Probiotics, Stress, and Irritable Bowel Syndrome

Irritable bowel syndrome (IBS) is a functional, gastrointestinal disease characterized by a combination of chronic or recurrent symptoms such as abdominal pain and abnormal bowel habit. Most of the IBS features occur without identifiable organic cause and are strongly influenced by stress and anxiety suggesting the involvement of brain–gut interactions in this disease. Microbiota changes have also been reported such as decreased abundance of the genera Bifidobacterium and Lactobacillus and increased firmicutes: bacteroidetes ratio but there is no consensus on a specific IBS microbiota signature. Psychological stress in rodents impacts intestinal epithelial barrier integrity as well as the composition of microbial communities and induces visceral pain, providing an interesting model for IBS pathophysiology investigation. Modulation of the intestinal microbiota using probiotics in preclinical trials prevents stress-induced visceral hypersensitivity directly through probiotic metabolites production or indirectly through prevention of the intestinal barrier function impairment. The clinical efficacy of probiotic treatments has also been suggested but the use of different scales to analyze the mean differences of symptoms in various studies has limited the ability of all existing meta-analyses in IBS to confirm the effectiveness of probiotics on major IBS symptoms and patient quality of life.