Calcium Requirement of Maintenance in Man,*

The demonstration upon laboratory animals by Osborne and Mendel,’ that calcium necessarily occupies a prominent place in the inorganic food supply, and that of McCollum, Simmonds, and Parsons,2 that calcium is one of the limiting fact’ors in a very large proportion of our staple foods, lends added interest to the measurement of the calcium requirement in man and the comparison of the amount of calcium required for normal human nutrition with the amounts found in the ordinary freely chosen food of representative families or other groups of people. Results obtained in this laboratory several years ago3 indicated that, in so far as could be judged from the limited data determined at that time, it was by no means safe to assume that a freely chosen food supply would always furnish calcium in quantity sufficient to afford a safe margin above the actual requirements of normal nutrition. Further study, therefore, seemed desirable and the purpose of the present paper is to summarize the data of a considerable number of additional laboratory experiments and to compare them wit,h t,he findings of further observat,ions upon actual food supplies.