Antioxidants iffy

I've been getting increasingly skeptical of the current obsession with antioxidants as I've been learning more about the supplement industry, the amount of money people are making off of multivitamin supplements, and the degree to which heavy marketing tactics are employed to get people to take them. Bad Science pushed me quite a bit more in that direction with the clinical trial evidence presented there showing no connection between increased antioxidant consumption and better physical health. But my opinion was still somewhat tentative, since it's hard to resist the feeling that all the people talking about this couldn't have it entirely wrong, and after all antioxidants aren't going to hurt.

Well, maybe not so fast.

Brooks Moses has a very interesting journal post this evening pointing at a recent medical study indicating that antioxidants prevent health-promoting effects of physical exercise in humans. Specifically, the researchers studied the effects of a vitamin C and vitamin E supplement on insulin sensitivity. Normally, physical exercise produces "oxidative stress," which helps ameliorate insulin resistance (the biological change underlying type II diabetes). However, this appears to be the case only in the absence of antioxidant supplements. Taking antioxidant supplements in the study caused the effect of exercise on insulin sensitivity to be lost.

I think we're fast getting to the point where we should be telling people to stop taking antioxidant supplements, particularly large-dose ones. (Those are, for those not as familiar with the term, mainly vitamin A, vitamin C, and vitamin E.) There's very little competent scientific evidence that they do anything for you at all except moderately reduce the duration of (but not the chances of contracting) the common cold in the specific case of vitamin C, and there's some evidence that they may actually be harmful, particularly for people in danger of developing type II diabetes who are attempting to ward that off via exercise. Just because they're present in nutritious foods doesn't mean that taking large doses in supplement form is doing what you expect.

Once again, one of the basic messages of Bad Science is reinforced: the best way to be healthy is to eat healthy food and exercise regularly. We're not as good at designing short-cuts as we think we are.