Why Do Doctors Tell Women To Drink Half as Much as Men?

Answers to your questions about the news.
Oct. 16 2012 4:40 PM

Alcohol and Sex

A mini-Explainer on why doctors tell women to drink less than men.

Woman and man drinking.
Why do men and women have different guidelines for "moderate" alcohol consumption?

Photo by iStockphoto/Thinkstock.

Medical studies suggest that “moderate” drinking, usually defined as no more than one drink per day for women and two for men, leads to longer lives. One Explainer reader wonders: Why are women told to drink so much less than men?

Breast cancer, for one thing. In epidemiological studies, a “J-shaped” curve shows that moderate alcohol consumption is beneficial while heavy drinking is bad. But it doesn’t apply to every ailment. Even moderate alcohol consumption seems to increases the risk of cirrhosis of the liver, hypertension, and many forms of cancer. Most problematic among these is breast cancer, which affects approximately 230,000 American women per year and kills nearly 40,000. Some studies have suggested that even moderate drinking increases a woman’s lifetime risk of developing breast cancer by 50 to 100 percent. Men have a comparatively tiny risk of developing the disease. Many doctors feel that this difference alone is sufficient to justify gender-based alcohol consumption recommendations.

In most studies that show the benefits of moderate imbibing, the positive outcomes disappear at lower doses for women than for men. Two drinks a day might decrease a man’s risk of diabetes, heart disease, or death, for example, but it has the opposite effect on the average woman. The difference holds even when researchers control for weight.

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Doctors are still trying to figure out why women tolerate alcohol differently than men. One theory is that since women’s bodies contain less water per pound than men’s, the same amount of alcohol will result in a higher concentration in the blood. In addition, a stomach enzyme that metabolizes alcohol seems to work less efficiently in women, so more of the alcohol women consume goes directly into the blood stream. Some researchers also believe that estrogen interacts with alcohol in a way that enhances the likelihood of liver damage. There are indications that hormonal changes that occur during the menstrual cycle also affect alcohol metabolism, but this is observation remains controversial.

The recommendation of two daily drinks for a man and one for a woman hasn’t been around forever, although it might seem that way. The 19th-century English physician Francis Anstie recommended that patients keep their consumption below “three or four glasses of port wine a day.” He did not make separate recommendations for men and women. In 1979, the U.K.’s Royal College of Psychiatrists noted that “four pints of beer a day, four doubles of spirits, or one standard size bottle of wine, constitute reasonable guidelines.” The Australian National Health and Medical Research Council recommended in 1987 that men drink no more than four servings of alcohol per day, a higher limit than in other English-speaking countries, but agreed that women should stick to two servings or fewer. In 2001, the council adjusted their guidelines, recommending no more than two drinks per day for both men and women.

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Explainer thanks reader Sean McKee for asking the question.

Brian Palmer writes about science, medicine, and the environment for Slate and Earthwire. Email him at explainerbrian@gmail.com. Follow him on Twitter.

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