Meta-analysis of vitamin C supplementation on immune function and upper respiratory tract infection risk after exercise
Peters EMGoetzsche JMGrobbelaar BNoakes TD
Evidence is still building up
Summary
A meta-analysis examining the effects of vitamin C supplementation on upper respiratory tract infection (common cold) risk following intense exercise (marathon, etc.). Vitamin C supplementation reduced upper respiratory infection risk by approximately 50% compared to placebo. In the general population (lower exercise intensity), preventive effects are limited, suggesting the benefit is greatest in specific contexts where intense exercise causes immune suppression. Contributions to neutrophil and lymphocyte function and collagen synthesis are also documented.
Key findings
- 1
Reduced upper respiratory infection risk by ~50% after intense exercise vs placebo
- 2
In the general population, risk reduction is limited (~8%)
- 3
Contributes to neutrophil and lymphocyte function maintenance
- 4
Essential cofactor role in collagen synthesis
- 5
Limited additional benefit beyond 1,000 mg/day
Related supplements
PR
Reduced post-exercise upper-respiratory infection risk reported in intense-endurance athletes (limited in the general population)
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Last checked: 2026-06-24