Now, The Cochrane Library has reviewed the data.
First, the details.
- 29 studies involving 11,306 participants contributed to the meta-analysis on the risk of developing a cold while taking vitamin C regularly.
- 31 comparisons examined the effect of regular vitamin C use on common cold duration (9745 episodes).
- The majority of included studies were randomized, double-blind — neither the researchers nor patients knew the treatment given.
And, the results.
- Regular ingestion of vitamin C had no effect on common cold incidence in the ordinary population.
- Regular supplementation of at least 1 gram of vitamin C daily had a modest but consistent effect in reducing the duration of common cold symptoms in adults (8%) and in children (18%).
- In participants exposed to short periods of extreme physical stress (including marathon runners and skiers) vitamin C reduce the common cold risk by up to half in some but not all studies.
- No adverse effects of vitamin C were reported.
The bottom line?
Based on what we know it appears there is no evidence that regular supplementation of vitamin C reduces the chance of coming down with a common cold, although it may reduce the duration and severity of illness.
The effect on people in extreme exercise situations is inconsistent.
2/14/13 09:06 JR