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This is Scientific American's 60-second Science. I'm Karen Hopkin. This will just take a minute.

Exercise is good for you. Antioxidants are good for you, but put them together, and it’s not as good as you think because a recent study shows that some vitamins block the beneficial effects of exercise. A good workout not only get your heart pumping, it makes you body better able to process glucose¹ and decreases your risk of diabetes² and it does so, in part, by firing up you cell’s mitochondria.  Stoking those mitochondrial flames boosts your metabolism³, but it also throws off so-called “free radicals⁴” which are usually considered harmful. So adding antidioxidants, which get rid of free radicals, should make your workout even healthier, right?

Well, no, forty men took part in a four-week training program, half the group also received daily doses of vitamins C&E. The researchers discovered that exercise on its own improves insulin sensitivity, which keeps diabetes at bay, but taking the vitamins erased⁵ that gain, findings that appear in the May 12th issue of Proceedings⁶ of the National Academy Sciences. So you actually need a burst of potentially damaging radicals to reap some of the important awards of a good sweat, which means that even on a molecular⁷ level: no pain, no gain.

Thanks for the minute for Scientific American's 60-second Science. I'm Karen Hopkin.