Vitamin D is a hot seller in the supplement aisles, but it won't help you ward off or recover faster from the common cold in adults.
That's according to a study in the October 3 issue of the Journal of the American Medical Association. In the randomized, double-blind placebo-controlled trial, 322 healthy men and women age 18 or older received either vitamin D pills or a placebo for 18 months, including two winter seasons. During that time, they also answered monthly questionnaires about their health and contacted researchers whenever they experienced cold symptoms.
There were 593 colds in the vitamin D group, and 611 in the placebo group, not a significant difference, according to the team led by researchers at the University of Otago in New Zealand.
The investigators also found no significant difference between the groups in the number of participants who had colds (3.7 per person in the vitamin D group and 3.8 per person in the placebo group, on average), duration of symptoms per cold (12 days in each group, on average), the number of days of missed work as a result of colds (less than a day in each group, on average), or the severity of colds.
"The fact that receptors for vitamin D exist in many organs and structures of the body has led to much speculation on the multifaceted prowess of this vitamin," said Marvin Lipman, M.D., Consumer Reports chief medical consultant. "But only randomized controlled clinical trials can turn such belief into truth."
Bottom line: Some prior research had hinted that vitamin D might improve immune function and possibly prevent respiratory infections like the common cold. But in this this well-designed study, monthly doses of 100,000 international units of vitamin D (a dosing regimen more than 5 times the recommended daily allowance of 600 IU for adults ages 19 to 70) did not significantly reduce the incidence or severity of colds. See our full report on alternative therapies to find out which cold and flu treatments our readers said helped a lot in our recent survey of subscribers to Consumer Reports.