Resveratrol — a natural antioxidant compound found in red grapes and other plants — counteracts many of the cardiovascular benefits of exercise in older men,  including reduced blood pressure and cholesterol, according to research conducted at The University of Copenhagen.

Lasse Gliemann, a PhD student who worked on the study at The University of Copenhagen, explains how they conducted the research, and the results they found:

“We studied 27 healthy, physically inactive men around 65 years old for 8 weeks. During the 8 weeks all of the men performed high-intensity exercise training and half of the group received 250 mg of resveratrol daily, whereas the other group received a placebo pill (a pill containing no active ingredient). The study design was double-blinded, thus neither the subjects nor the investigators knew which participant that received either resveratrol or placebo.

“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.”

This study suggests that reactive oxygen species, generally thought of as causing aging and disease, may be a necessary signal that causes healthy adaptations in response to stresses like exercise,  the researchers suggest.

This research adds to the growing body of evidence questioning the positive effects of antioxidant supplementation in humans, the researchers note.