When the balance between the beneficial and harmful bacteria in the bowel turns in favor of the harmful, the immune system reaction that we call inflammation develops, which cause inflammatory bowel diseases (such as Crohn's disease, ulcerative colitis).
In a study conducted by Abraham and colleagues In 2009, microbiota has been shown to play a key role in the development of inflammatory bowel diseases.
In 2011 Khor and colleagues published a study on the pathogenesis of these diseases in Nature. The pathogenesis of Crohn's disease is showed to be the immune system’s response to the deviation of microbiota on the malignant side. However, there is no data supporting the use of probiotics in Crohn's disease.
In patients with ulcerative colitis, Lactobacillus and Bifidobacterium species were found to be decreased in the intestinal flora, whereas Bacteriodes vulgarus and Fusobacterium, Enterococcus and invasive Escherichia coli were found to be increased. Meijer and colleagues published a study in the Journal of Clinical Gastroenterology in 2011, in which, probiotic use was found to be quite successful in this disease. Probiotics have positive effects on acute infectious diarrhea, diarrhea due to antibiotic use and irritable bowel syndrome.