J Am Coll Nutr. 1995 Apr;14(2):116-23.
Vitamin C and the Common Cold: a Retrospective Analysis of Chalmers’ Review.
Hemilä H1, Herman ZS.
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.
Vitamin C supplements and disease–counterpoint. [J Am Coll Nutr. 1995]
[Indexed for MEDLINE]