A natural antioxidant found in red grapes, resveratrol, may not be as beneficial as previously thought. New research in older men suggests that it may counteract the benefits of cardiovascular exercise.

The study comes from researchers at the University of Copenhagen, who suggest that eating an antioxidant-rich diet may hinder the health benefits of exercise, such as lower blood pressure and cholesterol.

The researchers note that since aging is associated with impaired vascular functions due to oxidative strain, resveratrol – which has been shown to decrease vascular disease and improve cardiovascular health – was initially expected to improve cardiovascular health in older men. After all, it has been proven in animal studies to be of benefit in that department.

But in a surprise twist, the researchers found that unlike in our animal counterparts, resveratrol actually impairs the cardiovascular benefits of exercise in older men.

For 8 weeks, the researchers followed 27 men who were around 65 years of age and in good health. During that time, the men all took part in high-intensity exercise, but half of the men received 250 mg of resveratrol each day, while the other half received a placebo pill.

Lasse Gliemann, a researcher who worked on the study, explains the results and design of the experiment:

The study design was double-blinded, thus neither the subjects nor the investigators knew which participant 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.”

So even though the men were gaining health benefits from exercising, the ones who took a daily dose of resveratrol saw many of these benefits effectively wiped out.

There have been several studies lately both lauding and denouncing the health benefits of resveratrol. A 2012 study, for example, shows resveratrol’s potential as a therapy for diabetes, Alzheimer’s disease and heart disease. Yet, another study from the same year reveals that the antioxidant may not benefit healthy women.

Though there are arguments for and against the compound found in red wine, this particular study from the University of Copenhagen suggests that “reactive oxygen species, generally thought of as causing aging and disease, may be a necessary signal that causes healthy adaptions in response to stresses like exercise.”

In short, ingesting too many antioxidants may not be a good thing, but the researchers do say that the amount of resveratrol given to the men in the study exceeds what would normally be ingested through food alone.

Written by Marie Ellis