A few weeks ago, Esquire ran a provocative piece claiming that Sam Adams founder Jim Koch uses a clever trick to avoid getting drunk during a long night of imbibing: he swallows active dry yeast to digest the alcohol before it can get into his system.

Today we'll look at the science of alcohol metabolism to find out if this trick could actually work.

How do humans digest alcohol?

When I wrote about alcohol metabolism before, I mentioned that humans metabolize alcohol in the liver. And while that's mostly true, it's more complicated than that.

When you drink alcohol, it travels from the mouth down the esophagus into the stomach. From here, many sources claim that about 20% of the alcohol you drink travels directly between the stomach and your blood vessels.1, 2

When I checked the research, it turns out that you directly absorb as much as 30% of alcohol through the stomach when you're drinking with food and as little as 10% without food.3 Since absorption through the stomach is slower than through the small intestines, this helps explain why we tend to get drunk more slowly when we're having our drinks with a meal.

Either way, though, the majority of alcohol eventually travels out the stomach into the small intestines, where the alcohol gets absorbed through the intestinal walls into the surrounding blood vessels.

The blood from the small intestines then goes through the liver, where the alcohol begins to be digested, but since the liver can't handle a whole lot of alcohol at a time, much of the alcohol passes through the liver without being digested. That alcohol circulates in the blood stream to the rest of your body and, well, gets you drunk.

Over time, the blood in your body continues to pass through the liver and your liver continues to process it, until you eventually convert all the alcohol in your blood into simple sugars or excrete it as acetic acid.

How does active dry yeast help metabolize alcohol?

Most yeast has an enzyme called Alcohol Dehydrogenase (ADH). There are several different types of ADH and other types of ADH can be found in plants and animals as well.

Humans possess ADH in both our stomachs and in our livers. The version we harbor can process not just alcohol from spirits, but also other alcohols that would be harmful to our bodies. In that way, our ADH protects us from small amounts of toxins that might occur in fermented foods and as a result of the fermentation that occurs during our own digestive processes.

The version of ADH found in yeast, specifically baker's yeast, is different than the ADH found naturally in the human body.4 It isn't as robust as the ADH in a human, but it can digest alcohol. How? Read on...

If you're a homebrewer or spirits enthusiast, you may know that yeast are responsible for converting simple sugars into, among other things, carbon dioxide and alcohol. So if you know them best for turning stuff into alcohol, why would they be used to transform alcohol back into non-hangover-inducing matter?

The short answer is that the ADH in yeast are part of a complex regulatory system. The yeast themselves digest sugars into ethanol, but yeast die when too much ethanol is present, so they had to evolve a system that would allow them to keep digesting optimally without committing suicide-by-alcohol.

How does all of this relate to Koch's trick? Follow my logic here:

Jim Koch referred specifically to active dry yeast

Fleischmann's brand active dry yeast contains only the yeast strain Saccharomyces cerevisiae 5

Saccharomyces cerevisiae yeast contains the ADH enzyme that digests ethanol.4

Big important takeaway: don't go swallowing random yeast strains. I'm looking at you homebrewers out there. As you well know, yeast can vary drastically depending on strain and geography. Much of the yeast used for brewing is Saccharomyces cerevisiae, but not all of it. I don't think you could get hurt eating other yeast used for brewing, but I haven't researched it in depth, so I can't recommend it.

So... does it work?

Believe it or not, I think so.

Almost as soon as the Esquire article was posted, clever citizens took to the internet and "debunked" the "myth", saying it couldn't possibly work.

The basic argument goes like this: ADH is most effective at a slightly basic pH.6 But the human stomach, where supposed yeast ADH metabolism of ethanol would occur, has a pH around 1.5 to 3.5 (and that's really acidic).

While I get the argument that's being made, science has already shown in multiple instances that ADH not only already exists in the stomach lining, but that it acts to breakdown ethanol in the stomach.3, 7, 8

Those who argue that ADH won't work in the stomach's acidic environment reference one paper on liver ADH and another paper that looked at yeast ADH in an acidic environment, but only after 24 hours.

Here's where understanding alcohol metabolism comes back into play. It doesn't really matter what happens to ADH after a day or even an hour in the stomach. Alcohol absorbs very quickly, so any effect from yeast ADH would have to happen in a matter of minutes to be effective.

Can yeast make a difference in that amount of time? I did a quick experiment to find out.

An experiment with yeast and liquor

I asked a simple question: what happens if I combine active dry yeast and alcohol in a bowl?

If it didn't do anything outside the stomach, I could be pretty sure nothing would happen inside.

I combined 2 ounces of unaged rum (I was out of vodka as a result of my glass-chilling experiments from a few weeks ago) and one packet of active dry yeast. Then I stood around and took pictures, looking for bubbles.

After about 5 minutes, and seeing only minimal bubbling activity, I carefully took a sip from the now fully-dissolved mixture. Result? It didn't taste as strong as full-proof alcohol, but it definitely still tasted like alcohol.

Even after I had let the mixture sit for over an hour, I went back and it still tasted distinctly like alcohol.

What did I learn?

While it seems that yeast ADH does help to decrease alcohol levels it's probably not that much. and it takes a few minutes, during which time some alcohol will inevitably make it into the blood.

My conclusions seem to match up with what has been observed in actual human studies. Dr. Joseph Owades, the biochemist and brewing expert Jim Koch credited with the yeast trick in the first place, actually patented the technique and includes in his patent application graphs that show the effect of yeast on blood alcohol levels.

As you can see from the graph, swallowing yeast does help to decrease the impact of drinking a beer on blood alcohol levels, but blood alcohol does definitely still rise. Keep in mind, also, that the graphs shown in the patent are the result of testing just one female and one male subject.

OK, so should I actually do this?

Let's first talk about who shouldn't use the yeast trick.

If you're allergic to alcohol , know that the ADH in yeast will not fully metabolize alcohol before it makes it into your bloodstream, so don't do this, because you will inevitably react to the alcohol that's present.

, know that the ADH in yeast will not fully metabolize alcohol before it makes it into your bloodstream, so don't do this, because you will inevitably react to the alcohol that's present. If you think you might be allergic to alcohol you may actually be sensitive to other compounds found in alcoholic beverages, not ethanol itself, so the yeast trick will do nothing for you. 9

you may actually be sensitive to other compounds found in alcoholic beverages, not ethanol itself, so the yeast trick will do nothing for you. If you're trying to avoid a hangover this trick may not be for you. Many researchers blame the byproducts of ethanol metabolism, acetaldehyde and acetate, and not just ethanol itself, for hangovers. The ADH in yeast only helps you digest ethanol into acetaldehyde and acetate and doesn't provide for further digestion of those two toxins. 10

this trick may not be for you. Many researchers blame the byproducts of ethanol metabolism, acetaldehyde and acetate, and not just ethanol itself, for hangovers. The ADH in yeast only helps you digest ethanol into acetaldehyde and acetate and doesn't provide for further digestion of those two toxins. Same goes for the Asian "glow." Researchers believe that the cause behind the Asian glow also has to do with acetaldehyde in the blood stream, not ethanol, so once again, the yeast trick might keep you from getting drunk, but probably won't do anything to help with flushing.

The only real situations I can see where this trick might be useful is if you were:

A super-lightweight. A person who likes the taste of alcohol, but doesn't like getting sloppy drunk after a two sips of wine. If you're going to keep your consumption moderate anyway, this might help you stay just a little more sober too.

A person who likes the taste of alcohol, but doesn't like getting sloppy drunk after a two sips of wine. If you're going to keep your consumption moderate anyway, this might help you stay just a little more sober too. A secret agent. You know, like if you had to get the Prime Minister really drunk and steal his briefcase of secrets when he thought you were passed out too? That sort of thing.

Notes:

1. Brown University, Alcohol and Your Body 2. George Washington University, Alcohol Absorption 3. Use of measurements of ethanol absorption from stomach and intestine to assess human ethanol metabolism 4. The three zinc-containing alcohol dehydrogenases from baker's yeast, Saccharomyces cerevisiae 5. Breadworld.com, The Science of Yeast 6. pH is a measure of acidity. 7 is neutral and 6 is 10 times more acidic than 7. For reference, limes have a pH around 2 or 3. 7. First pass metabolism of ethanol is strikingly influenced by the speed of gastric emptying 8. Human gastric alcohol dehydrogenase activity: effect of age, sex, and alcoholism. 9. About.com, Types of Alcohol Allergies and Intolerances 10. Yeast does also contain the enzyme aldehyde dehydrogenase (ALDH), but I suspect that this second step in metabolism wouldn't be activated in the stomach before the acetaldehyde was already absorbed into the bloodstream, where the ALDH would not follow.

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