Non-covalent dietary fiber - Polyphenol interactions and their influence on polyphenol bioaccessibility

Polyphenolic compounds have shown many potentially positive bioactivities. But these beneficial effects depend on the amount of polyphenols accessible for absorption in the upper or lower parts of the digestive tract (bioaccessibility) or on the amount actually absorbed. Dietary fibers can interact with polyphenols in the digestive tract creating associations with them, which might influence polyphenol bioaccessibility in the digestive tract and therefore their bioactivities. The aim of this review is to discuss recent literature about non-covalent dietary fiber - polyphenol interactions, the parameters that affect these interactions, the types of bonds between polyphenols and dietary fibers and the influence of dietary fibers on the polyphenol bioaccessibility in the upper and lower parts of the digestive tract. Dietary fibers create associations with polyphenols. This process depends on environmental conditions like pH value, temperature and ionic strength. In both, the upper and lower parts of the digestive tract, polyphenols can be released from various food matrices. Dietary fibers affect that process by lowering the polyphenol amount released in the upper digestive tract. By this mechanism, they also potentially increase the polyphenol amount that reaches lower parts of the digestive tract, where polyphenols, once released, can show beneficial effects. Dietary fibers might be a sort of a “control mechanism” for controlling the amount of bioaccessible polyphenols in the upper or lower parts of the digestive tract. Further studies are needed to clarify the role of dietary fibers in polyphenol bioactivities.