Availability of magnesium

镁（Mg）是一种众所周知的元素，是人体和动物必需的元素之一。在营养领域，Mg对人体有一个推荐剂量，2000年设定的Mg的膳食参考摄入量为300 Mg /d，上限为700 Mg /d，但数值会因性别和年龄的不同而略有变化。目前尚未见镁过量或缺乏症引起的人体毒性的报道。基于我们之前的研究结果，我们重点研究了镁对生殖功能和存活率的影响。缺镁组小鼠在正常饲粮组（Mg含量494.4mg/kg）的基础上，饲喂低Mg饲粮（Mg含量42.4mg/kg）。缺镁食品被订购到两个独立的公司，A和B)。在给予缺镁饮食后，两组小鼠的存活率差异很大。这一事实可以用共存的矿物含量来解释。至于性激素的影响，也可以认为是饮食成分的影响，即缺镁后男性血液中睾酮浓度下降，而女性血液中雌激素浓度没有变化。不同公司准备的饮食对激素效应的结果也有影响。当我们研究矿物时，重要的是要考虑到矿物之间的相互作用。

Magnesium (Mg) is one of universally well-known elements, and one of the essential elements in human and animals. In the nutrition fields Mg has a recommendable dose for human beings, and in 2000 the dose of dietary reference intake of Mg was set at 300 mg/day, and upper limit at 700 mg/day, although the values were slightly shifted depending upon the sex and ages. It has not reported human toxicity due to over dosage or deficient illness of magnesium up to now. Based upon the results of our previous study we have focused on the effects of magnesium on reproductive function and the survival rates. Mice of Mg-deficient group were given low Mg diet (Mg content 42.4mg/kg) in addition to the normal diet group (Mg content 494.4mg/kg). Mg deficient diets were ordered to two independent companies, A and B). After giving Mg deficient diets survival rates were much different from 2 diet groups. This fact might be explained by the coexisting mineral contents. As to the effects of sex hormones, it could be also considered as the ingredients of diets : namely testosterone concentration in blood in males decreased after Mg deficiency although that of estrogen in females showed no change. Diets prepared different companies also influenced to the results of hormonal effects. When we investigate minerals, it should be important to be taken account to the interaction of minerals.