"Even relatively modest amounts of alcohol may be protective if consumed frequently," said Kenneth Mukamal, M.D., M.PH., the lead author of the study. "Our results document that a pattern of regular consumption at least three to four days per week is associated with the lowest risk of heart attacks."

The research team analyzed data from the Health Professionals Follow-up Study based at Harvard University School of Public Health. The subject population was made up of 38,077 male health professionals between the ages of 40 and 75 years who responded to a detailed questionnaire regarding diet, medical history, and patterns of alcohol consumption in 1986 and every 4 years thereafter until 1998.

The researchers assessed 4 features of alcohol use: type of alcohol consumed (beer, liquor, red wine or white wine), average amount of alcohol consumed, whether or not the beverage was consumed with a meal, and the number of days per week that alcohol was consumed. The authors documented 1,418 cases of both fatal and nonfatal myocardial infarction among the study participants during the 12-year period.

After adjusting for a number of factors -- age, smoking, physical activity, parental history of heart disease, body mass index, diabetes, hypertension, hypercholesterolemia, aspirin use and diet - analysis showed that alcohol consumption was associated with a lower risk of coronary heart disease regardless of any of the 4 features of alcohol use such as type of beverage or quantity consumed per drinking day. The variable that was consistently associated with the lowest risk was the number of times per week that alcohol was consumed.

After separating study subjects into categories based on frequency of consumption (none, fewer than 1 to 2 times per week, 3 to 4 times a week, or 5 to 7 times a week), the researchers found that subjects in the categories of 3-4 or 5-7 drinks per week had a 32 to 37 percent reduced risk of coronary heart disease compared with those who drank no alcohol.

Mukamal said, "In general, alcohol raises levels of high density lipoprotein, the good cholesterol. But, in addition, alcohol impacts the body's sensitivity to insulin, as well as platelet function and clotting factors." Through these additional effects, he said, alcohol may improve how the body metabolizes blood sugar and may help to prevent coagulation.

"It seems that alcohol's influence on platelets and clotting is relatively short-term," Mukamal added. "This could explain why frequent alcohol intake is of greatest benefit in helping to guard against coronary heart disease."

Eric Rimm, Sc.D., the study's senior author, added that this was one of the first studies to document a lower risk of myocardial infarction among men who increased their alcohol consumption over time. Study subjects who increased consumption by 1 drink per day during the 12 years of the study had a 22 percent lower risk of heart attack than men whose consumption patterns remained unchanged.

Mukamal cautioned that the findings cannot be generalized without reservation. "It's always tricky to offer individual advice based on observational studies of large numbers of people," he noted. "You need to take into account other considerations -- for example, a person's family history, the risk of driving in an impaired state, the risk of developing liver problems -- before deciding on the safest level of alcohol consumption for that individual. However, among men who drink alcohol, consuming 1 or 2 drinks a day 3 or more times a week may help reduce the risk of coronary heart disease."