Submitted to: Biological Trace Element Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 5, 2005
Publication Date: May 1, 2006
Repository URL: http://handle.nal.usda.gov/10113/35393
Citation: Nielsen, F.H. 2006. A mild magnesium deprivation affects calcium excretion but not bone strength and shape, including changes induced by nickel deprivation, in the rat. Biological Trace Element Research. 110:133-149. Interpretive Summary: Bone is a tissue that continuously remodels throughout life. This remodeling responds to a large variety of nutritional factors. Thus, nutritional deficiencies are often suspected to contribute to impaired remodeling that leads to bone loss and diseases such as osteoporosis. Epidemiological studies have linked low dietary intakes of magnesium to decreased bone mass and osteoporosis in humans. However, controlled experimental studies in either humans or experimental animals showing that a mild magnesium deprivation, similar to that likely to be found in the general population, impairs calcium metabolism and bone strength are lacking. Therefore, an experiment with rats was performed to determine whether a mild magnesium deprivation (about 50% of the dietary requirement) changed calcium excretion, and bone mineral composition, shape and strength. Because foods low in magnesium are often low in nickel, the effect of nickel deprivation on the response to the mild magnesium deprivation was also determined. The mild magnesium deprivation decreased the urinary excretion of calcium and increased the tibia concentration of calcium, but did not affect femur shape or strength. Nickel deprivation did not alter the effects of magnesium deprivation. Nickel deprivation increased the urinary excretion phosphorus, and femur strength. Strength changes may have been the result of changes in bone shape. Magnesium deprivation did not alter the effects of nickel deprivation on bone. The findings indicate that a mild magnesium deficiency affects calcium and metabolism, but does not markedly affect bone strength, and these effects are not modified by nickel deprivation. Although these findings do not preclude a mild magnesium deprivation contributing to bone changes that lead to osteoporosis, they do suggest that if it does, a sustained long term deprivation may be required to have such an effect. The findings also indicate that diets low in nickel may impair bone development and strength and these changes are not affected by a mild magnesium deficiency. Nickel apparently is an element beneficial to bone health. Foods rich in magnesium and nickel include whole grains, nuts, and pulses (for example, beans, lentils, peas).
Technical Abstract: An experiment was performed to determine the effect of a mild magnesium deprivation on calcium metabolism, and bone composition, shape and strength in rats, and whether nickel deprivation exacerbated or alleviated any changes caused by the magnesium deprivation. Weanling male rats were assigned to groups of 10 in a factorial arrangement with variables being supplemental nickel at 0 and 1 mg/kg and magnesium at 250 and 500 mg/kg of diet. The basal diet contained about 30 ng Ni/g. Urine was collected for 24 h during weeks 8 and 12, and rats were euthanized 13 weeks after dietary treatments began. Mild magnesium deprivation decreased the urinary excretion of calcium, increased the tibia concentration of calcium but did not affect femur shape or strength (measured by a three-point bending test). Dietary nickel did not alter these effects of magnesium deficiency. Nickel deprivation increased the urinary excretion of phosphorus and the femur strength variables maximum force and moment of inertia. Strength differences may have been the result of changes in bone shape. Magnesium deprivation did not alter the effects of nickel deprivation on bone. The findings indicate that a mild magnesium deficiency affects calcium metabolism but that this does not markedly affect bone strength or shape, and these effects are not modified by dietary nickel. Also, nickel deprivation affects phosphorus metabolism and bone strength and shape; these effects apparently are not caused by changes in magnesium metabolism or utilization.