Alice Lichtenstein, a professor of nutrition science and policy at Tufts University's Friedman School of Nutrition, worries that supplements give Americans license to continue their unhealthful ways so long as they pop a pill after the steak and hot fudge sundae. A balanced diet is still the best source of nutrients. Adding supplements—or fruits and veggies, for that matter—to a high-calorie diet is not going to work magic. Good health begins with physical activity and a balanced diet that is heavy on fruits, veggies, whole grains, "good" fats, and fish and light on red meat, "bad" fats, and processed food—and not too high in calories. "Nature," says Lichtenfeld, "is probably better than our manufacturers."
Updated on 5/9/2012: This story was originally published on Dec. 9, 2008. It has been updated.