Comparative Analysis of Forms of Calcium and Inorganic Phosphorus in Human and Cow's Milk

Abstract

It is a common observation that rickets occurs less frequently in breast-fed infants than in those which are artificially fed. The antirachitic superiority of human milk is not due to a greater content of vitamin D. 1 Moreover, cow's milk contains more Ca and P than does breast milk and the ratio of Ca:P is lower in the former. It was thought that, in spite of its lower content of total Ca and P, human milk might contain a larger amount of the most effective forms of these elements and that therein might lie an explanation for the difference in antirachitic value of the 2 kinds of milk.

In a recent communication, 2 a technic was described which rendered it possible to separate the Ca of serum into 4 forms and the P into 2. The technic involved removal, by means of dry BaSO₄, of the adsorbable forms of Ca and of inorganic P from the serum and from the corresponding ultrafiltrate. It was shown 3 further that one of the forms, namely the filtrable, adsorbable Ca-P complex, was the one primarily involved in bone formation. Gyorgy, 4 as well as others, have suggested that the Ca and P of milk exist in the form of complex salts and Klinke 5 has demonstrated that more than half of the Ca of cow's milk can be adsorbed with Al(OH)₃. There is, thus, some indication that milk may contain a fraction similar to the filtrable, adsorbable Ca-P complex of serum. Accordingly, the above mentioned technic was applied to a study of the forms of the Ca and inorganic P in human and in cow's milk. Irradiated cow's milk was also included in the investigation because of its increasing importance as an antirachitic agent.