Effect of Dietary Magnesium on Strontium-Calcium Discrimination and Incorporation into Bone of Rats

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Abstract
Although strontium-calcium discrimination from diet to body (OR (observed ratio) body/diet) is relatively constant under typical conditions, it can be changed by dietary modifications. Since magnesium is known to affect calcium absorption, a study was made in rats of its effect on calcium and strontium absorption and on strontium-calcium discrimination. The OR bone/diet was markedly increased at dietary magnesium levels below about 0.4%. From a practical standpoint it is noted that the body burden of 90Sr from chronic ingestion decreases in direct proportion to the decrease caused in the value of OR body/diet, divided by the percentage dietary calcium (OR/% Ca). Previous attempts to reduce this value to a minimum by manipulation of calcium and phosphorus levels gave an OR/% Ca of about 0.1. In this study, by use of a diet containing 4% Ca, 4% P, and 0.5% Mg, a further reduction to 0.06 was obtained. Also, there is suggested a possible explanation for the varying results reported in the literature on the effect of dietary magnesium on calcium absorption.