Auto-Brewery Syndrome: How Your Body Can Make Itself Drunk

There is a condition called auto-brewery syndrome in which yeast trapped in the digestive system can cause a human to ferment alcohol in the stomach. After eating carbohydrates like bread, the sugar in the food mixes with the yeast and produces ethanol, causing intoxication. While it might sound like the most awesome disease ever, the implications are obviously quite dangerous.
In 2013, Barbara Cordell, dean of nursing at Panola College and Dr. Justin McCarthy, a gastroenterologist, published a paper in the International Journal of Clinical Medicine, detailing a bizarre case. A 61-year-old Texas man visited an emergency room, clearly intoxicated. A Breathalyzer test clocked him in at a blood alcohol concentration of 0.37 percent, enough to kill a person. He brewed his own beer at home, so it was no surprise to the attending staff that he’d overindulged. However, the man was adamant that he’d had nothing to drink. Doctors and the man’s wife figured he was sneaking off to guzzle liquor on the sly. But the case intrigued Dr. McCarthy, and he sequestered the patient in a room with no access to alcohol. Bizarrely enough, he continued to get drunker after only eating solid food.

After a while, they learned that the man’s digestive system was crawling with Saccharomyces cerevisiae—brewer’s yeast. Whenever he ate something starchy, such as a bagel, a simple chemical reaction occurred in his belly. The yeast devoured the sugars, leaving ethanol as a waste product and rendering the man instantly drunk, brewing a strong beer right inside his belly. It is normal for the human body to produce tiny amounts of alcohol called “endogenous ethanol” through various processes, but the concentration is so insignificant, you’d never notice it. However, the man in question had a blood alcohol level nearly five times the legal limit for driving a car.

Auto-brewery syndrome was not unknown, but it had only previously been described in Japan, where it is called “meitei-sho.” Again, it was a startlingly rare, but about half of people of East Asian descent possess a mutation in their liver enzymes which does not allow them to properly process alcohol, likely promoting the condition. Other contributing factors are thought to be the heavy consumption of carb-rich food like rice, gastrointestinal surgery, and taking antibiotics, which can wipe out the bacteria in the stomach and make room for infestations of yeast.

While free beer seems like the best side effect to the coolest medical condition of all time, there are several scary factors at play. Had the man been just slightly drunker, he likely would have succumbed to alcohol poisoning. And he could have easily been involved in an accident after doing something no more innocuous than eating breakfast. The man was treated with antifungal medication and a low-carbohydrate diet, and his symptoms thankfully cleared up.