Does alcohol prevent strokes and heart attacks?

“If you’re in good shape, moderate drinking makes you 25 percent to 40 percent less likely to have a heart attack, stroke, or hardened arteries,” says WebMD.com in its “Surprising ways alcohol may be good for you” slideshow.

Really?

In many studies that have tracked thousands of people for years, those who have one or two drinks a day do have a lower risk of heart disease and some types of stroke than non-drinkers or heavy drinkers.

But scientists were never sure if alcohol—or perhaps the healthier lifestyles of moderate drinkers—explained the link…until they studied genes that lead people to drink less.

“In East Asian populations, there are common genetic variants which alter the metabolism of alcohol,” explains Iona Millwood, senior epidemiologist at the University of Oxford.

When you drink alcohol, an enzyme converts it to acetaldehyde. In most people, the acetaldehyde is quickly broken down. But a genetic variant of the enzyme in many people of East Asian descent slows that breakdown, making the acetaldehyde build up. That can cause uncomfortable flushing.

A second variant causes flushing—though less so—by speeding up the conversion of alcohol to acetaldehyde.

“People with these variants have an unpleasant flushing reaction when they drink,” says Millwood. So they drink far less.

When her study in roughly 510,000 people in China used genes to estimate alcohol intake, the results were clear.

“There were no protective effects of moderate drinking for stroke,” says Millwood.

And since genes, not lifestyle, determined how much the participants drank, the results “are due to alcohol itself,” she adds.

What about heart attacks?

In a similar study​—on roughly 262,000 people of European descent—participants who had the second variant consumed 17 percent less alcohol per week and had a 10 percent lower risk of heart disease than those without the variant.

“For some time, observational studies have suggested that only heavy drinking was detrimental to cardiovascular health, and that moderate consumption may actually be beneficial,” says co-author Michael Holmes, now an associate professor and clinical epidemiologist at Oxford.

In fact, “individuals with a genetic predisposition to consume less alcohol had lower, not higher, odds of developing coronary heart disease,” concluded the study.

The bottom line

Don’t expect alcohol to protect your health.