Is it the grape, or the wine?

Summarized by Robert W. Griffith, MD
October 12, 1999 (Reviewed: January 21, 2005)

By now, most people are aware of the health benefits of moderate consumption of wine. Recently, researchers have tried to determine what it is in wine that confers the health advantages. Compounds called flavonoids, which are found in a variety of fruits and vegetables, are the likely candidates. Purple grape juice is a good source of certain flavonoids, and it has been shown in test-tube experiments to improve some biological circumstances that promote arteriosclerosis (i.e. clumping of blood platelets and oxidation of low density lipoprotein [LDL] cholesterol). Now researchers have demonstrated apparent beneficial effects of drinking purple grape juice on the function of the lining of arteries and on the behavior of LDL in patients with coronary artery disease.

Fifteen people (12 men, three women, average age 62 1/2) with coronary artery disease (as shown on angiography) drank roughly 20 ounces of purple grape juice twice a day for two weeks.

The main artery in the arm (the brachial artery), which resembles the coronary arteries from the way its lining functions, was examined using ultrasound. First, a blood pressure cuff was inflated for 4 1/2 minutes, and after it was let down, the blood flow in the forearm was measured. The flow after this temporary blockage was representative of the function of the lining of the artery. A second stimulus to increasing the blood flow, nitroglycerin placed under the tongue, was also used. These procedures were done at baseline, and after the two weeks' purple grape juice.

Full analysis of blood lipids was also done before and after the grape juice regime. Particles of LDL were obtained by ultracentrifuge, and examined to see how quickly they could be oxidized by a copper solution to form compounds harmful to the artery wall.

The results showed that after 14 days of drinking purple grape juice there was an increase in the average forearm blood flow following removal of the cuff from 2.2% at baseline to 6.4% after 14 days. Although both percentages were small, this result was highly significant. The nitroglycerin-induced changes were less dramatic - 9.4% at baseline increased to 12.1% after the grape juice regime.

This study supplies another link in the chain between swallowing flavonoids and reducing the risk of coronary artery disease. It is likely that flavonoids work in at least two ways - decreasing the clumping of platelets, and decreasing the oxidation of LDL to harmful products. Clearly, purple grape juice has effects that are favorable for people with arteriosclerosis involving arteries like the coronaries. People wishing to have the health advantages of red wine but who want to avoid the pleasures of alcohol now have a good alternative.

Source

• Purple grape juice improves endothelial function and reduces the susceptibility of LDL cholesterol to oxidation in patients with coronary artery disease. JH. Steine, JG. Keevil, DA. Wiebe, Circulation, 1999, vol. 100, pp. 1050--1055