The intestinal flora could influence mood, quality of life and depression, according to a study conducted by the Belgian University of Leuven.
In recent years, several studies have established links between the brain and our gut, our “second brain.” And indeed, these two organs are in constant communication with each other. The brain transmits information to the intestine through a very dense network of nerves. The gut responds by sending hormones that provide indications to the nervous system, such as the need to eat, drink or vomit.
There is, however, a third player that plays a fundamental role in this dialogue: the gut microbiota. A growing body of research suggests that bacteria inside the gut actively interact with it and could play a role in the onset of psychiatric illnesses such as depression or neurodegenerative diseases such as Alzheimer’s disease.
A recent study by the Belgian research team led by Jeroen Raes suggests that certain types of intestinal bacteria could have an impact on the quality of life and be linked to depression. The research was published in the journal Nature Microbiology on February 4th.
Intestinal bacteria linked to a better quality of life
The study was conducted by analyzing the intestinal microbiota of two independent cohorts, composed of about a thousand participants each. To evaluate the impact of the microbiota on the quality of life, the researchers used a questionnaire that took into account eight parameters, four concerning physical health, such as pain, and four concerning mental health, such as well-being. Emotional. They then looked for a correlation between the scores obtained in the questionnaire (from 0 to 100) and the presence or absence of certain types of intestinal bacteria.
The bacteria of the Faecalibacterium and Coprococcus type are associated with high scores, and therefore a good quality of life. Both produce butyrate, a fatty acid that strengthens epithelial defenses and reduces inflammation. The absence of this molecule is related to the appearance of chronic diseases of the intestine and depression.
The absence of certain bacteria in case of depression
The researchers then compared the microbiota of subjects with depression to that of non-depressed individuals and found that two types of bacteria, Coprococcus and Dialister, were absent in depressed patients. Depression could be the cause or the consequence of this bacterial deficiency; we do not know it. But scientists have verified that the absence of these bacteria is not due to the use of antidepressants.
To read also: Our intestinal bacteria, our second brain.
A catalog of neuroactive compounds produced by bacteria
Once the mood-altering bacteria were identified, the researchers tried to understand their action on the nervous system. For this, they isolated more than 500 bacteria from the intestinal flora. They then studied them to guess which “neuroactive” molecules, which therefore affect the brain, the microbiota was able to produce.
“Many neuroactive compounds are produced in the human gut, we wanted to know which gut microbes were involved in the production, degradation, or modification of these molecules, and our method not only allows us to identify the different bacteria that can play a role. role in mental health, but also the mechanisms involved in this interaction, “says Mireia Valles-Colomer, first author of the study.
The authors have discovered that certain bacteria produce a molecule, DOPAC, derived from dopamine and that this production is linked to a better quality of life (according to the criteria of the questionnaire).
Analyzes must be experimentally confirmed on individuals, but represent a significant step forward in understanding communication between the brain and intestine.