KIM GILBERT^1,2, RONAN GIRE³*, GUY ROUSSEAU¹
*Corresponding author
1. Hôpital du Sacré-Coeur de Montréal, Centre de biomédecine, 5400 Boulevard Gouin Ouest, Montréal, Québec, H4J 1C5, Canada
2. Université de Montréal, Département de pharmacologie, CP Centre-Ville, Montréal, Québec, H3C3J7, Canada
3. Lallemand Health Solutions, 8480 boulevard Saint-Laurent, Montréal, Québec, H2P 2M6, Canada

Abstract

Intestinal transit is often affected during stressful conditions, suggesting a link between brain and gut. Moreover recent experimental evidence has demonstrated that the gut might also influence the activity of the brain and the behaviour by different mechanisms including nervous transmission, the immune system and the microbiota. Indeed, the gut-brain axis is not only essential for the maintenance of gastrointestinal homeostasis but is also involved in the regulation of cognitive functions and stress.
The purpose of this review is to discuss the recent evidence on the gut-brain axis and how modulation of the microbiota using probiotics may be beneficial to our mental and intestinal health.

INTRODUCTION

Experimental and clinical evidence shows that the intestinal microbiota plays an important role in our behaviour. Conversely, behaviour modulates the composition of our microbiota, affecting our immune system and inflammatory condition (see Figure 1). Such bi-lateral communication allows us to consider the gut-brain axis as a key component for our well-being and its modulation by probiotics becomes a promising way of intervention. We will examine the evidence that allows us to consider the importance of the gut-brain axis in our well-being and how probiotics may be helpful.

INTESTINAL MICROBIOTA AND GUT HOMEOSTASIS
The gastrointestinal tract microbiota consists of 1013 to 1014 microorganisms, which is approximately 10 times the number of human cells in the body. The microbiome of an adult represents more than 1000 species and 7000 different strains of microorganisms. It is composed mainly of bacteria belonging to the genera: Bacteroides; Clostridium; Fusobacterium; Eubacterium; Ruminococcus; Peptococcus; Peptostreptococcus; and Bifidobacterium.
Maintenance of the microbiota homeostasis is essential fo ...