One beer or glass of wine a day could cause your brain to shrink, study suggests

Moderate consumption of alcohol — one drink a day for women and up to two for men — is associated with a reduction in brain volume, a new study suggests. The more you drink, the more your brain might shrink.

The brain naturally shrinks as you age. But alcohol intake could lead to an accelerated decline in the size of the brain and a faster decline in memory, decision-making and other brain functions, according to the research published in the journal Nature Communications.

Researchers studied MRIs of more than 36,000 middle-aged adults in the U.K. and compared the scans with their reported alcohol intake. After grouping the subjects by average daily alcohol intake — from none to two beers or glasses of wine or more a day — the researchers found consuming more alcohol was associated with a more pronounced decline in brain volume.

For someone who’s 50, an increase from drinking the equivalent of half a beer or a half glass of wine daily to a full pint or glass of wine was associated with brain shrinkage equivalent to aging two years. Those who drank more — 1½ beers or glasses of wine daily — had changes in the brain as if they had aged three and a halfyears, the researchers say.

Even the smallest increase, from not drinking to drinking the equivalent of half a beer a day, was associated with smaller brain volume — about a half year more brain aging. Drinking four drinks a day, versus not drinking, was associated with more than 10 years of brain aging.

What concerned the researchers is the findings “contrast with scientific and governmental guidelines on safe drinking limits,” said study co-author Henry Kranzler, who directs the University of Pennsylvania’s Center for Studies of Addiction.

The Centers for Disease Control and Prevention’s guidelines for moderate drinking are ”an amount that exceeds the consumption level associated in the study with decreased brain volume,” Kranzler said.

Past research had yielded somewhat conflicting results on alcohol and its brain effects. Heavy drinking has been linked to changes in the brain, including shrinkage. But some studies have suggested that moderate drinking might have no effect and that light to moderate drinking might even be beneficial for older adults.

This new study, combined with a growing body of research suggesting an increase in mortality with alcohol consumption, suggests “the idea that moderate drinking promotes health appears no longer defensible,” Kranzler said. “For pretty much any level of drinking, a reduction is likely to yield health benefits.”

But the study has limitations, said Emmanuela Gakidou, an alcohol researcher and professor of health metrics sciences at the University of Washington. “It seems that they only have information on how much people drank the year prior to when the images were taken,” not lifetime drinking, she said.

Cumulative consumption of alcohol is important in studying its effects on the brain and study subjects could have had higher or lower alcohol intake before the study, Gakidou said.

Also, at lower levels of alcohol consumption, the relationship with brain volume “appears very weak at best,” she said.

The researchers agreed that the study has limitations, but the large group of people included helped provide “a clearer picture” of alcohol’s effect on brain volume, Kranzler said. A larger, prospective study with repeated MRI scans is needed to track people and alcohol’s effects, as well as track whether abstinence or reduced drinking can change brain volume, too, he said.

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