Hallberg L, Rossander-Hultén L, Brune M, Gleerup A
Department of Medicine II, University of Göteborg, Sahlgren Hospital, Sweden.
Pediatr Res. 1992 May;31(5):524-7. doi: 10.1203/00006450-199205000-00024.
Iron absorption from human milk and cow's milk was compared in the same subjects using two radio-iron tracers and extrinsic labeling of the iron. Previously observed higher iron absorption from human milk was confirmed as 19.5 +/- 17.3% (mean +/- SD) in cow's milk versus 48.0 +/- 25.5% in human milk; mean individual absorption ratio was 0.39 +/- 0.18 (p less than 0.0001). Cow's milk has a several times higher content of calcium, recently established to be a potent inhibitor of iron absorption. Adding calcium chloride to human milk in amounts to equate the calcium content of cow's milk significantly reduced iron absorption [39.1 +/- 17.8% (mean +/- SD) versus 21.3 +/- 10.6%]; mean individual absorption ratio with or without added calcium was 0.58 +/- 0.12 (mean +/- SD) (p less than 0.0001). Differences in calcium content could explain at least 70% of the difference in iron bioavailability between milks. It is suggested that the remaining 30% difference may mainly be an artifact related to inhomogeneous radioiron-labeling of milk iron compounds, especially in human milk, and that the main difference in true iron absorption between human and cow's milk is related to their different calcium contents. The rather high fractional iron absorption from human milk can be explained by its low iron content. There is nothing to indicate that human milk contains any enhancer of iron absorption. The marked inhibiting effect of calcium on iron absorption should be considered in the design of infant formulas to achieve an optimal balance in the contents of calcium and iron.
在同一组受试者中，使用两种放射性铁示踪剂和铁的外源性标记，比较了人乳和牛乳中铁的吸收情况。先前观察到的人乳铁吸收更高这一现象得到了证实，牛乳中铁的吸收率为19.5±17.3%（均值±标准差），而人乳中为48.0±25.5%；个体平均吸收比为0.39±0.18（p<0.0001）。牛乳中的钙含量高出数倍，最近证实钙是铁吸收的有效抑制剂。向人乳中添加氯化钙以使钙含量与人乳相当，会显著降低铁的吸收[39.1±17.8%（均值±标准差）对21.3±10.6%]；添加钙与否的个体平均吸收比为0.58±0.12（均值±标准差）（p<0.0001）。钙含量的差异至少可以解释两种奶中铁生物利用度差异的70%。有人认为，其余30%的差异可能主要是与奶中铁化合物的放射性铁标记不均匀有关的假象，尤其是在人乳中，人乳和牛乳在真正的铁吸收方面的主要差异与其不同的钙含量有关。人乳铁吸收率相当高可以用其低铁含量来解释。没有迹象表明人乳中含有任何铁吸收增强剂。在设计婴儿配方奶粉时，应考虑钙对铁吸收的显著抑制作用，以实现钙和铁含量的最佳平衡。
