Schümann K, Classen H G, Hages M, Prinz-Langenohl R, Pietrzik K, Biesalski H K
Walter-Straub-Institut für Pharmakologic und Toxikologie, Ludwig-Maximilians-Universität, Munich, Germany.
Arzneimittelforschung. 1997 Apr;47(4):369-80.
Bioavailability of orally administered vitamins, minerals, and trace elements is subject to a complex set of influences. Still, administrative regulation is necessary on how to quantify it. The most common approach to this problem is to determine the fraction of an oral dose that reaches the systemic circulation. For micronutrients, however, this approach has to consider the physiological plasma concentration as well as the mechanisms that regulate intestinal absorption and distribution of micronutrients between functional and storage compartments in response to the demand. The rate of exchange between these compartments has an impact on the delivery of such compounds into the plasma compartment as well as on the plasma clearance. Monitoring the area under the plasma concentration time curve after oral administration is an inadequate tool for bioavailability determination if there are substantial impacts of homeostatic mechanisms on the plasma concentration of a micronutrient. In nutritional science the term "bioavailability" encompasses the sum of impacts that may reduce or foster the metabolic utilisation of a nutrient. Bioavailability in this sense can be quantified by the rate by which deficiency symptoms are cured or by the weight gain during growth. both of these endpoints, again, are influenced by homeostatic mechanisms. To exemplify the scope of impacts on parameters that are commonly used to quantify the bioavailability of oral micronutrient preparations the basic traits of homeostatic regulation are summarised and compared for iron, magnesium, vitamin A, folic acid, and vitamin B12. The mechanisms that adapt absorption, distribution, and excretion of these five micronutrients to the demand differ to such an extent that no common approach can be derived to consider these impacts in bioavailability determination. In consequence, therefore, we recommend to define and regulate individual strategies for bioavailability testing for each micronutrient with regulated kinetics.
口服维生素、矿物质和微量元素的生物利用度受到一系列复杂因素的影响。然而，对于如何对其进行量化仍需要行政管理规定。解决这个问题最常见的方法是确定口服剂量中进入体循环的部分。然而，对于微量营养素，这种方法必须考虑生理血浆浓度以及调节肠道吸收和微量营养素在功能和储存区室之间分配以响应需求的机制。这些区室之间的交换速率会影响此类化合物进入血浆区室的输送以及血浆清除率。如果稳态机制对微量营养素的血浆浓度有重大影响，那么监测口服给药后血浆浓度-时间曲线下的面积并不是确定生物利用度的充分工具。在营养科学中，“生物利用度”一词涵盖了可能降低或促进营养素代谢利用的所有影响因素。从这个意义上讲，生物利用度可以通过治愈缺乏症状的速率或生长期间的体重增加来量化。同样，这两个终点都受稳态机制的影响。为了举例说明对常用于量化口服微量营养素制剂生物利用度的参数的影响范围，总结并比较了铁、镁、维生素A、叶酸和维生素B12的稳态调节基本特征。这五种微量营养素使吸收、分布和排泄适应需求的机制差异很大，以至于无法得出一种通用方法来在生物利用度测定中考虑这些影响。因此，我们建议为每种具有规定动力学的微量营养素定义并规范生物利用度测试的个体策略。
