Whole Grain and Fiber Addition Study

The human gut microbiota is the complex community of bacteria that reside within the human
gastrointestinal tract. This community plays an important role in supporting normal immune
function and digestion. Disruption of the microbial communities within the gastrointestinal
tract, sometimes termed "dysbiosis" is linked to a wide range of human diseases, including
obesity, metabolic syndrome, malnutrition, and cancer. Stability of the microbiome is thought
to be important for human health, however the factors that drive microbiome community
stability are poorly understood.

Within the gastrointestinal tract, the microbiota is constantly exposed to complex mixtures
of foods and the products of digestion. Importantly, changes in diet have been shown to
rapidly induce shifts in microbial community composition. These compositional shifts can also
affect microbial production of bioactive metabolites, which may be one mechanism to explain
how the microbiome impacts host physiology and disease.

Fiber is often considered to be one of the largest contributors to microbial compositional
shifts that follow dietary interventions. Fiber resists digestion and persists through the
gastrointestinal tract to reach the large intestine where it can be metabolized by bacteria.
The end products of this metabolism are the short chain fatty acids (SCFAs), acetate and
butyrate, which are often associated with beneficial health outcomes. Fibrous foods are also
a source of polyphenols and other phenolic compounds that may be used by microbes in the
production of secondary metabolites or freed from the food matrix by microbial enzymes.

The purpose of this study is to: 1) to investigate the impact of high fiber, whole grain and
bran cereal on microbiome stability, and 2) to explore the microbial contribution to
polyphenol metabolism from whole grain in healthy individuals.