Vitamin C useless for preventing or treating colds

Reuters

For the average person, popping vitamin C pills is unlikely to ward off the common cold or shorten its length or severity. However, for people exposed to short bouts of extreme physical exercise or cold temperatures, vitamin C may markedly reduce their risk of catching a cold.

The findings stem from a review of 30 published studies involving 11,350 people who took at least 200 milligrams of vitamin C each day.

Based on pooled data, regular ingestion of vitamin C did nothing to lower the risk of the common cold in the ordinary population, report reviewers in the latest issue of The Cochrane Library, a publication of the Cochrane Collaboration, an international organization that evaluates medical research.

There was a slight reduction in the duration and severity of common cold symptoms with vitamin C, compared with placebo, but the magnitude of the effect was so small its clinical usefulness is doubtful, the experts report.

Therefore, it is senseless for most people to take vitamin C every day to reduce their risk of catching a cold, according to co-author Harri Hemila of the University of Helsinki, Finland and her colleagues.

An exception appears to be when individuals are exposed to short periods of extreme physical stress. In six trials involving a total of 642 marathon runners, skiers, and soldiers taking part in sub-arctic exercises, vitamin C supplements reduced the risk of the common cold by 50 percent.

Vitamin C, for the average person, also failed as a "therapeutic" for the common cold. Trials of high-dose vitamin C taken after the onset of cold symptoms showed "no consistent" effect on either the length of a cold or the severity of symptoms.

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