Vitamins Mess with Exercise Benefits

June 11th, 2009 | Sources: NY Times, PNAS

In a scientific study sure to qualify for the Hall of Fame of Counterintuitive Results, scientists in Germany and Boston have concluded that people who exercise to reduce diabetes risk ought to avoid antioxidants like vitamins E and C. 
wtfMichael Ristow, a nutritionist at Jena University, Ron Kahn of the Joslin Diabetes Center and their colleagues published the mind-bending findings in the Proceedings of the National Academy of Sciences

At the moment, “get more exercise” is just about the first thing that pops out of clinicians’ mouths when advising patients how to mitigate the risk of diabetes.

But exercise stimulates glucose metabolism in muscle cells and an unavoidable byproduct of this biochemical cascade is the release of oxygen-based free-radicals that damage normal tissue.

The damage, dubbed oxidative stress, accumulates with age and some posit it contributes to many deleterious cellular phenomena that are observed with increasing age.

Since human tissue has only a limited capacity to combat oxidative stress, antioxidant vitamins, which combat oxygen-based free-radicals, would seem to be a perfectly reasonable supplement.

Not so, say the scientists. They asked young men to exercise while giving half of them vitamins C and E and the others placebos. The scientists subsequently measured insulin sensitivity and several indicators of oxidative stress.

The team found that in the group taking the vitamins, insulin sensitivity did not improve and the body’s natural defenses against oxidative stress were not activated.

They suggest that’s because the vitamins destroy the free-radicals, thereby short-circuiting the body’s normal response to exercise.

“If you exercise to promote health, you shouldn’t take large amounts of antioxidants,” Ristow told the New York Times. “Antioxidants…inhibit otherwise positive effects of exercise, dieting and other interventions.”


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