For years, studies have shown a relationship between drinking a moderate amount of red wine and good heart health, but experts say it's important to understand what that means before you prescribe yourself a glass or two a day.
No research has established a cause-and-effect link between drinking alcohol and better heart health. Rather, studies have found an association between wine and such benefits as a lower risk of dying from heart disease.
It's unclear whether red wine is directly associated with this benefit or whether other factors are at play, said Dr. Robert Kloner, chief science officer and director of cardiovascular research at Huntington Medical Research Institutes and a professor of medicine at the University of Southern California.
"It might be that wine drinkers are more likely to have a healthier lifestyle and a healthier diet such as the Mediterranean diet, which is known to be cardioprotective," he said.
But you may not even have to drink red wine to get the benefit, Kloner said. Moderate amounts of beer and spirits also have been linked to a lower risk of heart disease.
It's a common assumption that red wine may be good for the heart because it contains antioxidants such as resveratrol, which is primarily found in the skin of grapes but also peanuts and blueberries. Some studies suggest resveratrol can reduce cholesterol and lower blood pressure.
"There's a debate about whether resveratrol is really cardioprotective or not," Kloner said. "In addition, there is debate about the amount of resveratrol you would need to ingest to get a protective effect. To get the equivalent of the amount of resveratrol that has been reported to be protective would probably mean ingesting an excess of wine."
Federal guidelines and the American Heart Association recommend that if you do drink alcohol, to do so in moderation. That means no more than one to two drinks per day for men and one drink per day for women. (According to the AHA, one drink is 12 ounces of beer, 4 ounces of wine, 1.5 ounces of 80-proof spirits or 1 ounce of 100-proof spirits.)
Studies have found that moderate alcohol consumption may have some health benefits, including raising "good" HDL cholesterol levels and lowering the risk of diabetes. However, excessive drinking can lead to a host of health problems, including liver damage, obesity, some types of cancer and stroke, not to mention its negative effect on the heart.
"Alcohol in excess is really bad for the heart," Kloner said. "It can cause high blood pressure and promote arrhythmias. It can cause cardiomyopathy where the alcohol is actually toxic to the heart muscle cells, and that can lead to heart failure."
Proving moderate alcohol use causes better heart health would be tricky, Kloner said. Ideally, it would require a large prospective study that not only randomly assigns people to a no-drinking group versus a moderate-drinking group, but that also compares different types of alcohol – red wine, white wine, beer, spirits – to determine if one really is better.
"And then you'd have to control for various factors – age, gender, cardiovascular risk, their diet. You'd have to follow them for many years," he said, noting the added ethical dilemma of taking people who are not drinkers and telling them to become drinkers.
For now, the message certainly isn't to go out and start drinking, Kloner said. "But if you do drink, drinking in moderation is the way to go."
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