Not curing the common coldBMJ 2012; 345 doi: https://doi.org/10.1136/bmj.e6610 (Published 03 October 2012) Cite this as: BMJ 2012;345:e6610
A large dose of oral vitamin D every month did not prevent a single upper respiratory tract infection in the latest trial to test supplements against a placebo⇑. Healthy adults from Christchurch in New Zealand took 100 000 IU a month for 18 months. They reported the same number of coughs and colds as controls (3.7 v 3.8 per person; risk ratio 0.97, 95% CI 0.85 to 1.11). Their upper respiratory symptoms were just as severe and lasted just as long as symptoms reported by controls, despite significantly higher serum concentrations of 25-hydroxyvitamin D (25-OHD). The supplements did not reduce sickness absence from work or the proportion of throat swabs containing pathogenic viruses.
This was a rigorous trial, big enough to report a trustworthy negative result, says a linked editorial (p 1375). There is no evidence here, or anywhere else, that vitamin D supplements help healthy adults avoid viral coughs, colds, or sore throats. The 322 participants were not deficient, but neither are the many thousands of people who look to vitamin D supplements for protection every winter. This trial ran through two winter seasons.
Vitamin D protects bone health but does not prevent or cure the common cold, says the editorial. It’s a pity, but we should believe it. Vitamin D can be added to the long list of other ineffective prophylactics and remedies that includes vitamin C, echinacea, garlic, intranasal corticosteroids, and zinc.
Cite this as: BMJ 2012;345:e6610