IRON SUPPLEMENTS AND ZINC IN PREGNANCY AND LACTATION

给世界各地的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。当开出治疗性剂量的铁时，很少会同时开出补充锌的处方。对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，被研究的14名妇女中有4名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，在哺乳期有显著变化，但在服用补充铁的四名妇女中没有观察到这种调整。孕期和哺乳期对锌的需求分别增加0.7 mg/d和1.4 mg/d。我们的研究表明，如果不补充铁，这种需要可以通过上调锌的吸收来满足。补充铁可能会损害怀孕和哺乳期间锌使用的这种变化。因此，这项拟议的研究的目的是确定补充铁对健康女性在妊娠和哺乳期锌利用的代谢调节的影响。我们假设，在妊娠晚期和哺乳早期，每天补充100毫克铁会抑制锌的吸收，并减少从胃肠道对锌的净吸收，而此时对锌的额外需求最大。将在怀孕早期招募两组妇女，每组15人，分别在怀孕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；另一组不补充铁。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基本稳定地摄入微量营养素。使用稳定的同位素，将测量铁和锌的吸收和锌的动力学。还将确定铁和锌状态的生化指标。在每次测试期间，所有女性将在新陈代谢单元居住6天。这项全面的纵向研究结果将为补充铁对孕期和哺乳期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.