the ions with which they are associated (mainly Ca2+, Mg2+, Mn2+, K+ and H + in natural phytates) and on the level of Ca in the diet. Thus, native phytates, free phytic acid, sodium and calcium phytates and commercial 'phytin' (a Ca-Mg phytate) do not necessarily behave in the same way.Vitamin D probably enhances the utilization of phytate P in two ways, by increasing the production of intestinal phytase and by stimulating Ca absorption, thus rendering the phytate more soluble. T h e requirements of animals for vitamin D increase as the proportion of the total dietary P as phytate increases.( 6 )