A new study led by scientists from the Complutense University of Madrid has found some compelling associations between gut bacteria composition and alcohol consumption. Not only is heavy drinking linked to a distinct microbiome profile but the research suggests certain bacteria may be responsible for increased alcohol consumption.
"The study represents a significant advance in our understanding of the role of gut microbiota in motivated behavior, specifically the behavior of voluntary alcohol consumption," said Elena Giné, an author on the new study.
The new research first looked at 507 young volunteers, each completing a drinking behavior questionnaire and offering fecal samples for analysis. Using a measure known as the Bristol Stool Scale, the study found a linear relationship between alcohol consumption and a subject’s stool type.
A small number of samples were then bacterially analyzed, comparing a group of non-drinkers to a group of heavy drinkers. In the heavy drinkers the researchers noted an increased abundance of Actinobacteria, compared to the non-drinkers.
The next step in the research was to study the relationship between alcohol consumption and the microbiome in a sample of animals. It became quickly clear that increased volumes of alcohol consumption in a rat did alter the composition of its microbiome, but was the relationship bi-directional? Could gut bacteria be making the animals drink more?
To test this the researchers performed a fecal transplant from alcohol-dependent animals to a healthy control group. And incredibly, those animals that received the alcohol-dependent fecal transplant did significantly increase their voluntary intake of alcohol compared to a control group.
Further affirming the possible casual association, the researchers then administered antibiotics to the alcohol-dependent animals which subsequently led to a decrease in their alcohol consumption.
One big question this study was unable to resolve is exactly which bacteria may be associated with these changes in alcohol consumption. The animal investigations did verify the human findings, associating Actinobacteria with higher levels of alcohol consumption. However, it became relatively clear increased abundance of Actinobacteria is a consequence of drinking more alcohol and not a causal factor in raising consumption levels.
The most significant bacterial change detected in the animal study was a decrease in the genus Porphyromonas. The researchers hypothesize a kind of feed-back loop where alcohol consumption causes a decrease in levels of Porphyromonas, which favors the growth of other bacteria subsequently changing the overall composition of the microbiome in a way that may, “modulate the host’s behavior to look for alcohol.”
All of these findings are still incredibly speculative. José Antonio López, lead author on the new study, says it is possible the microbiome plays a role in alcohol consumption behaviors. And if this association can be better understood then it’s plausible to assume modifying the microbiome could be a way to help treat those experiencing alcohol-use disorders.
"This could be done either through the use of probiotics (bacteria), prebiotics (the food of bacteria) and/or symbiotics (both prebiotics and probiotics)," explained José Antonio López Moreno.
The new study was published in the journal Translational Psychiatry.
Source: Complutense University of Madrid
