Vitamin C for preventing and treating the common cold.

Study answer

What this study found

Regular vitamin C supplementation did not reduce the incidence of the common cold in the general population, but it shortened cold duration and may have reduced symptom severity. Duration benefits were greater in children and in some studies of people under brief extreme physical stress. Therapeutic vitamin C started after symptoms began showed inconsistent benefit, although a few high-dose trials suggested possible improvement. Overall, routine vitamin C for cold prevention is not supported, but it may modestly reduce duration once a cold occurs.

Study & population

Systematic review/meta-analysis of randomized trials in adults and children from the general community, with some studies in participants under short-term extreme physical stress and some laboratory viral-challenge studies.

Intervention

Vitamin C was evaluated as regular daily supplementation for prevention and as short-course therapy started at the onset of cold symptoms.

Key limitation

The evidence was heterogeneous across populations, doses, treatment timing, and outcome definitions, limiting direct comparability.

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Original abstract