Longitudinal Gut Microbiome Changes in Alcohol Use Disorder Are Influenced by Abstinence and Drinking Quantity
Many patients with alcohol use disorder (AUD) consume alcohol chronically and in large amounts that alter intestinal microbiota, damage the gastrointestinal tract, and thereby injure other organs via malabsorption and intestinal inflammation. This study hypothesized that alcohol consumption and subsequent abstinence would change the gut microbiome in adults admitted to a treatment program.
Stool and oral specimens, diet data, gastrointestinal assessment scores, anxiety, depression measures and alcohol use amounts were collected longitudinally for up to 4 weeks in 22 newly abstinent inpatients with AUD who were dichotomized as less heavy drinkers [alcohol users] (LHD, <10 drinks [units]/d) and very heavy drinkers [alcohol users] (VHD, 10 or more drinks [units]/d). Next-generation 16 S rRNA gene sequencing was performed to measure the gut and oral microbiome at up to ten time points/subject and LHD and VHD were compared for change in principal components, Shannon diversity index and specific genera.
The first three principal components explained 46.7% of the variance in gut microbiome diversity across time and all study subjects, indicating the change in gut microbiome following abstinence. The first time point was an outlier in three-dimensional principal component space versus all other time points. The gut microbiota in LHD and VHD were significantly dissimilar in change from day 1 to day 5 (p = .03) and from day 1 to week 3 (p = .02). The VHD alcohol use group displayed greater change from baseline. The Shannon diversity index of the gut microbiome changed significantly during abstinence in five participants. In both groups, the Shannon diversity was lower in the oral microbiome than gut. Ten total genera were shared between oral and stool in the AUD participants. These data were compared with healthy controls from the Human Microbiome Project to investigate the concept of a core microbiome.
Rapid changes in gut microbiome following abstinence from alcohol suggest resilience of the gut microbiome in AUD and reflects the benefits of refraining from the highest levels of alcohol and potential benefits of abstinence.
Research in context
Gut microbiome are types of beneficial bacteria in the gut. Changes in the levels of these gut microbiome are linked with chronic heavy alcohol use which is a symptom of alcohol use disorder (AUD). Changes in the gut microbiome, often termed microbial dysbiosis, can lead to further downstream health problems such as liver disease, inflammation, and malnutrition.
This study analyzed gut microbiome levels of currently alcohol using patients with AUD who stopped alcohol use either before or onset of inpatient treatment. There were 22 adult participants grouped as less heavy and very heavy depending on their alcohol use. The researchers looked at microbial abundance, diversity, and changes in the microbiome over time, and compared differences between the two groups.
The study found that,
- At the start of abstinence the very heavy use group had less diversity of gut microbiome compared to the less heavy use group.
- Gut microbiome of both groups increased following abstinence.
- AUD patients who consumed alcohol very heavily before abstinence had more extensive changes in microbe diversity in their gut microbiome over time.
These findings suggest that the effects of heavy alcohol use on gut microbiome diversity can be reversed by abstinence and a healthy diet.