Effect of Gastrointestinal Conditions on the Mineral-Binding Properties of Dietary Fibers

Abstract

Investigations into the relationship between dietary fiber content and mineral-nutrient bioavailability of diets have generally shown an inverse relationship (Munoz, 1986). The inhibitory effect of fiber on mineral absorption, although perhaps more appropriately attributed to phytic acid in some studies, thus seems well established. The process by which fiber exerts its inhibitory effect is less well characterized. Three modes of inhibition have been hypothesized (Kelsay, 1981): 1) fiber greatly increases fecal bulk and motility, thus reducing the time available for absorption or access to transport mechanisms; 2) fiber directly or indirectly alters luminal-to-serosal transport mechanisms in the mucosa (such as the ferritin system); 3) the formation of stable, unabsorbable mineral-fiber complexes reduces the pool of available minerals. The latter hypothesis, utilized by most investigators, as well as in this work, posits that minerals bound to large macromolecules can not be absorbed directly nor transfer to mineral-transporter moieties. Thus, within the context of the subject matter of these proceedings, the present work addresses the issue of “To what extent might a plant-derived macromolecular complex (i.e., plant cell walls) impede mineral absorption?”

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