Folic acid utilization from high fiber diets in rats.

This study was designed to examine the effect of several sources of dietary fiber on the utilization of folic acid added to the diets of rats. Weanling rats were given a low folacin basal diet for 21 days, divided into various groups and then fed folic acid (pteroylglutamic acid) and/or fiber-supplemented diets for 7 or 8 days. The slope of the liver folacin response was measured as an indicator for utilization of added folic acid. Fecal folacin excretion was measured as an indicator of unabsorbed dietary folacin plus folacin synthesis by intestinal bacteria. There was no detectable effect of cellulose, xylan, pectin or wheat bran on the utilization of added folic acid. Liver and fecal folacin content indicated that some fiber sources contributed additional available folacin to the animals from intestinal synthesis or naturally occurring folacin. Cellulose acted as a simple dietary dilutant and had no significant effect on the utilization of added folic acid or total fecal folacin excretion. Xylan stimulated intestinal folacin synthesis, and this was reflected in higher fecal and liver folacin content. Wheat bran and beans (two varieties of each) contained measurable folacin or stimulated synthesis of bacterial folacin, which appeared to be available to the rat.