How does alcohol affect the gut microbiome?
A frothy beer or glass of wine can enrich a meal and calm the mind. But what does alcohol do to the trillions of microbes that live in your intestines?
As with much microbiome science, there's a lot we don't know, says Dr. Lorenzo Leggio, a physician-scientist who researches 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 investigate how drinking can affect your gut, they're learning that overdoing it can have unfortunate consequences.
How Does Heavy Drinking Affect Your Microbiome?
Most available research on alcohol and the microbiome has focused on people who drink regularly and heavily, said Dr. Cynthia Hsu, a gastroenterologist at the University of California, San Diego.
a handful of studiesfor example, have discovered that people with alcohol use disorder (the inability to control or stop problematic drinking) often have an imbalance of 'good' and 'bad' bacteria in their gut. This is called dysbiosis and is generally associated with greater inflammation and disease compared to having a healthier microbiome, said Dr. Hsu.
Heavy drinkers with dysbiosis may also have “leaky” or more permeable intestinal walls, said Dr. Leggio. A healthy intestinal wall acts as a barrier between the interior of the intestine — full of microbes, food and potentially harmful toxins — and the rest of the body, he said.
When the intestinal wall breaks down, bacteria and toxins can escape into the bloodstream and flow to the liver, added Dr. Hsu to it, where they can cause liver inflammation and damage.
Preliminary investigation suggests that an unhealthy 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 2023 studyFor example, researchers looked at the microbiomes of 71 people aged 18 to 25 who did not have an alcohol use disorder. Those who reported binge drinking more often (defined as four or more drinks within about two hours for women, or five or more drinks for men) had changes in the microbiome that correlated with greater alcohol cravings. That study also added to that previous research which showed that binge drinking was associated with greater blood markers of inflammation.
However, none of these studies have proven that alcohol causes dysbiosis in humans. The connection is clearer in animal studies, but in human studies it is more difficult for researchers to control for factors such as diet and other health problems.
What about those who drink less?
Federal guidelines define moderate drinking as no more than two drinks per day for men and one drink per day for women. Very little research has been done on how this amount of alcohol consumption affects your gut microbiome, says Jennifer Barb, a clinical bioinformatics scientist at the National Institutes of Health.
Scientists to have found it that compared to those who don't drink at all, people who drink at low to moderate levels have a more diverse gut microbiome – a characteristic generally associated with a healthy gut. This could be attributed to other dietary or lifestyle factors, or it could be that something in alcoholic drinks benefits the microbiome – although it's probably not the ethanol, said Dr. Barb.
In a 2020 study For example, among 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 association was found with beer or spirits. The researchers hypothesized that polyphenols, compounds found in grape skins and found in high concentrations in red wines, could explain their results.
But you don't need alcohol to find it polyphenolssays 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 spices, coffee and tea.
In general, consuming a variety of plant-based foods and fermented foods such as yogurt, kombucha and kimchi can also improve microbiome diversity.
Can cutting back on alcohol improve your gut health?
Researchers to have watched He examined the microbiomes of people treated for alcohol addiction and found that within two to three weeks after the people stopped drinking, their gut microbes began to show signs of recovery, said Dr. Barb, and that their intestinal wall became less “leaky”. .” But, she added, people treated for alcohol addiction also tend to eat healthier and sleep better, which can also improve gut health.
It's not clear how — or even if — quitting or cutting back on alcohol might affect the microbiomes of moderate drinkers, said Dr. Leggio. But we do know that alcohol can cause acid reflux, gastric 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's no doubt about it,” said Dr. Leggio, that drinking less is a valuable undertaking for your health.