NIH - Comments on Multivitamins
A large percentage of adults in the United States take multivitamins thinking that these pills will give them health benefits. The National Institutes of Health (NIH) said on May 17, 2006 that there is not too much evidence that these pills do the users much good. They could even give some of the users a vitamin overload.
“Half of American adults are taking MVMs [multivitamin/mineral] and the bottom line is that we don’t know for sure that they’re benefiting from them. In fact, we’re concerned that some people may be getting too much of certain nutrients,” said J. Michael McGinnis, M.D., M.P.P., Senior Scholar with the Institute of Medicine of the National Academy of Sciences, who chaired the panel.
The panel said that the combined use of calcium and vitamin D supplementation for postmenopausal women to protect bone health is recommended, and they also advocated anti-oxidants and zinc for use by non-smoking adults with macular degeneration, an eye condition that can cause blindness. The panel supported the recommendation that women of childbearing age take daily folic to prevent birth defects of the brain and spinal cord in infants.
The panel found several possible risks associated with multivitamin use, however. "Among these is the potential for overconsumption of certain nutrients, with the resulting possibility of adverse effects. Though health-conscious individuals are likely to be focused on ensuring that they meet the recommendations for essential nutrients, the combined effects of eating fortified foods, taking MVMs, and consuming single vitamins or minerals in large doses, may lead them to unwittingly exceed the Upper Levels (ULs) of nutrients, which can be harmful."