"Even relatively modest amounts of alcohol may be protective if consumed frequently," said the study's first author, Kenneth Mukamal, MD, MPH, of BIDMC's Division of General Medicine and Primary Care and Assistant Professor of Medicine at Harvard Medical School. "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 researchers analyzed data from the Health Professionals Follow-up Study based at HSPH. Subjects included a total of 38,077 male health professionals between the ages of 40 and 75. Beginning in 1986, the subjects responded to a detailed questionnaire regarding diet, medical history and patterns of alcohol consumption. They then completed follow-up questionnaires every four years thereafter until 1998.
The researchers assessed four features of alcohol use: type of alcohol consumed (beer, liquor, red wine or white wine); the 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, high blood pressure, high cholesterol levels, aspirin use and diet – the findings showed that alcohol consumption was associated with a lower risk of coronary heart disease, regardless of the type of beverage, the quantity consumed per drinking day, whether or not it was consumed with meals or the type of coronary outcome. The variable that was consistently associated with the lowest risk was the number of times per week a participant drank alcoholic beverages.
After separating study subjects into categories based on whether they drank no alcoholic beverages, drank fewer than once or twice a week, drank three to four times a week, or drank five to seven times a week, the researchers found that the subjects in the categories of three-to-four or five-to-seven drinks per week had a 32 to 37 percent reduced risk of coronary heart disease, compared with abstainers. The reasons behind these findings may be twofold, noted Mukamal. "In general, alcohol raises levels of HDL, 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 be improving how the body metabolizes blood sugar and helping to prevent the development of blood clots, which can lead to a heart attack.
"It seems that alcohol's influence on platelets and clotting is relatively short-term," he added. "This could explain why frequent alcohol intake is of greatest benefit in helping to guard against coronary heart disease."
Eric Rimm, ScD, Associate Professor of Nutrition and Epidemiology at the Harvard School of Public Health and the study's senior author, added that this was one of the first studies to document a lower risk of heart attacks among men who increase their alcohol consumption over time. Study subjects who increased consumption by one 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 these 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 one or two drinks a day three or more times a week may help reduce the risk of coronary heart disease."
Study co-authors include Katherine M. Conigrave, PhD, of the University of Sydney, Australia; Murray Mittleman, MD, DrPH of Beth Israel Deaconess Medical Center; Carlos A. Camargo, Jr., MD, DrPH, Meir J. Stampfer, MD, DrPH, and Walter C. Willett, MD, DrPH. of the Harvard School of Public Health.
This research was funded by grants from the National Institutes of Health.
Beth Israel Deaconess Medical Center is a major patient care, research and teaching affiliate of Harvard Medical School and a founding member of CareGroup Healthcare System. Beth Israel Deaconess is the third largest recipient of NIH research funding among independent U.S. teaching hospitals.
Harvard School of Public Health is dedicated to advancing the public's health through learning, discovery, and communication. More than 300 faculty members are engaged in teaching and training the 800-plus student body in a broad spectrum of disciplines crucial to the health and well being of individuals and populations around the world. Programs and projects range from the molecular biology of AIDS vaccines to the epidemiology of cancer; from risk analysis to violence prevention; from maternal and children's health to quality of care measurement; from health care management to international health and human rights.
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