Alcohol - How it Affects The Gut Microbiome

We know that our diet is one of the strongest modulators of the composition and function of the gut microbiome. This influence is so powerful that changes in what we eat can shape how our microbes grow and adapt. So what is the connection between alcohol consumption and gut health?

The Link Between the Gut and the Immune System

Our gut and immune system are in constant communication: which microbes are harmful and which should be tolerated?

A strong core of beneficial microbes maintains gut balance and regulates how our body responds to potential threats. When beneficial bacteria ferment complex carbohydrates, they primarily produce short-chain fatty acids (SCFAs), which are essential for regulating and mediating immune responses

SCFAs also support the intestinal cells that make up the gut lining. These cells and the mucus they produce form the gut barrier - the first line of defense against invaders. SCFAs strengthen this barrier and prevent unwanted “leaks.” This is crucial for stopping bacteria and toxins from passing through the gut wall into the bloodstream. If this happens, the consequences can be severe, including endotoxemia (bacterial toxins in the blood), autoimmune disease, mental health disorders (such as depression), diabetes, inflammatory bowel disease, and multiple sclerosis.

In addition, SCFAs have important anti-inflammatory effects on immune cells in the gut.

They also influence organs far beyond the intestine, including the brain, liver, pancreas, and skin.

Alcohol and Gut Health

We know that excessive alcohol consumption is harmful to human health. It costs European healthcare systems more than €22 billion each year. About 25% of heavy drinkers develop liver disease, such as alcoholic steatohepatitis or cirrhosis. These harmful effects also impact the gut microbiome and immune system.

How Does Alcohol Affect the Gut?

Heavy alcohol consumption changes the relative abundance of gut microbes, leading to major shifts in microbial diversity. In particular, it reduces anti-inflammatory bacteria such as those in the Bacteroidetes and Firmicutes phyla, while increasing microbes that thrive in inflammatory environments.

Alcohol abuse also disrupts the gut barrier and damages the intestinal lining. This allows bacteria and harmful components of their cell walls to leak into the bloodstream and reach other organs, where they can cause damage.

Together, these effects can lead to dysbiosis and intestinal inflammation.

The Gut–Liver Axis

The so-called “gut–liver axis” is a two-way interaction between the gut and the liver that also involves the immune system.

The portal vein provides a direct biological connection, carrying nutrients and gut-derived products to the liver, which produces bile acids, proteins, lipids, and immune components.

Excessive alcohol intake disrupts this gut–liver communication and triggers a cascade of inflammatory processes that damage the liver.

Practical Tips

When it comes to alcohol and gut health:

• Limit your intake: Aim for no more than 4 units per day or 10 units per week.

• Choose red wine: Red wine contains polyphenols that may benefit the microbiome.

• Avoid sugary drinks: Many cocktails, mixers, and sodas are high in sugar or artificial sweeteners. Some tonics contain more sugar than cola—always check labels.

• Drink the traditional way: In some cultures, wine is consumed only with meals. Treat alcohol as an occasional indulgence to be enjoyed responsibly and in moderation.

Do you want a look into your personal gut microbiome and what bacteria you have, then you can get insight with a gut microbiome test from Unseen Bio. 

If you want to dive deeper into the gut microbiome, then listen to our podcast "Mikrobiomet" (The Microbiome), where we explore everything science knows about gut health and the microbiome together with a broad range of microbiome experts. 

You can also read more about different food’s impact on the gut microbiome in our other articles. 

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By Cecilia Clausen (Clinical Dietitian)