CALCIUM AND MAGNESIUM ABSORPTION FROM THE COLON AND RECTUM ARE INCREASED IN RATS FED FRUCTOOLIGOSACCHARIDES

We investigated the effects of fructooligosaccharides on the absorptio n of calcium, magnesium and water from the colon and rectum of rats fe d a control diet or the control diet containing 50 g fructooligosaccha rides/kg. Chromium-mordanted cellulose was used as an unabsorbable mar ker to calculate apparent absorption of calcium and magnesium. There w as a positive correlation (r = 0.982, P < 0.001 in rats fed the contro l diet and r = 0.975, P < 0.001 in rats fed the fructooligosaccharides -containing diet) between the amount of chromium and the dry weight of each fecal pellet in the colon and rectum. Ratios of calcium to chrom ium and magnesium to chromium in fecal pellets in the colon and rectum were calibrated from the Ca:Cr and Mg:Cr ratios of cecal contents. In rats fed the fructooligosaccharides-containing diet, but not in rats fed the control diet, these ratios were correlated with the fractional length of transit along the colon and rectum, indicating linear disap pearance of calcium and magnesium during the colorectal passage. Total apparent absorption of calcium and magnesium, predicted from regressi on equations with the Ca:Cr and Mg:Cr ratios of cecal contents, agreed well with those calculated from the Ca:Cr and Mg:Cr ratios of feces. The consumption of fructooligosaccharides did not affect net water abs orption from the colon and rectum. These results indicated that fructo oligosaccharides significantly increased calcium and magnesium absorpt ion and that indigestible and fermentable carbohydrate facilitates col orectal absorption of calcium and magnesium.