Half a bottle of wine a day...

The researchers randomly assigned groups of six to nine healthy men, ages 35 to 65, to one of four regimens. Some were to drink daily a half-bottle of red wine, others the same amount of white wine either with or without capsules containing the polyphenols extracted from red wine. A final group just took the capsules with nonalcoholic drinks.

Before and after the test week, the researchers drew blood from each of the 30 participants and extracted the LDLs. They mixed these fat-bearing particles with a copper compound known to trigger oxidative reactions and measured how long it took the besieged lipoproteins to oxidize.

In the August American Journal of Clinical Nutrition, the researchers report that LDLs from the red-wine drinkers resisted oxidation longest—about 18 minutes longer than those collected from the same men before the test began, 3.5 minutes longer than those from the men just getting the polyphenol capsules, and 6 minutes longer than those who took the capsules with white wine. Among the men drinking just white wine, the LDLs showed no change.

In general, the LDL protection time correlated with the extent to which the beverages or capsules boosted the concentration of polyphenols circulating in an individual’s blood. However, that may not be the sole explanation for that French Paradox.

Because a number of epidemiological studies have shown that regular alcohol consumption—of any type—appears to cut an individual’s risk of heart attack (SN: 3/30/96, p. 197), the British team also had one group of men drink 400 milliliters of vodka in lemonade daily for 1 week. Despite having no polyphenols, the vodka too provided LDLs with a modicum of protection. At the end of the test week, lipoproteins from the men in this group resisted oxidation some 2.5 minutes longer than previously.

Though polyphenols can act as antioxidants, they may have protected the LDLs through another mechanism also, Howard’s team notes. Being capable of binding to some metals, such as copper, these pigments may effectively eliminate some of the agents responsible for fostering oxidation.

 

Ready for a wine trial?

If the new findings are confirmed, red wine’s coloring agents may offer some therapeutic benefit, the researchers say. "In view of the potential benefit," they advise, large-scale trials to test the idea "seem appropriate."

Not so fast, cautions an accompanying editorial by researchers at the University of California, Davis. Although the new study "supports, by inference, the theory that antioxidants prevent heart disease, we don’t know what in the [blood] or what in the LDLs is slowing the oxidation," says wine chemist Andrew L. Waterhouse, the editorial’s lead author.

"In other words," he told Science News Online, "it may not be a direct effect of phenolics" but instead some indirect change that they trigger—such as altered fat or protein metabolism.

Moreover, he notes, the LDL tests employed in the new study oxidized LDLs "under greatly accelerated conditions"—perhaps 1,000 to 1 million times faster than would occur in the body. "Because of the great disparity in the difference between what happens in the test tube and what actually happens in [the body], we feel strongly that the observed changes have to be better understood before we can justify a large-scale human trial"—either with wine or wine-based supplements.

As a cautionary example, his group points to similar studies with the antioxidant beta-carotene. Because many studies have suggested that diets rich in antioxidants reduce the risk of heart disease (SN: 8/1/92, p. 76) and lung cancer (SN: 11/4/89, p. 294), two large-scale prevention trials were begun in the early 1990s that provided groups of participants with this carotenoid. Both came to an abrupt halt, however, when interim findings showed that participants who received megadoses of beta-carotene experienced not only a higher incidence of lung cancer but also a greater risk of dying (SN: 1/27/96, p. 55).

 

  This week's Food for Thought has been prepared by Janet Raloff, senior editor of Science News.

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