Why are some people affected so differently by auto-brewery syndrome differently if the syndrome seems to be caused by the single organism saccharomyces cerevisiae? It is known that the syndrome has been used to waive DUI charges — like most recently for this New Yorker whose blood alcohol level was 0.4 but she had none of the usual symptoms of intoxication, even though she had ingested alcohol earlier that day. She also carried out most of her daily activities normally, even with high levels of alcohol in her system.

On the other hand, there was another case where the carrier experience the effects of auto-brewery syndrome differently:

Cases involving the yeast Candida albicans and Candida krusei have popped up in Japan, and in 2013 Panola College Dean of Nursing Barbara Cordell documented the case of a 61-year-old man who had frequent bouts of unexplained drunkenness for years before being diagnosed with an overabundance of Saccharomyces cerevisiae, or brewer's yeast, the same yeast used to make beer.

The quote can also be found at the link of the CNN article.

Could the difference in symptoms and effects due to variations in how the carrier bodies could deal with the overabundance (maybe depending on age, gender, or ethnicity) or are they attributed to variations in the nature of the yeast?

  • $\begingroup$ Did any of the people in those cases have diabetes? They likely have high levels of blood glucose. Women with diabetes are prone to recurrent complicated fungal vaginosis as they have higher than average amounts of blood glucose creating an environment where yeasts have abundant nutrients. The metabolic byproduct of yeast is ethanol. $\endgroup$ – AMR Jan 1 '16 at 16:32
  • $\begingroup$ People could also have a disruption in their bacterial microbiome, as is the case when we take antibiotics that allow the fungi more room to grow. The more space they take up, the more access to resources they have, the larger their numbers get and the more metabolic waste they produce. Yeast produce ethanol. So more yeast equals more ethanol. Also if the person has a defective alcohol dehydrogenase gene, then they are not going to be able to process the alcohol that the yeast are excreting. $\endgroup$ – AMR Jan 1 '16 at 16:36

The gut microbiome is extremely complicated, and almost anything related to it is only partially known, therefore prone to oversimplification. Trying to explain the phenomenon of gut fermentation syndrome in such a limited fashion (age, gender, ethnicity, quantity of one particular yeast, etc.) will not help us understand it.

Common yeasts (C. albicans, C. tropicalis and Torulopsis glabrata) and Saccharomyces cerevisiae are able to ferment sugars through the homolactic, heterolactic or mixed acid fermentation pathways, with ethanol as the major end product.

Candida is a very common yeast found in the environment and in and on our bodies wherever it's warm and moist (therefore the GI tract.) Candida species are the most common cause of invasive fungal infections in humans (followed by Cryptococcus and Aspergillus) and can involve any organ. Yet it's omnipresence does not result in clinically recognized cases of ethanol intoxication in even a minute fraction of people who carry it in their gut.

Case reports started appearing in the literature starting in 1972, yet it is still a rare event to see one. In 2001, the case of a 13 year old girl was published. She had short gut syndrome and became intoxicated after ingesting carbohydrates. She had been placed in a rehabilitation facility with no access to alcohol, but still had positive blood alcohols. Aspirates from her small intestines grew Candida glabrata and Saccharomyces cerevisiae. Short-gut syndrome is complicated.

We have no idea how common fermentation into alcohol is in the gut, or what the results are, but it is probably far more common than recognized, can probably result in effects other than intoxication (for example fatty liver disease in non-drinkers), and probably has a role in other illnesses. It's complicated:

Carbohydrate metabolism by gut microorganisms is a central process allowing supply of nutrients and energy to the host. This fermentative process is complex and involves several functional groups of bacteria with complementary metabolic activities that interact to ensure the biotransformation of polymers (resistant starch, nonstarch polysaccharides, proteins, mucins…) into end-products (mainly short chain fatty acids and gases). Hydrolytic communities transform complex substrates into smaller fragments that can also be used by other bacterial groups unable to hydrolyse polymers. Other microbial cross-feeding interactions are related to the utilisation of fermentative products such as succinate, lactate or hydrogen and involve specific groups of microorganisms.

All we know is that it happens in some people, and that it can respond to antifungal treatment and some probiotic supplementation. "Why" is still a mystery, and speculation only.

Gut fermentation syndrome
Invasive Fungal Pathogens: Current Epidemiological Trends
IwataK., “A Review of the Literature on Drunken Syndromes Due to Yeasts in the Gastrointestinal Tract,” University of Tokyo Press, Tokyo, 1972, 260-268. Not available online
Functional dysbiosis within the gut microbiota of patients with constipated-irritable bowel syndrome
Obesity and female gender increase breath ethanol concentration: potential implications for the pathogenesis of nonalcoholic steatohepatitis

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    $\begingroup$ Interesting. Also how often do we routinely test for blood alcohol levels? Plus as one of the science writers in those articles put it, if we think about alcoholism and how the body grows accustomed to increased blood alcohol levels, then that could mean that it is very prevalent, it is just that we never look and we don't feel the effects because we are acclimated to it. Though I also wonder how much diabetes and elevated blood sugar levels might play in the syndrome. $\endgroup$ – AMR Jan 2 '16 at 2:16
  • $\begingroup$ @AMR - It is. In one study after a 50 g glucose challenge of people suspected of gut fermentation into ethanol, 61% (311/510) had positive blood alcohol levels, whereas "almost none" of the controls did. What a summary! It makes one wonder. $\endgroup$ – anongoodnurse Jan 2 '16 at 2:58

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