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Vitamin C for preventing and treating the common cold.
R M Douglas1, H Hemila, R D'Souza
1National Centre for Epidemiology and Population Health, Australian National University, 34 Nungara Place, Aranda, ACT, Australia, 2614.
The Cochrane Database of Systematic Reviews
|October 21, 2004
Summary
Vitamin C (ascorbic acid) supplementation does not prevent common colds for the general population but may reduce cold duration and severity, especially for those under extreme physical stress. Therapy initiated after symptom onset shows no significant benefit.
Area of Science:
- Nutrition Science
- Public Health
- Immunology
Background:
- Oral vitamin C (ascorbic acid) has been debated for decades regarding its effectiveness against the common cold.
- Despite controversy, public interest and usage of vitamin C for cold prevention and treatment remain high.
Purpose of the Study:
- To determine if daily oral vitamin C (≥200 mg) reduces common cold incidence, duration, or severity.
- To assess efficacy whether used as continuous prophylaxis or initiated after symptom onset.
Main Methods:
- Systematic review and meta-analysis of randomized controlled trials.
- Searched databases including CENTRAL, MEDLINE, and EMBASE up to June 2004.
- Included trials with ≥200 mg daily vitamin C, placebo comparison, and adequate outcome reporting.
Main Results:
- Prophylaxis with vitamin C did not significantly reduce cold incidence in the general population (RR 0.96).
- A subgroup of individuals under severe physical stress (e.g., marathon runners) showed a reduced incidence (RR 0.50).
- Vitamin C prophylaxis significantly reduced cold duration by 8% in adults and 13.5% in children, and severity.
Conclusions:
- Routine vitamin C prophylaxis is not recommended for the general population.
- Vitamin C may be beneficial for individuals facing extreme physical exercise or cold exposure.
- While not effective as a therapy initiated after cold onset, regular vitamin C intake appears to support respiratory defense mechanisms.