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).
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.
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.
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.
Just eating a carb-rich diet can be a trigger in some people, as can rare genetic variations that stop the liver from processing alcohol properly.
Diagnosing ABS can be a long-winded process involving blood alcohol tests carried out a few hours after eating carbs or sugar, or stool tests to look for excess levels of yeast.
Dr Lindsey Edwards, a research scientist at King’s College London, says faecal transplants can improve the lives of those suffering from ABS, as it boosts good bacteria in the gut
Treatment usually involves anti-fungal drugs as well as avoiding foods (such as carbs) that trigger bouts of ‘drunkenness’.
But the latest research, published earlier this month, has identified new culprits behind the condition and hinted at a possible new treatment.
Scientists from Massachusetts General Hospital in Boston and the University of California in San Diego studied 22 volunteers with ABS and compared the make-up of their gut microbiome with their healthy peers by analysing stool samples.
The ABS sufferers had much higher levels of Escherichia coli and Klebsiella pneumoniae, which were both responsible for producing alcohol in the gut.
It’s been known for years that gut organisms cause ABS but the new study, one of the largest ever to investigate the problem, is the first to provide solid evidence on which ones are to blame.
‘This study shows E. coli and Klebsiella bacteria produce clinically significant amounts of alcohol inside the gut,’ says Dr Lindsey Edwards, a research scientist specialising in the gut microbiome at King’s College London.
‘This matters because it gives patients much-needed validation in a condition which is often dismissed or misunderstood.’
It may also potentially help improve diagnosis.
As part of the study, researchers also tracked one patient who underwent an experimental faecal transplant to see if it might cure the problem. Here, tiny poo samples from a healthy donor are inserted into the gut using a long probe called an endoscope, or freeze-dried into a capsule which is swallowed. This proved very successful in combating Clostridium difficile, a gut infection.
Now these faecal transplants are being investigated for a range of disorders, including inflammatory bowel disease, liver disease, food allergies and even anxiety.
The researchers found the ABS patient experienced no more bouts of ‘drunkenness’ during the 16 months of the study.
The same team are now studying a further eight volunteers.
‘This is a great example of how faecal transplants can solve medical mysteries and improve lives,’ says Dr Edwards.
