A team led by nutritionist Michael Ristow of the University of Jena in Germany asked a group of young men to exercise after giving half of them moderate doses of vitamins C and E. In the pill-takers, exercise failed to improve insulin sensitivity, which is believed to be one of the important benefits of activity. (The more sensitive the body is to insulin, the better able it is to convert glucose into energy, keeping blood sugar levels on an even keel.) Antioxidant takers also failed to experience a boost in their body’s natural defense mechanism against oxidative damage.

Quoted in The New York Times, Dr. Ristow didn’t beat around the bush. “If you exercise to promote health, you shouldn’t take large amounts of antioxidants,” he said. As he points out, the study results suggest that taking antioxidant vitamins may short-circuit the body’s own natural antioxidant system.

The researchers were quick to say that antioxidant-rich fruits and vegetables are fine, since they contain many substances that are known to be healthy.

This isn’t the first study to point to potential risks from taking high doses of antioxidants. But then other findings continue to suggest that there may be real benefits. In people with early signs of macular degeneration, for instance, a mix of antioxidants seems to slow the progression of the vision-robbing disease. And there’s provocative evidence from early trials that a mix of antioxidants may prevent or slow noise-induced hearing loss.

For now, it’s probably wise to go easy on antioxidants unless your doctor says you need a supplement. And, of course, to help yourself to an extra serving or two of fruit or vegetables.

© 2009 PDQhealth