It almost sounds like a Sherlock Holmes case: A 61 year old man staggers into a Texas emergency room feeling light-headed, nauseous, and dizzy. The nurses think he looks kinda hammered, they give him a breathalyzer test, and sure enough, his blood alcohol concentration clack in at a very drunk .37 percent. But the thing is, the guy claims he hasn't had a single drink today. In fact, he's been experiencing sudden and unexplained bouts of drunkenness for years. So what's up? Is this guy a closet drinker? Is he suffering some kind of amnesia, or sleep-boozing, or what?

The doctors decide to check the man's pockets for hidden booze, then monitoring him in an isolated hospital room for 24 hours. They have him eat a lot of carb-heavy foods while staff take various readings and watch what happens to his blood alcohol content. What they eventually find, is that the guy has an over-abundance of brewer's yeast in his digestive system, and it's basically turning his guts into a fermentation vat, converting carbohydrate sugars into ethanol, and getting him sloshed. 

As you've probably guessed by now, this story actually happened, back in 2010. And in the end, the man's doctors diagnosed hum with auto-brewery, or gut fermentation syndrome. Basically, his digestive system was turning carbohydrates into alcohol. Cue the beer belly jokes. Here's what the doctors figured was happening: When most people eat yeasty foods, the yeast passes right on through their body. But sometimes it's possible for that yeast to stick around on larger numbers.

The Texan man's troubles seem to have started he completed a hardcore round of antibiotics that wiped out his good gut bacteria, eliminating the competition and allowing yeasts and other fungi to take over. So whenever he'd eaten carbohydrates, the extra yeast in his digestive system would start fermenting those carbs into alcohol, which would end up in his bloodstream. 

He was literally getting drunk on bread!

The doctors treated the man by having him take anti fungal drugs and probiotics to restore his good bacteria. They also had him eat a low-carb diet to keep the yeast in check. Now, this wasn't the first-ever case of auto-brewery syndrome. Some children with short bowel syndrome, an intestinal condition that makes proper nutrient absorption difficult, have also signs of extra yeast causing intoxication. And researchers in Japan have documented similar reports of serious digestive yeast infections and spontaneous tipsiness dating back to the 1970s.

Even so, this syndrome is both rare and controversial, because all we have is this handful of mysterious case studies. It's just hard to figure out what's actually causing the problem without more research, like a controlled clinical trial. Plus, when it comes to getting drunk without drinking, an over-abundance of yeast may not be the only factor involved. There's also a problem with certain enzymes. 

Normally, alcohol gets broken down by particular liver enzyme. But in some people, genetic mutations mean they don't produce those enzymes properly so they can end up feeling drunk after drinking a relatively small amount of alcohol. This mutation affects a disproportionate number of Asian people, about one in three, which could help explain why Japan has the highest number of reported gut fermentation syndrome cases. Combine extra yeast with rice-heavy diet and abnormal enzymes and you might find yourself getting accidentally sauced as those carbohydrates turn to ethanol that doesn't get processed quickly enough. 

It's pretty easy to test for these enzyme deficiencies, but so far there's no definitive test for auto-brewery syndrome in people with the usual enzymes. Since it's so difficult to clearly diagnose, it would be hard for researchers to set up studies and trials. So, until there's a better way to diagnose it, auto-brewery syndrome is a condition that will probably continue to be rare and mysterious. 

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