A review published in the November issue of Nutrition Research and an article published in the October, 2008 Journal of Gerontology: Biological Sciences report positive findings for grapes and grape polyphenols in reducing risk factors for cardiovascular disease. Polyphenols, including resveratrol, phenolic acids, anthocyanins, and flavonoids, are antioxidant compounds that occur in grapes and other plant foods, which are believed to be responsible for many of the health-promoting effects associated with these foods.
In their review, Wayne R. Leifert, PhD, and Mahinda Y. Abeywardena, PhD, of Commonwealth Scientific and Industrial Research Organisation in Adelaide, Australia evaluated the growing evidence for a protective effect of grape polyphenols against cardiovascular disease and other diseases mediated by inflammation. They conclude that, while grape polyphenols’ primary mechanism appears to be that of reducing low-density lipoprotein oxidation via their antioxidant property, the compounds also decrease blood clotting, improve abnormal heart rhythms and help reduce narrowing of the blood vessels, possibly through effects on cellular signaling and gene activity. Although most of the research involving grape polyphenols has been of the laboratory variety, clinical trials have demonstrated improved cholesterol levels and blood flow in human volunteers. Observation of populations who regularly consume red wine has noted a lower rate of heart disease despite consumption of fatty foods.
"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," the authors conclude. "Therefore, 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."
In the Journal of Gerontology, researchers at Michigan State University and the University of Michigan report that laboratory rats bred to develop salt-sensitive hypertension experienced a reduction in blood pressure and improved heart function after consuming powdered table grapes.
Mitchell Seymour, MS and colleagues administered low or high salt diets which were supplemented with or without grape powder. Some of the animals also received an antihypertensive drug. After 18 weeks of treatment with grape powder, the rats had reduced blood pressure and inflammation, improved heart function, and less heart muscle damage compared to animals that did not receive grapes. Treatment with the antihypertensive drug also reduced blood pressure, but did not protect the animals’ hearts from damage. "These findings support our theory that something within the grapes themselves has a direct impact on cardiovascular risk, beyond the simple blood pressure-lowering impact that we already know can come from a diet rich in fruits and vegetables," Seymour commented.
"The inevitable downhill sequence to hypertension and heart failure was changed by the addition of grape powder to a high-salt diet," noted coauthor Steven Bolling, MD, in whose laboratory the research took place. "Although there are many natural compounds in the grape powder itself that may have an effect, the things that we think are having an effect against the hypertension may be the flavanoids – either by direct antioxidant effects, by indirect effects on cell function, or both. These flavanoids are rich in all parts of the grape - skin, flesh and seed, all of which were in our powder."
"There is, as we now know, a great variability, perhaps genetic even, in sensitivity to salt and causing hypertension," Dr Bolling added. "Some people are very sensitive to salt intake, some are only moderately so, and there are perhaps some people who are salt resistant. But in general we say stay away from excess salt."