Bioavailability of food polyphenols: current state of knowledge

(Poly)phenols, including flavonoids, phenolic acids, and tannins, are a diverse class of compounds found in plant-based foods and beverages. Their bioavailability has been extensively described and detailed metabolic pathways elucidated. Although some parent (poly)phenols are absorbed intact in the small intestine, most pass to the colon where they are extensively catabolized and their microbial products absorbed into the circulation. The sum of the metabolites absorbed can reach almost 100% in some cases and in some individuals. In recent years, there have been three major areas of advancement: (a) comprehensive and systematic reviews have brought together bioavailability data, including detailed metabolic pathways in humans, and quantitative estimates of absorption and excretion; (b) the action and importance of the gut microbiota in (poly)phenol metabolism have been better defined and our understanding of the important role of the microbiota in intra- and interindividual variation has greatly expanded; and (c) strategies to improve (poly)phenol bioavailability such as encapsulation employing various nanoformulations or cyclodextrins have been developed.