Too Many Antioxidants: Resveratrol Blocks Heart Benefits of Exercise in Men

How much is too much? That's a good question, especially when it comes to your health. Antioxidants are generally touted as being good for you. In fact, the compound found in red grapes and other plants, called resveratrol, has received widespread attention as a possible anti-aging agent. New research, though, seems to indicate that this natural antioxidant may block many of the cardiovascular benefits of exercise in older men.

Earlier studies in animals showed that resveratrol improved cardiovascular effects of exercise. This latest study, though, seems to indicate that the compound has the opposite effect in humans. It seems that antioxidants are not a fix for everything and, like most things, should be taken in moderation.

In order to test the effects of resveratrol, the researchers studied 27 healthy, physically inactive men around 65 years of age for eight weeks. During that time, all of the men performed high-intensity exercise training. While half of the group received 250 mg of resveratrol daily, the other half received a placebo pill. Neither the participants nor the researchers knew which participant was receiving what pill.

"We found that exercise training was highly effective in improving cardiovascular health parameters, but resveratrol supplementation attenuated the positive effects of training on several parameters including blood pressure, plasma lipid concentrations and maximal oxygen uptake," said Lass Gliemann, one of the researchers, in a news release.

In other words, the researchers found that the resveratrol supplements in aged men reduced the positive cardiovascular health benefits of exercise. This was especially surprising since animal studies showed the exact opposite effect. That said, the researchers were quick to note that the men in the study were given much higher quantities of resveratrol than what could be obtained by intake of natural foods.

"In addition to the surprising findings on exercise and resveratrol, this study shows the continuing need for mechanistic studies in humans," said Michael Joyner, from The Mayo Clinic, in a news release. "Too often human studies focus on large scale outcomes and clinical trials and not on understanding the basic biology of how we adapt."

The findings are published in the Journal of Physiology.