The microbiome and nutrition in critical illness.

The present review aims to describe the relationship between nutrition and the gut microbiome in critical illness. Critical illness disrupts not only cells of human origin but also the intestinal microbiome, with a decrease in bacterial diversity and transformation into a pathobiome. Under basal conditions, nutrition profoundly alters microbial composition with significant salutatory effects on human health. In critical illness, enteral nutrition is recommended and has theoretical (but not proven) advantages towards improved inner microbial health and diminution of bacterial translocation. Dietary supplements such as probiotics and fiber have been shown to improve microbial derangements in health. However, their impact on the microbiome in critical illness is unclear and although they may have some beneficial effects on patient-centric outcomes, they do not alter mortality. The precise mechanisms of how nutrition and dietary supplements modulate the gut microbiome remain to be determined. Nutrition and supplements such as probiotics appear to play a significant role in modulating the microbiome in health, yet the relationship in critical illness is unclear. Further investigation is required to determine the mechanistic determinants of the impact of nutrition on the microbiome in critical illness and the potential clinical implications of this.