Take vitamin C and you will not catch a cold. Take more vitamin C and you'll knock the cold out faster. Linus Pauling, two-time Nobel laureate, said so. Mums said so. Berocca's tube said so. Every winter shelf at Chemist Warehouse says so. The logic was airtight: vitamin C is involved in immune function, oranges have a lot of it, you can't really overdose because the excess just leaves in your urine, so a 1,000mg effervescent every morning between June and August was an obvious win. Nobel laureate. Tube. Mum. Three sources.
It does almost nothing. The Cochrane Review pooled 29 trials and 11,306 people and found regular vitamin C supplementation cuts cold duration by about 8% in adults, around half a day off a seven-day cold, and does not reduce the chance of catching one in the first place. The exception is people doing serious physical stress (marathon runners, soldiers in subarctic conditions), where supplementation roughly halves the risk of catching a cold. If that is not your week, an effervescent on day one is mostly producing very expensive urine. Pauling was wrong. He spent his later years recommending 18,000mg a day to prevent cancer, which is also wrong. The body uses what it needs and excretes the rest, and the rest is most of it. The actual cold-shorteners are sleep, fluids, zinc within the first 24 hours (modest evidence), and patience. None of those fit on a Berocca label.
Reception
Go deeper
- Coeliac disease basics: what gluten really does · gluten.refdat.com
Sources
- Vitamin C Cold Prevention PRIMARY
- Cochrane Vitamin C REFERENCE
- Vitamin C and Common Cold - Cochrane Review PRIMARY
- Snopes: Vitamin C Colds REFERENCE
- Cochrane Database: Vitamin C and Common Cold PRIMARY
- Mayo Clinic: Cold Prevention REFERENCE