A study performed in mice hints that moderate amounts of alcohol may support brain health by reducing inflammation and flushing away metabolic byproducts, including the protein plaques associated with Alzheimer’s and Parkinson’s diseases.

"Prolonged intake of excessive amounts of ethanol is known to have adverse effects on the central nervous system," said lead author Maiken Nedergaard, MD, DMSc, co-director of the Center for Translational Neuromedicine at the University of Rochester Medical Center. "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 research, published in Scientific Reports, unexpectedly demonstrated that alcoholic consumption analogous to about 2.5 drinks a day boosts the productivity of the brain’s glymphatic system, a network of waste-clearing vessels within the organ's tightly controlled fluid environment.

Prior to its discovery by Nedergaard and her colleagues in 2012, scientists did not fully understand how waste molecules that accumulate outside brain cells are transported out of the sealed-off tissue area, called parenchyma. We now know that well-hidden channels surrounding the brain’s blood vessels allow exchange between the parenchyma and the cerebrospinal fluid (CSF) ventricles that ultimately drain into the lymphatic vessels of the head and neck. (Early investigations of the glymphatic system also revealed that it is most active during sleep, thus first identifying the crucial link between neurological health and adequate sleep time.)

Following multiple findings that low-to-moderate drinking is actually associated with an increase in overall health and longevity, the Rochester team sought to examine what goes on in the glymphatic system after indulging in a tipple or two.

Their experiment involved getting mice drunk.

First, conscious mice were injected with low (0.5 g/kg), intermediate (1.5 g/kg), or high doses (4 g/kg) of ethanol – corresponding to about 44 milliliters (1.4 ounces), 133 ml (4.5 oz), or 354 ml (12 oz) of pure alcohol for a 70-kilogram (154-pound) human. 

Subsequently, a tracer compound was administered into the brain so that the flow of CSF could be observed.

Roughly 45 minutes after receiving the alcohol, mice in the low-dose group showed an average 40 percent increase in glymphatic flow, when compared to mice given a non-alcoholic control liquid. In contrast, the mice who were sloshed on intermediate and high doses displayed 34 percent and 28 percent reductions in glymphatic function, respectively.

To get a sense of how regular drinking can impact our brain’s garbage-disposal ability, the authors gave a different set of mice the same doses every day for 30 days, then examined their brains. In this experiment, the low-dose mice showed somewhat improved glymphatic circulation compared to controls, though the difference was not as dramatic. These mice also displayed perfectly normal behavior and motor skills at all times.

As expected, the medium dose decreased functionality, this time by about 19 percent. The authors did not assess a 30-day high-dose group because such intense levels of alcohol might have messed the mice up so much that isolating the effect on one body system alone would have been impossible. Plus, “in our pilot study, chronic exposure to the high dose of alcohol had a mortality rate of 40 percent,” they wrote.

Now, before you sprint out the door to your nearest happy hour, bear in mind that this study was not designed to assess the long-term consequences of alcohol on brain health and that the outcomes may be different in people. 

But, as too-good-to-be-true as it may sound, the results suggest that a glass of wine (or two) could be an excellent way to end the day.