Vitamin C Scientific References and Clinical Study Library

Search for Vitamin C online and you will find confident claims on every side, but rarely the studies behind them. This library fixes that. It gathers the key human trials, reviews, safety studies, mechanistic papers and animal studies on ascorbic acid in one place, labels each by the strength of its evidence, and links to the original record wherever a DOI or official page exists. Use it to check a claim, trace a statistic to its source, or find the right paper to read next. Everything here is organized so you can tell a randomized trial from a test-tube result at a glance.

How This Vitamin C References Library Is Organized

The library is arranged from the strongest kind of human evidence to the weakest, then moves to laboratory and animal work. Each entry gives the full citation, a link, and one line on what it adds.

Evidence tier key

• Human, clinical: systematic reviews, meta-analyses and randomized controlled trials (RCTs) in people. These are the best basis for conclusions about health outcomes.
• Human, observational: cohort and similar studies. They reveal associations and safety signals but cannot prove cause and effect.
• Human, pharmacokinetic: studies of how the body absorbs, distributes and excretes the vitamin. They explain dosing but do not show health benefit.
• Mechanistic: biochemical and cell-level work that explains how something might work.
• Preclinical: animal and cell-culture experiments. Results often fail to carry over to people.

A mechanism or an animal result is a reason to run a human trial, not evidence of a human benefit. We keep these tiers separate throughout. Our companion article on the clinical evidence explains what the human trials show in plain language.

Systematic Reviews

Systematic reviews use predefined methods to find and appraise all relevant studies on a question. Tier: human, clinical.

• Hemila H, Chalker E. Vitamin C for preventing and treating the common cold. Cochrane Database Syst Rev. 2013;(1):CD000980. DOI. Pooled trials showing little effect on how many colds occur in the general population, a modest shortening of colds, and a possible preventive effect under extreme physical stress.
• Al-Khudairy L, Flowers N, Wheelhouse R, et al. Vitamin C supplementation for the primary prevention of cardiovascular disease. Cochrane Database Syst Rev. 2017;(3):CD011114. DOI. Found no evidence that supplementation reduces cardiovascular events.
• Bjelakovic G, Nikolova D, Gluud C, et al. Antioxidant supplements for prevention of mortality in healthy participants and patients with various diseases. Cochrane Database Syst Rev. 2012;(3):CD007176. DOI. No convincing mortality benefit for ascorbic acid; raised concerns about some other antioxidants.

Meta-Analyses

Meta-analyses statistically combine results from several trials. Tier: human, clinical.

• Juraschek SP, Guallar E, Appel LJ, Miller ER 3rd. Effects of vitamin C supplementation on blood pressure: a meta-analysis of randomized controlled trials. Am J Clin Nutr. 2012;95(5):1079-1088. DOI. Small average reductions in blood pressure across short trials.
• Juraschek SP, Miller ER 3rd, Gelber AC. Effect of oral vitamin C supplementation on serum uric acid: a meta-analysis of randomized controlled trials. Arthritis Care Res. 2011;63(9):1295-1306. DOI. Modest lowering of a laboratory marker; effect on gout attacks not established.

Randomized Controlled Trials

RCTs assign participants by chance to treatment or comparison, which limits bias. Tier: human, clinical.

• Sesso HD, Buring JE, Christen WG, et al. Vitamins E and C in the prevention of cardiovascular disease in men: the Physicians' Health Study II randomized controlled trial. JAMA. 2008;300(18):2123-2133. DOI. No reduction in major cardiovascular events in male physicians.
• Gaziano JM, Glynn RJ, Christen WG, et al. Vitamins E and C in the prevention of prostate and total cancer in men: the Physicians' Health Study II randomized controlled trial. JAMA. 2009;301(1):52-62. DOI. No reduction in prostate or total cancer.
• Cook NR, Albert CM, Gaziano JM, et al. A randomized factorial trial of vitamins C and E and beta carotene in the secondary prevention of cardiovascular events in women: the Women's Antioxidant Cardiovascular Study. Arch Intern Med. 2007;167(15):1610-1618. DOI. No effect in women at higher cardiovascular risk.
• AREDS Research Group. A randomized, placebo-controlled, clinical trial of high-dose supplementation with vitamins C and E, beta carotene, and zinc for age-related macular degeneration and vision loss: AREDS report no. 8. Arch Ophthalmol. 2001;119(10):1417-1436. DOI. Combination formula reduced progression to advanced disease; the vitamin's own contribution cannot be separated.
• Moertel CG, Fleming TR, Creagan ET, et al. High-dose vitamin C versus placebo in the treatment of patients with advanced cancer who have had no prior chemotherapy. N Engl J Med. 1985;312(3):137-141. DOI. No survival benefit from 10 g daily by mouth.
• Fowler AA 3rd, Truwit JD, Hite RD, et al. Effect of vitamin C infusion on organ failure and biomarkers of inflammation and vascular injury in patients with sepsis and severe acute respiratory failure: the CITRIS-ALI randomized clinical trial. JAMA. 2019;322(13):1261-1270. DOI. Primary organ-failure outcome not improved.
• Fujii T, Luethi N, Young PJ, et al. Effect of vitamin C, hydrocortisone, and thiamine vs hydrocortisone alone on time alive and free of vasopressor support among patients with septic shock: the VITAMINS randomized clinical trial. JAMA. 2020;323(5):423-431. DOI. No improvement in the primary outcome.
• Lamontagne F, Masse MH, Menard J, et al. Intravenous vitamin C in adults with sepsis in the intensive care unit. N Engl J Med. 2022;386(25):2387-2398. DOI. More death or persistent organ dysfunction with the infusion than with placebo.
• Ma Y, Chapman J, Levine M, et al. High-dose parenteral ascorbate enhanced chemosensitivity of ovarian cancer and reduced toxicity of chemotherapy. Sci Transl Med. 2014;6(222):222ra18. DOI. Early-phase study combining laboratory and small clinical components; cannot show survival benefit.
• Paulsen G, Cumming KT, Holden G, et al. Vitamin C and E supplementation hampers cellular adaptation to endurance training in humans: a double-blind, randomised, controlled trial. J Physiol. 2014;592(8):1887-1901. Link: locate via PubMed title search. Suggests high doses may blunt some training adaptations.

Observational Human Studies

These studies follow people without assigning treatment. Tier: human, observational. Treat findings as associations.

• Khaw KT, Bingham S, Welch A, et al. Relation between plasma ascorbic acid and mortality in men and women in EPIC-Norfolk prospective study. Lancet. 2001;357(9257):657-663. DOI. Higher blood levels were associated with lower mortality, which may reflect overall diet and lifestyle.
• Harding AH, Wareham NJ, Bingham SA, et al. Plasma vitamin C level, fruit and vegetable consumption, and the risk of new-onset type 2 diabetes mellitus: the EPIC-Norfolk prospective study. Arch Intern Med. 2008;168(14):1493-1499. DOI. Higher plasma levels were associated with lower diabetes risk.
• Thomas LD, Elinder CG, Tiselius HG, Wolk A, Akesson A. Ascorbic acid supplements and kidney stone incidence among men: a prospective study. JAMA Intern Med. 2013;173(5):386-388. DOI. Supplement users had a higher rate of kidney stones.

Pharmacokinetic Studies

These describe absorption and blood levels. Tier: human, pharmacokinetic.

• Levine M, Conry-Cantilena C, Wang Y, et al. Vitamin C pharmacokinetics in healthy volunteers: evidence for a Recommended Dietary Allowance. Proc Natl Acad Sci USA. 1996;93(8):3704-3709. DOI. Blood levels plateau at modest daily intakes.
• Levine M, Rumsey SC, Daruwala R, Park JB, Wang Y. Criteria and recommendations for vitamin C intake. JAMA. 1999;281(15):1415-1423. DOI. Frames dose recommendations around plasma saturation.
• Padayatty SJ, Sun H, Wang Y, et al. Vitamin C pharmacokinetics: implications for oral and intravenous use. Ann Intern Med. 2004;140(7):533-537. DOI. Shows IV dosing reaches far higher concentrations than oral dosing.

Safety and Toxicology Studies

Tier: mixed; noted per entry.

• Institute of Medicine. Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium, and Carotenoids. Washington, DC: National Academies Press; 2000. Official page. Source of the 2,000 mg adult upper limit. Tier: expert consensus based on human data.
• European Food Safety Authority. Scientific opinion on dietary reference values for vitamin C. EFSA Journal. 2013;11(11):3418. DOI. Independent European assessment of intake and safety.
• Massey LK, Liebman M, Kynast-Gales SA. Ascorbate increases human oxaluria and kidney stone risk. J Nutr. 2005;135(7):1673-1677. Link: locate via PubMed title search. Tier: human, small controlled study of urinary oxalate.
• Hallberg L, Brune M, Rossander L. Effect of ascorbic acid on iron absorption from different types of meals. Hum Nutr Appl Nutr. 1986;40(2):97-113. Link: locate via PubMed title search. Tier: human, absorption study; relevant to people with iron overload.
• National Institutes of Health, Office of Dietary Supplements. Vitamin C: Fact Sheet for Health Professionals. Official summary of intakes, sources and safety.

Mechanistic Studies

These explain how ascorbic acid may act. Tier: mechanistic; they do not show health benefit.

• Padayatty SJ, Levine M. Vitamin C: the known and the unknown and Goldilocks. Oral Dis. 2016;22(6):463-493. DOI. Review of the vitamin's enzyme cofactor and antioxidant roles.
• Carr AC, Maggini S. Vitamin C and immune function. Nutrients. 2017;9(11):1211. DOI. Describes effects on immune cells in laboratory and some human settings.
• Pullar JM, Carr AC, Vissers MCM. The roles of vitamin C in skin health. Nutrients. 2017;9(8):866. DOI. Covers collagen synthesis and skin biology.

Preclinical Studies

These use animals or cultured cells. Tier: preclinical. Findings often do not translate to people.

• Chen Q, Espey MG, Sun AY, et al. Pharmacologic doses of ascorbate act as a prooxidant and decrease growth of aggressive tumor xenografts in mice. Proc Natl Acad Sci USA. 2008;105(32):11105-11109. DOI. Tumor growth slowed in mice at very high concentrations.
• Yun J, Mullarky E, Lu C, et al. Vitamin C selectively kills KRAS and BRAF mutant colorectal cancer cells by targeting GAPDH. Science. 2015;350(6266):1391-1396. DOI. Cell and mouse work suggesting a cancer-cell vulnerability.
• Maeda N, Hagihara H, Nakata Y, et al. Aortic wall damage in mice unable to synthesize ascorbic acid. Proc Natl Acad Sci USA. 2000;97(2):841-846. DOI. Mouse model of deficiency and blood vessel damage.

Vitamin C Clinical Studies at a Glance: Study Table

The table lists the main human studies above with year, design, population and dose.

Links, DOIs and Official Sources

Every entry above links to its DOI record or an official page where one exists. A DOI is a permanent identifier that can be pasted after doi.org/ to reach the publisher's page, where abstracts are usually free even when full text is not. For entries marked to locate via PubMed, search the exact title at pubmed.ncbi.nlm.nih.gov. Cochrane reviews are also summarized in plain language on the Cochrane Library website.

Reporting standards we follow when describing evidence include the PRISMA 2020 statement for systematic reviews (Page MJ, et al. BMJ. 2021;372:n71, DOI) and the GRADE approach to rating certainty (Guyatt GH, et al. BMJ. 2008;336(7650):924-926, DOI).