Magnesium Metabolism in College Women: Observations on the Effect of Calcium and Phosphorus Intake Levels

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Abstract
Nine healthy college women served as subjects for a mineral metabolism study. During the first 4 weeks all subjects were maintained on a basal diet which supplied approximately 260 mg magnesium, 300 mg calcium, and 800 mg phosphorus. This was followed by a second 4-week period during which three of the subjects were continued on the basal diet, three were given a supplement of 1,200 mg calcium, and the remaining three supplements of 1,200 mg calcium and 600 mg phosphorus. During weeks 2, 3, and 4, the mean daily fecal excretion of magnesium was 153.5 mg with a standard error of 3.8 mg, the urinary excretion was 96.2 mg with a standard error of 3.2 mg, and the retention was 11.6 mg with a standard error of 2.9 mg. Statistically significant differences between subjects were observed in each instance. Using partial correlations as criteria, a significant relationship was observed between fecal calcium and phosphorus, but not between magnesium and either of these elements. When the same statistical technique was applied to the retention data, there was no evidence of association between calcium and magnesium or between phosphorus and magnesium, although a highly significant association between calcium and phosphorus retention was observed. Urinary excretion of magnesium was significantly correlated with the intake levels of both calcium and phosphorus.