Vitamin C and the Common Cold

In our review of antioxidants and vitamins, we note that they don't appear to have a significant effect on major illnesses such as heart disease, cancer and Alzheimer's. However, many people take large quantities of vitamin C to prevent and mitigate the impact of the common cold, an approach attributable to Dr. Linus Pauling, a Nobel prize winner in chemistry. Is this an effective approach?

A new review ("meta-study") of available data, published in PLoS Medicine provides some insight into this issue. The results utilize 55 comparative studies carried out over a period of 65 years. The goal was to determine whether 200 miligram (or more) of vitamin C daily reduces the incidence (or, at least, the severity) of the common cold. In most of the sudies, doses up to 2 grams daily did not alter the incidence of colds, with one exception: six studies involving people exposed to extreme stresses (marathon runners, skiers and soldiers exposed to extreme cold) indicate that there is a reduction of 50% in the incidence of common colds. The Margin of Error is between 38% and 66%.

Another outcome, that is less dramatic, is that regular vitamin C consumption reduces the length of colds - for adults, by 8% (Margin of Error between 3% and 13%) and for children, by 14% (Margin of Error between 6% and 22%). However, taking vitamin C at the beginning of a cold does not seem to provide any benefit (duration reduced by 3%, but Margin of Error is between 10% reduction and 5% increase).

There is one exception to this last conclusion: one large study shows that a dose of 8 grams on the first day of a cold results in a statistically significant reduction in the duration of the cold.

The article concludes that the "lack of effect of prophylactic vitamin C supplementation on the incidence of the common cold in normal populations throws doubt on the utility of this wide practice". It states that the reduction in the duration of the common cold due to vitamin C intake is minor and questionable. Only under special circumstances (extreme stress) was a significant beneficial effect measured. The reduction in the duration of colds using 8 grams of vitamin C on the first day needs to be further corroborated.

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Last Modification - June 29, 2005