How much alcohol is healthy? Depends where you are

How many drinks is OK? The world disagrees.

A recent study from researchers at Stanford University shows that countries have very different ideas about how much alcohol is safe or healthy, and the standards even within a country can be confusing.

""There's a substantial chance for misunderstanding," said study co-author Keith Humphreys, a professor of psychiatry and behavioral sciences at Stanford, in a press release. "A study of the health effects of low-risk drinking in France could be misinterpreted by researchers in the United States who may use a different definition of drinking levels. Inconsistent guidelines are also likely to increase skepticism among the public about their accuracy. It is not possible that every country is correct; maybe they are all wrong."

The researchers started with the one of the closest things to an international standard: the World Health Organization. According to the study, the WHO identifies a standard drink as having 10 grams of pure ethanol — a little more than a third of an ounce. Its guidelines recommend no more than two drinks per day on average for both men and women.

But across a pool of 37 countries with national drinking guidelines, the researchers found wide variations in how tall a "standard" drink is, and how many drinks are safe in a day or a week.

Some countries define a standard drink more liberally than the WHO does. American guidelines consider 14 grams of pure alcohol to be a standard drink, four grams more than the WHO's definition.

But that is just the start. U.S. guidelines say women should consume no more than 42 grams of pure alcohol in a single day day (about three drinks). That is double or more than the WHO limit and the daily limits in most other countries on the list.

Now consider Vietnam, Poland and France. All three say a standard drink is a more modest 10 grams — in line with WHO recommendations.

Standards for men are similarly all over the map, so to speak. Austria defines a single standard drink at having 20 grams of pure alcohol — double the WHO standard. But its government suggests men limit their daily maximum to little more than one drink per day, and only about 8½ drinks per week. Malta says anything between 168 and 210 grams a week is acceptable for men.

American men are advised to have no more than four drinks in a day, they are also advised to have no more than 196 grams of alcohol in a week—about 14 drinks.

Some countries might opt for a weekly or a daily limit, but not both. Others, such as Australia do not distinguish between men and women.

"At the very least, we should know whether it's true that women should drink less than men," said Humphreys in a press release. "But even this is unclear."