Then, you wake up with a throbbing head, slurred speech, and the unmistakable dizziness of a hangover even though you didn’t drink a single drop the night before. For most, it sounds like a medical mystery or a bad joke, but for those diagnosed with Auto-Brewery Syndrome (ABS), it’s a harrowing everyday reality. Researchers are now able to pinpoint the gut bacteria and metabolic pathways responsible for this rare “drunkenness disease,” a breakthrough study published in Nature Microbiology in early January 2026 reported.
What is Auto-Brewery Syndrome?
Auto-Brewery Syndrome (also known as Gut Fermentation Syndrome), is an unusual condition where the digestive system turns itself into an internal distillery. When a person eats carbohydrates such as bread, pasta or fruit select overgrown microbes in his or her gut ferment those sugars into ethanol (alcohol).
During digestion, the human body, by necessity, releases just a few drops of alcohol, but the liver normally clears it immediately. In ABS patients, however, such production levels reach levels that inundate the bloodstream, driving blood alcohol concentration (BAC) to levels that exceed the legal driving limit.
The “New” Culprits: It’s Not Just Yeast
In the past, medical colleagues believed that yeast--namely Saccharomyces cerevisiae (brewer's yeast)--is the chief cause of ABS. But 2026 brought experts from Mass General Brigham and UC San Diego to the forefront, leading them to shift attentions towards bacteria. With the largest dataset of ABS patients so far to date, scientists discovered two primary bacteria-dependent drivers.
Klebsiella pneumoniae
Escherichia coli (E. coli). In "flares," these bacteria utilize elaborate metabolic pathways involving mixed-acid and heterolactic fermentation to produce ethanol at rates previously thought impossible for bacteria. Symptoms and Warning Signs. It’s often misdiagnosed as “closet drinking,” which has resulted in a tremendous amount of social stigma and even criminal cases. To add to the sensation of intoxication, victims also discuss:
- Brain Fog: Severe trouble focusing or forgetting.
- Physical Impairment: Coordination, slurring and dizziness.
- Gastrointestinal Distress: Sudden bloating, gas and abdominal pain.
- Chronic Fatigue: Being tired, constant fatigue a constant state of exhaustion due to the body’s failure to handle inner toxins.
The Optimistic Future: Fecal Transplants
Perhaps the most exciting finding of the latest research is the success of Fecal Microbiota Transplantation (FMT). In a landmark case, a patient who had refractory to all other treatment remained symptom-free for over 16 months after having had a stool transplant to “reset” their gut microbiome. Experts believe that these findings will help drive standardised stool-based diagnostic tests, as opposed to the cumbersome 24-hour glucose challenge testing currently required to perform the diagnostic process.
