Supplements

vitamin C prevents common cold

In plain terms: Does vitamin C stop you catching colds?

Refuted Supplements 🔬 Includes disconfirming

RefutedContestedStrong support

consensus score -0.69

No—for the general population regular vitamin C does not reduce how often you catch colds (the one exception is people under extreme physical stress).

📅 Last reviewed: 2026-07-15 ⓘ

Evidence ladder

How far up the ladder this claim has climbed. A high consensus on a low rung means "consistent so far," not "proven in people."

Top evidence so far: All trials, pooled (Meta-analysis)

MechanismIn-vitroAnimalObservationalRCTMeta-analysis

How the studies fall

0 support 3 contradict 0 tested null 2 mixed · 5 sources, 3 independent groups

What the evidence shows

The headline claim is not supported: regular vitamin C supplementation does not reduce common-cold incidence in the general population (Cochrane pooled RR ≈ 0.97). The one real exception is people under extreme short-term physical stress (marathon runners, soldiers, subarctic troops), in whom incidence was roughly halved.

Cochrane agrees with us see how our grade compares ▾

Cochrane · not stated Agrees with our grade

no explicit GRADE certainty rating reported in this 2013 review; conclusion based on 29 trials / 11,306 participants for prevention)

“The failure of vitamin C supplementation to reduce the incidence of colds in the general population indicates that routine vitamin C supplementation is not justified, yet vitamin C may be useful for people exposed to brief periods of severe physical exercise. Regular supplementation trials showed no effect on cold incidence in the general community (pooled RR 0.97, 95% CI 0.94 to 1.00; 10,708 participants), whereas in a subgroup exposed to extreme physical stress (marathon runners, skiers, soldiers) it halved cold risk (RR 0.48, 95% CI 0.35 to 0.64; 598 participants).”

Why we agree: we reached the same direction independently, from our own appraisal of 5 sources. Two methods landing in the same place is a stronger signal than either alone.

What is Cochrane, and why trust it?

Cochrane produces systematic reviews: instead of running a new study, they gather every trial ever done on a question, judge how well each was run, and pool the results. They take no commercial or industry funding, which is why the medical community treats their reviews as a gold standard — and why we check our own verdicts against theirs.

About Cochrane ↗ · Get involved / support ↗

Read the Cochrane review ↗

The evidence (5)

Source	Grade	Stance	Quality	Finding
Hemila & Chalker 2013 · Cochrane Database Syst Rev	meta-analysis	contradicts	high	Cochrane (29 trials, 11,306 participants): regular vit C did NOT reduce cold incidence in the general community (RR ~0.97, ns); incidence ~halved only in extreme-physical-stress subgroups.
Coulehan et al. 1976 · N Engl J Med	RCT	contradicts	moderate	Double-blind RCT (868 schoolchildren): NO difference in number becoming ill, episodes, or duration vs placebo.
Johnston et al. 2014 · Nutrients	RCT	mixed	low	RCT in men with MARGINAL vit C status: fewer cold episodes (RR 0.55) — benefit only in low-status subgroup, consistent with the general-population null + deficiency/stress exception.
Sasazuki et al. 2006 · Eur J Clin Nutr	RCT	mixed	moderate	RCT: vitamin C did not reduce overall common-cold incidence (limited effect on frequency of more-severe colds).
Cerullo et al. 2020 · Front Immunol	observational	contradicts	low	Review: available data do not support that oral vitamin C boosts immunity; no recommendation for high-dose vit C to lower respiratory-infection risk in well-nourished general population (exception: athletes/military/low-plasma-C).

Disagree, or know a study we missed?

We grade by evidence, not opinions. The way to weigh in is to point us to a study we haven't cited (check the evidence table above first), or to flag a problem with one we have. Every submission is reviewed; if it holds up, the grade updates and shows in Science Changes Its Mind.

📚 Suggest a study ⚑ Flag / request reclassification

Opens a short form. You'll sign in with Google so submissions are tied to a real account — we don't display your identity, and we only accept a link we can verify (PubMed, DOI, ClinicalTrials.gov).

Educational only, not medical advice. Grades and scores reflect published evidence weighted by study design and quality; see the methodology.