Interaction of Dietary Fluoride and Magnesium in Guinea Pigs

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Abstract
Weanling male guinea pigs were fed a magnesium-deficient diet (25 ppm) based on EDTA-treated soybean protein, to which graded levels of magnesium and fluoride were added as supplements in an attempt to determine the nature of the physiological interaction of the two elements. A 100 ppm level of fluoride in the diet was the most efficacious in the stimulation of growth, prevention of mortality and prevention of kidney calcification. When magnesium was severely limiting, 200 ppm F was toxic and caused lameness and swollen feet; adequate magnesium largely overcame the deleterious effect. Fluoride (100 ppm) decreased from 1,600 to 600 ppm the dietary magnesium concentration required to support the maximum growth rate. At the lower level of dietary magnesium, fluoride supplementation resulted in higher plasma magnesium concentration, but the increase was not sufficient to restore the elevated level of plasma inorganic phosphorus to normal. Fluoride tended to increase rather than decrease plasma phosphate. The increase in plasma magnesium could not be explained by an effect of fluoride on bone magnesium. Fluoride had no effect on the rate of release of magnesium from bone in magnesium-deficient guinea pigs. Fluoride spares magnesium in the guinea pigs and it is postulated to do so by activating a catalyst jointly with magnesium.