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. 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. 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.
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. A platelet has to be activated to form blood clots.