Dietary Fiber and Non-extractable Polyphenols
Dietary fiber (DF) features beneficial health effects that are directly related to its composition, physicochemical properties and associated antioxidant compounds. Such compounds are a class of as polyphenols (PP), the non-extractable polyphenols (NEPP). They are polymeric PP or small PP linked/trapped in an insoluble food matrix. NEPP are important constituents of DF, but are omitted in the usual methods of determination. These compounds are not extracted from food by the organic aqueous solvents that are traditionally used, nor are they released from the food matrix by chewing, by the acidic pH of the stomach nor by the action of digestive enzymes. Thus, these PP are not bioavailable in the small intestine, reaching the colon intact, along with the DF. Scientific evidence has been increasingly proving that DF–PP interactions are biologically important and provide a differentiated physiological action to these PP. Furthermore, these compounds are able to confer specific properties to DF because of their antioxidant capacity. In this context, this chapter aims to show that DF and NEPP are interrelated compounds that present a common physiological fate and complementary health effects, considering DF as an important carrier of antioxidant compounds into the human organism.