In a study of more than 1,000 male physicians who are taking part in a large long-term health study, Lisa M Hines and MJ Stampfer and colleagues found that moderate drinkers who carry 2 copies of a specific version of a gene, alcohol dehydrogenase - 3 (ADH3), have a substantially lower risk of having a heart attack compared with those who have only 1 copy or no copies of the gene. The gene controls how fast alcohol is broken down in the blood, or oxidized.

In general, the men who drank at least one alcoholic drink a day had a lower risk for heart attack than those who drank fewer than one a week. However, the most dramatic effect, was seen among the moderate drinkers who carry both copies of a specific form of ADH3, the slow-oxidizing form.Those with "slow oxidizers" had a reduction in their risk of heart attack of 86% and were also found to have high levels of HDL (good type) cholesterol. The same relationship was found between ADH3 gene type, alcohol use and HDL levels, in an independent study of 325 postmenopausal women from a different large-scale health study. The researchers say that the differences in HDL among people with different gene type accounts for some, but not all, of the differences in risk for heart attack. The speed with which alcohol is oxidized in the group also must play a role they contend.

Edward A. Fisher, MD, PhD, ( Professor of Medicine and Director of Lipoprotein Research at the Cardiovascular Institute at Mount Sinai Medical Centre in New York) who served on an American Heart Association advisory panel on alcohol and heart disease commented on the findings, if borne out by further research, "Would be consistent with the notion that its alcohol in any form which give the majority of the protective effect" The fact that the slow oxidizers had the lowest risk for heart attack indicates alcohol itself, rather than a specific by-product released during its breakdown, may be responsible for the differences seen in the study subjects, says Fisher. "Basically, we know that people who drink moderate amounts of alcohol are at lower risk of heart disease, and part of that is because alcohol raises HDL, and people with this variant gene also have higher HDL levels; thats part of it," comments Meier Stampfer, MD, DrPH, Associate Professor of Epidemiology at Havard School of Public Health . "But we know that alcohol also works in other ways, because the HDL elevation doesnt explain everything, and its likely that anything that influences the rate of metabolism of alcohol is also going to affect alcohols impact on other pathways that arent as well understood as cholesterol." The study , says Stampfer, goes a long way towards debunking at least one proposed explanation for the heart-healthy effects of alcohol, which some researchers feel may be due to other factors such as diet, exercise, and lifestyle. "This should help to convince doubters, if there are any still around, about the cause-and -effect relationship of alcohol with heart disease, because the distribution of the genetic variation in the population is obviously unrelated to any of the characteristics that go along with moderate alcohol consumption for example, that people who choose to drink moderately are also the same ones who go jogging etc ..But you cant argue that this gene is distributed that way; people dont jog according to whether or not theyve got this gene, so it helps strengthen the cause-and-effect relationship."