Phytate breakdown and apparent absorption of phosphorus, calcium and magnesium in germfree and conventionalized rats

Abstract

Male germfree and conventionalized rats, 4 weeks old, were fed a phytate-free diet or a diet containing sodium phytate (1.2% in the first experiment and 2.4% in the second experiment) for 3 weeks. Phytate breakdown and apparent absorption of P, Ca and Mg were determined using Cr 2O 3 as a non-absorbable marker and analyzing not only the feces but also the contents of the lower small intestine and cecum. No lower phytate breakdown was observed in GF rats than in conventionalized counterparts. Thus, the presence of gastrointestinal microflora did not increase phytate breakdown, which means that gastrointestinal microflora play no major roll in phytate breakdown in rats. Furthermore, it became apparent by comparing the fecal data with those of the lower small intestine that the large intestine was not a major site of phytate breakdown. Germfree rats showed higher apparent absorption of P, Ca and Mg than their conventionalized counterparts except for Ca in rats fed the diet containing 2.4% sodium phytate. Comparison between rats fed the phytate-free diet and those fed the phytate-containing diets made clear that phytate P was less available than inorganic P and that dietary phytate decreased apparent absorption of Mg but not that of Ca.