Vitamin C for preventing and treating the common cold

Hemila H, Chalker E

Published in Cochrane Database of Systematic Reviews

Abstract

Regular vitamin C supplementation modestly reduced the duration and severity of common cold symptoms.

Methodology

Cochrane systematic review and meta-analysis of 29 placebo-controlled trials (11,306 participants) of regular vitamin C supplementation (>=200 mg/day) for prevention and treatment of the common cold, plus 5 trials in people under heavy short-term physical stress.

Key Findings

Regular supplementation had no effect on common cold incidence in the general population (RR 0.97), but reduced cold duration by 8% in adults and 14% in children; in five trials of marathon runners, skiers and soldiers, incidence was roughly halved (RR 0.48).

Conclusions

Routine vitamin C supplementation does not prevent colds in the general population but consistently produces a small reduction in duration and severity; prophylaxis may be justified for people under extreme physical stress.

Limitations

Therapeutic trials starting after symptom onset showed no consistent benefit; heterogeneous doses and populations; many older trials.

Supplements Studied

Vitamin C

Vitamin

Regular supplementation had a modest but consistent effect in reducing the duration of common cold symptoms... in five trials with participants under heavy short-term physical stress, the common cold risk was halved.

Outcomes Measured

Pathogen Resistance

Regular vitamin C did not reduce cold incidence in the general population but shortened duration modestly

Immune Function

Regular vitamin C supplementation reduced common cold duration in the general population.

Bacterial Infection Prevention

Regular vitamin C supplementation did not reduce common cold incidence in the general population.

Cold Prevention

Primary

The failure of vitamin C supplementation to reduce the incidence of colds in the general population indicates that routine vitamin C supplementation is not justified, yet vitamin C may be useful for people exposed to brief periods of severe physical exercise.