Synergistic Two-Way Interactions of Dietary Polyphenols and Dietary Components on the Gut Microbial Composition: Is There a Positive, Negative, or Neutralizing Effect in the Prevention and Management of Metabolic Diseases?

Polyphenol is an intricate bioactive molecule abundant in humans/animals' diet particularly plant foods, and has been evidenced in numerous reports with health-promoting functions, owing to its free radical scavenging properties and a broad spectrum of bioactivities. However, the beneficial functions are linked and restricted to bioavailability, which is dictated by the diversity of the gut microbiota. The human/animal's gut harbours a complex community of trillions of microbial species and their symbiotic relationship goes beyond mere aiding the host's digestive system, with important functions such as host nutrition and health by encouraging nutrient metabolism and absorption, regulation of the gastrointestinal development, protection against pathogens, maintenance of the gut mucosal barrier functions and host immune system. The disruption of the gut community (i.e., dysbiosis) is suggested to reflect several pathological processes, such as diabetes, obesity, and other metabolic-related comorbidities. Recent improvements in deep-sequencing technologies and bioinformatics have enabled a more complex understanding of the reciprocal interactions of dietary polyphenols and gut microbiota, as well as their metabolic impact. Hence this review seeks to discuss the two-way synergistic interactions of dietary polyphenols and dietary constituents on the gut microbial composition with an updated and pivotal finding from literature suggesting whether these interactions depict a positive, negative, or neutralizing effect in the prevention of metabolic diseases.