If you’re trying to ward off the sniffles, you can take vitamin D supplements out of your shopping cart: A new study reports that dosing with the vitamin does nothing to prevent colds or other forms of upper respiratory tract infections (URTI).
The effect of vitamin D on the immune system has been debated for a long time. Controlled laboratory research has shown that vitamin D has several beneficial effects on the immune system, and some studies conducted in the past have suggested that people with low levels of the vitamin are at higher risk for URTIs. But the authors of the new study, published Tuesday in the Journal of the American Medical Assn., point out that the previous studies were poorly controlled and results have been mixed, calling into question whether the vitamin does anything at all for URTIs.
To answer the question, the researchers, who are based in New Zealand, conducted a randomized trial nicknamed VIDARIS, for "Vitamin D and Acute Respiratory Infection Study." They gave 161 subjects doses of vitamin D once a month for 18 months, and another group of 161 people a placebo. The doses used were those that appeared to have been the most effective against colds in previous studies.