What Binge Drinking Does to the Brain, and the Gut

"The hard part about being a bartender is figuring out who is drunk and who is just stupid." –Richard Braunstein

John Cryan and Ted Dinan are a pair of dynamic Irish researchers who, over the past decade, have been busily advancing the remarkable science of the gut-brain axis. They coined the term psychobiotic to refer to probiotics and prebiotics that can improve your mood. The idea that mere gut microbes could affect the lofty human brain is humbling. As Cryan puts it, “If microbes are controlling the brain, then microbes are controlling everything.”

Cryan, Dinan, and their team at APC Microbiome, based at University College Cork, recently looked at what happens to gut microbes in young binge drinkers. Once again, there was an interesting connection between gut microbes and the brain—in this case, the boozy brain.

Binge Drinking, Gut Microbiota, and Cognition

The study, appearing in The Lancet and headed by Carina Carbia, found that binge drinking among young people aged 18 to 25 had a long-term impact on their gut microbiota and their cognition. Bingeing increased inflammation and slowed reaction times. Testing showed bingers had emotional deficits and alcohol cravings that were strongly associated with their altered microbiota. Cryan says, “This study highlights the importance of the gut microbiota in regulating craving, social cognition, and emotional functioning.”

I had the wonderful opportunity to write a book with Cryan and Dinan: The Psychobiotic Revolution from National Geographic. During our collaboration, a Guinness or two may have been downed, but no bingeing. We were writing for the layperson, but our prose pales next to Ireland’s legendary hard-drinking bards. The Emerald Isle is known for outstanding literature and enthusiastic imbibing, often pursued simultaneously. Dubliners James Joyce, Oscar Wilde, Jonathan Swift, and Samuel Beckett were brilliant writers who were all known to crawl the pubs for a drop or two. Some of these pubs are famed for that literary patronage.

Irish playwright George Bernard Shaw famously declared that whiskey is liquid sunshine. Less cheerfully, he also asserted that “alcohol is the anesthesia by which we endure the operation of life.” The Irish novelist Brendan Behan, well-known for both his wit and his binges, once described himself as a drinker with a writing problem. Funny, yes; but, sadly, drinking led to his death after he collapsed at the Harbour Lights Bar in Dublin. He was only 41.

Short of killing you, binge drinking can have more subtle effects, including blunted emotional perception. The APC study found that binge drinkers had a difficult time recognizing expressions of sadness or disgust.

Alcohol Cravings

Specific microbial species were associated with impulsive behavior and cravings for alcohol. We now know that many of our cravings may be encouraged by these tiny creatures. By secreting neurotransmitters like serotonin and dopamine, they yank our reins to guide us to their favorite foods. When we binge drink, we encourage a certain class of party bacteria that tend to draw us back to the bar for another round. Some species of Alistipes, for instance, are reduced by binge drinking, while species of Veillonella are increased. You might blame Veillonella for that urge to celebrate.

The study defined binge drinking as “consumption of a large amount of alcohol within a short period of time, leading to a blood alcohol concentration of at least 0.8 g/l.” That works out to about five drinks in a single sitting, which is more common in Ireland (19 percent) than the European average (6 percent). However, averages are deceptive, and Ireland is not the booziest country in Europe. It has some stiff competition from Germany, Latvia, and the Czech Republic, among others.

Still, Ireland has a reputation for drinking, deserved or not. Tina Fey, the comedic actress (with some Irish heritage) said, “In a study, scientists report that drinking beer can be good for the liver. I’m sorry, did I say ‘scientists’? I meant Irish people.” So, perhaps an Irish study of bingeing isn’t totally inappropriate.

Drinking is a deeply entrenched part of humankind. In fact, throughout most of our history, alcohol has been a lifesaver, killing the ubiquitous pathogens in ordinary water. Louis Pasteur, eponymous for killing microbes, said that “wine is the most healthful and most hygienic of beverages.” Alcohol, produced by microbial fermentation, is a potent antiseptic. Pasteur knew that it takes a microbe to fight a microbe.

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For as long as there have been guts, beneficial microbes have made a home there, and they play an important role in fending off pathogens. They are an unsung but important part of our immune system.

Our gut microbes, some of which can double in number every half hour, respond quickly to our dietary and drinking habits. As mentioned, depending on what we consume, some microbes thrive while others languish. Amazingly, the complex communities they form can alter our mood and cognition.

Long-Term Problems

These alterations can be persistent, and bingeing at a young age may set us up for lifelong behaviors that can be hard to reset. So, if you are thinking of taking an alcoholiday to visit Margaritaville, pace yourself. Your booze-loving bacteria may enjoy a binge, but the joy you find in the evening will be subtracted from the following morning. Worse yet, you may be setting yourself up for enduring behavioral problems.

Quitting is an obvious solution, but, for many, that can be tough. As Henny Youngman put it: "When I read about the evils of drinking I gave up reading." But, like many things in life, the dose makes the poison. A recent large study of 4 million Koreans found that three glasses of alcohol or more per day was associated with an increase in rates of dementia. However, one or two glasses a day lowered dementia rates compared with those of teetotalers.

That should cheer moderate drinkers and encourage the rest of us to drink less. Binge drinking, it turns out, might not be the smartest move.

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