A Little Alcohol Helps the Brain Flush Waste

If you drink moderately – say, a couple of glasses of wine per day – you may want to toast your glymphatic system. It helps clear your brain of metabolites, including the proteins that are associated with Alzheimer’s disease and other forms of dementia. According to new research from the University of Rochester, the glymphatic system may work better if you consume low amounts of alcohol.

Be advised, however, that the glymphatic system may perform more poorly if you drink too much alcohol. When animals are exposed to high levels of alcohol over a long period of time, the University of Rochester scientists observed, markers of inflammation rise in their brains. Also, the animals suffer impaired cognition and motor skills.

Both the encouraging and dispiriting findings appeared in the journal Scientific Reports, in an article entitled “Beneficial Effects of Low Alcohol Exposure, but Adverse Effects of High Alcohol Intake on Glymphatic Function.” This article describes the effects of acute and chronic ethanol exposure and withdrawal from chronic ethanol exposure on glymphatic function, which is a brain-wide metabolite clearance system connected to the peripheral lymphatic system.

“Prolonged intake of excessive amounts of ethanol is known to have adverse effects on the central nervous system,” said Maiken Nedergaard, M.D., D.M.Sc., co-director of the Center for Translational Neuromedicine at the University of Rochester Medical Center (URMC) 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.”

The new study adds to a growing body of research that point to the health benefits of low doses of alcohol. While excessive consumption of alcohol is a well-documented health hazard, many studies have linked lower levels of drinking with a reduced risk of cardiovascular diseases as well as a number of cancers.

Dr. Nedergaard’s research focuses on the glymphatic system, the brain’s unique cleaning process that was first described by Dr. Nedergaard and her colleagues in 2012. They showed how cerebral spinal fluid (CSF) is pumped into brain tissue and flushes away waste, including the proteins beta amyloid and tau that are associated with Alzheimer’s disease and other forms of dementia. 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.

Here’s the sobering news from the current study: “Acute and chronic exposure to 1.5 g/kg (binge level) ethanol dramatically suppressed glymphatic function in awake mice. Chronic exposure to 1.5 g/kg ethanol increased GFAP [glial fibrillary acidic protein] expression and induced mislocation of the astrocyte-specific water channel aquaporin 4 (AQP4), but decreased the levels of several cytokines.”

Here’s the more cheering news: “Surprisingly, glymphatic function increased in mice treated with 0.5 g/kg (low dose) ethanol following acute exposure, as well as after one month of chronic exposure. Low doses of chronic ethanol intake were associated with a significant decrease in GFAP expression, with little change in the cytokine profile compared with the saline group.”

Animals that were exposed to low levels of alcohol consumption, analogous to approximately two and a half drinks per day, actually showed less inflammation in the brain and their glymphatic system was more efficient in moving CSF through the brain and removing waste, compared to control mice who were not exposed to alcohol. The low-dose animals’ performance in the cognitive and motor tests was identical to the controls.

“The data on the effects of alcohol on the glymphatic system seemingly matches the J-shaped model relating to the dose effects of alcohol on general health and mortality, whereby low doses of alcohol are beneficial, while excessive consumption is detrimental to overall health,” said Dr. Nedergaard. “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. This study may help explain why this occurs. Specifically, low doses of alcohol appear to improve overall brain health.”