Bitter taste and polyphenols; beneficial physiological activity via gastrointestinal hormones

Recently, there has been a notable emphasis on the homeostatic regulation by taste receptors that are expressed in extra-oral cavities. Bitter receptors (type 2 taste receptors, T2Rs) are abundant in the lower gastrointestinal tract and activated by bitter compounds in food. Activation of T2R triggers the release of gastrointestinal hormones such as cholecystokinin (CCK) or incretin as glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1). These peptides regulate appetite and amount of food consumption by affecting gastrointestinal motility. Besides, incretins are also known to regulate blood glucose homeostasis through insulin secretion. Polyphenols are micronutrients commonly found in plant-based food that possess a strong bitter taste. Additionally, they are not well absorbed by the upper digestive tract and thus tend to move to the colon and get excreted in the feces. Previous epidemiological and intervention studies suggest a negative correlation between polyphenol intake and the risk of diabetes. The beneficial functions that follow the ingestion of polyphenols might be caused by the mediation of T2R, which regulates glucose tolerance and gastrointestinal motility. This review explores the relationship between bitter taste and polyphenol bioactivity to understand better the mechanisms by which polyphenols exert their health benefits.