Unravelling the mystery of autobrewery syndrome

This strange condition can blight the lives of the people who suffer from it, leading them to become intoxicated without consuming alcohol, but scientists are closing in on what causes it.It would happen two to three times a week. Nick Carson would start slurring his words and then become progressively less steady on his feet. His conversations would go around in circles and eventually he would collapse into a deep sleep. The father-of-two was showing all the signs of being drunk. Except Carson hadn’t consumed any alcohol. His apparent intoxication, however, was accompanied by other symptoms – stomach pains, bloating and tiredness. He would often be sick and pass out. It first occurred around 20 years ago when his family noticed he started to have episodes of mental disorientation. “Before this I had never seen him drunk,” says Carson’s wife, Karen. Carson himself could only recall the events of these episodes in a foggy way the next day. “I did not have a clue what was happening.” says 64-year-old Carson, who lives in Lowestoft, Suffolk, in the UK. “Six to eight hours later I would wake up like there is nothing wrong with me, very rarely feeling hungover.” Eventually Carson and his wife found the intoxication and other symptoms seemed to be triggered after eating meals that were high in carbohydrates, such as potatoes. After multiple visits to doctors and nutritionists, Carson was diagnosed with a rare condition called Auto-Brewery Syndrome. Auto-Brewery Syndrome (ABS), which is also known as gut fermentation syndrome (GFS), is a largely mysterious condition that raises the levels of alcohol in the blood and produces the symptoms of alcohol intoxication in patients, even when they have had minimal or no alcohol intake. It can lead them to fail breathalyser tests, and brings social and legal consequences for sufferers. But this unusual phenomenon is also highly controversial, not least because its exact cause is still poorly understood. Despite this, the condition has also been used as a legal defence in drink-driving cases.Nick Carson (left) and his wife Karen have been struggling to understand the underlying causes of his autobrewery syndrome for nearly 20 years (Credit: Nick and Karen Carson)”I think most toxicologists at this point would acknowledge that this is a real medical condition and you can in fact achieve significant concentrations of alcohol from internal fermentation,” says Barry Logan, executive director of the Center for Forensic Science Research and Education in Philadelphia. “We all produce small amounts of alcohol from fermentation but in most individuals, the levels are far too small to be measured.” Normally any fermentation that occurs in the gut is removed before it can get into the blood stream – an effect known as first-pass metabolism. “If someone has ABS, they would have to be producing alcohol at a rate which exceeds what can be removed in the first pass,” says Logan. One suggested mechanism underlying the condition revolves around imbalances in gut microbes, which lead to overgrowth of certain microbes that later, under particular conditions, ferment a high-carbohydrate meal into alcohol. Recently a new variation of this condition – called urinary ABS or “bladder fermentation syndrome” – has been found to occur due to imbalances among the microbes living in the bladder and leads to otherwise unexplained alcohol in the urine. (This variant of the condition has been seen in patients with diabetes, which if uncontrolled leads to sugar in the urine which the microbes can feed upon), But what might be triggering this sudden and dramatic change in the microorganisms living inside our bodies that in the right circumstances leads to ABS? Although ABS has been found in otherwise healthy individuals, a higher prevalence is reported in people suffering from comorbidities including diabetes, obesity-related liver disease, Crohn’s disease, prior intestinal operations, pseudoobstruction (an impaired ability to pass food or gas through the intestine but without any sign of a blockage), or small intestinal bacterial overgrowth. The first reported cases of this syndrome appeared in Japan as early as the 1950s, and there have been suggestions that the Japanese population is particularly prone to it. Some researchers have suggested that a particular genetic variation that reduces the ability of the liver to break down ethanol, may contribute to the prevalence of the condition in certain populations, such as the Japanese. Essentially it means the people who have this variant are less able to clear their bodies of alcohol, so any fermentation in the gut can result in ethanol levels accumulating.But a medical report of two cases from 1984 highlighted another culprit – yeasts living in the patients’ digestive tracts. Doctors at Hokkaido University School of Medicine reported how a 24-year-old previously healthy nurse had, over a period of five months, developed symptoms of dizziness, nausea and vomiting one to two hours after eating high-carbohydrate meals. One day, two hours after her breakfast, she complained of general malaise and dizziness, becoming unconscious and needing hospital admission. Ethanol concentrations in her breath and blood were found to be extremely high, even though she had not consumed any alcohol. Laboratory tests revealed she had increased numbers of the yeast Candida albicans, in her gut. Although this yeast is typically found among the microbes in the human gut, it had clearly got out of control. Similar tests on the study’s second case, a 35-year-old cook who complained of an alcoholic odour on is breath, together with blurred vision and a weaving gait when he walked, was also found to have elevated levels of Candida albicans in his gut. Laboratory tests on the yeast from both patients showed they were strongly fermenting carbohydrates to alcohol. The researchers at the time suggested that the otherwise normal Candida in their patients’ guts had grown out of control and started fermenting the carbohydrate from their meals. When the patients ate a lot of carbohydrates, the alcohol levels in their bodies jumped accordingly. When the nurse and the cook were given an anti-fungal medication and the carbohydrates in their diets were restricted, the drunk-like symptoms disappeared completely. More recently, other studies have revealed it often takes a combination of factors to increase the risk of ABS. A number of alcohol-producing fungi and bacteria in both the gastrointestinal, but also the urinary tract in some diabetic patients, can lead to overproduction of alcohol. The majority of the culprit species are Candida yeasts, including Candida albicans, Candida kefyr, and Candida galbrata, but also Saccharomyces cerevisiae, the yeast used in winemaking and brewing, and a gut bacteria called Klebsiella pneumoniae.The brewers yeast Saccharomyces cerevisiae can be found among the microbes living in our guts (Credit: Steve Gschmeissner/Science Photo Library/Getty Images)We each have about 100 trillion of microorganisms within our gut, including bacteria, fungi, phages, viruses, protozoa, and archaea with, so far, an estimate of more than 1,000 species of bacteria. Research reveals their immense role in our survival, ranging from digestion of our meals to determining the extent of local and bodily inflammation, regulating our immune system, to also being involved in glucose metabolism and insulin signaling. These microorganisms are highly dynamic and can change in numbers and species depending on our lifestyle choices.A significant number of studies show that the more diverse these species are the better for our physical and mental health. Read about how exercise can boost our gut microbes.Alone, abnormal levels of these microorganisms in patients’ guts may not lead to ABS. Eating meals rich in carbohydrate meal are an obvious contributor, as it gives the microbes plenty of raw material to convert into alcohol. People with gastrointestinal problems that cause food to stagnate in their digestive tract are also particularly prone to ABS as it may alter the environment in the stomach in ways that favour alcohol-producing microorganisms. Having a low tolerance for alcohol may also play a role, as the alcohol produced by the microbes has a greater effect on the human who hosts them. “Treatment and diagnosis of ABS have made substantial progress in the last decade,” says Barbara Cordell, a researcher at Panola College, Carthage, Texas, who studies ABS and is president of the non-profit organisation Auto-Brewery Information and Research.  But exactly what might cause the imbalance of microbes and lead to excessive species capable of fermenting alcohol has been much harder to pinpoint. “We are talking about massive infections here with ABS – many times the amount of fermenting yeast and bacteria than in a healthy person,” says Cordell. “It overwhelms the system much like any other out-of-control infection.” You might also be interested in: Frequent or long-term use of antibiotics has been suggested as a risk factor, as it is often reported by patients who suffer from the condition, or that they can suffer a relapse after a course of the medication. This would make some sense as excessive antibiotic use in general is known to upset the gut microbiota, but further research is needed to confirm whether this is what directly leads to ABS. Eating too much of the wrong types of foods could also be playing a role. Excessive consumption of ultra-processed foods has also been linked to upsets in the gut microbiota. “We also know that a large component of treatment must be a low-carbohydrate diet whether the provider and patient decide to use medication or not,” says Cordell. In the case of Saccharomyces cerevisiae and Candida albicans, these gut microbes are known to grow better and produce more ethanol in mildly acidic conditions, at a pH of around 5-6. “Normally, the stomach’s pH is [very acidic] between 1.5-3.5,” says Ricardo Dinis-Oliveira, a toxicologist at the Cooperativa de Ensino Superior Politécnico e Universitário in Portugal. “Whenever food enters it, however, its pH goes higher [becoming less acidic]. In the cases of people suffering from conditions which lead to food stagnation this means that the stomach’s pH will stay at those higher values for longer, which could favour the pH for microorganisms responsible for producing ethanol.”In a recent paper, Dinis-Oliveira outlined his own theory for what creates the optimal conditions for ABS to develop. He describes it as a “perfect metabolic storm” where the pH of the stomach increases and combines with food stagnation and the backflow of food into the stomach from the intestines, as seen in certain medical conditions. Carson, the 64-year-old ABS patient from the UK, recently discovered he suffers from a genetically inherited disorder that affects the connective tissues in his body, known as hypermobile Ehlers Danlos Syndrome (hEDS). These connective tissues are primarily composed of the protein collagen and tend to provide support to other tissues in the skin, tendons, ligaments and blood vessels, as well as in some internal organs. Patients with hEDS can have hyper-flexible joints, but it also affects the digestive tract, where it can cause abnormal movements of the involuntary muscles that control digestion. This can make a patient’s gut more sluggish, leading to a delayed emptying of the stomach contents into the small intestine. (Read more about the effects of Ehlers Danlos Syndrome.) No link has been studied yet between hEDS and ABS, but Carson believes this delayed emptying of his stomach could have contributed to his own ABS. Around one in 5,000-20,000 people suffer from hEDS, so more research is needed to determine if there is a link. Cordell believes there could be other causes too. “We’ve also learned much more about dietary triggers and external triggers such as solvents/chemicals, pollution, stress, and trauma in causing ‘flares’ of endogenous alcohol production,” she says.  Solvents are something Carson has associated with his own ABS – one of his early experiences with ABS occurred shortly after he had re-sealed a wooden floor using products containing volatile organic compounds. However, as solvents themselves can cause intoxication if inhaled, this relationship requires more research. Following a strict diet guided by nutritionists, combined with antifungal treatments and multivitamins has allowed Carson to get his own ABS under control. “It is like a tightrope walk still,” he adds. “I am constantly saying: ‘Am I ok, am I alright?’ When I am feeling a bit tired, we do a breath-analyser.” For Carson the most upsetting part of his experience with ABS has been the effect it has had on his mental health. He uses the “mind palace” memory technique made famous by the TV series Sherlock as an analogy. In the TV show, the Sherlock Holmes describes how he recalls information by keeping it stored in imagined rooms inside a large building – as an analogy. “When I am in that blackout state, I no longer have access to the mental rooms of these events,” says Carson. “This is extremely unsettling and you end up doubting yourself.” Carson says while he knows these episodes have taken place from his family, his own memories of them frustratingly out of reach. “There are several rooms where I cannot get into, as those rooms are locked and I have to accept that I will never get to them,” he says. “It is not that the memories are not there, it is just that in your conscious state you cannot access them.” But as Carson has learned more about his condition, and what might be causing it, he and his wife hope fewer of those rooms will be locked in the future.  — Join one million Future fans by liking us on Facebook, or follow us on Twitter or Instagram. 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