Gut: a breeding ground for alcohol

Have you ever felt lightheaded after a heavy meal? Foggy. A little off balance. Most people dismiss it as a food coma.

But for a few people, the sensation is far more literal. They are getting drunk. Without drinking a single drop of alcohol.

What is going on?

Your gut is home to trillions of microbes. Many of them help you digest food. Some produce vitamins. Others regulate your immune system. But a few, under the right conditions, do something unexpected.

They ferment the carbohydrates you eat and convert them directly into ethanol. The same ethanol found in wine, beer, and spirits. Produced inside your own intestines.

This is auto-brewery syndrome. And for the first time, scientists have identified the exact bacteria responsible.

A January 2026 Nature Microbiology study examined 22 patients, their household partners, and healthy controls.

Stool samples from patients during active flare-ups produced significantly more ethanol than those from healthy individuals.

The culprits were specific gut bacteria, including Escherichia coli and Klebsiella pneumoniae, which ferment sugars into ethanol through multiple metabolic pathways.

Here is what makes this unsettling.

Every human gut produces trace amounts of alcohol during normal digestion. Your liver clears it before it ever reaches your bloodstream. But in people with auto-brewery syndrome, the production overwhelms the clearance.

Blood alcohol levels can climb high enough to cause legal intoxication. Slurred speech. Impaired coordination. Liver damage. All without a single drink.

The condition is extremely rare, with fewer than a hundred documented cases worldwide, but researchers suspect it is significantly underdiagnosed because of stigma and disbelief.

Patients are often accused of hiding an addiction. Many endure years of misdiagnosis.

The breakthrough here is not just identification. One patient achieved over 16 months of symptom-free living after receiving a microbiota transplant.

Your microbiome is not passive. It is a living chemistry lab, constantly producing compounds that shape how you feel, think, and function. Sometimes it brews something you never ordered.

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