Moderate drinkers have lower rates of heart disease, as research has shown, but they may have a price to pay: Alcohol can thin the blood, perhaps increasing the risk of bleeding strokes.

That's the finding from a study published in the October issue of Alcoholism: Clinical & Experimental Research.

Study author Dr. Kenneth Mukamal, a researcher at Beth Israel Deaconess Medical Center, in Boston, found that alcohol intake thins the blood, which is good for preventing clots that can lead to heart attacks but not good when it comes to the risk of bleeding strokes.

"The contrasting effects of alcohol are similar to the effects of blood thinners like aspirin, which clearly prevent heart attacks but at the expense of some additional bleeding strokes," Dr. Mukamal said in a statement.

In the study, Mukamal's team evaluated more than 3,000 participants in the Framingham Offspring Study, which looked at risk factors for cardiovascular disease. The study, began in 1971, included the sons and daughters of participants in the Framingham Heart Study, which began in 1948.

"There has been a lot of circumstantial evidence over the years that alcohol consumption is both good and bad," said study co-author Dr. Kenneth Ault, director of the Research Institute at the Maine Medical Center, in Portland. "The simple story is that moderate alcohol consumption is protective for a lot of cardiovascular problems."

The new study confirms previous evidence, Ault said, suggesting that alcohol is often beneficial but may have a downside.

The new study focused on platelets, small particles in the blood that contribute to clotting, Ault explained. It evaluated how fast they start the clotting process, known as "activation," and how much they clump together, known as "aggregation" or "stickiness." Previous research has shown that moderate drinkers tend to have less sticky platelets than nondrinkers.

"In men, both activation and aggregation went down with moderate drinking," Ault said. Moderate drinking was considered to be three to six drinks a week or more.

"In women, only aggregation went down. But I wouldn't make a big deal of that," said Ault, explaining the finding could have been a statistical fluke.

Another expert, Dr. Marc Siegel, an associate professor of medicine at New York University School of Medicine, said the study was "fairly well-done."

"The bottom line is alcohol has a plus and a minus," he said, and the new study "puts the two things together, and give you more clinical wisdom."

The message to consumers? "Don't start thinking of alcohol as a panacea," Siegel said. "Even if there is some benefit, there is a cautionary flag. A drink a night is generally believed to cut the risk of heart disease, but it is hardly medicinal. And this study reminds you of that."