Vitamin C and the Common Cold: What Cochrane and Trials Found
What a Cochrane review of placebo-controlled trials found about vitamin C for preventing and shortening colds, who was studied, and where the evidence is limited.
Content last updated . This page has not been medically reviewed.
How the review defined its question
The Cochrane authors looked at two different uses. "Regular" use means a supplement taken every day for the length of a study. "Therapeutic" use means starting after cold symptoms appear. They included only placebo-controlled trials and left out trials using less than 0.2 g a day. [1] Studies are study amounts, not recommendations.What the review found
| Question | What the source found | Strength of evidence |
|---|---|---|
| Does daily vitamin C prevent colds in the general community? | In 10,708 people, pooled risk ratio 0.97 (95% CI 0.94 to 1.00). [1] | No good evidence of benefit |
| Does it prevent colds in people under brief, severe physical stress? | In 598 marathon runners, skiers and soldiers on subarctic exercises, pooled risk ratio 0.48 (0.35 to 0.64). [1] | Promising but limited (small, specific groups) |
| Does daily use shorten colds? | Colds were 8% shorter in adults and 14% shorter in children. In children, 1 to 2 g a day shortened colds by 18% in that analysis. [1] | Mixed |
| Does starting vitamin C after symptoms begin help? | No consistent effect on duration or severity in seven comparisons. [1] | Mixed |
What the numbers mean in plain words
A risk ratio of 0.97 with a range that touches 1.00 means the trials found almost no difference in how many people caught a cold. The 0.48 result applies to a small number of people doing short periods of very hard exercise in cold or demanding conditions. The review does not show the same result for other groups. Trials in people with low vitamin C intake and in well-nourished people should not be treated as the same.Frequently asked questions
Does vitamin C stop you getting a cold?
For people in the general community, no. The Cochrane review found a risk ratio of 0.97 (0.94 to 1.00). [1]
Does vitamin C make a cold shorter?
Taken daily over time, colds were 8% shorter in adults and 14% in children on average. Starting after symptoms began showed no consistent effect. [1]
Is there a group where vitamin C did seem to help prevent colds?
In five trials of marathon runners, skiers and soldiers on subarctic exercises, the risk ratio was 0.48. These were small, specific groups. [1]
Should I take vitamin C when I feel a cold starting?
Trials of starting after symptoms began showed no consistent effect. [1] MedlinePlus says it does not appear to be helpful. [2] Ask a pharmacist if you take medicines or have a health condition.
Can food provide enough vitamin C?
The NHS says you should be able to get all you need from a varied and balanced diet. [3]
More details: evidence, limits and cautions
The details behind this page: cautions, limits of the evidence and where sources disagree. Open any note to read it.
How to read the evidence labels
Labels used on this page: no good evidence of benefit, mixed, promising but limited and insufficient evidence.
Limits and uncertainty
- The review was published in 2013, with searches to November 2012. [1] We did not find a newer Cochrane update that we could read this session.
- The reviewers noted that the failure to reduce cold incidence in the general population means routine supplementation is not justified. They also said it may be worthwhile for people to test on an individual basis whether therapeutic vitamin C helps them, and called for more therapeutic trials. [1]
- Drink-mix, effervescent and combination products: Proper evidence not found. We searched PubMed on 2026-10-23 for "effervescent vitamin C common cold" and found no records. Evidence on one product type or a combination such as vitamin C with zinc should not be assumed from the Cochrane result.
- If symptoms are severe, get worse or last a long time, ask a clinician rather than relying on a supplement. See Colds, flu and respiratory infections.
Safety and who should ask first
For the wider picture of immune health, including food, sleep and activity, see Immune wellness and Vitamin C, vitamin D and zinc for immunity. The full nutrient profile is Vitamin C.
References
- Hemila H, Chalker E. Vitamin C for preventing and treating the common cold. Cochrane Database of Systematic Reviews, 2013. Read 2026-10-23.
- MedlinePlus Medical Encyclopedia (US National Library of Medicine). Vitamin C. Review date 1/21/2025. Read 2026-10-23.
- NHS (UK). Vitamins and minerals: Vitamin C. Page last reviewed 3 August 2020. Read 2026-10-23.