNA fragmentation, or live-birth rates versus placebo.

Trust comment: Well-conducted multicenter double-blind RCT, but intervention was a multi-ingredient antioxidant formulation so vitamin C–specific effects cannot be isolated; sample size limited for live-birth outcome.

Study Details

PMID:32111479
Participants:174
Impact:No statistically significant change
Trust score:4/5

cumulative live birth (6 months)

1 evidences

A randomized, double-blind trial of a multi-ingredient antioxidant (including 500 mg vitamin C) found no improvement in semen parameters, sperm DNA fragmentation, or live-birth rates versus placebo.

Trust comment: Well-conducted multicenter double-blind RCT, but intervention was a multi-ingredient antioxidant formulation so vitamin C–specific effects cannot be isolated; sample size limited for live-birth outcome.

Study Details

PMID:32111479
Participants:174
Impact:15% (antioxidant) vs 24% (placebo)
Trust score:4/5

HDP incidence overall

1 evidences

Large multicenter prospective study found no overall reduction in hypertensive disorders of pregnancy (HDP) with antioxidants, but reported reduced HDP incidence in a predefined high-risk subgroup.

Trust comment: Large multicenter prospective randomized allocation, but limited reporting on blinding and intervention combined vitamins with herbal medicine; subgroup benefit reported.

Study Details

PMID:21034626
Participants:4814
Impact:3.55% (antioxidants) vs 4.18% (control); no significant difference
Trust score:3/5

HDP incidence in high-risk women

1 evidences

Large multicenter prospective study found no overall reduction in hypertensive disorders of pregnancy (HDP) with antioxidants, but reported reduced HDP incidence in a predefined high-risk subgroup.

Trust comment: Large multicenter prospective randomized allocation, but limited reporting on blinding and intervention combined vitamins with herbal medicine; subgroup benefit reported.

Study Details

PMID:21034626
Participants:4814
Impact:7.14% → 3.81% (control → antioxidants); −3.33 percentage points (P < 0.01)
Trust score:3/5