People have known for centuries that drinking too much alcohol is bad for you. The short-term physical effects on cognition and motor function speak for themselves. The longer-term physical consequences of abusing alcohol — liver damage, jaundice, and cancer — have long been impossible to ignore.

So why, in that case, has there been a widespread belief, even among many physicians, that moderate drinking might actually be good for you?

We can thank the so-called French paradox for this. In the early 1990s, French scientist Serge Renaud concluded that the French had low rates of cardiovascular disease despite their affinity for fatty foods like beef and cheese because they otherwise adhere to a healthy Mediterranean diet — and because they consumed “moderate” amounts of red wine. Scientists have theorized that the antioxidants in red wine could play a role in reducing cholesterol, for example.

Subsequent studies appeared to affirm the correlation, strengthening the belief among the general public about the benefits of red wine. But over the past decade, new studies and public health warnings have called that conventional wisdom into question, stating emphatically that no level of alcohol consumption could be considered safe — much less beneficial.

Alcohol after all, absolutely is a toxin, and has long been recognized by experts, if not the broader public, as a carcinogen, after all.

Since many people enjoy alcohol to some extent, says Timothy Naimi, director of the University of Victoria’s Canadian Institute for Substance Use Research, “there’s been a far more relaxed scientific standard.” “We all love studies that show, ‘oh, sex makes us live longer, or coffee is good for us, or chocolate is good for us.’ There is this irresistible idea.”

Science has clearly established that excessive drinking is bad for you. But what remains confusing, especially with the steady stream of new studies that sometimes seem to contradict each other, is how bad moderate drinking is — and what “moderate” even means. Here’s what we actually know.

“Moderate” drinking is elusive — and it’s very easy to drink too much

One of the most important things to understand about drinking and its health effects is what amount of alcohol is actually considered to be excessive. It is a common trope among doctors and alcohol researchers that people misunderstand what moderate drinking means.

“None of us like to think of ourselves as drinking to excess, right?” Naimi said. “Who among us wants to think of ourselves as immoderate? Of course, we’re all moderate drinkers.”

Even if we agree in colloquial terms that “one drink a night” is moderate, the details matter. Medical science has far more precise definitions for what constitutes a “drink” than the average person pouring themselves a glass of Chablis. One 12-ounce can of 5-percent alcohol beer, a 5-ounce glass of wine with 12-percent alcohol, or a 1.5-ounce glass of 80-proof liquor are all what constitutes a “standard drink.” So when we pour an extra-large glass of wine at night, we may consider it only one drink, but a doctor sees two or even three. The kind of beer or wine matters too: Your favorite 9 percent IPA is actually closer to two drinks than it is to one, according to medical........

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