Supplement evidence

010 / 575Vitamin

Vitamin C

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The short answer

Preventing or treating deficiency; regular use may slightly shorten cold duration for some people.

Evidence and scope: Established for an indicated use
This status does not grade the ingredient for every goal, outcome, or person.
Important limitation: It does not prevent most colds or have demonstrated human lifespan effects.
Before deciding: High doses can cause gastrointestinal symptoms and increase kidney-stone risk in susceptible people.

01 / PRACTICAL GUIDE

Dose, absorption, and combinations

These are indication-specific reference or studied ranges—not a personalized prescription. Start with the objective, then check the form, label, medicines, and health conditions.

Reference range by objective

Meeting usual needs75 mg/day women; 90 mg/day men

Reference or studied range—not a personalized prescription. The product label or a clinician may specify a different dose.

Dose source ↗

Respiratory researchCold-prevention trials commonly use 200 mg/day or more, with modest context-specific effects

Reference or studied range—not a personalized prescription. The product label or a clinician may specify a different dose.

Dose source ↗

More is not automatically better. A clinician or product label may specify a different amount.

Absorption / solubilityWater-soluble

Water-soluble or readily water-dispersible. This does not mean excess is always harmless.

How it is commonly taken

May be taken with food; divide gram-level doses for tolerance.

Do not combine casually

High doses can cause diarrhea and may increase oxalate-stone risk; consider hemochromatosis.

Dose and use source ↗

Dose and use links lead to primary or official source material. Search links are discovery tools, not proof that every returned paper applies.

02 / EVIDENCE

What the research says

We keep supportive, mixed, negative, safety, and contextual findings together. The headline never replaces the underlying papers.

5research papers in this ledger

50unique primary studies represented

26,837unique participants represented

These are audited counts for this JIVANA collection, not search-result totals. Participants are counted once when multiple papers use the same cohort; review papers are not added again to participant totals.

Open the research timelineResearch timeline

Entries are ordered by publication year. A study period appears only when the source reports it.

2023

Mixed or qualifiedPMID 37791386

Vitamin C supplementation and blood pressure: updated systematic review and meta-analysis

Systolic pressure fell by about 3 mm Hg, with short follow-up and no evidence that the change reduces clinical events. Vitamin C should not replace established hypertension care.

Published: 2023Duration: Median 6 weeksn=890 participants20 primary studies represented

Study design and methods

Design: Systematic review and meta-analysis of 20 randomized trials
Population: 890 adults, including people with hypertension or diabetes
Intervention: Vitamin C alone, median 757.5 mg/day, versus control
Outcome: Systolic and diastolic blood pressure

Open research record ↗

2016

Safety signalPMID 26463139

Total, dietary, and supplemental vitamin C intake and risk of incident kidney stones

Supplemental intake of at least 1,000 mg/day was associated with more kidney stones in men but not women. Observational design cannot prove causality, yet supports caution with high doses in stone-prone people.

Published: 2016Duration: Median 11.3–11.7 yearsn=197,271 participants

Study design and methods

Design: Prospective analysis of three large cohorts
Population: 156,735 women and 40,536 men
Intervention: Reported dietary and supplemental vitamin C intake; no randomized treatment
Outcome: Incident kidney stones

Open research record ↗

2014

Does not support the tested claimPMID 25008853 · NCT00270647

Vitamin E and C supplementation and risk of cancer in men: posttrial follow-up

Vitamin C did not prevent total or site-specific cancer during or after the trial. This is the same cohort as the cardiovascular report and is excluded from aggregate totals.

Published: 2014Duration: Trial plus mean 2.8 years posttrial follow-upn=14,641 participants · counted once

Study design and methods

Design: Posttrial follow-up of the Physicians' Health Study II randomized cohort
Population: 14,641 male physicians from the cardiovascular-prevention trial above
Intervention: Prior vitamin C 500 mg/day allocation versus placebo
Outcome: Total, prostate, and site-specific cancer incidence after the intervention ended

Open research record ↗

2013

Mixed or qualifiedPMID 23440782

Vitamin C for preventing and treating the common cold

Routine vitamin C did not reduce cold incidence in the general population, though incidence fell in a small extreme-exercise subgroup. Regular use modestly shortened duration; starting only after symptoms showed no consistent benefit.

Published: 2013n=11,306 participants29 primary studies represented

Study design and methods

Design: Cochrane systematic review; 29 regular-supplement comparisons for cold incidence
Population: 11,306 participants in the incidence analysis, with separate duration and treatment-onset analyses
Intervention: At least 200 mg/day vitamin C used regularly or started after symptoms
Outcome: Cold incidence, duration, and symptom severity

Open research record ↗

2008

Does not support the tested claimPMID 18997197 · NCT00270647

Vitamins E and C in the prevention of cardiovascular disease in men

Vitamin C did not reduce major cardiovascular events or individual cardiovascular endpoints. This large primary-prevention trial does not support antioxidant-based cardiovascular prevention.

Published: 2008Duration: Mean 8 yearsn=14,641 participants · counted once

Study design and methods

Design: Randomized, double-blind, placebo-controlled factorial trial
Population: 14,641 U.S. male physicians aged 50 or older
Intervention: Vitamin C 500 mg/day or placebo, with a separate vitamin E randomization
Outcome: Major cardiovascular events, myocardial infarction, stroke, and cardiovascular death

Open research record ↗

Unscreened discovery appendix—not evidence3,556 candidate publicationsSearch run: Aug 21, 2026

Complete for the displayed PubMed query at the search timestamp—not for all databases or every possible synonym. Candidates can be irrelevant, duplicate the same study, or report negative findings. They are never summed as evidence or participants until screened.

03 / SOURCES

Start with the source material

Official evidence overviewNIH Office of Dietary Supplements Live PubMed discovery searchNational Library of Medicine

The live search is for discovery only. Search-result counts change and are not included in the audited totals above.

Recent PubMed discovery recordsDirect links to the first 12 records returned by the reproducible search. These are discovery candidates—not reviewed summaries or a count of supportive findings.

04 / EXPERT CONTEXT

Expert context—not evidence

Expert positions are dated context—not scientific evidence. They never raise the evidence status or become consensus by repetition.

No direct, source-verified endorsement is currently recorded. Research authorship or discussion alone is not treated as endorsement.