Auto-brewery syndrome (ABS) (also known as gut fermentation syndrome, endogenous ethanol fermentation or drunkenness disease) is a condition characterized by the fermentation of ingested carbohydrates in the gastrointestinal tract of the body caused by bacteria or fungi.

ABS is a rare medical condition in which intoxicating quantities of ethanol are produced through endogenous fermentation within the digestive system. The organisms responsible for ABS include various yeasts and bacteria, including Saccharomyces cerevisiae, S. boulardii, Candida albicans, C. tropicalis, C. krusei, C. glabrata, C. kefyr, C. parapsilosis, Klebsiella pneumoniae, and Enterococcus faecium.

These organisms use lactic acid fermentation or mixed acid fermentation pathways to produce an ethanol end product. The ethanol generated from these pathways is absorbed in the small intestine, causing an increase in blood alcohol concentrations that produce the effects of intoxication without the consumption of alcohol.

Researchers speculate the underlying causes of ABS are related to prolonged antibiotic use, poor nutrition and/or diets high in carbohydrates,and to pre-existing conditions such as diabetes and genetic variations that result in improper liver enzyme activity.

In the last case, decreased activity of aldehyde dehydrogenase can result in accumulation of ethanol in the gut, leading to fermentation. Any of these conditions, alone or in combination, could cause ABS, and result in dysbiosis of the microbiome.

Another variant, urinary auto-brewery syndrome, is when the fermentation occurs in the urinary bladder rather than the gut. Claims of endogenous fermentation have been attempted as a defense against drunk driving charges, some of which have been successful, but the condition is so rare and under-researched they are currently not substantiated by available studies.

This disease can have profound effects on everyday life. Symptoms that usually accompany ABS include elevated blood alcohol levels as well as symptoms consistent with alcohol intoxication - such as slurred speech, stumbling, loss of motor functions, dizziness, and belching.[8] Mood changes and other neurological problems have also been reported. Several cases in the United States and one in Belgium have argued endogenous fermentation as a defense against drunk driving. Continue reading

Auto-Brewery Syndrome - A woman kept getting drunk despite not drinking. Fungi in her gut were brewing their own alcohol.   Live Science - June 3, 2024

A woman kept ending up in the emergency room with excessive sleepiness, slurred speech and the scent of alcohol on her breath, but she had not ingested a drop of liquor. It turns out that microbes in her gut were brewing their own booze - and making her drunk.