Stimulatory Effects of Indigestible Carbohydrates(Fructooligosaccharides) on Mineral Absorption.

Abstract

The importance of indigestible carbohydrates such as dietary fiber is well recognized. In recent years, the stimulatory effects of indigestible sugars such as fructooligosaccharides (FOS) on mineral absorption have been discovered and examined. This review provides an overview of current research work in this field. FOS are not digested by human enzymes. Dietary FOS are effective for increasing not only apparent but also true intestinal calcium (Ca) absorption in rats. Dietary FOS also stimulate magnesium (Mg) and iron (Fe) absorption. These effects show dose dependency and are long-lasting. FOS increase the absorption of Mg from natural foods such as cocoa and rice bran. The increase in Ca and Mg absorption is diminished by cecectomy. Ca and Mg disappear from the colorectal contents in the course of transit from the cecum to the anus. The absorption of cecally infused Ca and Mg is increased by dietary FOS. Moreover, dietary FOS increase large intestinal calbindin-D9k. These results suggest that the stimulatory action of FOS is exerted in the large intestine. FOS improve the bioavailability of these minerals in sever disease models rats. Dietary FOS prevent osteopenia in both ovariectomized rats and gastrectomized rats. In gastrectomized rats, FOS feeding also prevents anemia. Supplying a diet with a high Ca and high phosphorus content markedly decreases Mg absorption, and rats fed such a diet exhibit typical symptoms of Mg deficiency. However, these symptoms are suppressed by FOS feeding. The Ca absorption-promoting effect of FOS has been confirmed in humans by two different methods (balance study and double isotope method). Therefore, it is expected that many clinical applications of FOS will be established in the near future.