American Journal of Clinical Nutrition, Vol 19, 296-306, Copyright © 1966 by The American Society for Clinical Nutrition, Inc.

Effect of Magnesium on Calcium Metabolism in Man

¹ From the Departments of Biochemistry and Medicine, Columbia University, College of Physicians and Surgeons, and the First (Columbia University) Medical Division, Bellevue Hospital, New York, New York

Calcium and magnesium metabolism were studied using standard balance and radioisotope technics in four male subjects ranging in age from thirty-seven to sixty-four years, and one sixty-eight year old female subject with rheumatoid arthritis who were hospitalized on a metabolic research ward.

An increase of 1 gm. of magnesium per day in a diet of constant calcium content induced sustained increases in serum calcium and magnesium, calciuria and magnesiuria, and diminished fecal loss of both metals. The intestinal absorption and the net retention by the body of both metals was increased, the effect being quantitatively greater for calcium than for magnesium. The diurnal variation in urinary calcium excretion was greater in two patients during the period of excess magnesium intake than during the control period. The specific activity of Ca⁴⁷ in blood serum was depressed, whereas the calcium pool size and turnover rates were augmented by the high magnesium intake. Calculations of renal tubular reabsorption rates of both calcium and magnesium indicated an enhanced rate of reabsorption despite the increased urinary output. The decreased urinary output of phosphate was accompanied by an increased fecal loss. It is suggested that increasing the magnesium content of the diet induces greater parathyroid gland activity or thyrocalcitonin suppression during the day with a compensatory reversal during the night, resulting in greater oscillations in secretory activity than normal. There was no evidence of chronically diminished levels of circulating parathyroid hormone.

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