Wait, Now Antioxidants are Bad?

There are already plenty of good reasons to avoid expensive vitamin supplements and just make sure to eat enough healthy foods, but here's a new one: some supplements might interfere with some of the the benefits of exercise.

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.

That's thanks to the other beneficial effects of those foods, which brings us to another reason vitamin supplements are generally not a great idea. Vitamins separated from the foods that had contained them might help prevent scurvy or other diseases caused by deficiency. But they don't provide many of the micronutrients that are contained in foods, many of them not even discovered yet. Eating a healthy diet will provide plenty of both.

Still, this is just one study. It could be that for at least some people, even those who exercise, antioxidant supplements are helpful, or at least not harmful. But The New York Times, in search of balance, apparently could come up with just one person to go negative on the research: a guy from the Council for Responsible Nutrition, a lobbying firm for the dietary supplement industry.