Study Suggests Purple Grape Juice Is Good for the Heart

March 19, 1997

There appears to be something special about the fruits of the vine when it comes to preventing heart disease.

Three years ago, John D. Folts, professor of medicine and director of the Coronary Artery Thrombosis Research and Prevention Laboratory at the University of Wisconsin Medical School, published early findings showing that red wine may prevent blood cells called platelets from becoming hyperactive and sticking to the arterial wall, a process which can contribute to coronary artery disease.

Folts' latest findings indicate that purple grape juice, but not orange or grapefruit juice, also inhibits platelet activity in the small group of human subjects tested. So what do purple grape juice and red wine contain that orange and grapefruit juice don't?

Probably certain types of flavonoids given to them by nature. "That's not to say orange and grapefruit juices don't contain flavonoids -- they do -- and both juices are good for you for a number of reasons. However, our findings suggest specific flavonoids in purple grape juice and red wine have stronger antiplatelet and, quite possibly, antioxidant properties than those in orange or grapefruit juices," says Folts. He presented his findings March 18 at the American College of Cardiology 46th Annual Scientific Session in Anaheim.

Flavonoids are vitamin-like compounds found naturally in many fruits and vegetables, in addition to dark beer and tea. A number of well designed epidemiological studies from around the world have concluded that increased consumption of flavonoids may prevent heart disease and stroke. About 1,000 different kinds of flavonoids exist and many researchers are trying to find out which ones protect against heart disease. Folts' research has focused on beverages containing flavonoids.

Folts says his latest findings add to the scientific body of evidence on the benefits of flavonoids. However, as a researcher, he emphasizes people should discuss the ramifications of his work with their cardiologist or primary care physician.

"These physicians can study our research and determine what's appropriate for you given your medical history," says Folts. Adds Dr. David J. Ende, UW Medical School associate professor of medicine and a cardiologist at UW Hospital and Clinics: "Physicians are familiar with a lot of studies and can present the big picture. I'd also emphasize there is no substitute for eating a healthy diet and exercising regularly."

Folts' studies were divided into two phases. The first compared the abilities of grape, orange and grapefruit juices to reduce platelet activity. Folts began with a variety of animal species and moved on to test a small group of healthy human volunteers. Each person had his or her platelet activity measured 60 minutes before and after drinking 20 to 24 ounces (about three glasses) of one of the three juices.

In all of the studies, purple grape juice reduced platelet activity by more than 40 percent, making it about as effective as aspirin therapy for those who are at risk of or who have heart disease. Neither orange nor grapefruit juice appeared to have antiplatelet properties.

In addition, unlike aspirin, the flavonoids in purple grape juice remained effective when adrenaline levels in the blood were increased. High blood adrenaline commonly results from stress or physical activity.

These dual effects suggest flavonoids might be more effective than aspirin therapy for people with heart disease, though Folts stresses the findings are preliminary. Both he and Ende emphasize that under no circumstances should a person taking aspirin therapy automatically stop it in exchange for grape juice. More research is also needed to determine if purple grape juice might be beneficial when combined with aspirin.

"The flavonoid findings relative to aspirin are an exciting new direction, but they are preliminary, and it would be premature and irresponsible to make broad recommendations," says Folts.

The study's second phase looked at how much purple grape juice was needed to reduce platelet activity if, instead of drinking 20 ounces of purple grape juice all at once, it was consumed daily over a week. Results in both men and women showed that it took about half as much purple grape juice, 10 to 12 ounces in a 160 pound volunteer, if it was given regularly for a week. In other words, purple grape juice appears to have a cumulative protective effect over time.

Folts' studies with humans involved subjects who weren't on medications and didn't have heart disease. Next, Folts, Ende and Dr. Jon Keevil, who is an internal medicine resident at UW Hospital and Clinics, will conduct studies involving humans with known coronary artery disease and who have hyperactive platelets. They want to determine if grape juice turns down platelet activity in patients with heart disease as effectively as it appears to in subjects who do not have heart disease.

Those working with Folts on the flavonoids studies, aside from Drs. Keevil and Ende, were Nabil Maalej, Ph.D.; and Hashim Osman, D.V.M., all of the University of Wisconsin. Folts' research was underwritten in part by Nutricia Research Foundation, Netherlands; Welch Foods Inc., A Cooperative; and the Oscar Rennebohm Foundation, Madison.

CONTACT: Judy Kay Moore, (608) 263-5561