How alcohol alters the gut microbiota -

Drinking alcohol promotes the growth of certain gut bacteria

Alcohol is absorbed through the mouth and stomach and usually does not enter the intestines. Nevertheless, the regular consumption of alcohol modifies the composition of the intestinal flora. The reasons for this association are so far unclear. A research team has just discovered the underlying mechanism.

Researchers from the University of California, San Diego (USA) have discovered why alcohol consumption affects the gut microbiota, even though alcohol itself does not enter the gut. The causes were recently described in the famous journal "Nature Communications" and explain why heavy alcohol consumption has a negative effect on the intestinal flora.

Alcohol consumption alters the intestinal flora

Alcohol damages the liver and is responsible for many deaths from liver disease worldwide each year. What is less known, however, is that alcohol can also have a negative effect on the intestinal flora. This connection has been observed for a long time, but the reasons for it were a mystery.

Acetate responsible for changes

The University of California working group has just discovered that the changes in the intestinal microbiome are due to acetates. In the liver, alcohol is first transformed into acetaldehyde. In a next step, the intermediate product is transformed into acetates.

The acetates then diffuse into the intestine. There, they serve as a food source for certain types of bacteria, which triggers a growth spurt in certain gut microbes.

Fertilizer for certain intestinal bacteria

"You can imagine it a bit like fertilizing a garden," compares Professor Karsten Zengler of the research team. However, not all species benefit from fertilization, only some, causing an unbalanced growth spurt.

"Chronic alcohol consumption is associated with lower expression of antimicrobial molecules in the gut," says Zengler. According to him, people who suffer from alcohol-related liver disease often also have bacterial overgrowth in their intestines.

How do acetates affect the body?

Acetates are a carbon source used in cellular metabolism and play a role in the regulation of appetite, energy expenditure and immune response.

In moderate amounts, acetates may provide general health benefits, such as improving heart function, stimulating red blood cell production, and aiding memory.

However, high levels of acetate in the body have been linked to metabolic changes that can promote diseases such as cancer.

Acetates modify the intestinal flora

Experiments on mice, which were carried out as part of the study, also suggest that acetates are responsible for changes in the intestinal flora. Animals given a molecule that can be broken down into three acetates developed the same changes in the gut microbiome as mice given regular alcohol, but without liver damage.

“Our results show that ethanol is not directly metabolized by the gut microbiota and that ethanol-associated gut microbiota changes are a side effect of high acetate levels, conclude the scientists involved.

Microbial ethanol metabolism does not contribute significantly to gut microbiome imbalance. Acetates, on the other hand, are not directly responsible for alcohol-related liver damage, but only for changes in the intestinal flora.

Two different mechanisms

"The situation is more complicated than previously thought," said Zengler. Previously, it was assumed that the same mechanism that damages the liver is also responsible for affecting the intestinal flora. Now it turns out that two completely different mechanisms are at work.

Further studies should show whether and how this knowledge can be used medically. Now that the cause of the change is known, it is possible to study more precisely which bacteria benefit from acetates and what effects these changes have on the intestinal flora and therefore on health. (vb)

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This text corresponds to the specifications of the specialized medical literature, medical guidelines and current studies and has been verified by health professionals.


Graduate editor (FH) Volker Blasek


Martino C, Zaramela LS, Gao B et al. Acetate reprograms the gut microbiota during alcohol consumption; in: Nature Communications (2022). nature.comUniversity of California San Diego: Alcohol Use Can Alter Gut Microbes, but Not in the Way You Might Think (Published: 11/08/2022),

Important note:
This article contains general advice only and should not be used for self-diagnosis or treatment. It cannot substitute a visit to the doctor.