Protection Against Heart Disease
In a study in which blood samples were drawn from 20 healthy volunteers both before and after they drank grape juice, researchers found several beneficial effects from their juice consumption.
First, an increase occured in levels of nitric oxide, a compound produced in the body that helps reduce the formation of clots in blood vessels. Second, a decrease occurred in platelet aggregation, or blood clotting, by red blood cells. Lastly, researchers saw an increase in levels of alpha-tocopherol, an antioxidant compound that is a member of the vitamin E family, and this increase was accompanied by a 50% increase in plasma antioxidant activity.
These findings confirmed the benefits found in an earlier study, where researchers found not only an increase in blood antioxidant activity, but also discovered that grape juice protected LDL cholesterol from oxidation, a phenomenon that can turn LDL into an artery-damaging molecule. (Although LDL is often called the "bad" form of cholesterol, it is actually benign and only becomes harmful after it is damaged by free radicals or "oxidized."
Additionally, investigators have found that phenolic compounds in grape skins inhibit protein tyrosine kinases, a group of enzymes that play a key role in cell regulation. Compounds that inhibit these enzymes also suppress the production of a protein that causes blood vessels to constrict, thus reducing the flow of oxygen to the heart. This protein, called endothelin-1, is thought to be a key contributing agent in the development of heart disease.
A study published in the journal Hypertension sheds new insight on the mechanisms of action through which resveratrol inhibits the production of the potent blood vessel constrictor, endothelin-1 (ET-1). Resveratrol appears to work at the genetic level, preventing the strain-induced expression of a gene that directs the production of ET-1. Normally, ET-1 is synthesized by endothelial cells (the cells comprising the lining of blood vessel walls) in response to free radicals formed as a result of strain or stress. Resveratrol prevents the expression of ET-1, at least in part, by significantly lessening free radical formation, thus preventing the production of the agents that, in turn, activate the signaling pathways that control the creation of ET-1.