The claimEvidence A · guideline-tier
Mega-dose vitamin C prevents colds
The evidence
Taking 200 mg a day or more does not lower how often you catch colds; it only shortens them by about 8% (Cochrane review, Hemilä 2013, more than 11,000 people).
The mechanism, in brief
The body cannot make vitamin C (ascorbic acid) and does not store much of it, so it has to come from fresh fruit and vegetables every day. And it is sensitive to three things: heat, oxygen, and water.
Sources (1)
- National Institutes of Health, Office of Dietary Supplements. (2021). Vitamin C — Fact Sheet for Health Professionals.