SINGAPORE - It was morning when the man was pulled over by the police, who assumed he was driving under the influence.
His blood alcohol level was found to be more than twice the legal limit - 200 milligrams per 100ml of blood (200mg/dL). Singapore's legal drink-driving limit is strictly enforced at 80mg/dL, or 0.08 per cent blood alcohol content.
The man, who was 46 at the time of the incident in 2014, also experienced brain fog, dizziness and memory loss - much like the symptoms an alcoholic exhibits.
But he told the police that not a drop of alcohol had ever passed his lips.
It was only after multiple consultations with various doctors in different specialties over a few years that he was diagnosed with auto-brewery syndrome (ABS).
ABS, which is also known as gut fermentation syndrome, is an extremely rare condition where bacteria and fungi in the gastrointestinal tract turn the carbohydrates in everyday foods into alcohol.
If left untreated, it can lead to alcoholic fatty liver disease.
There were fewer than 100 cases of ABS reported worldwide in a 2021 report, with the man being one known case in Singapore. His doctors did not identify him.
The rare metabolic condition made the news earlier in 2024 when a Belgian man with ABS had a drink-driving charge against him dismissed in court in April.
The 40-year-old proved that he has ABS, resulting in signs of intoxication. His lawyer told Reuters later that three doctors independently examined him and confirmed his condition.
The syndrome had been described in medical research for more than 50 years, but researchers are still learning more about it.
In ABS, the body has an unbalanced gut microbiome comprising bacteria, fungi and viruses in the intestines.
Different ABS patients have different triggers for the condition. For the Singapore man, his doctors believe the antibiotics he took for a thumb injury was his trigger.
Dr Jonathan Lee, a senior consultant from the Division of Gastroenterology and Hepatology at the Department of Medicine at the National University Hospital (NUH), said when there is too much carbohydrates, the gut of someone with ABS converts them into alcohol.
When the liver is unable to digest or metabolise every bit of carbs into energy for the body, alcohol builds up in the blood, producing the same effects as drinking too much.
Dr Lee said that in the past, a sample had to be taken and grown in a petri dish before the bacteria, virus or fungus could be categorised and doctors could decide on the treatments.
"Science has changed this, allowing us to make better sense of it. Today, we sequence the sample to look for the DNA before we classify what pathogen it is and have an idea of its blueprint. With sequencing, we learnt to appreciate that there are a lot more hidden microbes and sites... and are able to track and predict their metabolic function and the way they synergise," he added.
According to Dr Lee, the Singaporean man with ABS, who is now in his 50s, started having dizziness, brain fog, memory loss and aggression issues in 2011. ST understands it was about a week after he completed a round of antibiotics for the thumb injury.
Unable to figure out what was wrong with himself, he consulted various doctors in different specialities over the span of a few years but none of them could diagnose his condition. He was even referred to a psychiatrist, who prescribed antidepressants, but that did not help his symptoms.
ST also learnt that he went for more tests and eventually doctors found in his stool sample the fungus Saccharomyces cerevisiae, also known as brewer's yeast, a one-celled fungus used in making top-fermenting beer.
He was prescribed anti-fungal medication and told to stop eating carbs, but that did not work.
Eventually, he went to see Associate Professor Dan Yock Young, a senior consultant gastroenterologist at the Department of Medicine at NUH.
"He exhibited intermittent unexplained debilitating symptoms, which suggested an organic cause," Prof Dan told ST. "We screened him for metabolic causes and found that blood alcohol levels were raised, despite no history of alcohol intake."
Dr Lee said: "On top of that, (the patient) had bloating, which was similar to another medical condition called Sibo, or small intestinal bacterial overgrowth. (He) had the symptoms of bacterial overgrowth, which improved (only) a little bit when we treated (him) with a course of antibiotics."
The doctors were also looking towards Dr Lee for a faecal microbiota transplant as the last resort. This is a medical procedure to treat a severe bacterial infection in the colon - faecal matter from a healthy donor is processed and administered into a patient's gastrointestinal tract to stabilise the microbiome by reintroducing beneficial microbes.
It involves transferring the entire gut ecosystem from a healthy donor to a patient. In the end, it took the team "about three to six months before we suspected, tested for and diagnosed the patient with ABS", Prof Dan said.
The man was given a combination of antibiotics and anti-fungal medicine "based on culture and sensitivity results for the identified yeast and bacteria", as well as probiotics to treat his condition.
He was also told to avoid simple carbohydrates such as sugars and refined foods, and to maintain a low-sugar diet, Dr Lee said.
This meant he had to avoid consuming sodas, juice, fruit, flour, pastries, bread, alcoholic beverages, and even certain "health" foods such as kimchi, sauerkraut, yogurt, kefir and kombucha - all of which may worsen the condition since these fungi in the gut proliferate by feeding on these foods and drinks.
Instead, he had to take a high-fat, very low-carb diet until the bacterial and fungal levels normalised and symptoms resolved in a few weeks.
Dr Lee said eating the right food groups in the right order also helps keep ABS symptoms at bay.
"If you were to eat high fibre first, you actually cut down the digestion of sugars because the microbes and enzymes are all targeting the fibre," he added.
Prof Dan said that while the prognosis of this patient was good, "as symptoms were ameliorated through diet management and treatment... achieving a long-term cure is uncertain".
"But I believe he felt vindicated by the diagnosis, knowing that his symptoms were real," he said. "He has achieved good results with treatment, though there were episodes of relapse."
The patient has also since given up driving, Prof Dan added.
This article was first published in The Straits Times. Permission required for reproduction.
