Free radicals have important jobs and deserve some respect.

Q: I read that taking antioxidant vitamins can cancel out the benefits of exercise. I thought that the more antioxidants I take the healthier I’ll be. What’s the scoop?

A: You’re referring to some intriguing research done in Germany. Scientists studied 40 people, half of whom took 1000 milligrams of vitamin C and 400 international units of vitamin E daily, and half who did not. They asked all participants to exercise for 85 minutes a day, five days a week, for four weeks. Muscle biopsies showed that those who did not take the vitamins had double the amount of free radicals in their tissues after exercise. In those who did take the vitamins the antioxidant vitamins were doing their job mopping up free radicals.

The researchers also measured insulin sensitivity, which is normally increased during exercise, and is one of the great benefits of moving the body. Decreased insulin sensitivity is a important precursor to type 2 diabetes and heart disease. In this study they found that participants who did not take the vitamins had significantly improved insulin sensitivity, while those who did take the vitamins had no improvement in insulin sensitivity after exercise. In other words, the antioxidant vitamins canceled out the benefits of exercise.

Free Radicals Aren’t All Bad
There’s no doubt that in excess, free radicals are harmful and accelerate aging. However, the key word here is excess—free radicals have beneficial jobs to do in the body so it’s not helpful to go overboard and mop them all up.

The downside of taking lots of supplements of any kind is that they are highly concentrated biochemicals, and therefore have the potential to make the liver work very hard to process them. Meanwhile, the liver is also working hard to help regulate blood sugar and insulin levels, neutralize toxins that come in through the air and skin, and filter impurities from whatever you’ve eaten recently before the nutrients enter the bloodstream.

In Moderation, Supplements are Powerful Allies
Vitamins and other nutritional and herbal supplements can be powerful allies in preventing and treating disease, and maintaining optimal health. However, it’s important to be thoughtful and discriminating about what’s going down the hatch. Taking handfuls of vitamins every day may do as much harm as good, especially as we age and liver function declines. A balanced diet of wholesome foods will provide an adequate baseline of nutrients for most people. Concentrated fresh fruit and vegetable juices can provide an additional level of nutritional support. For individual weaknesses and ailments, a moderate amount of high quality, targeted supplements can provide the extra boost needed to optimize health.

Ristow M, Zarse K, Oberbach A et al, “Antioxidants prevent health-promoting effects of physical exercise in humans,” Proc Natl Acad Sci U S A. 2009 May 11.