Diet, the gut microbiome and the metabolome in IBD

The human gut contains a vast number of microorganisms known collectively as the gut microbiota. Despite its importance in maintaining the health of the host, growing evidence suggests the gut microbiota may also be an important factor in the pathogenesis of various diseases, a number of which have shown a rapid increase in incidence over the past few decades. In some of these diseases, such as inflammatory bowel disease (IBD), the microbiota is dysbiotic with an abnormal community structure and decrease in diversity. If the dysbiotic microbiota plays a role in disease pathogenesis, interventions that modify its composition to make it more similar to the microbiota observed in health, might be a strategy to treat certain disease processes. Indeed, the high-level efficacy of fecal microbiota transplantation in the treatment of refractory Clostridia difficile infection supports this notion as proof-of-principle. The composition of the microbiota can be influenced by many factors including age, genetics, host environment, and diet. With respect to the later, diet has an impact upon both the composition and function of the microbiota. There are epidemiologic data associating diet with the development of IBD as well as evidence that diet can influence both the form and function of the microbiome in a manner that impacts upon the development of intestinal inflammation. Based on this evidence, studies are now underway to examine the effect of defined formula diets, an effective therapeutic modality in Crohn's disease, on both the gut microbiome and its metabolome as a therapeutic probe with the hope of better defining the 'healthy' diet in patients with IBD.