Vitamins C. E may block exercise benefit

BOSTON, May 13 (UPI) -- Taking antioxidants such as vitamins C and E may nullify the benefit of exercise to reduce the risk of diabetes, U.S. researchers suggest.

Dr. C. Ronald Kahn of the Joslin Diabetes Center and Harvard Medical School in Boston says that part of the reason that exercise improves insulin sensitivity is that it causes oxidative stress on the muscles, HealthDay reported.

Insulin resistance occurs when the cells of the body become resistant to the effects of insulin increasing blood sugar and diabetes risk.

"If you take anti-oxidants like vitamins C and E, you block the oxidative stress response, but you also block the beneficial effects of exercise on insulin sensitivity," Kahn said.

Kahn's team looked at the benefit of exercise in increasing insulin resistance in 39 young men -- roughly half took supplemental vitamins C and E.

The study, published in the online edition of the Proceedings of the National Academy of Sciences, found the men taking the vitamins had no change in their insulin resistance and almost no activation of the body's natural defense mechanism against oxidative damage.

"If you are exercising, in part, to reduce diabetes risk, you shouldn't take vitamin C and E, because you are going to block some of the beneficial effect of the exercise to prevent the diabetes," Kahn told HealthDay.