Tea phenolics as prebiotics

Due to the relatively low bioavailability of tea phenolics in the small intestine, their reciprocal interaction with gut microbiota in the colon may contribute largely to their beneficial health effects. This implies that tea phenolics may be considered as prebiotics. This review summarizes the current knowledge on the metabolic fates of phenolics from green and black tea, the health benefits of tea phenolics and their microbial metabolites, and the potential underlying mechanisms. Additionally, the prebiotic effects of tea phenolics and conventional oligosaccharide prebiotics are compared. Phenolics from green tea are promptly metabolised into a series of (hydroxylated) phenylcarboxylic acids by gut microbiota, whereas lower degradation rates and metabolite yields are documented for black tea phenolics. Despite these differences, phenolics from green and black tea exhibit comparable gut microbiota modulatory effects. Moreover, intact green and black tea phenolics and their microbial metabolites provide various health benefits upon consumption, most likely due to their anti-oxidation, anti-inflammatory, gut barrier protection, and bile acid metabolism regulatory effects. Overall, the health benefits conferred by tea phenolics via modulation of gut microbiota composition and via formation of health-promoting metabolites is in many ways analogous to the prebiotic action of conventional oligosaccharides prebiotics. Therefore, we conclude that phenolics from green and black tea have the potential to be considered as prebiotics. Gaining better insights in the prebiotic effects of phenolics from green and black tea may pave the way for their high-value application in food and pharmaceutical industries.