What Is Auto-Brewery Syndrome?

A Belgian man was recently charged with a DUI and then later acquitted after claiming that he didn’t drink a drop of alcohol even though his BAC showed otherwise. Is it possible to become intoxicated without drinking any alcohol? 

While this isn’t the case for most of us, those who are diagnosed with auto-brewery syndrome do experience this phenomenon. To get a better idea of how this condition can be dangerous with or without consuming alcohol, let’s first understand what auto-brewery syndrome is.

What Is Auto-Brewery Syndrome?

Auto-brewery syndrome is a rare condition that is also known as gut fermentation syndrome. It’s characterized by the overgrowth of certain bacteria and fungi in our gut that can turn carbohydrates into alcohol.

While we all have healthy fungi and bacteria that live in our gut microbiome, overgrowth of these bacteria can lead to issues such as auto-brewery syndrome. 

The overgrowth of yeast feeds on sugars that we consume and converts them into energy, producing carbon dioxide and ethanol as byproducts. Ethanol, the intoxicating component of alcohol, enters our bloodstream and travels throughout our body causing symptoms of intoxication. This means that our blood alcohol concentration (BAC) can be elevated without consuming any alcohol and significantly elevated with minimal amounts of alcohol. How did we figure this out?

The History of Gut Fermentation Syndrome

One of the earliest cases of gut fermentation syndrome was documented in 1948. A five-year-old African boy had passed away after swelling in his GI tract caused his stomach to rupture. When his body was examined postmortem, it was noted that the gas and liquid found in his abdominal cavity smelled like alcohol. 

Other early cases were documented in Japan dating back to the 1950s. In 1976, researchers documented a case of a 24-year-old woman who became intoxicated after consuming carbohydrates. Her condition was a result of an overgrowth of fungi, and she was prescribed antifungals while restricting her carbohydrate intake. This resolved her symptoms and paved the way for what we know now about auto-brewery syndrome. 


Less than 100 cases are reported worldwide; however, researchers believe the condition is underdiagnosed. To determine how auto-brewery syndrome is diagnosed, let’s first understand why it happens.

What Causes Auto-Brewery Syndrome?

Since auto-brewery syndrome is caused by an imbalance of our gut microbiome, several underlying conditions, GI disease, and habits that damage our gut microbiome can lead to the development of the condition. A specific type of yeast, saccharomyces cerevisiae, is commonly found at abnormal levels in patients with auto-brewery syndrome. 

Stemming from gut microbiome imbalance, other conditions can also contribute to the risk of developing auto-brewery syndrome:

• Crohn’s disease
• Irritable bowel syndrome
• Small intestinal bacterial overgrowth 
• Diabetes 
• Obesity 
• Weakened immune system 

Habits that impact our gut microbiome can also increase the risk of auto-brewery syndrome. Excessive and continuous antibiotic use destroys healthy bacteria in our gut. This significantly disrupts our gut microbiome, which can contribute to the overgrowth of bacteria and fungi. A poor diet high in carbohydrates or processed foods can also cause GI distress and imbalances in our gut microbiome. 

Now that we understand what can cause auto-brewery syndrome, let’s take a look at the symptoms.

Auto-Brewery Syndrome Symptoms

As the name suggests, auto-brewery syndrome means our body produces alcohol inside from within. This explains the symptoms of the condition, which are synonymous with alcohol intoxication and hangover symptoms. 

The initial symptoms of auto-brewery syndrome mimic alcohol intoxication:

• Loss of coordination
• Brain fog 
• Dizziness 
• Slurred speech
• Mood changes 
• Delirium

Once our body metabolizes the alcohol produced by auto-brewery syndrome, we may feel symptoms synonymous with an alcohol hangover:

• Headaches
• Fatigue
• Bloating
• Burping
• Nausea and vomiting
• Difficulty concentrating
• Memory issues

Symptoms of auto-brewery may subside once our body detoxes the alcohol. If not addressed, symptoms can continue when we consume carbohydrates and sugars. If we experience symptoms of auto-brewery syndrome, how can we be sure it’s not something else?

How To Diagnose Auto-Brewery Syndrome

Auto-brewery syndrome is diagnosed by a physician using a combination of laboratory and observational tests. Since it’s such a rare condition, most physicians will run tests to rule out other common illnesses first.

Preliminary measures, such as reviewing medical history, documenting current symptoms, and completing a physical exam can give our physician a better idea of what may be going on. Blood and urine tests can help rule out underlying conditions. Additional tests such as stool samples and endoscopies may be ordered to check for bacterial or fungal overgrowth. 

Once everything else is ruled out, we may undergo a carbohydrate challenge test. This test consists of consuming a carbohydrate-rich meal or glucose pills on an empty stomach and then measuring our BAC. An elevated BAC without drinking alcohol would indicate auto-brewery syndrome. And if our body is producing alcohol on its own, we might want to think twice about drinking alcohol.

Can You Drink With Auto-Brewery Syndrome?

Since patients with auto-brewery syndrome convert carbohydrates and sugar, producing alcohol on its own, drinking alcohol can be extremely dangerous. Our BAC may be significantly elevated compared to those without the condition. High BAC can lead to dangerous symptoms of intoxication and cause greater long-term health effects. 

Even after auto-brewery syndrome is treated with antifungals, symptoms can often recur. Since alcohol is a substance that disrupts our gut microbiome, drinking alcohol after initial treatment can increase the risk of yeast overgrowth and symptoms of auto-brewery syndrome. Alcohol also puts a damper on our immune system, which plays a major role in protecting our body from harm by keeping harmful bacteria and fungi at bay. 

Although our body producing alcohol from carbohydrates and sugars may not seem like such a bad thing, it can be dangerous and difficult to manage. Can you imagine getting drunk from eating a donut? This is just one of many ways auto-brewery syndrome can interfere with our daily life. Let’s explore some other consequences of the condition.

Dangers of Auto-Brewery Syndrome

Auto-brewery can be extremely dangerous, especially when not understood or diagnosed. Alcohol has dangerous effects but usually, we’re making a conscious decision to drink. For those of us with auto-brewery syndrome, we can get intoxicated just from eating a meal with carbs. Synonymous with consuming alcohol, intoxication from auto-brewery syndrome can have many dangers:

• Increased risk of accidents
• Alcohol poisoning
• Increased risk of participating in risky behavior
• Decreased motor control 
• Impaired judgment 

Alcohol produced by auto-brewery syndrome is also associated with the same long-term health conditions as consuming alcohol:

• Liver damage or disease 
• Cardiovascular disease
• Certain types of cancer
• Diabetes
• GI issues

Even though we may not be consuming alcohol, the ethanol produced by auto-brewery syndrome can lead to cravings and dependence on alcohol. Auto-brewery syndrome can also be associated with legal implications and affect our academic or employment performance. We may not have consumed a drop of alcohol, but our BAC may show otherwise. This can lead to termination from employment, fines for underage drinking, and charges for driving under the influence (DUI) which has happened recently. That being said, the condition can be treated.

Treating Auto-Brewery Syndrome

Treatment for auto-brewery syndrome often includes a combination of lifestyle changes and medication. Lifestyle changes consist of making dietary adjustments that include the following:

• Avoiding carbohydrates 
• Avoiding processed foods 
• Avoiding added sugars
• Eating a higher-protein diet for satiety

Since auto-brewery syndrome is caused by fungi overgrowth, antifungals (and sometimes antibiotics) are used to treat the condition. Specifically, medications used to treat yeast infections in the gut are commonly used:

• Fluconazole
• Itraconazole
• Nystatin
• Echinocandins 

Sometimes, probiotic supplements are recommended to help balance the gut microbiome. However, since the condition is not fully understood, individual recommendations may vary. Even after treating auto-brewery syndrome, it can reoccur. For those of us with chronic auto-brewery syndrome, long-term management may be needed.

Managing Auto-Brewery Syndrome

Making long-term lifestyle changes can help prevent auto-brewery syndrome from coming back. Here are some ways we can better manage auto-brewery syndrome:

• Treat underlying conditions. Many underlying conditions can contribute to imbalances in our gut microbiome — increasing the risk of auto-brewery syndrome. By managing related underlying conditions, we can minimize the risk of recurrence of auto-brewery syndrome. 
• Exercise regularly. Research shows that exercise can help with maintaining a healthy gut microbiome. It also has positive effects on our immune system, helping balance bacteria and fight off infections.
• Limit food and drinks with added sugar. Excessive consumption of sugars can disrupt the gut microbiome. It also increases the risk of obesity and diabetes, which are both associated with an increased risk of auto-brewery syndrome.
• Choose complex carbohydrates. Complex carbohydrates take longer to break down — limiting drastic spikes in our blood sugar. This can help us maintain a healthy gut microbiome and prevent severe blood alcohol increases when auto-brewery syndrome is present. Try complex carbs from whole grains and vegetables such as oats and potatoes rather than simple carbs from processed foods like candy and pastries.
• Quit/cut back on alcohol. Alcohol can feed the overgrowth of yeast — elongating the presence of the condition. It can also negatively affect our gut microbiome, increasing the risk of recurrence. 

Even though alcohol isn’t always a part of auto-brewery syndrome, it can further complicate the issue. Additionally, if untreated, auto-brewery syndrome can cause alcohol dependence — exponentially adding to the dangers.

Key Takeaways

Auto-brewery syndrome, although extremely rare, is like drinking alcohol without consuming any alcohol. Just as alcohol is produced through yeast fermentation, an overgrowth of yeast in our gut reproduces the same process inside our body. This can be extremely dangerous if left untreated. For those with auto-brewery syndrome, drinking can be exponentially dangerous. That said, quitting or cutting back on alcohol can be beneficial for all of us.