Auto-brewery syndrome: When the body makes its own alcohol

By Naveed Saleh, MD, MS | Medically reviewed by Kristen Fuller, MD
Published November 19, 2022

Key Takeaways

  • With auto-brewery syndrome, patients “brew” their own alcohol by means of disruption of gut homeostasis caused by bacteria and fungal overgrowth in the gut.

  • Although a limited number of cases are documented in the literature, risk factors include antibiotic use, diabetes, autoimmune diseases, inflammatory bowel disease, and laparotomy.

  • Key steps in the diagnosis and treatment include carbohydrate challenge and the provision of antifungals and probiotics to re-establish balance in the gut microbiome.

It typically takes the ingestion of alcohol into the body for an individual to become intoxicated. However, a rare condition known as auto-brewery syndrome (ABS), also known as gut fermentation syndrome, makes people into “human breweries” of sorts, meaning that an individual can become intoxicated and have an elevated blood alcohol concentration (BAC) without drinking.

Affected individuals turn carbohydrates into ethanol by the actions of gut fungi and in some cases, certain bacteria, according to an article published in Practical Gastroenterology.[]

Further research is underway to improve the diagnosis and treatment of this syndrome.

Historical background

Little research exists on this condition, despite its documentation in the literature dating back to the 1960s. The similarity in symptoms with other conditions as well as the stigma associated with this being a “made-up disease” also make diagnosis difficult, as reported in Practical Gastroenterology.

The first reported case is believed to have occurred in 1946 when a 5-year-old South African child experienced a 3-inch stomach wall tear during an emergency laparotomy. Alcohol was observed in the child’s stomach.

Subsequently, various cases of ABS have presented in individuals in Japan, with Candida yeast overgrowth identified as the primary cause. It appears more commonly in patients with diabetes, inflammatory bowel disease, and short bowel syndrome.

It also occurs frequently in immunocompromised individuals, although this condition can also occur in healthy people, according to the Practical Gastroenterology authors.

Pathophysiology of ABS

It’s unclear what triggers ABS, although its pathology results from alteration of the gut microbiome that yields an overgrowth of fungi and, more rarely, alcohol-producing bacteria such as Klebsiella.

Antibiotic exposure leads to this disruption in the gut microbiome, with one cohort study documented in the literature with all cases exhibiting a history of antibiotic exposure. Antibiotics could jostle the homeostasis of the gut microbiome, leading to yeast overgrowth, according to Practical Gastroenterology.

When ABS presents

Patients with ABS may complain of neurological symptoms, such as mood changes and loss of coordination, but not present with the usual symptoms associated with alcohol intoxication, according to research published by StatPearls.[]

This diagnosis should be a differential in all patients who test as having an elevated blood alcohol level and claim no history of imbibement, such as DUI arrests.

Some patients do present with signs of inebriation and psychiatric symptoms such as altered mood, anxiety, or depression, in addition to brain fog, changes in mental status, ataxia, and seizures, according to the Practical Gastroenterology authors. Such patients have been known to register 3–4 times the legal blood-alcohol level on a breathalyzer.

In chronic cases, ABS can lead to fatty liver, cirrhosis, and pancreatitis. ABS is more common in patients with chronic intestinal obstruction, diabetes, gastroparesis, or liver dysfunction such as nonalcoholic steatohepatitis, according to StatPearls.

An interdisciplinary strategy, with a psychiatrist on board, may be best when managing patients with ABS. Other members of the team could include a PCP, gastroenterologist, ID specialist, and nutritionist. If the patient has diabetes, then an endocrinologist and hepatologist should be involved to help prevent liver complications, as recommended in the StatPearls research.

Risk factors for ABS

There are no clearly identifiable risk factors for ABS, although many patients who present with the condition have had previous laparotomy, as well as functional disturbance such as dilated duodenum, which could lead to stagnation of intestinal contents.

Probiotics could also predispose individuals to this syndrome and result in Saccharomyces fungemia, according to a study published in AGC Case Reports Journal.[]

Based on the results of aspiration, fecal culture, and analysis of duodenal fluid, Saccharomyces is the second-most common fungal cause of ABS, according to this study.

Diagnosing ABS

In the Practical Gastroenterology article, investigators suggested a stepwise approach to identifying, diagnosing, and treating patients with ABS:

  1. ABS is suspected

  2. Detailed history and physical examination

  3. Positive breath and blood alcohol levels

  4. Basic labs

  5. Endoscopy to analyze gut secretions

  6. Carbohydrate challenge

  7. Treatment

The approach proposed by this group of gastroenterologists based on their cohort of patients differed from existing guidance in that it involved carbohydrate testing.

"Until now there had been no known standardized screening test for ABS."

Malik, et al., Practical Gastroenterology

“Therefore, sensitivity and/or specificity of this test is unstudied,” the authors wrote. “We are the first to propose a carbohydrate challenge test to identify ABS patients. If BAC or blood alcohol is negative, it is unlikely to see a positive carbohydrate challenge test, even if there is a strong suspicion for ABS.”

“When this carbohydrate challenge test is accepted and used more widely, we would have a better idea of the sensitivity, specificity, and validity of this test,” the authors continued. “In our literature review, we have found less than 100 cases since 1952. We are now studying these patients and might be able [to] provide more statistical information in the future.”

Treatment strategies

Initially, patients with the syndrome must be treated for alcohol intoxication using intravenous fluids, open airways, and the correction of nutrient deficiencies (ie, thiamine and folate), according to Practical Gastroenterology. Alcohol withdrawal is treated with benzodiazepines.

Following stabilization, treatment for ABS can begin in earnest. For 6 weeks, patients are placed on a nearly carbohydrate-free diet (with some fruits or vegetables allowed). Gastrointestinal secretions are then used to determine antifungal sensitivities and the appropriate antifungal treatment, such as nystatin or azole. Gut microbiome homeostasis is re-established with probiotics.

Antifungal treatments are gradually tapered after 6 weeks if blood-alcohol concentrations are negative, whereas probiotics are continued long-term, the Practical Gastroenterology authors wrote.

Post-treatment outcomes

Following successful treatment for ABS, patients can be treated in an outpatient setting. They should adhere to dietary changes, supplements, and any necessary medications. Following the abatement of symptoms, patients may crave alcohol and should be referred to the appropriate specialists, according to StatPearls.

Some patients experience long-term symptom resolution by stopping antibiotics and consuming a low-carbohydrate diet, whereas others will also need to take antifungals.

Although probiotics can help prevent a recurrence, some patients struggle with relapse and have difficulty returning to gut homeostasis, as reported in the StatPearls research.

What this means for you

Although uncommon, ABS is serious and can lead to short-term signs of drunkenness and long-term impacts such as neurological deficits and liver problems. Caring for patients with ABS is complex and requires a multidisciplinary approach. This condition should be considered in any patient with positive breath or blood alcohol levels who claims no history of imbibement—for example, an arrest for DUI.

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