The Vitamin C Controversy

Many claims have been made about the role of vitamin C (ascorbic acid) in the prevention and treatment of the common cold. It has been over twenty years since Linus Pauling wrote the book "Vitamin C and the Common Cold." Pauling based his views on several studies that showed that vitamin C was very effective in reducing the severity of symptoms and the duration of the common cold. Since 1970, there have been over twenty double-blind studies designed to test Pauling's assertion. Yet despite the fact that in every study, the group that received vitamin C had a decrease either in duration or in severity of symptoms, for some reason the clinical effect is still debated in the medical community. A 1995 article that appeared in the "Journal of the American College of Nutrition" has shed some light on the controversy.

*In 1975, Thomas Chalmers analyzed the possible effect of vitamin C on the common cold by calculating the average difference in the duration of cold episodes between vitamin C groups and control groups in seven placebo-controlled studies. He found that episodes were 0.11 day shorter in the vitamin C groups and concluded that there was no valid evidence to indicate that vitamin C is beneficial in the treatment of the common cold. Chalmers's review has been extensively cited in scientific articles and monographs.

However, other reviewers have concluded that vitamin C significantly alleviates the symptoms of the common cold. A careful analysis of Chalmers's review reveals serious shortcomings. For example, Chalmers did not consider the amount of vitamin C used in the studies; he included in his meta-analysis a study in which only 25 to 50 mg/day of vitamin C was administered to the test subjects. For some studies, Chalmers used values that are inconsistent with the original published results.

Using data from the same studies, the authors of a new study calculated that vitamin C at a dosage of 1 to 6 g/day decreased the duration of the cold episodes by nearly a full day, or roughly twenty-one percent. The argument in the medical literature that vitamin C has no effect on the common cold seems to be based in large part on a faulty review written two decades ago.

Encyclopedia of Natural Medicine, Drs Michael Murray and Joseph Pizzorno

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