Drinking even moderate amounts of alcohol is linked to changes in brain structure and an increased risk of worsening brain function, scientists say.



In a 30-year study that looked at the brains of 550 middle-aged heavy drinkers, moderate drinkers and teetotallers, the researchers found people who drank more alcohol had a greater risk of hippocampal atrophy — a form of brain damage that affects memory and spatial navigation.



People who drank more than 30 units a week on average had the highest risk, but even those who drank moderately — between 14 and 21 units a week — were far more likely than abstainers to have hippocampal atrophy, the scientists said.

"And we found no support for a protective effect of light consumption on brain structure," they added.



The research team — from the University of Oxford and University College London — said their results supported a recent lowering of drinking limit guidelines in Britain, but posed questions about limits recommended in the United States.

The researchers defined a unit as 10 millilitres (ml) of pure alcohol.



U.S. guidelines suggest that up to 24.5 units of alcohol a week is safe for men, but the study found increased risk of brain structure changes at just 14 to 21 units a week.

Canada's Low-Risk Alcohol Drinking Guidelines say to reduce long-term health risks, no more than two drinks a day, five times a week or 10 drinks total a week for women are recommended and no more than three drinks a day, five times a week or 15 drinks total a week are recommended for men.

In the Canadian guidelines, "a drink" means:

341 ml (12 oz.) bottle of 5% alcohol beer, cider or cooler.

142 ml (5 oz.) glass of 12% alcohol wine.

43 ml (1.5 oz.) serving of 40% distilled alcohol (rye, gin, rum, etc.)