The claimEvidence A · guideline-tier
Mega-dose vitamin C prevents colds
The evidence
Hemilä 2013 Cochrane (n>11,000): ≥200 mg/d doesn't reduce incidence; only shortens duration ~8%.
The mechanism, in brief
Ascorbic acid is destroyed by three things: heat, oxygen, water.
Sources (1)
- National Institutes of Health, Office of Dietary Supplements. (2021). Vitamin C — Fact Sheet for Health Professionals.