We live in symbiosis with billions of bacteria, they inhabit our intestinal microbiota. While the role these bacteria play in mental health has long been underestimated, over the past 10 years research has shown that they have a significant impact on stress, anxiety and depression. 

 

Our digestive tract is colonized by bacteria, yeasts, viruses, parasites and fungi. These microorganisms form our microbiota. The microbiota is essential for us to digest certain foods. He degrades those we can’t digest, such as cellulose (found in whole grains, salad, endives, etc.), or lactose (milk, butter, cheese, etc.); facilitatesnutrient uptake ; participate in the synthesis of certain vitamins…

 

The microbiota is also the guarantor of the proper functioning of our immune systembecause 70% of our immune cells come from the intestines. 

 

 

On the other hand, more and more studies show that the intestinal microbiota also participates in the development and good brain function.

 

When the microbiota is balanced, the approximately 100 billion good and bad bacteria live in symbiosis. When it is out of balance, bad bacteria take up more space. We then speak of dysbiose : an imbalance of the intestinal flora. 

 

La overgrowth of bad bacteria then causes its share of disorders in the body. It is also estimated that a very large number of chronic diseases are linked to a disruption of the microbiota. Among the disorders caused by this imbalance, stress, anxiety and depression are increasingly highlighted by scientific research. 

 

The intestine is often called ” second brain “. And for good reason, 200 million neurons line our digestive tract! 

 

We also know that our gut communicates directly with the brain via the vagus nerve, the longest nerve in the human body. Our brain is therefore constantly processing information that comes to it from the intestine. 

 

Moreover, serotonin, also known as the sweet hormone of happiness, is 95% produced by the digestive system. Serotonin plays an important role in regulating mood, or sleep, and has been identified as deficient in people with depressive disorders. In fact, the most commonly prescribed antidepressant drugs, called selective serotonin reuptake inhibitors (SSRIs), work in a targeted manner on serotonin. 

 

We know that digestive bacteria such as Bifidobacterium infantis, Bifidobacterium longum and Lactobacillus helveticus produce serotonin, but alsogamma-aminobutyric acid (GABA), an amino acid that helps reduce anxiety or nervousness. 

 

If at the beginning of studies on the microbiota, we thought that the bacteria that constitute it were only useful for digestion, several studies, carried out from the 2000s, have shown its major role in the development of the central nervous system. 

 

Among recent research, published in 2020, two support an impact of the microbiota on depression. Researchers from the Institut Pasteur, Inserm and CNRS have in fact discovered that healthy mice can fall in trough when the microbiota of a depressed mouse is transferred to them. 

 

While further research is needed to understand the link between gut health and mental health, we now know that the intestine and the brain are so closely linked that a degradation of the microbiota leads to changes in behavior. 

 

To optimize your intestinal flora, we must play on the diet, because the intestinal bacteria feed on what we eat and respond very quickly to changes in the diet. Thus, for a balanced microbiota, care must be taken to consume a maximum ofplant foods and limit its consumption ofprocessed food. 

 

In particular, it is recommended to integrate more than fibers to its diet, the preferred substrate for good bacteria, but also to consume daily prebiotics (artichokes, onions, leeks, asparagus, etc.), fermented foods, sources of probiotics (soy sauce, miso, kéfir…). 

 

As to probiotic capsules, studies tend to show that they are less effective than dietary interventions. According to the results of a systematic review published in the journal General Psychiatry, and covering 21 studies, a change in diet would have a greater impact on the microbiota than taking a probiotic supplement.