For one month, researchers from the University of Rochester fed mice the human equivalent of two drinks every day for seven days, or seven drinks two days in a row, in an attempt to simulate regular moderate drinking and weekend binge drinking. At the end of that month, levels of LDL cholesterol—the bad, artery-clogging kind—were 19 percent higher among the “binge drinking” mice compared to a control (read: sober) group of mice. The moderate-drinking mice actually had lower levels of LDL cholesterol than the sober mice.

And what was the effect of all that LDL? Hard-partying mice had 60 percent more artery blockages than mice that didn’t receive any alcohol, while the moderate-drinking mice had 40 percent fewer blockages than the sober mice.

That’s mice, but what about people? Well there’s evidence human beings can also benefit from a little bit of booze. Coronary heart disease dropped more than 50 percent among moderate drinkers compared to non- and heavy drinkers in a recent Virginia Tech study. And all-cause death rates also dropped among light drinkers when compared to the abstainers.

Study author John Cullen, Ph.D., says a normal person would likely see similarly negative effects from heavy alcohol consumption in as little as 6 years of regular weekend boozing. “Drinking this heavily every weekend would lead to a very unhealthy person in his 30s,” Cullen says.

The root of the problem could be high post-binge levels of acetaldehyde, the same byproduct of alcohol metabolism that causes bad hangovers, Cullen explains. “While people who only have two drinks can usually process out the acetaldehyde, after a night of heavy drinking you’re left with lots of it in your system,” he says.

In a separate study, Cullen found that acetaldehyde makes white blood cells stick to the insides of blood vessels, marking the beginning of artery blockages. So why doesn’t moderate drinking cause the same symptoms to a lesser extent? In small doses, alcohol was shown to actually prevent white blood cells from sticking to your arteries, Cullen says. It’s only when you overload your system with booze that acetaldehyde levels spiral out of your liver’s control.

Drinking plenty of water after a night out—the classic hangover cure—might prevent dehydration, but it won’t reduce the harmful levels of acetaldehyde, Cullen explains. Instead, you’ll need to limit your alcohol intake to four drinks (three drinks for women). Swallow any more, and you cross the line separating a fun night out from a potentially heart-endangering bender, Cullen says.