Positive Health Online

Abstract

HEMILA, Department of Public Health, University of Helsinki, Finland writes that placebo-controlled trials have demonstrated that vitamin C supplementation decreases the duration and severity of common cold infections, but that the magnitude of the benefit has varied substantially, hampering conclusions regarding the clinical significance of vitamin C. The authors reviews the literature (54 references) on this subject.

Background

Methodology

The author analysed the data of 23 studies with regular vitamin C supplementation of > 1 g/day to discover factors which could account for part of the variation in the results.

Results

On average vitamin C produces greater benefit for children compared with adults. The dose affects the magnitude of the benefit, with a dose of > or = 2 g/day producing greater benefit compared with 1 g/day . In 5 studies in adults given 1 g/day vitamin C, the median decrease in cold duration was only 6%, whereas in 2 studies with children given 2 g/day, the median decrease was 4 times greater, 26%.

Conclusion

The trials analysed above used regular vitamin C supplementation, but it is possible that therapeutic supplementation started early at the onset of the cold episode could have produced comparable benefits. Since few trials have studied the effects of therapeutic supplementation and their results have been variable, further therapeutic trials are needed to definitively establish the beneficial role of vitamin C in the treatment of colds.

References

Hemila H. Vitamin C supplementation and common cold symptoms: factors affecting the magnitude of the benefit . Medical Hypotheses 52(2): 171-8. Feb 1999.