It’s possible to become intoxicated without taking a single sip of alcohol—and scientists think they’re closer to fully understanding why.
Due to a rare condition called auto-brewery syndrome, or ABS, some people’s bodies produce enough ethanol to cause intoxication. That’s the same substance found in wine, beer, and other types of alcoholic drinks.
In individuals with ABS, microbes in the gut break down carbohydrates and turn them into high amounts of ethanol that make their way into the bloodstream. In most people, this process produces tiny concentrations of alcohol that don’t have any effect. Scientists aren’t sure how exactly this phenomenon occurs, and the limited research so far includes case reports on individual patients and a small study with five patients published in 2023.
Fewer than 100 cases of ABS have been recorded around the globe, but researchers suspect the condition is underdiagnosed. It comes with stigma, for one, as patients may be mislabeled as drinkers who hide their habits. And diagnosis requires close supervision to rule out drinking and detailed monitoring of one’s blood-alcohol concentration. Such testing can be hard to access and may not be covered by insurance.
“Auto-brewery syndrome is a misunderstood condition with few tests and treatments,” explained Elizabeth Hohmann, a physician at the Mass General Brigham Department of Medicine, in a statement.
People with ABS can face arrest, family conflict, and other serious consequences, case studies have found. The condition can also lead to medical issues such as cognitive impairment, liver damage, and withdrawal symptoms.
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Researchers suspect that imbalanced gut microbes are to blame, and the condition might be linked to gastrointestinal illnesses like Crohn’s disease and short-gut syndrome. Some case reports have identified types of ethanol-producing bacteria called Klebsiella in samples from ABS patients, who recovered with antibiotics. But the precise causes behind this mysterious condition remain elusive.
To learn more about ABS triggers and treatments, Hohmann and her colleagues examined the makeup of gut microbes from 22 people diagnosed with the condition, along with 21 unaffected people from their households to see whether their environments and diets play a role. The study, which was published today in Nature Microbiology, also included 22 healthy control participants.
Stool samples and blood tests revealed that, during a flare, median ethanol concentrations in ABS patients were significantly higher—nearly three times more—than those seen in the household partners. This hints that ABS could be diagnosed with a stool test, which may prove a far more convenient and accessible option than the other testing methods outlined above.
Those with ABS also had higher amounts of bacteria such as Escherichia coli and Klebsiella pneumoniae in their stool. These microbes are known to turn sugars into alcohol. Previously, research had suggested that certain fungi were to blame. But overall, the precise types of tiny perps behind ABS are still unclear, and it’s tough to tease out all the species involved.
The scientists also noticed that, during flare-ups, some ABS patients had elevated levels of certain enzymes that are known to be involved in fermentation. “The authors note that rather than focusing on specific bacteria species, treatments that target microbial enzymes involved in ethanol production may be a more effective strategy,” according to the statement.
The study examined the outcome of an individual with ABS who received a fecal transplant with healthy bacteria as well. During remission, the composition of microbes in his gut had transformed to mirror those of the donor’s. And after a second transplant, the patient didn’t experience any symptoms for more than 16 months. Hohmann’s team is now working on a phase 1 clinical trial testing this type of transplant in eight patients with ABS.
“Our findings may lead the way toward easier diagnosis, better treatments, and an improved quality of life for individuals living with this rare condition,” Hohmann said. 
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Lead image: Dirk Wohlrabe / Pixabay
