It's a real chicken and egg dilemma: Which holds greater health benefits—a bunch of grapes or a glass of wine? As scientists continue to explore the potential of chemical compounds found in grapes and wine, it remains a nagging question. While the moderate consumption of wine, especially red, has been linked to several health benefits in the past two decades, recent studies are now looking at grapes and, more specifically, the polyphenolic compounds they contain, in an attempt to understand these compounds' potential.
Not that wine is being ignored. A recent roundtable discussion by prominent researchers, slated to be published in the February 2009 issue of Alcoholism: Clinical & Experimental Research, agreed that light to moderate alcohol consumption provides myriad health benefits. And University of South Florida researchers published findings last month that suggest that the compound resveratrol, when combined with alcohol—as in red wine—can help break down fat before it accumulates in livers and leads to disease.
But several new studies support the possibility that many of wine's health benefits come directly from the grapes. The juice, pulp and skins of grapes contain an abundance of polyphenols (chains of organic compounds containing carbon, hydrogen and oxygen in a particular structure) such as resveratrol, tannins and flavonoids.
A review article published in the November issue of Nutrition Research examined the results of 26 studies on grape polyphenols. In some of the included studies, patients treated with grape-seed extracts showed improvements in blood flow and cholesterol levels. In another study, drinking grape juice improved circulation in patients with coronary artery disease and lowered blood pressure in patients with hypertension. Separate studies on rats and dogs showed lower levels of blood clots and heart arrhythmia when the animals' diets were supplemented with resveratrol or anthocyanins, a type of flavonoid.
Another recent study, conducted at the University of Michigan Cardiovascular Center and published in the October issue of the Journal of Gerontology: Biological Sciences, took the research a step further by examining the effects of grape powder on the circulation of rats already living with hypertension. The researchers administered high levels of salt to a group of rats, inducing high blood pressure. They then fed grape powder to the rats and found several benefits, notably lower blood pressure and reduced vascular inflammation.
"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," lead researcher Mitchell Seymour said in a statement.
University of Michigan heart surgeon Dr. Steven Bolling added that the rodents in the study mimic millions of Americans who have high blood pressure related to diet and may develop heart failure over time as a result. "Although there are many natural compounds in the grape powder that may have an effect, the things that we think are having an effect against the hypertension may be the flavonoids, either by direct antioxidant effects, by indirect effects on cell function, or both," he said.
Grapes' potential health benefits are not limited to the circulatory system. Two studies published recently in the Journal of Agricultural and Food Chemistry also found benefits in consuming grape and grape extracts. The first, from the department of viticulture and enology at the University of California at Davis, found that anthocyanins extracted from Cabernet Sauvignon grapes aided digestion in pigs and could possibly even prevent colon cancer in humans.
"Results from this study suggest that consumption of Cabernet Sauvignon grape anthocyanins could lead to the formation of specific metabolites in the human gut," wrote authors Sarah Forester and Andrew Waterhouse. "It is possible that these metabolites offer the protective effect against colon cancer attributed to anthocyanin consumption,"
The other study, from the U.S. Department of Agriculture, found that several chemical reproductions of resveratrol reversed the effects of aging in 19-month-old rats, primarily by improving the rodents' cognition. That study is perhaps a clear indication of the desire of researchers to use knowledge of grape polyphenols' potential as a springboard for developing clinical applications for humans.
The more scientists learn about the compounds in grapes, the more they may be able to custom-design new treatments. A study in the Nov. 5 issue of Cell Metabolism, for example, found that mice on a high-fat diet did not become obese when treated with SRT1720, an experimental drug designed by Sirtris Pharmaceuticals to mimic and enhance the effects of resveratrol. The rodents' triglyceride, cholesterol and insulin levels were all comparatively reduced and they could run for about twice the time of a control group.
As research continues, it may not matter if scientists focus on wine or grapes. The compounds within both may hold great potential for medicine's future. Still, that doesn't mean munching on grapes or enjoying a daily glass of red wine isn't healthy and enjoyable.