Diet and the intestinal microbiome: associations, functions, and implications for health and disease

Abstract

The mutual relationship between the intestinal microbiota and its mammalian host is influenced by diet. Consumption of various nutrients affects the structure of the microbial community and provides substrates for microbial metabolism. The microbiota can produce small molecules that are absorbed by the host and affect many important physiological processes. Age-dependent and societal differences in the intestinal microbiota could result from differences in diet. Examples include differences in the intestinal microbiota of breastfed vs formula-fed infants or differences in microbial richness in people who consume an agrarian plant-based vs a Western diet, which is high in meat and fat. We review how diet affects the structure and metabolome of the human intestinal microbiome and may contribute to health or the pathogenesis of disorders such as coronary vascular disease and inflammatory bowel disease.

Keywords: Diet; Inflammation; Intestine; Microbiota.

Copyright © 2014 AGA Institute. Published by Elsevier Inc. All rights reserved.

Figures

Figure 1. Development of the human intestinal microbiota and the effects of environmental exposures

Colonization of the early intestinal microbiota depends on multiple environmental exposures. The taxa that colonize the relatively sterile newborn intestine are largely determined by the mode of delivery. The intestinal microbiota also develops differently determined by differences in infant feeding (breast feeding vs formula feeding). Throughout infancy and early childhood, the microbiota changes with dietary alterations, infections, and exposure to antibiotics. The intestinal microbiota of the infant is characterized by instability and low levels of diversity. However, by the toddler years, the intestinal microbiota is similar in diversity and stability to that of adults.

Figure 2. Interactions among diet, the intestinal microbiota, and the host

Diet can directly affect the host or it can have an indirect effect through, for example, the intestinal microbiota. The composition and duration of diet can affect not only on bacteria in the intestine, but also viruses, Archaea, and fungi. Existing bacteria also affect these other microoganisms in a number of ways (co-abundance groups, enterotypes, richness/diversity). In addition to the composition of the intestinal microbiota, diet affects its production of metabolites, which can influence host physiology. Finally, the direct effects of diet on the host can produce changes that alter the intestinal microbiota.

Figure 3. Pathways by which diet could affect health, through the production of metabolites by the intestinal microbiome

Specific components of diet can serve as substrates for the intestinal microbiome, allowing it to produce specific metabolites that interact with mammalian cells, some in a receptor-mediated fashion. These processes affect host physiology and the development of diseases such as atherosclerosis and the inflammatory bowel diseases. *Possible therapeutic targets.