Lönnerdal B
Department of Nutrition, University of California, Davis 95616.
J Nutr. 1989 Dec;119(12 Suppl):1839-44; discussion 1845. doi: 10.1093/jn/119.suppl_12.1839.
The bioavailability of the trace elements iron, zinc, copper and manganese from human milk is high compared to cow's milk and infant formulas. This high bioavailability may be explained by the presence of lactoferrin in human milk, which may facilitate iron and manganese uptake via an intestinal receptor for this protein. High concentrations of ascorbate and citrate may also facilitate uptake of trace elements from human milk and milk formulas, while a high concentration of casein in cow's milk and cow's milk formulas may limit trace element absorption from these diets. Trace element absorption from soy formula is low, mostly due to the presence of phytate but possibly also due to some protein fraction. Trace elements sharing absorptive pathways compete for uptake, and imbalances in the ratios between trace elements (Fe/Zn, Zn/Cu, Fe/Mn) in formulas may impair trace element absorption. These factors need to be taken into consideration when setting upper limits for trace elements in formulas. With our present knowledge, an upper limit for iron of 14 mg/l, for zinc, 12 mg/l, copper, 1.2 mg/l, and manganese, 0.6 mg/l are suggested. The capacity of infants to homeostatically adapt to varying intakes of trace elements needs to be further evaluated.
与牛奶和婴儿配方奶粉相比，人乳中微量元素铁、锌、铜和锰的生物利用率较高。这种高生物利用率可能是由于人乳中存在乳铁蛋白，它可能通过该蛋白的肠道受体促进铁和锰的吸收。高浓度的抗坏血酸盐和柠檬酸盐也可能促进人乳和奶粉中微量元素的吸收，而牛奶和牛奶配方奶粉中高浓度的酪蛋白可能会限制这些饮食中微量元素的吸收。大豆配方奶粉中微量元素的吸收较低，主要是由于植酸盐的存在，但也可能与某些蛋白质成分有关。共享吸收途径的微量元素会竞争吸收，配方奶粉中微量元素（铁/锌、锌/铜、铁/锰）之间的比例失衡可能会损害微量元素的吸收。在设定配方奶粉中微量元素的上限时，需要考虑这些因素。根据我们目前的知识，建议铁的上限为14毫克/升，锌为12毫克/升，铜为1.2毫克/升，锰为0.6毫克/升。婴儿对不同微量元素摄入量进行稳态适应的能力需要进一步评估。
