Vitamin C vs colds — the Cochrane verdict nobody shares
- Claim
- VITAMIN C THE COLD VERDICT
- Catch
- NO CONSISTENT EFFECT
- Verdict
- THE CATCH SCIENCE
Vitamin C is the world's best-selling cold remedy — but when the Cochrane review pooled the placebo-controlled trials (Hemilä & Chalker, Cochrane Database Syst Rev 2013; DOI 10.1002/14651858.CD000980.pub4), the story split in two. What vitamin C did: in adults, colds lasted about 8% less time; in children about 14%, and up to 18% in trials giving children 1–2 g/day. What it didn't do: for the general population, taking daily vitamin C (≥200 mg/day) did NOT reduce the number of colds you catch. The exception was extreme physical stress — marathon runners, skiers and soldiers exercising in subarctic conditions roughly halved their cold incidence (risk ratio ~0.48) while on supplements. And once you're already sick, starting vitamin C treatment shows no consistent effect in trials. The catch: prevention only works as a daily habit started before you get sick, not as a rescue dose; the adult safe upper limit is 2 g/day (2000 mg), and doses above it can cause diarrhea, cramps and stomach upset. Citrus is fine — megadoses are not evidence, they're a laxative.
SOURCES
- Hemilä H, Chalker E. "Vitamin C for preventing and treating the common cold," Cochrane Database of Systematic Reviews 2013, Issue 12, Art. No. CD000980. DOI: 10.1002/14651858.CD000980.pub4
- NIH Office of Dietary Supplements, Vitamin C Fact Sheet (safety/upper limits, 2 g/day UL)
- Linus Pauling Institute, Micronutrient Information Center: Vitamin C
For information only, not medical advice. If you have recurring infections, kidney stones or take medication, talk to a doctor before high-dose supplements.
