The role of dietary fiber in the bioaccessibility and bioavailability of fruit and vegetable antioxidants

Abstract

Antioxidants are abundant compounds primarily found in fresh fruits and vegetables, and evidence for their role in the prevention of degenerative diseases is continuously emerging. However, the bioaccessibility and bioavailability of each compound differs greatly, and the most abundant antioxidants in ingested fruit are not necessarily those leading to the highest concentrations of active metabolites in target tissues. Fruit antioxidants are commonly mixed with different macromolecules such as carbohydrates, lipids, and proteins to form a food matrix. In fruits and vegetables, carbohydrates are the major compounds found, mainly in free and conjugated forms. Dietary fiber, the indigestible cell wall component of plant material, is considered to play an important role in human diet and health. Most studies on antioxidant bioavailability are focused on foods and beverages from which antioxidants are easily released. There is evidence indicating that food microstructure affects the bioaccessibility and bioavailability of several nutrients, referring mostly to antioxidants. Nevertheless, the specific role of dietary fiber in the absorption of antioxidants has not been widely discussed. In this context, the purpose of the present review is to compile and analyze evidence relating to the association between dietary fiber and antioxidants, and the physical and chemical interactions that modulate their release from the chyme in the gastrointestinal tract.

Figure 1

General human bioabsorption of phenolic compounds contained in beverages or similar foods poor in fiber.

Figure 2

General human bioabsorption of carotenoids contained in food poor in dietary fiber.

Figure 3

General human bioabsorption of carotenoids contained in foods with high contents of dietary fiber.

Figure 4

General human bioabsorption of phenolic compounds contained in foods rich in dietary fiber, such as fruits and vegetables.

Figure 5

(A) Native flavonoid structure bond to saccharides found in fruits and vegetables. Enzymatic hydrolysis between both molecules during digestion is needed for free absorption of flavonoid in the intestine. (B) Electrostatic and van der Waals interactions between flavonoids (F) and other phenolic compounds with polysaccharide chains (P).