Wait, now antioxidants are bad?

New research shows that preventing diabetes through exercise -- recommended by all physicians -- might be harder when exercisers also take antioxidant supplements like vitamins C and E.

It sounds counterintuitive. During exercise, muscle cells metabolize glucose. That causes tissue-damaging oxygen molecules to be released. Antioxidants are thought to be good for you because they attack those molecules. But according to the study, by scientists at the University of Jena in Germany, those "free radical" molecules seem to increase the body's sensitivity to insulin and hence may stave off Type II diabetes.

The research was published this week in The Proceedings of the National Academy of Sciences.

One of the researchers told The New York Times that if you exercise, "you shouldn't take large amounts" of antioxidant vitamins." Eating fruits and vegetables, though, is fine -- even those that contain antioxidant vitamins.