New Study Sheds More Light on Antioxidants in Red Wine

New research presented at the California Institute of Food and Agricultural Research's Dec. 11 conference, "A Scientific Perspective on Antioxidants for Sustaining Health," may shed additional light on the health benefits associated with moderate consumption of red wine.

Researchers at University of California, Davis, have demonstrated that catechin, the most abundant polyphenol (a category of plant-based compounds) in grape skins and seeds, significantly delays tumor onset in mice. The discovery adds to a growing body of evidence detailing the cancer-prevention effects of flavonoids (a class of polyphenols), which are found in grapes, as well as in other fruits and vegetables.

"We know that catechin can act as an antioxidant [a substance that helps the body's cells resist certain kinds of damage] and prevent free-radical formation in vitro," said researcher Susan Ebeler, an analytical chemist in UC Davis' department of viticulture and enology. "But we don't know yet if it acts similarly in the body."

In 1996, Ebeler and her colleagues discovered that dietary supplements of wine solids with high total levels of polyphenols (including catechin) delayed tumor onset in mice.

In her latest study, which has been accepted for publication in the American Journal of Clinical Nutrition, Ebeler isolated catechin and identified it as an important anticancer element.

In the new study, mice were fed a nutritionally complete diet that was supplemented either with concentrated catechin or with alcohol-free solids from red wine that contained low levels of catechin.

The mice -- which were genetically predisposed to tumors -- were examined daily, and the age at which a first tumor appeared was recorded. Concentrated catechin supplements were found to significantly delay tumor onset in the mice, increasing the tumor-free period by as much as 45 percent compared to the group that was fed alcohol-free wine solids.

According to Ebeler, the daily amounts of catechin that were effective in delaying tumors in mice might be similar to what a human would consume in a liter of red wine.

Because catechin is found in grape skins and seeds, only red wines, which remain in contact with skins and seeds during fermentation, contain significant amounts of the antioxidant. Ebeler's team found that catechin levels may also vary in wines depending upon grape varieties, viticultural and vinification methods and variations in terroir.

In addition to providing insight into which components of wine convey potential health benefits, Ebeler's experiments are significant in that they demonstrated that tumor onset due to a genetic predisposition can be affected by environmental factors such as diet.

However, Ebeler cautioned that although "we feel mice are a good model for the development of tumors in humans, human studies are needed before we can conclusively say that catechin can influence tumor development in humans."

In a separate but related experiment, catechin was found to be readily absorbed into the human bloodstream, according to Andrew Waterhouse, vice chair of UC Davis' department of viticulture and enology, another presenter at the antioxidant conference. In Waterhouse's experiments, volunteers adhered to a flavonoid-free diet for two days, then drank a large glass of red wine at 8 a.m. on the third day. The subjects' blood plasma levels of catechin were then tracked over the following eight hours.

Waterhouse pointed out that humans eliminate catechin fairly rapidly (within 8 hours of hitting the bloodstream) from their systems, so only people who drink on a regular basis will experience red wine's beneficial effects. "One glass of wine per week isn't going to do it," he said.

Both Waterhouse and Ebeler were quick to mention that consumers should not assume that drinking red wine is a cure-all. Waterhouse said there is strong epidemiological evidence that people who drink wine regularly have a lower risk of cardiovascular disease, but that the evidence on cancer is "more ambiguous" and much work remains to be done to show clear cause and effect.

In addition to the latest news about red wine, Carl Keen, chairman of the department of nutrition at UC Davis, presented research on the potential role of chocolate in human nutrition. According to Keen, "Cocoa is one of the richest dietary sources of flavonoids, including catechin and epicatechin -- almost 10 percent by weight, depending upon how it is processed."

In addition to the powerful antioxidant effects of catechin, Keen pointed out that it may also help to prevent blood clotting, "similar to low doses of aspirin."

"If you had to tell someone at a clinical meeting 10 years ago that chocolate was good for you, it would never have passed the chuckle test," quipped Keen. "Today, it's a different story, and we are recognizing that there may be potential health benefits to be derived from this ancient food."

For a comprehensive look at how drinking wine may increase longevity, check out senior editor Per-Henrik Mansson's feature Eat Well, Drink Wisely, Live Longer: The Science Behind A Healthy Life With Wine

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