The Heart-Healthy Cup Runneth Over -- With Grape Juice

November 10, 1998

DALLAS, Nov. 10 -- Purple grape juice seems to have the same effect as red wine in reducing the risk of heart disease, according to a study presented today at the American Heart Association's 71st Scientific Sessions.

Intrigued by research showing lower rates of heart disease in people who drink one to two glasses of red wine per day, Jane E. Freedman, M.D., and colleagues studied purple grape juice to determine if it has similar effects. "Alcohol is a potent inhibitor of the platelet aggregation, or blood clotting, that can lead to heart attack and stroke. But alcohol inhibits blood clots only at high levels in the blood -- high enough to cause intoxication," she says. "We were interested in finding out how to get the benefits of clot inhibition seen with red wine, but without the intoxicating effects of alcohol."

Freedman, an assistant professor of medicine and pharmacology at Georgetown University Medical Center, Washington, D.C., studied blood platelets -- cells in the blood that clump to form blood clots -- in a solution containing purple grape juice and in "control" solutions that did not. Platelets in purple grape juice clotted about 30 percent less than did the controls and released three times more nitric oxide, a chemical that dilates, or widens, blood vessels and also serves as a powerful inhibitor of clotting because it keeps platelets from sticking together. Both effects of nitric oxide help reduce the likelihood that blood clots will block the arteries and cause a heart attack.

In addition, platelets in purple grape juice released 55 percent less superoxide -- one of the reactive oxygen molecules known as free radicals. Free radicals react with cholesterol, possibly making it more dangerous to blood vessels. Freedman says she decided to look for superoxide because it quickly inactivates the beneficial effects of nitric oxide.

In another set of experiments, researchers tested the effects of a substance in grape juice called quercetin. Quercetin is one of a group of compounds called flavonoids, which are thought to have antioxidant properties. Significant amounts of flavonoids are found in onions, apples, tea, broccoli, berries and red wine, with each of those items containing its own unique combination of flavonoids. "Platelets in quercetin were less likely to be activated, or 'turned on,'" Freedman explains. "A platelet has to be activated to form blood clots. The study showed that this flavonoid inhibits platelets, which may explain the beneficial effect of purple grape products in heart disease."

Freedman says the grapes used to make red wine and purple grape juice are often different from the red and white grapes at the grocery store. "Eating pitted purple grapes may not have the same effect as drinking purple grape juice because of the variety of grapes available and the concentration of flavonoids that results from juice processing," she says.

Co-authors are Ryan Sauter, B.S., and John D. Folts, Ph.D.
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For more information Nov. 8-11 contact Carole Bullock or Brian Henry at the Dallas County Convention Center: (214) 853-8056.
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American Heart Association

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