Two alcoholic drinks a day are good for your brain

US study finds low level boozing improves brain health. Jeff Glorfeld reports.

At low doses, daily alcohol intake can have positive outcomes, a mouse study shows.
At low doses, daily alcohol intake can have positive outcomes, a mouse study shows.
Sally Anscombe/Getty Images

Scientific journals are littered with reports documenting positive effects from drinking moderate amounts of alcohol, all of which are also at pains to point out the many negative outcomes that result from over-consumption. Cited benefits include psychological (1985), vascular (2000) and social (2017), to name just a few.

Now a new study in the journal Nature says low levels of alcohol consumption improves overall brain health by reducing inflammation and clearing away toxins, including the proteins beta amyloid and tau, both associated with Alzheimer's disease and other forms of dementia.

"Prolonged intake of excessive amounts of ethanol is known to have adverse effects on the central nervous system," says Maiken Nedergaard, from the Centre for Translational Neuromedicine at the University of Rochester Medical Centre in New York, and lead author of the study.

"However, in this study we have shown for the first time that low doses of alcohol are potentially beneficial to brain health, namely it improves the brain's ability to remove waste."

Nedergaard was part of the team of researchers who in 2012 first described the glymphatic system, a macroscopic waste clearance system that uses cerebral spinal fluid to promote efficient elimination of soluble proteins and metabolites from the central nervous system. They postulated that the system may also help distribute non-waste compounds, such as glucose, lipids, amino acids, and neurotransmitters in the brain.

Subsequent research has shown that the glymphatic system is more active while we sleep, can be damaged by stroke and trauma, and improves with exercise.

This latest report says acute and chronic exposure to 1.5 grams of ethanol per kilogram of body weight – that is, binge drinking level – dramatically suppresses glymphatic function in awake mice, and damaged a range of genetic functions.

“Surprisingly, glymphatic function increased in mice treated with 0.5 grams per kilogram (low dose) ethanol following acute exposure, as well as after one month of chronic exposure,” the report says.

The researchers say their observations suggest that ethanol has a J-shaped effect on the glymphatic system, whereby low doses of ethanol increase glymphatic function, but chronic 1.5 g/kg ethanol intake disturbs glymphatic function, which may contribute to the higher risk of dementia observed in heavy drinkers.

Animals that were exposed to low levels of alcohol consumption, analogous to about 2 ½ drinks a day, had less inflammation in the brain and their glymphatic system was more efficient in moving cerebral spinal fluid through the brain and removing waste, compared to control mice who were not exposed to alcohol.

Nedergaard says the new research indicates that low doses of alcohol are beneficial, but excessive consumption is detrimental to overall health.

"Studies have shown that low to moderate alcohol intake is associated with a lesser risk of dementia, while heavy drinking for many years confers an increased risk of cognitive decline,” she says. “This study may help explain why this occurs. Specifically, low doses of alcohol appear to improve overall brain health."

Jeff Glorfeld is a former senior editor of The Age newspaper in Australia, and is now a freelance journalist based in California, US.
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