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Forget Resveratrol, Tannins Key to Heart Health from Wine

Wine's beneficial effects on heart health depend more on the traditional vintner's art than the wonder molecule resveratrol.
old man with red wine



¿ CORBIS
Resveratrol, a molecule found in the skin of red grapes, among other places, has been found to have a host of health effects, most recently prolonging the life spans of obese mice. But the natural wonder drug does not play a role in the beneficial effects of wine drinking, according to research published in the November 28 issue of Nature. "There are some fascinating effects of resveratrol in animal systems," notes plant biochemist Alan Crozier of the University of Glasgow. "To get similar doses into humans through red wine, you would have to consume more than 1,000 liters of red wine a day."

Because drinking that much wine is beyond even the hardiest oenophile--yes, even those in France--Crozier and his colleague Roger Corder of Queen Mary's School of Medicine and Dentistry in London set out to identify exactly the compounds in red wine that promote heart health. Using the endothelial cells that line human artery walls, the researchers tested which compounds in wine had the greatest effect. The tests showed that flavonoids called oligomeric procyanidins--essentially condensed tannins, the compounds that impart bitterness to young reds--suppressed production of the peptide responsible for hardening arteries. Such procyanidins can make up as much as 50 percent of the bioactive compounds in a given wine, the researchers observed. "Resveratrol," Crozier notes, "is available at one one-hundredth or one one-thousandth of the levels of procyanidin." Corder adds: "The role of resveratrol in the health benefits of wine has been popularized without any scientific evidence to support it, given the amounts needed for these actions are approximately 1,000-fold greater than could be achieved by wine consumption."

Using French census data, the two researchers then compared regions that had unusually long-lived men with the wine produced in those areas. The Nuoro province of Sardinia and the Gers region of southwestern France both support relatively more men who survive past 75 years of age. Not coincidentally, these regions also produce local wines that are as much as four times richer in procyanidins than other wines. Traditional wine-making techniques proved key: by allowing the grapes to linger on the vine for as long as possible and then leaving them to ferment for as long as four weeks (compared with the more typical one-week period of major wineries, which keeps the level of harsh tannins low), vintners in these regions produce prodigious amounts of procyanidin.

Also crucial are the type of grape involved (Tannat in Gers, a small, seedy fruit rarely grown outside the southwest of France) and the elevation at which it is grown (ultraviolet helps catalyze the production of procyanidins in the high-elevation vineyards of Sardinia). "It is not something that in theory is unique to these areas," Crozier adds. "It could become more widespread." Of course, understanding exactly how procyanidins work in the human body remains to be investigated, and the researchers plan to dose people with the compound in a future clinical trial. In the meantime, a few glasses of wine--particularly a full-bodied one--remain a recipe for a stronger heart.

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