As little as a single glass of wine or beer per week can significantly reduce a man's risk of a stroke, according to the biggest study ever to examine the link.
The study found that light to moderate drinkers can lower their risk by about 20 percent compared with teetotalers. It involved more than 22,000 men, but one of the researchers said the results could also apply to women.
Numerous studies have shown that modest drinking reduces the risk of heart disease. But until now, the evidence of an effect on strokes has been less convincing.
The American Heart Association estimates that 600,000 people in the United States suffer a stroke each year. It is the third leading cause of death in this country, and the leading cause of serious, long-term disability.
Earlier studies were criticized because they simply compared drinkers to nondrinkers. This latest study, published in Thursday's New England Journal of Medicine, examined varying levels of alcohol intake.
It found that between one drink a week and one a day reduces the risk, and the lesser amount was about as good as the higher one.
There were not enough heavy drinkers in the study to look at the effects of more than one a day, but the heart association warns that drinking to excess can raise blood pressure and, in fact, lead to a stroke.
The study's authors stressed that it would be unwise for doctors to advise patients who don't drink to suddenly start or for those who drink small amounts to begin consuming more heavily. The study found no added protection from stroke by drinking more than light to moderately.
"Absolutely it has benefits, but it also has harm," said study co-author Julie E. Buring, an epidemiologist at Harvard-affiliated Brigham and Women's Hospital in Boston.
She and other researchers warned of liver damage, the dangers of driving while drunk and the risks to fetuses of drinking while pregnant. What's more, there are other ways reduce stroke risk, such as quitting smoking or lowering blood pressure.
Researchers attribute alcohol's benefits to its ability to increase the amount of HDL, or good cholesterol, in the bloodstream. HDL cholesterol helps keep arteries clean. Researchers also said that alcohol can break up blood clots.
The men studied were all doctors between the ages of 40 to 84 who took part in the Physicians' Health Study, which began in 1982. They were tracked for about 12 years. In all, the study subjects reported 679 strokes.
Small amounts of alcohol were shown to decrease the risk of ischemic stroke, which is the most common type and is caused by clots that reduce blood flow to the brain. Drinking had no effect on the risk of a rare hemorrhagic stroke, which is caused by sudden bleeding in the brain.
While Buring said the findings may apply to women as well, she stressed that light to moderate alcohol intake for a woman is defined as about one drink per day vs. approximately two drinks per day for a man. Also, research has suggested that drinking may raise the risk of breast cancer in women.
"For any individual, the use of alcohol to reduce risk of stroke should be discussed with one's physician in order to make the healthiest decision," Buring said.
Similarly, Dr. Thomas Pearson, a cardiologist at the University of Rochester and author of the heart association's guidelines on alcohol use, warned: "We know that there are substantial diseases related to alcohol. We have this cardiovascular benefit, but this should not prompt us to be putting up billboards up on the interstate."