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Vitamin C for preventing and treating the common cold.

Cochrane review of placebo-controlled trials: regular vitamin C did not meaningfully lower cold incidence in general-community trials (pooled RR 0.97) but showed a large pooled relative reduction in athletes, skiers, and subarctic exercisers (RR 0.48); therapeutic vitamin C at symptom onset did not show consistent benefit on duration or severity.

Design

  • Cochrane systematic review; placebo-controlled trials using ≥0.2 g/day vitamin C
  • Outcomes: incidence during regular supplementation; duration and severity of episodes; therapeutic trials at onset

Pooled prevention (incidence)

  • Community trials (n ≈ 10,708): pooled RR 0.97 (95% CI 0.94–1.00)
  • Marathon runners, skiers, soldiers on subarctic exercise (5 trials, n = 598): pooled RR 0.48 (95% CI 0.35–0.64)

Duration / severity themes (regular supplementation)

  • Abstract: cold duration reduced ~8% in adults and ~14% in children with regular use; 1–2 g/day shortened colds ~18% in children in reviewed trials

Therapeutic vitamin C (onset of symptoms)

  • Seven comparisons (3249 episodes): no consistent effect on duration or severity

Publication

Hemilä H, Chalker E. Cochrane Database Syst Rev. 2013 Jan 31;(1):CD000980. PMID 23440782.

Outcomes

  • All-Cause Mortality Risk
    Events: /
  • All-Cause Mortality Risk
    Events: /
  • Therapeutic vitamin C started at cold onset: no consistent effect on duration or severity across 7 trial comparisons in the Cochrane abstract.
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