While research has linked moderate drinking to better heart health, a new study suggests that those benefits disappear when drinkers add the occasional binge to the mix.
Pooling data from 14 previous studies of moderate drinkers, researchers found that those who drank heavily every so often were 45 percent more likely to develop coronary heart disease — where plaque buildup in the heart's arteries impedes the flow of blood and oxygen.
For comparison, overall, about 8 percent — or about one in 12 — Americans has heart disease, according to the American Heart Association.
Occasional heavy drinking was defined as having five or more standard drinks in a day at least a dozen times per year. "Regular" heavy drinkers, those who averaged at least five drinks per day, were excluded from the analysis.
The findings suggest that bingeing at even irregular intervals may undo any heart benefits of lighter drinking, the investigators report in the American Journal of Epidemiology.
In general, moderate drinking — a drink or two per day — is considered a potentially heart-healthy habit. A number of studies have found that moderate drinkers have lower risks of heart disease than teetotalers do, even when other factors, like education, exercise, and other lifestyle habits, are taken into account.
Supporting the idea that moderate drinking itself bestows the benefit, research suggests that alcohol can raise "good" HDL cholesterol, has anti-inflammatory effects in the blood vessels, and may make the blood less prone to clotting.
On the other hand, regular heavy drinking may raise blood pressure, promote blood clotting, and contribute to heart-rhythm disturbances.
The new findings show that even when people typically drink moderately, occasional heavy drinking may boost heart risks — at least when compared with modest drinking alone, as the study did not look at abstainers.
The study essentially reinforces the message that "not all alcohol consumption is good for health," lead researcher Michael Roerecke, of the Center for Addiction and Mental Health in Toronto, Canada, told Reuters Health by e-mail.
He added that besides the potential effects of heavy drinking on the heart, alcohol is associated with other health risks, including cancer. Studies have linked drinking — sometimes even at moderate levels — to elevated risks of cancers of the throat, stomach, colon, breast, and liver.
Roerecke and colleague Jurgen Rehm arrived at their findings by combining data from 14 international studies conducted between 1982 and 2006. Four studies compared a total of 2,171 heart disease patients with 3,475 people without heart disease. The other 10 followed participants over time, documenting new cases of heart disease; the current analysis included 1,637 cases of coronary heart disease among more than 50,000 drinkers from those studies.
These types of studies, known as observational studies, cannot prove cause-and-effect. Instead, they reveal associations — in this case, between occasional heavy drinking and a higher heart disease risk versus moderate drinking only.
Still, the findings support what other studies have found to be true of heavy drinking.
Roerecke said it is best for drinkers to avoid binges altogether — not only because of the possible heart effects, but also because of more-immediate risks, like accidents and violence.
Experts also generally stress that there are numerous ways, other than moderate drinking, to guard heart health. That includes exercising regularly, not smoking, and eating a balanced diet rich in fruits, vegetables, high-fiber grains, and heart-healthy unsaturated fats.
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