LAUSR

75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 Rdemonstrate an important role for gut microbiota in generation of symptoms in patients with functional gastrointestinal disorders (FGIDs) in general and irritable bowel syndrome (IBS) in particular. Clinical observations that support the involvement of gut microbiota in symptom generation in IBS and other FGIDs include (a) a substantial proportion of patients with IBS report onset of their GI symptoms after a bout of gastroenteritis (ie, postinfection IBS) and this group of patients has abnormal gut microbiota composition, (b) a proportion of individuals develop functional GI symptoms after receiving systemic antibiotics, presumably owing to the development of (transient) gut dysbiosis, and (c) use of the nonabsorbable antibiotic rifaximin, as well as the use of probiotics, improve IBS symptoms, presumably through effects on gut microbiota. Furthermore, several studies indicate that at least a subset of patients with IBS demonstrate abnormal gut microbiota composition and that this is associated with the severity and pattern of symptoms. Taken together, these clinical and research observations implicate that modulating the gut microbiota might be a relevant treatment strategy for a substantial proportion of these patients. Dietary factors are central for patients with IBS and the majority of patients report worsening of symptoms after intake of certain food items, particularly foods containing carbohydrates and fat. Part of this finding might be explained by diet–microbiota interactions, because the gut microbes have an important role in the digestion of dietary components, resulting in metabolites that may directly or indirectly contribute to IBS symptoms. Food items rich in indigestible carbohydrates (ie, fermentable oligosaccharides, disaccharides, monosaccharide and polyols [FODMAPs]) seem to be particularly relevant, because they can provoke IBS symptoms in susceptible individuals through osmosis and fermentation by gut microbes. Several studies have demonstrated the clinical efficacy of a low FODMAP diet in IBS, an effect that goes beyond the placebo response frequently reported in patients with IBS, but not clearly superior to traditional IBS dietary advice. The clinical effect of a low FODMAP diet is partly mediated through diet–microbiota interactions; a reduction of carbohydrates, that is, the substrate for bacterial fermentation in the colon, leads to lowered gas production and thereby reduced intestinal distension. However, the