LAY SUMMARY

Food Structure, Diet, and the Gut Microbiota

Studies of the human gut microbiota show that not only does diet shape what microorganisms exist in the digestive system but also determines how those microorganisms work and relate to the host. The gut microbiota seems to be responsive to not only individual nutrients but also to the diet's overall composition and structure over time.

Research on food habits suggests that foods high in complex carbohydrates, fiber and minimally processed plant matter create a milieu supportive of a more varied microbial community. These foods serve as substrates that the small intestine does not digest but find their way into the colon to be fermented by resident bacteria. This fermentative process generates short-chain fatty acids, involved in gut health, metabolic signaling, and immune function.

Diets which consist largely of highly refined and/or quickly digested foods potentially minimize fermentable material in the colon. Some research proposes that this has been associated with changes in microbial composition and activity with implications for gut barrier function, as well as inflammatory responses. These results are not the effect of one food ingredient, but of how food is processed, combined and eaten as an element of an overall dietary pattern.

The studies surveyed suggest that there is a dynamic link between diet and the gut microbiome and that it is determined by dietary habits and not changes in behavior. Structures of eating, such as the size of food particles, fiber integrity, and resistance to digestion, seem to be important contributors to how nutrients are introduced to gut microorganisms. These ideas have been expanded on and the insights that they provide help highlight how dietary patterns can promote health with effects that are greater than just calories.

Source
Conlon, M. A., & Bird, A. R. The Impact of Diet and Lifestyle on Gut Microbiota and Human Health. Nutrients (2014).