Take a shot of bourbon.
Likely, you’ll feel an immediate burn in your mouth and throat. Give it a few seconds. Your body temperature starts to rise. Your cheeks flush.
If you take another drink, there might be some dizziness, too.
There are effects of drinking alcohol that you can feel pretty much immediately. But there’s an entire field of study that takes a harder look at the effects of alcohol under the surface — specifically when it comes to the bacteria in our guts.
And you should care what happens to your gut bacteria because disturbing it could lead to short- and long-term health problems, from digestive issues to tissue damage.
That’s where Louisville doctor Craig McClain comes in. His NIH-designated Alcohol Research Center at the University of Louisville is one of only 20 in the country. There, he conducts research assessing how food and drink can impact our intestinal microbiome, or gut bacteria.
And his work, he and others hope, could lead to new treatments for liver disease associated with alcohol consumption.
First, What is the Gut?
“So, I am a gastroenterologist, and normally we think of the gut as having a bunch of different functions,” McClain says. “The stomach starts to break down food, has a lot of acid in it and the small intestine does mainly absorptive functions, so that’s where most of your nutrients are absorbed. And then the colon kind of regulates water absorption.”
But something McClain says many people don’t realize is that this entire tract is lined with bacteria. Lots and lots of bacteria.
“There are more bacteria in our GI tract than we have cells in our body,” he says. “There are more genes in the bacteria — a hundred times more — than we have genes in our body. So in a way, we are just kind of a receptacle for our gut bacteria.”
You might hear the term bacteria and think of something dirty or sickness — but McClain says our gut bacteria are totally natural, and they’re even helpful. They play an important role in the immune system, make critical nutrients like vitamin K, maintain gut barrier functions.
“Now, when the bacteria gets altered inappropriately, called dysbiosis, then you can have big problems,” he says. “Nutrients play a critical role in happy bacteria, and our whole focus is looking at kind of alcohol-nutrition interactions with a focus on the GI tract.”
While alcohol has calories — bourbon has about 145 per serving — McClain says alcohol has “no critical nutrients in it,” but that doesn’t mean it can’t affect our gut bacteria.
“Too much alcohol can disrupt your normal bacterial homeostasis, so you get overgrowth of bacteria and not enough good bacteria,” he says. “And the tight junctions in the GI tract that keep bad stuff out get leaky, and junk goes across.”
According to McClain, this “leaking” might explain some basic things like some hangover symptoms. But learning more about how the bacteria respond to alcohol can have bigger health effects as well.
In a paper he co-wrote in 2015, McClain found that liver diseases resulting from chronic alcohol consumption and excess fat in the diet are also associated with changes in the intestinal microbiome.
For example, alcoholism seems to change the composition of the intestinal microbiome to include bacterial species that produce more alcohol, plus other toxic compounds, that can cause inflammation and tissue damage.
This is a new area of study that may lead to new treatments for liver damage that results from alcoholism and excessive dietary fat.
“We actually have a study looking at people with alcoholic liver disease — where they’re randomized to either get a placebo or probiotic, good bacteria for the GI tract,” McClain says. “And so we’re part of an NIH trial looking at that right now.”
For now, the study is still underway. In the meantime, McClain says according to current research, moderate drinking has no real effect on the microbiome, so you can safely raise an occasional glass to gut health.