Eastern Virginia Medical School, Medical Service, Hampton Veterans Affairs Medical Center, Hampton, Virginia 23667, USA.
Nutr Res Rev. 2000 Dec;13(2):141-58. doi: 10.1079/095442200108729043.
The experimental and epidemiological evidence demonstrating that Ca inhibits Fe absorption was reviewed, with the objectives of estimating the potential impact of variations in Ca intake on dietary Fe bioavailability and of providing some guidelines for predicting the effects on Fe status of recent recommendations for higher dietary Ca intake. In animal models Ca salts reduced both haem- and non-haem-Fe absorption, the effect being dependent on the amount of Ca administered rather than the Ca:Fe molar ratio; dairy products had a variable effect; factors other than Ca may have been important. In single-meal human absorption studies, both haem- and non-haem-Fe absorption was inhibited by Ca supplements and by dairy products, the effect depending on the simultaneous presence of Ca and Fe in the lumen of the upper small intestine and also occurring when Ca and Fe were given in the fasting state. The quantitative effect, although dose dependent, was modified by the form in which Ca was administered and by other dietary constituents (such as phosphate, phytate and ascorbic acid) known to affect Fe bioavailability. The mechanism by which Ca influences Fe absorption has not been elucidated. The effects of factors that modulate Fe bioavailability are known to be exaggerated in single-meal studies, and measurements based on several meals are more likely to reflect the true nutritional impact. The results of most multiple-meal human studies suggest that Ca supplementation will have only a small effect on Fe absorption unless habitual Ca consumption is very low. Outcome analyses showed that Ca supplements had no effect on Fe status in infants fed Fe-fortified formula, lactating women, adolescent girls and adult men and women. However it should be noted that the subjects studied had adequate intakes of bioavailable Fe and, except in one study, had relatively high habitual Ca intakes. Although cross-sectional analyses in Europe have shown a significant inverse correlation between Ca intake (derived primarily from dairy foods) and Fe stores, the quantitative effect was relatively small. The general conclusion is that dietary Ca supplements are unlikely to have a biologically significant impact on Fe balance in Western societies unless Ca consumption is habitually very low; however, increased consumption of dairy products may have a small negative effect that could be functionally important in pregnancy if Fe supplements are not taken. It is uncertain whether the inverse relationship between consumption of dairy products and Fe status is due entirely to increased Ca intake; substitution of milk proteins for meat may also have negative effects on Fe balance.
本文回顾了实验和流行病学证据，证明钙能抑制铁的吸收，目的是估算钙摄入量变化对膳食铁生物利用度的潜在影响，并为预测近期高钙饮食摄入建议对铁状态的影响提供一些指导。在动物模型中，钙盐减少了血红素和非血红素铁的吸收，其效果取决于给予的钙量而不是钙与铁的摩尔比；乳制品的效果则各不相同；其他因素可能也很重要。在单次用餐的人体吸收研究中，钙补充剂和乳制品均抑制了血红素和非血红素铁的吸收，其效果取决于上消化道腔内钙和铁的同时存在，并且即使在空腹状态下给予钙和铁时也会发生这种情况。尽管这种效果与剂量有关，但由于钙的给药形式以及其他已知影响铁生物利用度的膳食成分（如磷酸盐、植酸和抗坏血酸）而发生改变。钙影响铁吸收的机制尚未阐明。众所周知，调节铁生物利用度的因素在单次用餐研究中的影响会被夸大，而基于多顿饭的测量更有可能反映真实的营养影响。大多数多餐人体研究的结果表明，除非习惯性钙摄入量非常低，否则钙补充剂对铁吸收的影响将很小。结果分析表明，钙补充剂对喂养铁强化配方的婴儿、哺乳期妇女、青春期女孩和成年男女的铁状态没有影响。然而，应该注意的是，所研究的受试者有足够的可利用铁摄入量，并且除了一项研究外，他们的习惯性钙摄入量相对较高。尽管欧洲的横断面分析表明，钙摄入量（主要来自乳制品）与铁储存之间存在显著的负相关，但定量效应相对较小。总的结论是，除非习惯性钙摄入量非常低，否则膳食钙补充剂不太可能对西方社会的铁平衡产生生物学上的显著影响；然而，增加乳制品的消费可能会产生较小的负面影响，如果不服用铁补充剂，这在怀孕期间可能具有重要的功能意义。目前还不确定乳制品消费与铁状态之间的负相关是否完全归因于钙摄入量的增加；用牛奶蛋白代替肉类也可能对铁平衡产生负面影响。
