Cereals and Rickets: XII. The Effect of Calcium and Vitamin D on the Availability of Phosphorus

Abstract

In feeding experiments with rats the availability of phytic acid phosphorus was markedly affected by the calcium and vitamin D content of the diet. With an optimal intake of phosphorus and a calcium-phosphorus ratio of 1/1 phytic acid phosphorus was almost as readily utilized as the inorganic form. However, with an increase in the calcium-phosphorus ratio to 2/1 the availability of phytic acid phosphorus was markedly decreased. Further increases in the calcium content of the rations decreased the availability of phytic acid phosphorus still more. On the other hand, inorganic phosphorus was not markedly affected by an increase in calcium even up to a ratio of 6/1. Different sources of calcium had a small but definite differential effect on the utilization of phosphorus. Calcium chloride produced a more severe rickets than either the carbonate or the sulfate. Calcium sulfate produced more bone ash than calcium carbonate. Vitamin D improved the utilization of both forms of phosphorus. This effect was more pronounced with phytic acid since the increment of improvement possible within the limits of calcification was less with the inorganic form. Even in the presence of vitamin D phytic acid phosphorus was not so readily available as the inorganic form. The aforementioned relative effects of different sources of calcium were also noted in the presence of vitamin D.