Roughly 90% of American adults do not eat enough fruits and vegetables, but many are trying to make up for it by popping pills. According to the Council for Responsible Nutrition, 75% of U.S. adults take a dietary supplement of some kind. Multivitamins, many people believe, are a one-step way to get the nutrients they need.But new research published in the Annals of Internal Medicine suggests that vitamins and supplements may not be enough to keep you healthy.