Effect of Intake Level on the Utilization and Intestinal Excretion of Calcium in Man

Abstract

The endogenous fecal calcium, total digestive juice calcium and the utilization of ingested calcium have been measured in two adults at different levels of calcium intake. Endogenous fecal calcium was found to be of the same order of magnitude as urinary calcium, 100 mg/day, and was independent of the level of calcium intake in both patients. The maximum total digestive juice calcium was ∼ 150 mg/day in one patient and ∼ 360 mg/day in the other, values which are substantially lower than those estimated in the literature. Changes of the dietary calcium intake had little effect upon the total digestive juice calcium. Approximately 45 and 65% of the dietary calcium was absorbed in the two patients respectively. Excellent agreement was found between the values obtained by three independent methods. The minimum daily calcium requirements under the experimental conditions were calculated to be 8.6 mg/kg body weight for patient I.B. and 3.5 mg/kg body weight for patient B.L. The values for the utilization of dietary calcium and the minimum dietary calcium requirements as calculated from the Ca⁴⁵ data agree well with those obtained by the metabolic balance technique, confirming the validity of the radiocalcium calculations.