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Research Newsletter-Spring/Summer 2006

Vitamin C and the Common Cold

The debate about the value of vitamin C in preventing and treating the common cold has raged for over three decades following the publication in 1970 of Vitamin C and the Common Cold by Linus Pauling. After Pauling was alerted by Irwin Stone in 1965 to the possible value of high-dose vitamin C in preventing colds, he and his wife began to routinely take several grams per day. Pauling had been troubled for many years by severe colds that interfered with his work, and he was pleased to find that the vitamin C supplements greatly decreased the number of colds he caught. He reviewed the clinical literature, then consisting of about four double-blind, placebo-controlled trials that used at least 100 mg of vitamin C per day, and published his book, expecting that the news that a safe and cheap substance could provide a simple way of preventing and ameliorating colds would be embraced by the medical community and the public. The medical community was generally skeptical or disdainful, but the public responded. Interest in the use of vitamin C for colds expanded, and 21 clinical studies using at least one gram of vitamin C per day were published between 1971 and 1994. These studies were reviewed by Dr. Harri Hemila in 1994. He found that vitamin C supplements reduced the duration of colds by about 23% and ameliorated symptoms, although there was no consistent effect on incidence.

In 2004, Dr. Hemila and colleagues again reviewed the relevant studies for The Cochrane Database of Systematic Reviews. To study the prevention of colds by vitamin C, they pooled and analyzed the results of 29 trials involving more than 11,000 subjects. With the exception of six trials with over 600 runners, skiers, or soldiers, no preventive effect was found for vitamin C. In those six subgroups, the incidence of colds was halved. Thirty studies were examined that addressed the effect of vitamin C on the duration of colds. In these studies, there was a consistent benefit, with a reducton in duration of 8% to 14%. Fifteen trials assessed the effect of vitamin C on symptoms, which were significantly ameliorated by vitamin C.

A Japanese study on vitamin C and colds was published in 2006 in the European Journal of Clinical Nutrition. This study was a five-year, randomized, double-blind (but not placebo-controlled) trial designed to evaluate the effect of a daily dose of 50 mg or 500 mg of vitamin C on the development of gastric cancer among 244 subjects. (The 50-mg dose of vitamin C served as a quasi-placebo.) The researchers evaluated the effects of the vitamin C supplements on the common cold at the completion of the study. The risk of contracting three or more colds in the five-year period was decreased by 66% by the daily intake of the 500-mg vitamin C supplement. There was little difference in severity or duration of colds between subjects in the low-dose or high-dose groups. This study deserves special mention because it was much longer (five years) than the trials reported by Hemila and covered many cold seasons in which subjects were probably exposed repeatedly to many cold viruses.

Last updated December, 2006