The Calcium Requirement of Man: Balance Studies on Seven Adults

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Abstract
This study reports the calcium requirement of seven adults ranging in age from 21 to 42 years. The requirement was computed from data on calcium balances secured at levels of intake almost sufficient to induce calcium equilibrium and from data concerning the extent to which each subject could utilize milk calcium. Balances of +24, +5, -39, -5, -13, -36 and -22 resulted when the respective subjects ingested 574, 568, 498, 603, 580, 451 and 873 mg. of calcium daily. Since these subjects could utilize, respectively, only 35, 31, 30, 20, 18, 15 and 20% of the calcium of milk, the following adjustments in calcium intake would have been necessary in order to bring about calcium equilibrium: -68, -16, +129, +25, +74, +235 and +108 mg. The total respective requirements, therefore, would be 506, 552, 627, 628, 654, 686 and 981 mg. calcium daily; they average 662 mg. which, when it is based on weight, height and surface area, amounts to 10.7 mg. per kilogram, 3.9 per centimeter and 391 per square meter. These requirements, calculated on a 70-kg. weight basis, average 752 mg.—which is 67% greater than Sherman's 450-mg. requirement. But the latter figure is too low because it is predicated on the assumption that adults utilize 100% of their dietary calcium.