Zinc and copper metabolism in pregnancy and lactation of adolescent women

Abstract

Objective Pregnant and lactating adolescent women are at risk of zinc and copper deficiency but their capacity for metabolic adaptation is poorly known. This study investigated the effect of pregnancy and lactation on zinc and copper metabolism in adolescent women by comparing biochemical indices between groups in different reproductive states. Methods Habitual dietary intake and biochemical indices (zinc, copper, alkaline phosphatase, and ceruloplasmin in plasma; zinc [E-Zn], metallothionein [E-MT], and superoxide dismutase [E-SOD] in erythrocytes) and their relation were compared among non-pregnant non-lactating adolescents (NPNLs; n = 26), third-trimester pregnant adolescents (PAs; n = 26), and lactating adolescents up to 3 mo postpartum (LAs; n = 21). Results Zinc and copper intakes were not different across groups (on average, 8.7 and 1.0 mg/d, respectively). PAs had lower plasma zinc but higher plasma copper, alkaline phosphatase, and ceruloplasmin levels than did LAs and NPNLs ( P < 0.05). E-SOD and E-Zn were similar in all groups but E-MT was higher in the PA and LA groups than in the NPNL group ( P < 0.05). Correlations between plasma copper and ceruloplasmin and between E-MT and E-Zn were observed in the LA and NPNL groups ( r ≥ 0.64, P < 0.01) but not in the PA group. In contrast, correlations between plasma alkaline phosphatase and plasma zinc, between E-MT and plasma zinc, and between E-SOD and E-Zn were observed only in the PA group ( r ≥ 0.46, P < 0.05). Conclusion Zinc and copper biochemical responses to pregnancy and lactation in the adolescent women studied appeared qualitatively similar to those described in previous studies in adult women. However, the significant correlations observed between the activity of zinc-dependent enzymes and plasma (or erythrocyte) zinc suggest that a poor maternal zinc status may limit the metabolic adaptation capacity of these adolescent women especially during pregnancy.