IRON SUPPLEMENTS AND ZINC IN PREGNANCY AND LACTATION

给全世界所有孕妇补充铁是一种常见的做法。剂量从60毫克/天到240毫克/天不等。当治疗剂量的铁被规定，它是罕见的同时也规定补充锌。实验动物和人类的研究表明，补充铁会干扰锌的吸收。在我们最近进行的一项关于孕期锌吸收的纵向研究中，14名女性中有4人的医生给她们开了补充铁的处方。虽然锌的吸收在怀孕期间增加，在哺乳期发生了显著的变化，但在补充铁的四名妇女中没有观察到这种调整。吸收锌的需求在怀孕期间增加0.7毫克/天，在哺乳期早期增加1.4毫克/天。我们的研究表明，如果没有补充铁，这种需要可以通过上调锌的吸收来满足。在孕期和哺乳期补充铁可能会影响锌的使用。因此，本研究的目的是确定补充铁对孕期和哺乳期健康妇女锌利用代谢调节的影响。我们假设，每天补充100毫克铁会抑制锌的吸收，并减少妊娠后期和哺乳期早期对锌的额外需求最大时胃肠道对锌的净吸收。在妊娠早期招募两组妇女，每组15名，分别在妊娠12-14周、32-34周和产后4-6周进行研究。一组每天补充100毫克铁；另一组将不补充。所有妇女都将在产前服用维生素补充剂，外加8毫克铁和5毫克锌，以确保在整个研究过程中微量营养素的基础摄入量稳定。使用稳定同位素，铁和锌的吸收和锌动力学将被测量。铁和锌的生化指标也将被确定。在每次测试中，所有女性都将在一个代谢单元中生活6天。这项全面的纵向研究的结果将为孕期和哺乳期补铁对锌利用的影响提供新的数据。

It is a common practice to give supplemental iron to all pregnant women world-wide. The dose can vary from 60 mg/d to as much as 240 mg/d. When therapeutic doses of iron are prescribed, it is rare to also prescribe supplemental zinc. Studies in experimental animals and humans show that supplemental iron interferes with zinc absorption. In a recent longitudinal study of zinc absorption during pregnancy done by us, four of the 14 women studied were prescribed supplemental iron by their physicians. Although zinc absorption increased during pregnancy reaching a significant change during lactation, this adjustment was not observed in the four women taking supplemental iron. The need for absorbed zinc increases by 0.7 mg/d during pregnancy and 1.4 mg/d during early lactation. Our study showed that this need is met by upregulating zinc absorption if supplemental iron is not given. Administration of supplemental iron may impair this change in zinc use during pregnancy and lactation. The purpose of this proposed study, therefore, is to define the effect of supplemental iron on the metabolic adjustments in zinc utilization in healthy women during pregnancy and lactation. We hypothesize that a daily supplement of 100 mg iron inhibits zinc absorption and reduces the net uptake of zinc from the gastro-intestinal tract during late pregnancy and early lactation when the additional need for zinc is the greatest. Two groups of 15 women each will be recruited in early pregnancy and will be studied at 12-14, 32-34 weeks of gestation, and at 4-6 weeks postpartum. One group will receive 100 mg supplemental iron daily; the other group will be unsupplemented. All women will be given a prenatal vitamin supplement plus 8 mg iron and 5 mg zinc to assure a stable basal intake of the micronutrients throughout the study. Using stable isotopes, iron and zinc absorption and zinc kinetics will be measured. Biochemical measures of iron and zinc status will also be determined. All women will reside in a metabolic unit for 6 days during each test. Results from this comprehensive, longitudinal study will provide new data on the effects of iron supplementation on zinc utilization during pregnancy and lactation.