A daily multivitamin has no effect on the incidence of cardiovascular disease and related conditions in men, according to a large study published Monday in the Journal of the American Medical Assn.
The study, conducted by researchers at Harvard Medical School and the Harvard School of Public Health, used data from the Physicians’ Health Study II, which has been tracking the effects of multivitamin use in over 14,000 physicians age 50 and above from 1997 until 2011. The PHS-II is the only large, long-term, placebo-controlled clinical trial of multivitamin use conducted to date, allowing its investigators to ask questions about any number of potential health impacts of multivitamins on older men; in a paper published last month, data from the PHS-II showed that daily multivitamin use slightly reduced the risk of cancers in men.
Vitamins are big business in the U.S., with annual sales in the billions of dollars. Many people take them not because they have a vitamin or mineral deficiency but because they believe the supplement can help prevent chronic disease.
And while there are numerous potential biological reasons that multivitamin use might improve cardiovascular health — including the proven positive impact of fruit and vegetable intake — the results of studies looking at their effects have been mixed, with some showing positive results and others showing no effect whatsoever. That may be in part because such studies have been primarily observational and conducted by questionnaire, making it more likely that an unobserved factor, such as exercise or diet, is the true cause of a subject’s improved cardiovascular health. After all, people who take vitamins may just be the types of people who watch what they eat and work out regularly.