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Alcohol and the Microbiome: Interesting Interactions

Drinking and it's effect on gut health.

by Malay Nanavaty

How Does the Microbiome React to Alcohol?

We have discussed the effects of diet composition on the microbiome across many posts. It is well established that different types of macronutrients require different types of bacteria for breakdown. This, in turn, alters the composition of one’s microbiome over time. As it would be expected, alcohol has a similar effect on the microbiome. Just as bad eating habits can significantly impair your microbiome, bad drinking habits can do so as well at a much more rapid rate.

Microbiome Populations and Alcohol

There have been a few studies done on different human and animal populations regarding alcohol consumption and microbiome composition. The response of the microbiome to alcohol seems dependent on the type of alcohol, frequency of drinking, and duration of the drinking period. Additionally, there seems to be differences across species with regards to microbiome response. For example, when mice are given alcohol for 3 weeks, their microbiome responds with an increase in Bacteroidetes and a decrease in Firmicutes. This is not the case in an equivalent human study, as we will see.

Human Studies on Alcohol and the Microbiome

Chronic alcohol consumers tend to have elevated levels of Proteobacteria. This increase is generally not a good thing; the Proteobacteria generate toxic waste products which increase the permeability of the intestinal walls to molecules. This allows more bacterial waste products to enter the blood. As a result, the liver will have to work even harder to detoxify any potentially dangerous substances. This is not good because the liver is already stressed out from the metabolism of all the alcohol being consumed.

On the same note, chronic drinkers of hard liquor have a lower diversity of gut microbes. This is because hard alcohol is able to reach the gut at a high concentration. The toxic effects of the alcohol kill off the microbial community faster than they can grow, destabilizing the population.

Moderation and Potential Benefits

While there is a lot of bad news regarding alcohol and the gut, there is evidence that mild consumption of low strength alcohol has some beneficial effects on gut microbiome health. When observing the microbiomes of people who drink one glass of wine a day, an increase in the beneficial bacteria within the phylum Bacteroidetes is observed. At the same time, the wine drinkers observed a decrease in the population of the pathogenic strain Clostridium. This suggests that the polyphenol molecules in wine, paired with the low concentration of ethanol, are beneficial to the gut at the proper dosage.

Potential Prebiotic Treatment

There has also been some research done regarding effective ways to restore the gut microbiome of alcohol users. One of the most effective solutions involved administration of prebiotics every day. While prebiotics may not directly colonize the gut, they are useful in their stimulation of the gut immune system. It is possible that this stimulation enables the body to push back against growth of pathogenic bacterial strains in favor of the growth of more beneficial strains.


The field of alcohol-microbiome interactions is still very new. However, preliminary studies seem to show a tight correlation between drinking and altered microbiome compositions. This is a pretty intuitive conclusion, since all other parts of the diet have an effect on the microbiome. With modern sequencing technology, we are now able to look more deeply into these questions and understand exactly how our choices affect us. Hopefully, this blog post helped you understand what we currently know about this very specific topic.

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