More than a decade ago, a landmark study drove home a message that resonated with wine lovers everywhere: Drink red wine in moderation to lower your risk for a heart attack. Now, new results suggest that some white wines protect the heart just as well, at least in rats. The study, which was partially funded by the grape industry, suggests that more heart-protective chemicals exist in grapes than scientists had suspected.
Wine lovers got their first big boost in 1992, when researchers reported that French people, who drink more red wine, suffered less from coronary heart disease than people in other developed countries, even though they ate food that was just as fatty. To explain this phenomenon, dubbed the French Paradox, others have identified chemicals in red grapes and red wines that neutralize oxygen radicals, chemical saboteurs that harm the heart by damaging key cellular components. Those chemicals, called resveratrol and anthocyanins, are concentrated in the skin of the grape rather than the fruit. Researchers therefore suspected that white wines, which are made without the skin of the grape, would not protect hearts. But in 2002, cardiovascular scientist Dipak Das of the University of Connecticut School of Medicine in Farmington and colleagues reported that some white wines protected rat hearts as well as red wine did.
In the new study, the researchers decided to find out how. For 30 days, they fed rats either grape skins, grape flesh, or a sugar-water solution, in addition to their normal chow. Then they sacrificed each rat and kept its heart beating in the lab with a contraption that bathed it in nourishing fluid. To see how well the rat's diet protected its heart, the team mimicked a heart attack by stopping fluid flow for 30 minutes, then restarting it to revive the heart.
By several measures, grape skins and grape flesh protected the hearts equally well. The artificial heart attack killed an average of 35% of the heart muscle in rats fed sugar water, but only about 20% of the heart in rats fed grape flesh or grape skin, respectively. Hearts from the grape-eating rats retained about twice the pumping capacity of control hearts, no matter whether the rats ate grape flesh or grape skins.
By chemically analyzing four varieties of wine grapes, Das' colleagues at the University of Milan confirmed that grape skin contains most of the resveratrol and anthocyanins. But both skin and flesh extracts did an equally good job mopping up a particularly dangerous type of oxygen radical, according to results just published in the Journal of Agricultural and Food Chemistry. That means "the flesh has different kinds of antioxidants," Das says.
"That's a very significant piece of information," says biochemist Joseph Wu of the New York Medical College in Valhalla, who called the study "very good and very thorough." The results suggest that "white wine would have some benefit," Wu says. But how exactly it protects the heart remains a mystery.