Clinic & Laboratory of Experimental Medicine and Endocrinology, Katholieke Universiteit Leuven, Herestraat 49, Leuven, Belgium.
Best Pract Res Clin Endocrinol Metab. 2011 Aug;25(4):693-702. doi: 10.1016/j.beem.2011.06.008.
Vitamin D is a precursor for a secosteroid ligand of a major transcription factor, VDR, and is vital for normal bone mineralization. It also regulates many other genes so that it may be involved in many extra skeletal health effects. The optimal vitamin D status is controversial but there is a wide unanimity that the vitamin D status can and should be improved for some risk groups. To normalize serum calcium homeostasis as based on normal levels of serum 1,25(OH)₂D₃ or parathyroid hormone, or to optimize intestinal calcium absorption or bone mineral density in adults or elderly subjects, serum 25OHD should be 20 ng/ml or higher. A daily vitamin D supplement of at least 400 IU or preferably 800 IU of vitamin D₃ can reduce the risk of fractures and probably also falls in elderly subjects, especially when combined with an optimal calcium intake. There is no formal proof of causality to define an optimal vitamin D intake or serum 25OHD based on its presumed extra skeletal health effects but the guidelines for bone health would probably eliminate also most negative extra skeletal health effects. The recommended vitamin D₃ supplement of 400-800 IU/d for adults also corresponds to the daily replacement dose calculated from metabolic clearance studies.
维生素 D 是一种主要转录因子 VDR 的甾体配体前体，对于正常的骨骼矿化至关重要。它还调节许多其他基因，因此可能参与许多骨骼外的健康效应。最佳的维生素 D 状态存在争议，但广泛认为某些风险群体的维生素 D 状态可以而且应该得到改善。为了使血清钙的内稳态正常化，需要基于血清 1,25(OH)₂D₃ 或甲状旁腺激素的正常水平，或者为了优化成人或老年患者的肠道钙吸收或骨密度，血清 25OHD 应达到 20ng/ml 或更高。每天至少补充 400IU 或最好是 800IU 的维生素 D₃ 可以降低骨折风险，尤其是在与最佳钙摄入量相结合时，还可以降低老年人跌倒的风险。目前还没有明确的因果关系证据来定义基于其假定的骨骼外健康效应的最佳维生素 D 摄入量或血清 25OHD，但骨骼健康指南可能也会消除大多数骨骼外的健康效应。推荐的成人维生素 D₃ 补充量为 400-800IU/d，这也与从代谢清除研究中计算得出的每日替代剂量相对应。
