Effects of Calcium Supplementations on Mineral Metabolism during Pregnancy with Calcium-Deficient Young Adult Rats

ABSTRACT

We examined the effects of calcium intake levels on mineral metabolism during pregnancy using calcium-deficient young adult rats. Five week-old female Sprague-Dawley rats were fed normal Ca (NCa, 0.5%) and low Ca (LCa, 0.15%) diets for five weeks (pre-pregnancy). The low Ca intake group was then divided into three groups and fed low Ca (0.15%), normal Ca (0.5%) and high Ca (1.5%) diets for 3 weeks (pregnancy). All of the rats were mated with normal male rats. The control group was fed a consistently normal Ca (0.5%) diet during pre-pregnancy and pregnancy. On the day after delivery, dams and their pups were sacrificed. We measured total protein, albumin, alkaline phosphatase and mineral content in serum and weight, length, breaking force, ash and mineral content in the femur and lumbar (L2-L4) of the dams. Whole body mineral content was measured in the pups. There was no difference in weight gain and food intake among the groups. Serum total protein and albumin were in the normal range but a little lower during pregnancy. High Ca supplementation decreased serum Mg and Fe during pregnancy. Weight, ash and Ca of the femur and lumbar significantly decreased in rats fed a chronically low Ca diet during pre-pregnancy and pregnancy. Calcium supplementation levels were above normal during pregnancy and increased the bone weight and breaking force of rats fed the low Ca diet during pre-pregnancy. However, Ca supplementation did not increase the ash and Ca contents in the bones. High Ca supplementation during pregnancy significantly decreased Mg in the bones and increased Ca and P in the kidneys. Ash content of pups from dams fed the chronically low Ca diet decreased but there was no difference in whole body Ca among the groups. Mg and Fe in the whole body decreased in pups from dams fed the high Ca diet. Pregnancy performance was reduced in dams fed the low Ca diet. These results suggest that above normal Ca supplementation levels during pregnancy restored maternal bone status to some extent in rats fed the chronically low Ca diet. The same could not be said for mineral content. Also, high Ca supplementation during pregnancy may deteriorate mineral composition in bones and other tissues. Therefore, more detailed research is needed to facilitate sound recommendations on appropriate calcium intake during pregnancy.