Q. I thought alcohol was supposed to be good for your heart, but now I hear it causes strokes, should I drink or not?

A. Moderate alcohol consumption — defined as one drink daily for women and two drinks daily for men — may be beneficial in preventing heart disease and strokes, especially red wine. But drinking more than that cancels the benefits.

A study published in September's issue of Circulation adds to the large body of evidence that heavy drinking can significantly increase the risk of stroke.

Researchers at Boston's Beth Israel Deaconess Medical Center used information from the Copenhagen City Heart study that tracked 16,415 people for 18 years. The researchers analyzed data on the consumption of beer, wine and spirits.

Results showed that in men, 35 or more drinks per week (about five drinks a day) increased the risk of atrial fibrillation. This is a condition that produces a rapid, irregular heartbeat preventing blood from being completely pumped from the heart. This can cause blood to pool in the heart and form clots. The blood clots can travel to the brain and block an artery there, causing a stroke.

Atrial fibrillation causes 15 percent to 20 percent of strokes. During the study, 1,071 cases of atrial fibrillation were documented. Risk of atrial fibrillation increased by 45 percent in men who were heavy drinkers compared to non-drinkers and light drinkers. The risk rose to 63 percent after researchers adjusted for other conditions that can cause atrial fibrillation such as high blood pressure.

No increased incidence of atrial fibrillation was seen in women. However, few of them were heavy drinkers. It would be safe to assume that if women drank the same amount as men, their risk would also increase.

Most men in the heavy-drinking category consumed mostly beer. The pattern of drinking daily or just on weekends didn't matter, only the weekly total.

Heavy drinking also increases blood pressure. High blood pressure increases stroke risk, even when atrial fibrillation is not present, by straining blood vessels, leading to narrowing of the arteries and the formation of blood clots.

You can also decrease your risk of stroke by quitting smoking, eating healthily, exercising and controlling your blood pressure.

Amy Tousman is a registered dietitian with the Health Education Center of Straub Clinic and Hospital. Hawai'i experts in traditional medicine, naturopathic medicine and diet take turns writing the Prescriptions column. Send your questions to: Prescriptions, Island Life, The Advertiser, P.O. Box 3110, Honolulu, HI 96802; fax 535-8170; e-mail islandlife@honoluluadvertiser.com. This column is not intended to provide medical advice.