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WASHINGTON, D.C. – April 19, 2025 – New research presented at the Gut Microbiota for Health (GMFH) World Summit 2025 sheds light on the perplexing condition known as Auto-Brewery Syndrome (ABS), identifying specific gut bacteria and fermentation pathways as key culprits. Dr. Bernd Schnabl from the University of California, San Diego, detailed findings from what may be the largest research cohort of ABS patients to date, offering insights into the diagnosis and potential treatment of this often-misunderstood disorder.
Auto-Brewery Syndrome occurs when microorganisms in the gut ferment carbohydrates into ethanol, leading to elevated blood alcohol levels and symptoms of intoxication, even when no alcoholic beverages have been consumed. Patients often report debilitating symptoms like severe brain fog and difficulty concentrating, leading to significant personal, social, and legal complications.
“Patients constantly talk about brain fog; they can’t concentrate, and it can be very severe,” Dr. Schnabl stated at the summit, convened by the American Gastroenterological Association and the European Society of Neurogastroenterology and Motility. He noted that ABS is often considered rare, but argued, “it’s rarely diagnosed because many physicians don’t know of the diagnosis, and many are actually very skeptical about the disease.”
The investigation began after a 2019 paper by Dr. Jing Yuan in Beijing, detailing an ABS case caused by Klebsiella pneumoniae, prompted inquiries from US individuals suspecting they had the condition. Dr. Yuan reached out to Dr. Schnabl, whose work focuses on alcohol-associated liver disease and the gut microbiome’s role.
Dr. Schnabl’s team established a cohort of 22 patients whose ABS diagnosis was confirmed via an observed glucose challenge. These patients, primarily middle-aged men without liver disease, provided stool samples during both symptom flares and periods of remission.
Key findings from the soon-to-be-published study include:
- Elevated Blood Alcohol: During flares, patients had a mean Blood Alcohol Content (BAC) of 136 mg/dL, significantly above the US legal driving limit of 80 mg/dL. Even after a diagnostic glucose load, the mean BAC reached 73 mg/dL within about 4 hours.
- Increased Ethanol Production: Stool samples from patients during flares produced significantly more ethanol in culture compared to samples from remission periods or from household partners.
- Bacterial Culprits: Experiments using antibiotics (chloramphenicol) versus antifungals indicated that bacteria, not fungi, were the primary ethanol producers in this cohort.
- Specific Bacteria Identified: Taxonomic profiling revealed significantly higher levels of Proteobacteria, particularly Escherichia coli and Klebsiella pneumoniae, in patients during flares.
- Heightened Fermentation: Functional analysis showed markedly increased activity of fermentation pathways in the gut microbiota during flares compared to controls.
While endogenous ethanol production by gut microbes has been known for over a century and linked to conditions like metabolic dysfunction–associated steatotic liver disease (MASLD), Dr. Schnabl’s study specifically focused on ABS patients without liver disease.
Diagnosing ABS remains challenging due to the lack of standardized tests. Dr. Schnabl proposed a clinical approach starting with an oral glucose tolerance test to check for ethanol production. He suggested fecal yeast tests and, ideally, identification of specific ethanol-producing bacteria through cultures and sequencing to guide treatment. Potential treatments include targeted antibiotics, probiotics, prebiotics, and potentially fecal microbiota transplantation (FMT).
Dr. Schnabl shared a case where FMT, following antibiotic pretreatment, successfully reduced E. coli levels, ethanol production, and symptoms in an ABS patient, although monthly treatments were needed for six months to maintain remission. He and Dr. Elizabeth Hohmann at Massachusetts General Hospital are now recruiting confirmed ABS patients for an NIH-funded Phase 1 trial investigating FMT’s safety and tolerability.
Dr. Schnabl speculated that milder forms of ABS might exist, potentially contributing to chronic fatigue or brain fog in some individuals, though he stressed this is currently “complete speculation.” He urged physicians to consider checking blood alcohol levels in patients with unexplained symptoms consistent with ABS.
Disclaimer: This news article is based solely on the information provided in the text excerpt concerning Dr. Bernd Schnabl’s presentation and research on Auto-Brewery Syndrome. It may not encompass the full scope of current knowledge or research on the topic. This article is for informational purposes only and should not be considered medical advice. Readers experiencing symptoms or health concerns should consult with a qualified healthcare professional for diagnosis and treatment. Dr. Schnabl disclosed several industry affiliations and roles as noted in the source material.
