Effect of diet on the intestinal microbiota and its activity.

PURPOSE OF REVIEW: To summarize and discuss recent findings concerning diet-microbiota-health relations. RECENT FINDINGS: Mouse and other model animal studies have provided detailed insight into host-microbiota interactions, but cannot be extrapolated easily to humans that have different dietary habits, intestinal architecture, and microbiota composition. In spite of the fact that all humans have a personalized microbiome, the discovery of the high-level clusters, such as enterotypes, offer great potential for stratifying individuals in intervention studies based on their intestinal microbiota. A highly diverse microbiota seems to be key to adult human health. Long-term dietary patterns have been found to be associated with specific microbiota compositions and in some cases enterotypes. Fecal transplantations indicate that homeostasis can be restored and indicate that diet-microbiota-induced disorders can be improved by therapeutic modification of the microbiota. The specificity of complex carbohydrate conversion is the driving ecological force in the colon, while competition for sugars with the host is the driver for the small intestinal ecosystem. At both locations, the microbial fermentation of dietary components occurs in trophic chains and insight into these multispecies conversions is essential to understand the impact of diet on health. SUMMARY: There are clear associations between the microbiota, our diet and our health. However, as microbiota correlations with human health and diet are generally based on baseline comparisons between populations, there is a need for dedicated dietary intervention studies in humans to differentiate between correlation and causality.