12至48个月大儿童的镁潴留情况。

Griffin Ian J, Lynch Mary Frances, Hawthorne Keli M, Chen Zhensheng, Hamzo Maria, Abrams Steven A

USDA/ARS Children's Nutrition Research Center, 1100 Bates St., Houston, TX 77030, USA.

J Am Coll Nutr. 2008 Apr;27(2):349-55. doi: 10.1080/07315724.2008.10719711.

OBJECTIVES

In adults, adaptation to changes in magnesium intake is largely due to changes in fractional magnesium absorption and urinary magnesium excretion. We sought to examine whether these homeostatic mechanism also occurred in young children.

METHODS

Children, 12-48 m old were studied (n=30). They were adapted to a home diet representative of their usual magnesium intake for 7 d then admitted for a stable isotope study. Children received 5 mg Mg-25 intravenously, and 10 mg Mg-26 orally (5 mg with breakfast and 5 mg with lunch). Magnesium absorption was calculated from the relative fractional excretion of the oral and intravenous isotopes in the urine samples. Endogenous fecal magnesium absorption was calculated in a subgroup from the fecal and urinary excretion of the intravenous tracer.

RESULTS

Magnesium intake (mean +/- SD; 106 +/- 25 mg/d) was significantly greater than the Estimated Average Requirement (EAR) described by the Institute of Medicine in the US (65 mg/d, p < 0.0001). Across the range of intake studied, fractional magnesium absorption was significantly (P = 0.0383) but weakly (r(2) = 0.144) related to magnesium intake. Absolute magnesium absorption (the product of fractional absorption and intake) significantly increased as intake increased (r(2) = 0.566, P < 0.0001). Urinary magnesium excretion was unrelated to magnesium intake (r(2) = 0.036, P = 0.31). Endogenous fecal magnesium excretion tended to increase as magnesium intake increased (r(2) = 0.312, P = 0.12). Magnesium retention (absolute absorption minus urinary and fecal losses) was positive in 26 of the 30 subjects studied, and was linearly related to magnesium intake (r(2) = 0.157, P = 0.0304). A magnesium intake of 52-78 mg/d would appear to be required to meet the needs for absorbed magnesium for half the children at this age range, suggesting that the current EAR is broadly appropriate.

CONCLUSIONS

In young children, consuming magnesium intakes typical of the US population, fractional magnesium absorption is a major site of magnesium homeostasis, but magnesium retention increased linearly across the intake range studied. Our results support at EAR for magnesium of 55-80 mg/d and an RDA of 70-100 mg/d.

目的

在成年人中，对镁摄入量变化的适应很大程度上归因于镁的分数吸收和尿镁排泄的变化。我们试图研究这些稳态机制是否也在幼儿中出现。

方法

对12至48个月大的儿童进行了研究（n = 30）。他们先适应代表其日常镁摄入量的家庭饮食7天，然后入院进行稳定同位素研究。儿童静脉注射5毫克Mg-25，口服10毫克Mg-26（早餐时5毫克，午餐时5毫克）。根据尿液样本中口服和静脉注射同位素的相对分数排泄计算镁的吸收情况。在一个亚组中，根据静脉注射示踪剂的粪便和尿液排泄计算内源性粪便镁吸收情况。

结果

镁摄入量（平均值±标准差；106±25毫克/天）显著高于美国医学研究所描述的估计平均需求量（EAR）（65毫克/天，p < 0.0001）。在所研究的摄入量范围内，镁的分数吸收与镁摄入量显著相关（P = 0.0383），但相关性较弱（r² = 0.144）。绝对镁吸收量（分数吸收与摄入量的乘积）随着摄入量的增加而显著增加（r² = 0.566，P < 0.0001）。尿镁排泄与镁摄入量无关（r² = 0.036，P = 0.31）。内源性粪便镁排泄量倾向于随着镁摄入量的增加而增加（r² = 0.312，P = 0.12）。在所研究的30名受试者中，有26名的镁潴留（绝对吸收量减去尿液和粪便损失量）为正值，并且与镁摄入量呈线性相关（r² = 0.157，P = 0.0304）。这个年龄范围的儿童中，似乎有一半需要摄入52 - 78毫克/天的镁才能满足对吸收镁的需求，这表明当前的EAR大致合适。