A man in the US started producing beer in his gut after it accidentally became colonised by high levels of brewer’s yeast.

The normally healthy 46-year old began to experience mental fogginess, dizziness and memory loss in 2011 and had to give up his job. He saw multiple doctors, but they could not work out what was wrong.

A psychiatrist prescribed him antidepressants in 2014, but this did not help.

A few months later, the man was arrested for erratic driving. His blood alcohol reading was 200 milligrams per 100 millilitres, about the level that would be expected if he had consumed 20 standard alcoholic drinks. He said that he had not had anything alcoholic to drink, but the police did not believe him.

Baffled, the man saw a gastroenterologist, who discovered high levels of a fungus called Saccharomyces cerevisiae in his stool. This fungus is also known as brewer’s yeast, because it is used to convert carbohydrates into alcohol.

Subsequent tests showed that a similar conversion process was happening in the man’s gut. Every time he ate carbohydrates,
his blood alcohol level shot up, sometimes to as high as 400 milligrams per 100 millilitres.

In 2017, the man attended a specialist clinic at Richmond University Medical Centre in New York, where he was diagnosed with auto-brewery syndrome.

This case of auto-brewery syndrome was probably triggered by a prolonged course of antibiotics that the man took in early 2011 for a thumb injury. These antibiotics probably disrupted the his balance of gut microbes, causing abnormal growth of S. cerevisiae, which normally exists at low levels in the human gut. It is believed to be the first case of autobrewery syndrome resulting from antibiotic use.

However, it has also been reported in people with gut disorders like Crohn’s disease, most commonly due to the overabundance of other fungi. The man was treated with antifungal medication, probiotics and a low-carb diet to get rid of the excess brewer’s yeast in his gut. He has now been symptom-free for almost two years.