Study: Excessive Alcohol Consumption Causes Gut Microbiome Imbalance


Although alcohol is not absorbed by the intestines, research has demonstrated that excessive drinking causes the liver to produce too much acetate which may lead to intestinal bacterial overgrowth.

Almost 30,000 people in the United States die from alcoholic liver diseases every year. Alcohol, especially in excess amounts, has a slew of negative adverse effects (AEs) on the liver, stomach, and the intestinal gut microbiome. The cause for the latter condition has not yet been identified, but new data suggest the liver may be the cause of the gut microbiome imbalance.

Investigators at the University of California San Diego (UCSD) recently proposed that alcohol negatively affects the gut microbiome because of acetate in particular. When drinking, acetate is produced by the liver then diffused into the intestines where it becomes a carbon source that supports growth of bacteria. However, not all of the resulting bacteria growth is beneficial.

"You can think of this a bit like dumping fertilizer on a garden," said co-corresponding author Karsten Zengler, PhD, professor in the departments of Pediatrics and Bioengineering at UCSD School of Medicine and Jacobs School of Engineering, in a press release. "The result is an explosion of imbalanced biological growth, benefitting some species but not others."

Known to regulate appetite, energy, and immune response, acetate can be health promoting by improving cardiac function, enhancing red blood cell production, and improving memory function. However, like many nutrients, an excess amount of acetate can create dysbiosis, which is associated with metabolic changes that can cause cancer.

To understand the issue further, Zengler and his colleagues conducted a study in mice. They fed the mice a molecule that the gut broke into 3 acetates, the third of which altered the rodents’ intestinal microbiome similarly to that of the effects of alcohol. However, it did not damage the rodents’ livers.

Following the experiment, Zengler explained that the intestines express fewer antimicrobial molecules by consuming alcohol frequently.

“Persons with alcohol-related liver disease commonly have bacterial overgrowth in their guts. These findings suggest that microbial ethanol metabolism does not contribute significantly to gut microbiome dysbiosis (imbalance) and that the microbiome altered by acetate does not play a major role in liver damage," Zengler said in the press release. "The situation is more complicated than previously assumed. It's not as simple as more ethanol equals microbiome changes and thus, microbiome dysbiosis equals more liver disease.”

The study authors noted that the findings do not provide a direction for new treatments for alcoholic liver disease. However, the authors explained that the results can guide future research toward the investigation of the effects of acetate on gut microbiota.

Zengler also noted that in future research that will be conducted among his colleagues at UCSD, the investigation of how ethanal consumption changes the gut microbiome is no longer necessary. Instead, Zengler and colleagues will begin to look to identify the bacteria that are causal for deleterious effects of alcohol consumption, rather than the AEs of consumption or disease.


University of California – San Diego. Alcohol use can alter gut microbes, but not in the way you might think. Science Daily. Aug 11, 2022. Accessed on Aug 15, 2022.

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