Suboptimal intake of magnesium in rats. Effects during growth and gestation

Abstract

To investigate the interaction of magnesium depletion and source of protein and the effect of this interaction on growth, female weanling Sprague-Dawley rats were fed diets based on 20% casein or 20% soy protein isolate which contained eithe adequate (800 mg/kg) or suboptimal (200 mg/kg) levels of magnesium. The initial suboptimal level of approximately 100 mg/kg magnesium was increased to approximately 200 mg/kg magnesium on day 6 of the study. The nutritional stress of rapid growth resulted in clinical signs of deficiency including audiogenic seizures in the animals fed the casein diet which was low in magnesium. Some clinical manifestations of deficiency persisted through almost all of the 6-week growth period. The lower nutritional quality of soy protein isolate and/or the components of soy which depress mineral bioavailability resulted in a higher rate of alopecia and skin sores in the rats fed the soy low magnesium diet than in those fed the casein low magnesium one. Growth retardation in the magnesium deficient animals occurred during the post-weaning growth phase. Gestational weight gain was also depressed by low magnesium intake to a greater extent than has been previously reported in response to a mild magnesium restriction. Because of recent reports of suboptimal intakes of magnesium by humans, further research of combined effects of subacute magnesium deficiency and utilization of foods containing soy protein is needed.