Antioxidant Supplements May Block One of the Benefits of Exercise

A study published this week in The Proceedings of the National Academy of Sciences claims that taking antioxidant vitamins C and E may prevent exercise from improving insulin sensitivity. This may be important information if you're working out to stave off diabetes -- and taking a daily dose of vitamins. The researchers found that healthy male subjects who exercised and took the vitamins didn't show an improvement in how their bodies react to insulin, while the subjects who exercised, but didn't take the supplements, showed an increase in insulin sensitivity.

This is one of those studies that makes me think, "Hmmmmmm...."

It's interesting and something I've never thought of before. We know exercise is a good strategy for people who are at risk for diabetes because it helps to reduce high blood pressure, makes it easier to stay trim and improves how your body responds to insulin. In fact, most people with diabetes or who are pre-diabetic are told to exercise.

While exercise is extremely beneficial for your health, it also increases production of some extra free-radical oxygen molecules that can damage the healthy cells in your body. Some vitamins, especially vitamins A and C function as antioxidants; that is they counteract those free radical oxygen molecules before they do any damage.

Taking vitamins seems like the perfect solution for stopping those post-exercise free-radicals in their tracks. And they probably do, but, according to the researchers of this new study, reducing the amount of free-radicals may actually eliminate some of the benefits of exercise, at least insulin sensitivity.

Why? I'll try to explain. For exercise to improve your body's reaction to insulin, a certain threshold of free-radical production may be necessary for to trigger that reaction. The increased levels of free-radicals stimulates your body to take certain steps to protect itself -- like increasing insulin sensitivity. Taking those antioxidant vitamins may wipe out enough free-radicals so that threshold isn't reached. It doesn't mean the exercise isn't beneficial for other reasons, but at least in this study, the lack of free radicals appear to have reduced some of the benefit of exercise.

I think it's important to know this is a small study, and the subjects were healthy young men, so we don't know if the results would be the same in older people, women, or anyone at a high risk for diabetes. But it is an interesting study.

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