A team of researchers in London and Glasgow has determined which polyphenol in red wine may help keep the heart and blood vessels working well--but it's not the compound that's gotten all the press lately.
Procyanidin, a polyphenol also common in dark chocolate, keeps heart tissue healthy by regulating the production of a peptide known as endothelin-1, according to the new research. Endothelin-1 helps to prevent blood clots and maintain the overall health of veins and arteries but, in excessive amounts, can constrict vascular tissue, leading to diseases such as hypertension and even heart failure.
The research, reported in the Nov. 30, 2006, issue of Nature, was led by Roger Corder, a professor of experimental therapeutics at the Queen Mary University of London and author of The Wine Diet, being released next week by Little Brown. Back in 2001, Corder's team found that red wine helped to slow production of endothelin-1.
For the latest research, "We wanted to know what it is in red wine that helps prevent cardiovascular diseases since drinking it in moderation seems to be a sure way to a longer, healthier life," said Corder.
Many recent studies have focused on the benefits of the red-wine compound resveratrol, which has been found helpful in preventing a number of ailments. Research using mice found resveratrol limited damage caused by a stroke, boosted endurance and kept chubby mice alive longer. But in Corder's study, resveratrol was not found in sufficient quantities to be able to keep human heart tissue healthy.
Corder and his team designed their study so they wouldn't know which compound worked best until the end of the trial. The researchers cultured endothelial cells, then added small amounts of red wine to the petri dishes. The team used chromatography to isolate and measure the biological activity of each polyphenol in red wine.
In hundreds of experiments, using wines from all over the world, procyanidin proved to be the best at regulating production of endothelin-1 to achieve the most favorable levels. Procyanidins suppressed overproduction by 50 percent.
Other compounds, such as resveratrol and quercetin, were found to have an "irrelevant effect," Corder said. "In order to consume enough red wine to get a beneficial amount of resveratrol, you would need concentrations that were 100- to 1,000-fold greater than what is in red wine." That claim is echoed by scientists who have conducted resveratrol studies and found that the concentration of the polyphenol found in wine is insufficient to increase longevity and boost endurance. But the procyanidins were effective at levels found in wines.
Corder also found that procyanidin concentrations varied greatly according to winemaking style and vineyard location. Wines with high levels of tannins--due to prolonged exposure to grape skins and seeds during fermentation--had much higher concentrations of beneficial polyphenols.
More rustic styles of wine were richer in procyanidin than wines popular for international export. Tannat grown in southwestern France had the highest concentration of the wines tested, while several varietals from Sardinia's Nuoro province had the next-highest levels. Wines from the United States, Australia, South Africa and other parts of Europe generally had significantly lower levels of procyanidin.
"It's the style of wine that is important, not the country," Corder said. "There were some wines from Mount Veeder in Napa Valley, produced using old-fashioned methods, that are outstanding [in terms of heart health]," he added. "But these wines are an acquired taste."
Corder also noted that exposure to ultraviolet B rays increases the level of procyanidin in grapes, so the proximity of the vineyards to the sun is a factor as well. For example, according to the study, the average Sardinian wine had comparably low levels of procyanidins, but the wines from Nuoro came from vineyards on high slopes directly facing the sun, providing maximum exposure to UV-B rays.
Despite his findings, Corder cautioned against changing one's drinking habits or taking unregulated dietary supplements in the hope of mimicking the results of lab studies.