Sept. 7, 2012 -- Wine lovers, get ready for a buzz kill. A new study has found that drinking two glasses of red wine a day can help lower blood pressure and reduce the risk of cardiovascular disease -- but only if the alcohol has been removed.
Writing in the journal Circulation Research, Spanish investigators reported on 67 men with several cardiovascular risk factors or diabetes. The men spent three periods of four weeks each, enjoying either non-alcoholic red wine, red wine, or gin with their meals, switching to a different beverage at the end of every phase.
During the month they indulged in regular red wine or gin, the men's blood pressures showed little or no change. But there was a drop in their blood pressure when they drank the non-alcoholic wine. The dip in pressure was modest -- just a few points -- but it translated into a 14 percent reduced risk for coronary heart disease and a 20 percent decrease in risk for strokes.
Polyphenols are the antioxidant compounds in red wine thought to bestow its heart-healthy benefits, including reduced blood pressure. However, previous studies haven't found that drinking red wine corresponds to a drop in blood pressure. Just last year a Dutch study reported that drinking a dairy beverage infused with polyphenols didn't budge the blood pressures in those with mild hypertension.
Why would removing the alcohol from the wine improve pressure in this particular study? The authors speculate that the virgin wine increased nitric oxide in the bloodstream, a chemical that relaxes blood vessels.
Drinking alcoholic red wine raised nitric oxide slightly and gin, not at all. According to Dr. Franz Messerli, a cardiologist at St. Luke's-Roosevelt Hospital in New York., this could mean that alcohol cancels out some of the good done by the antioxidants.
"Since alcohol in larger doses narrows the blood vessels, it can override the beneficial relaxation of the vessels by the polyphenols in the red wine," he said.
More Proof Needed
Dr. Malissa Wood, a cardiologist at the Massachusetts General Hospital Heart Center in Boston, said she thinks there could be other reasons why the nonalcoholic wine lowered blood pressure but they weren't clearly laid out in the study.
"Maybe it's related to the type of grape and process used to make the wine -- the authors didn't specify whether or not all the wines were made from the same grapes using the same techniques. It's also possible that the process for removal of alcohol leads to formation of another potentially beneficial compound or increases the content of antioxidants," she said.
The study had additional limitations that should be considered as well. For one thing, both the researchers and the men knew what each glass contained. Perhaps this influenced them in some way. The subjects also didn't do a "washout" period before switching drinks so their blood pressures didn't get a chance to reset to their baseline.
"There could be a carry-over effect between treatments that was cumulative with time, resulting in lower blood pressure as the trial continued in time," said Donna Arnett, the current president of the American Heart Association and a professor at the University of Alabama School of Public Health in Birmingham.
Including a group of teetotalers would have served as a useful comparison, Arnett said. And, she said, the findings might not hold for women or healthy individuals.
Given these limitations, the experts say wine lovers hoping to lower their blood pressure should stay tuned for larger, better designed studies. In the meantime, moderate drinking (one drink a day for women, two a day for men) has been found to confer a host of other cardio-protective effects, including a reduced buildup of plaque in the arteries and an increase of "good" cholesterol. Over-imbibing is clearly associated with a greater risk of heart disease and stroke.
People who wish to abstain from alcohol completely -- and anyone under 21 years of age -- should note that beverages labeled "non-alcoholic" aren't completely alcohol-free. By law, they're allowed to contain up to half a percent of alcohol by volume. A drink that truly has no alcohol is labeled "alcohol free."