Can Sugar Turn to Alcohol in the Body? Understanding Auto-Brewery Syndrome

January 2, 2026 •

4 min read

While the body's normal metabolism clears trace amounts of naturally produced ethanol, a rare condition called Auto-Brewery Syndrome (ABS) proves that yes, sugar can turn to alcohol in the body, leading to symptoms of intoxication.

Quick Summary

Auto-Brewery Syndrome is a rare medical condition where an overgrowth of gut microbes ferments carbohydrates into ethanol within the GI tract, causing intoxication without alcohol consumption.

Key Points

Rare but Real: Yes, sugar can turn into alcohol in the body, but only under the rare medical condition known as Auto-Brewery Syndrome (ABS).
Microbial Culprits: The conversion is caused by an overgrowth of fermenting microorganisms, such as certain yeasts (like Saccharomyces cerevisiae) and bacteria (Klebsiella pneumoniae), in the GI tract.
Intoxication from Food: Individuals with ABS can become intoxicated after consuming carbohydrates and sugars, exhibiting symptoms like dizziness, brain fog, and slurred speech without drinking alcohol.
Triggering Factors: Risk factors for developing ABS include a high-sugar or high-carb diet, chronic antibiotic use, and pre-existing conditions like diabetes or Crohn's disease.
Diagnosis is Key: Confirming ABS often requires a specialized glucose challenge test to monitor for endogenous ethanol production, along with stool cultures to identify the culprit organisms.
Diet and Drugs are Primary Treatment: Treatment focuses on a strict low-carb diet to limit fermentation, combined with antifungals or antibiotics to eradicate the problematic microbial overgrowth.

The Gut's Microbial 'Brewery'

Under normal circumstances, the human body produces a small, physiologically insignificant amount of ethanol through the metabolism of carbohydrates by the gut microbiota. Our liver efficiently clears this before it can accumulate. However, in rare cases of Auto-Brewery Syndrome (ABS), a significant overgrowth of certain microorganisms in the gastrointestinal tract overwhelms the body's metabolic capacity. These microbes, primarily yeasts and certain bacteria, ferment ingested sugars and starches into ethanol, leading to symptoms of alcohol intoxication.

Key Microbes Responsible for Fermentation

The fermentation process that creates endogenous alcohol is not caused by human cells but by the gut's microbial residents. The primary culprits in ABS are:

Saccharomyces cerevisiae: Commonly known as brewer's or baker's yeast, this fungus is a frequent cause of ABS.
Candida species: Various types, including C. albicans, C. glabrata, and C. kefyr, have been implicated.
Klebsiella pneumoniae: Certain strains of this bacteria are also capable of producing significant amounts of alcohol.
Enterococcus faecium and E. faecalis: These bacteria have been linked to some cases of ABS.

Who is at Risk for Auto-Brewery Syndrome?

ABS typically affects individuals with specific pre-existing conditions that disrupt the delicate balance of the gut microbiome. Factors that increase the risk include:

Chronic Antibiotic Use: Repeated or long-term antibiotic courses can wipe out beneficial gut flora, allowing fermenting microorganisms to flourish.
Underlying Health Conditions: Individuals with diabetes, liver cirrhosis, or other metabolic diseases are more susceptible. High blood sugar in diabetics provides ample fuel for the fermenting microbes.
Gastrointestinal Disorders: Conditions that cause stagnant intestinal content, such as Small Intestinal Bacterial Overgrowth (SIBO) or Crohn's disease, create a favorable environment for microbial overgrowth.
High-Carbohydrate Diet: A diet rich in simple and complex sugars provides the fuel necessary for the microbial fermentation process.
Post-Surgical Complications: Patients who have undergone certain gastrointestinal surgeries, like jejunal bypass, are at higher risk.

Comparison: Normal Gut vs. Auto-Brewery Syndrome


Feature	Normal Gut	Auto-Brewery Syndrome (ABS)
Microbial Balance	Healthy and diverse microbiome, with yeasts and bacteria in check.	Imbalanced, with an overgrowth of fermenting yeasts or bacteria.
Carbohydrate Metabolism	Carbohydrates are digested and absorbed as nutrients in the small intestine.	Unabsorbed carbohydrates are fermented into ethanol by overgrown microbes.
Ethanol Production	Trace, clinically insignificant amounts produced as a metabolic byproduct.	Significant amounts of ethanol produced endogenously, exceeding the liver's capacity.
Impact on Health	Contributes positively to digestion and nutrient absorption.	Leads to symptoms of intoxication, GI distress, and long-term health issues like liver damage.
Symptoms	No intoxication symptoms from food consumption.	Unexplained episodes of dizziness, slurred speech, confusion, and fatigue after meals.

How is Auto-Brewery Syndrome Diagnosed?

Diagnosis of ABS can be challenging due to its rarity and symptoms mimicking other conditions. A healthcare provider will typically consider the diagnosis if a patient reports signs of intoxication without consuming alcohol.

Diagnostic procedures may include:

Thorough Medical History: The doctor will take a detailed history of the patient’s diet, health issues, and medication use (especially antibiotics).
Blood Alcohol Testing: Elevated blood alcohol levels without alcohol intake are the primary indicator. However, this may be inconsistent.
Glucose Challenge Test: This is considered the gold standard for confirmation. Under medical supervision, the patient ingests a high dose of glucose after fasting. Breath and blood alcohol levels are monitored over several hours. A rise in ethanol levels confirms endogenous fermentation.
Stool and Endoscopy Cultures: Lab tests on stool or samples from an endoscopy can identify the specific overgrowing microbial organisms.

Managing Auto-Brewery Syndrome: Diet and Treatment

Managing ABS requires a multi-pronged approach focused on eliminating the microbial overgrowth and restricting the carbohydrate fuel source. Treatment is typically overseen by a team of specialists, including a gastroenterologist and a nutritionist.

Treatment Protocols

Strict Low-Carbohydrate Diet: The cornerstone of treatment is drastically reducing or eliminating all carbohydrates and sugars to starve the fermenting organisms. This includes simple sugars, starches, and processed foods.
Antifungal or Antibiotic Medication: Medications are prescribed based on the identified causative organism. Antifungals like fluconazole are used for yeast overgrowth, while specific antibiotics may target fermenting bacteria.
Probiotics: After treating the overgrowth, probiotics may be used to help repopulate the gut with beneficial bacteria and restore microbial balance. More research is needed to determine efficacy.
Fecal Microbiota Transplant (FMT): For refractory or recurring cases, an FMT may be considered. This procedure introduces healthy gut microbiota from a donor to re-establish a normal microbiome.

For more detailed information on Auto-Brewery Syndrome, the National Center for Biotechnology Information (NCBI) offers comprehensive reviews. https://www.ncbi.nlm.nih.gov/books/NBK513346/

Conclusion

While a common party trick suggestion, the idea that sugar can turn to alcohol in the body is a genuine, albeit rare, medical phenomenon known as Auto-Brewery Syndrome. This condition arises from an overgrowth of fermenting microbes in the gut, fueled by a high-carbohydrate diet and often exacerbated by factors like antibiotic use or underlying metabolic diseases. The resulting endogenous ethanol production can lead to involuntary intoxication, posing significant health and social challenges. Though complex to diagnose, effective management involves a strict low-carbohydrate diet, targeted medication, and the restoration of a healthy gut microbiome, offering a path to recovery for those affected by this bewildering disorder.

Frequently Asked Questions

Auto-Brewery Syndrome, also known as gut fermentation syndrome, is a rare medical condition where an overgrowth of yeast or bacteria in the gut ferments ingested carbohydrates into ethanol, causing intoxication without drinking alcohol.

No, a healthy person cannot get drunk from eating too much sugar. The human body's normal metabolism and liver are extremely efficient at clearing the trace amounts of ethanol produced by the gut, so it never accumulates to intoxicating levels.

The overgrowth of fermenting microbes can be caused by prolonged antibiotic use, underlying health issues like diabetes or gut motility disorders, certain gastrointestinal surgeries, and a consistently high-carbohydrate diet.

Symptoms of ABS mimic alcohol intoxication and can include dizziness, disorientation, slurred speech, unsteady gait, fatigue, brain fog, and gastrointestinal issues like bloating and gas.

Diagnosis is often confirmed with a glucose challenge test, where a patient is given a sugar dose and their blood or breath alcohol levels are monitored over several hours. Stool or intestinal cultures are also used to identify the specific fermenting organisms.

The primary treatment involves a strict, long-term, low-carbohydrate diet to remove the fuel source for fermentation. This is often combined with antifungal or antibiotic medications to eliminate the microbial overgrowth. Probiotics may also be used to help restore gut balance.

Yes, ABS can be dangerous. The constant intoxication can lead to accidents and injuries, impair driving and job performance, and strain relationships. Long-term exposure to endogenous ethanol can also contribute to liver damage and other health complications.