Influence of low dietary calcium during pregnancy and lactation on zinc levels in maternal blood and bone in rats

The effect of low dietary calcium on maternal zinc nutritional status was studied. Two groups of 6 adult female Wistar rats were fed during pregnancy and lactation with experimental diets containing either 0.2 g (LCa) or 0.6 g (NCa) of calcium/100 g. Both diets contained/100 g: 20.0 g protein (potassium caseinate), 3.5 mg Zn, 0.6 g P. A third group (n = 6) was fed a “stock diet” (SG), containing/100 g: 24.8 g protein, 1.5 g Ca, 0.6 g P, 11.6 mg Zn. Maternal blood samples were drawn from the tail before mating (To), at delivery (D) and at weaning (W); dams were sacrificed at weaning and the right femur was excised. Determinations (atomic absorption spectrometry) were: Zinc in red blood cells (RBC), Zn and Ca in ashed femur. The results (mean ± SD) were: RBCZn (μg/mL) at To: 8.65 ± 1.80, which did not change in the SG or in the NCa groups, but increased significantly in the LCa group (p < 0.001) (D: 18.20 ± 4.63; W: 26.70 ± 6.02), regarding To. Femur Zn (μg/100 mg) showed an increase (p < 0.001) in the LCa group (30.2 ± 2.1) regarding both SG (25.3 ± 0.7) and NCa groups (24.1 ± 0.7). Femur Ca (mg/100 mg) decreased (p < 0.05) in the LCa group (19.2 ± 0.9) regarding both SG (24.0 ± 0.5) and NCa groups (21.4 ± 0.7) and leading to a significant increse in Zn/Ca ratio (p < 0.001) in the LCa group. Therefore, dietary calcium deficiency during pregnancy and lactation would produce an increase of Zn utilization, reflected in the increase of maternal blood Zn levels and in femur Zn content.