by A frothy beer or glass of wine can enhance a meal and calm the mind. But what effect does alcohol have on the trillions of microbes that live in the gut?
As with much of microbiome science, “there’s a lot we don’t know,” said Dr. Lorenzo Leggio, a physician-scientist who studies alcohol use and addiction at the National Institutes of Health.
That said, it’s clear that happy microbes are essential for proper digestion, immune function, and gut health. And as scientists begin to explore how drinking can influence the gut, they’re learning that overdoing it could have some unpleasant consequences.
How does excessive alcohol consumption affect your microbiome?
Most of the available research on alcohol and the microbiome has focused on people who drink regularly and excessively, said Dr. Cynthia Hsu, a gastroenterologist at the University of California, San Diego.
TO a bunch of studiesFor example, they have found that people with alcohol use disorder (the inability to control or stop problematic alcohol use) often have an imbalance between “good” and “bad” bacteria in their intestines. This is called dysbiosis and is generally associated with increased inflammation and disease compared to having a healthier microbiome, Dr. Hsu said.
Heavy drinkers with dysbiosis may also have more leaky or permeable intestinal linings, Dr. Leggio said. A healthy intestinal lining acts as a barrier between the inside of the intestine (full of potentially harmful microbes, foods and toxins) and the rest of the body, he said.
When the intestinal lining breaks down, bacteria and toxins can escape into the bloodstream and flow to the liver, Dr. Hsu added, where they can cause inflammation and damage to the liver.
Preliminary investigation suggests that a diseased gut could even contribute to alcohol cravings, said Dr. Jasmohan Bajaj, a hepatologist at Virginia Commonwealth University and the Richmond VA Medical Center.
in a study 2023For example, researchers looked at the microbiomes of 71 people ages 18 to 25 who did not have an alcohol use disorder. Those who reported excessive alcohol consumption more frequently (defined as four or more drinks in about two hours for women, or five or more drinks for men) had changes in the microbiome that correlated with increased alcohol cravings. This study also contributed to previous research which found that heavy alcohol consumption was associated with higher blood markers of inflammation.
However, none of these studies have shown that alcohol causes dysbiosis in humans. The link is clearer in animal studies, but in human studies, researchers find it more difficult to control for factors such as diet and other health conditions.
What happens to those who drink less?
federal guidelines define moderate alcohol consumption such as no more than two drinks per day for men or one drink per day for women. There is very little research on how this amount of alcohol consumption affects the gut microbiome, said Jennifer Barb, a clinical bioinformatics scientist at the National Institutes of Health.
Scientists have found that, compared to those who don’t drink at all, people who drink at low to moderate levels have more diverse gut microbiomes, a characteristic generally associated with a healthy gut. This could be attributed to other diet or lifestyle factors, or it could be that something in alcoholic beverages could benefit the microbiome, although it’s probably not ethanol, Dr. Barb said.
in a study 2020 For example, of 916 women in Britain who consumed two or fewer drinks per day, researchers found that those who drank red wine (or, to a lesser extent, white wine) had greater gut microbial diversity than those who did not. No such link was found with beer or liquor. The researchers hypothesized that polyphenols, compounds found in the skin of grapes and found in high concentrations in red wines, could explain their results.
But you don’t need alcohol to find polyphenolssaid John Cryan, a neuroscientist who studies the microbiome at University College Cork in Ireland; They are also found in grapes and most other fruits and vegetables, as well as many herbs, coffee, and tea.
In general, eating a variety of plant-based foods and fermented foods like yogurt, kombucha, and kimchi can also improve microbiome diversity.
Can reducing alcohol consumption improve intestinal health?
Researchers have I look looked at the microbiomes of people who have been treated for alcohol use disorder and found that within two to three weeks after people stopped drinking, their gut microbes began to show signs of recovery, Dr. Barb said, and their intestinal linings became less “leaky”.” But, he added, people who receive treatment for alcohol use disorder also tend to start eating healthier and sleeping better, which can also improve gut health.
It’s unclear how (or even whether) stopping or reducing alcohol consumption might influence the microbiomes of moderate drinkers, Dr. Leggio said. But we do know that alcohol can cause acid reflux, inflammation of the stomach lining and gastrointestinal bleeding, he added, and can increase the risk of several types of cancer, including those of the esophagus, colon and rectum.
So “there is no doubt,” Dr. Leggio said, that drinking less is a worthwhile endeavor for your health.
