Effects of Dietary Fiber on the Bioavailability of Folic Acid Monoglutamate

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Abstract
Low bioavailability of folacin has been previously reported for a variety of foods of plant origin. This study was conducted to examine the possible role of various types of dietary fiber on the bioavailability of folic acid monoglutamate. Cellulose, pectin, lignin, sodium alginate and wheat bran were selected for their differing physical and chemical properties. In vitro binding studies by equilibrium dialysis showed no evidence of physical or chemical binding of folic acid under physiological conditions. In vivo effects were evaluated by a chick bioassay with graded levels of folic acid in semipurified diets containing the fiber materials at 3% (weight/weight). Total liver and plasma folacin concentration and chick growth were used as response indicators. Doseresponse curves indicated that pectin, lignin and alginate significantly reduced chick growth at all levels of dietary folacin. Plasma and liver folacin dose-response curves were not significantly different for any of the fiber materials, which indicated that the growth impairment was not due to a fiber effect on folic acid absorption. These results suggest that added dietary fiber has little or no effect on the bioavailability of folic acid monoglutamate.