Vitamin C and the common cold: a retrospective analysis of Chalmers' review.
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 in vitamin C and control groups in seven placebo-controlled studies. He found that episodes were 0.11 +/- 0.24 (SE) days 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' 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' review reveals serious shortcomings. For example, Chalmers did not consider the amount of vitamin C used in the studies and included in his meta-analysis was a study in which only 0.025-0.05 g/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, we calculated that vitamin C (1-6 g/day) decreased the duration of the cold episodes by 0.93 +/- 0.22 (SE) days; the relative decrease in the episode duration was 21%. The current notion 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.
Hemilä
H
H
Department of Public Health, University of Helsinki, Finland.
Herman
Z S
ZS
D001205:Ascorbic Acid / Q000008:administration & dosage / Q000627:therapeutic use*; D003139:Common Cold / Q000188:drug therapy* / Q000517:prevention & control; D018849:Controlled Clinical Trials as Topic; D006801:Humans; D015201:Meta-Analysis as Topic; D010919:Placebos
D010919:Placebos; D001205:Ascorbic Acid