Question
Does vitamin C help cure a cold?
Answer
Mostly no.
Explanation
The idea that high doses of vitamin C (1,000 - 40,000 mg) could prevent and treat the common cold became popular in the 1970s as a result of the advocacy by Nobel laurate Linus Pauling. The popularity of this idea is largely unjustified.
Using 3 meta-analyses of a total of 55 studies, a 2005 Cochrane review attempted to answer the questions of whether vitamin C in daily doses of 200 mg or more reduces the occurrence and duration of the common cold, either when used as a continuous supplement or as soon as symptoms are felt.
In summary, their conclusions on any significant effects:
| Supplementation | Decreases occurrence | Decreases duration |
|---|---|---|
| Continuous | No | Yes (by ~8-14%) |
| At onset of symptoms | No | No |
| Before extreme physical exertion | Yes | N/A |
Sources
Hemilä H., E. Chalker, Vitamin C for preventing and treating the common cold (Cochrane Database of Systematic Reviews, Issue 1. Art. No.: CD000980, 2013)