More than half of American adults take a vitamin or mineral supplement, says Harvard Medical School's Dr. JoAnn Manson, chief of preventive medicine at Brigham and Women's Hospital. And many wonder whether they really should be. Or whether they're taking the right ones, or the right doses. "It's really important to get help separating fact from fiction," Manson says, "because there's so much hype about dietary supplements, and very often the benefit is quite limited." Quite limited indeed, at least for the general population, according to the evidence so far. Manson is lead author on a sweeping new overview of vitamin and mineral supplements in the journal JAMA, and here's how she sums it up: The key message is that for most of the population, it's best to get these vitamins and minerals from the diet, from foods. That's where they're best absorbed, and they're in the optimal biological ratios. However, some subgrou...