Last year, the Iowa Women’s Health Study found no health benefits from daily multivitamins. That was, however, an observational study in which women who were taking vitamins anyway were compared to those who did not.
Randomized controlled trials offer much more reliable evidence. The Physicians Health Study II randomly assigned more than 14,000 male doctors to take a multivitamin or a placebo. The study ran from 1997 to 2011, and during that time the men taking multivitamins were 8 percent less likely to develop cancer. That difference is statistically significant although the effect is modest.
[Journal of the American Medical Association, online Oct. 17, 2012]
