L’influence du microbiote intestinal sur la santé mentale

Abstract

The intestinal microbiota constitutes a complex ecosystem composed of bacteria, viruses, microscopic fungi, and archaea, which plays an essential role in human health by regulating digestion, producing vitamins and short-chain fatty acids (SCFAs), supporting the immune system, and protecting the intestinal mucosal barrier. Its composition and functions are influenced by various factors such as diet, age, genetics, environment, and lifestyle, with dietary components having a direct impact on microbial diversity and metabolic activity. Fibers promote beneficial bacteria and the production of SCFAs, whereas saturated fats may promote inflammation and induce dysbiosis. Moreover, the microbiota contributes to the regulation of neural functions through the production of neurotransmitters such as serotonin, dopamine, and GABA, thereby influencing mood and mental health. Nutritional and therapeutic interventions, including probiotics, prebiotics, synbiotics, and postbiotics, aim to restore microbial balance in order to improve intestinal, immune, and neural health, confirming the essential role of the microbiota as a functional interface between nutrition, immunity, and brain functions. The gut microbiome is closely linked to mental health through the so-called gut–brain axis, a bidirectional communication system between the digestive system and the central nervous system. The composition of the microbiome can influence brain functions, mood, and behavior through several mechanisms, including the production of neurotransmitters such as serotonin, dopamine, and GABA, which play a key role in the regulation of emotions and psychological state. Thus, any imbalance in this microbial system may affect stress responses, anxiety levels, and overall mood. Recent studies also show that diet is a key factor in modulating the microbiome, as the quality and type of diet can help maintain its balance or, conversely, disrupt it, which may have direct effects on mental health. The objective of this thesis is to analyze the influence of diet on the composition and functions of the intestinal microbiota, as well as its involvement in the modulation of mental health.