Mounting Evidence Shows Health Benefits of Grape Polyphenols

29/10/08 A growing body of research data suggests that consuming foods rich in polyphenols from grapes, including red wine, helps reduce the risk of heart disease, according to a review article in the November issue of Nutrition Research.

"Consumption of grape and grape extracts and/or grape products such as red wine may be beneficial in preventing the development of chronic degenerative diseases such as cardiovascular disease," write Wayne R. Leifert, Ph.D., and Mahinda Y. Abeywardena, Ph.D., of Commonwealth Scientific and Industrial Research Organisation in Adelaide, Australia.

The authors review the accumulating evidence that grape polyphenols work in many different ways to prevent cardiovascular and other "inflammatory-mediated" diseases. Polyphenols are natural antioxidants found in grapes and some other plant foods. Their types and actions vary, depending on where in the grape they are found. Grape seeds, grape skin, and grape juice contain several types of polyphenols, including resveratrol, phenolic acids, anthocyanins, and flavonoids.

Through their antioxidant effects, grape polyphenols help to slow or prevent cell damage caused by oxidation. Polyphenols decrease oxidation of low-density lipoprotein cholesterol ("bad" cholesterol)—a key step in the development of atherosclerosis (hardening of the arteries). Grape polyphenols also have other protective effects on the heart and blood vessels, including actions to reduce blood clotting, abnormal heart rhythms, and blood vessel narrowing. It's not yet clear exactly how these benefits of polyphenols occur, although there is evidence of effects on cellular signaling and on the actions of certain genes. The wide range of health-promoting effects suggests that several different, possibly interrelated mechanisms may be involved.

So far, most of the evidence on grape polyphenols comes from laboratory experiments and animal studies. However, a few studies support the disease-preventing benefits of grapes in humans. Studies in patients treated with grape seed extracts have shown improvements in blood flow and cholesterol levels. In other studies, drinking Concord grape juice has improved measures of blood flow in patients with coronary artery disease and lowered blood pressure in patients with hypertension.

Studies investigating the lower rates of heart disease in France—the so-called "French paradox"—first raised the possibility that red wine might have health benefits. The subsequent research reviewed by Drs. Leifert and Abeywardena helps build the case that grapes and grape products might be a useful part of strategies to lower the high rate of death from cardiovascular disease.

At a time of growing interest in the use of "functional foods and nutraceuticals" to promote heart health, grapes and grape polyphenols are "attractive candidates" for use in such supplements, Drs. Leifert and Abeywardena believe. "Therefore," they conclude, "supplementation with grape seed, grape skin or red wine products may be a useful adjunct to consider for a dietary approach in the prevention of cardiovascular diseases, although additional research is required to support such a strategy."