Understanding Polyphenols' Health Effects Through the Gut Microbiota

The gut microbiota transforms most dietary polyphenols (90%) in the intestine of humans and other mammals. This conversion is often essential for absorption and controls the biological activity of these compounds. Different studies have been performed to understand how gut microbiota transforms the different polyphenols into smaller molecules called microbial metabolites or postbiotics. These studies include intervention studies in humans and animals as well as in vitro culture using fecal inoculum. Some of the bacterial species implicated in polyphenol transformations have been identified, and the modulation of the gut microbial ecology by polyphenol consumption has been demonstrated. However, recent investigations have shown large interindividual differences in the production of bioactive microbial metabolites from dietary polyphenols because of the specific gut microbiome of each individual. Therefore, the potential biological activity derived from polyphenols intake is conditioned by the gut microbiome ecology of each individual. In this chapter, we review the potential production pathways of microbial metabolites in humans from the different polyphenolic groups, the known gut microbial species responsible for their production, the ability of dietary polyphenols to modulate the individual gut microbiota, and the concept of polyphenol gut metabotypes and their potential health implications.