Vieth Reinhold
Department of Nutritional Sciences, Laboratory Medicine and Pathology, University of Toronto, Ontario, Canada.
Ann Med. 2005;37(4):278-85. doi: 10.1080/07853890510007313.
The need for vitamin D to prevent rickets was the drive for selection of lighter skin color in temperate climates. Anthropologists also know that as human populations developed more sedentary lifestyles, this coincided with a decline in bone quantity, quality, and fracture resistance. Since osteoporosis occurs after the reproductive years, there is no way that natural selection could have adapted our biology to prevent it. However, osteoporosis can be largely prevented by optimizing physical activity, and the vitamin D-related factors of environment, and nutrition. The role of vitamin D3 in osteoporosis is conclusively established from a very simple meta-analysis of the four randomized, placebo-controlled clinical trials into the effect of 20 microg (800 IU) per day. These have all demonstrated that this dose prevents approximately 30% of hip or non-vertebral fractures compared to placebo, in adults older than 65 years. Intakes less than this have never been found effective. The lowest average serum 25-hydroxyvitamin D concentration in any study demonstrating fracture reduction was 74 nmol/L. Thus, 25-hydroxyvitamin D levels in older adults should exceed this amount. The role of vitamin D supplementation is to provide humans with the nutrient in an amount closer to our species' biological norm. This amount of vitamin D results in the optimal function of many aspects of health, including balance and muscle strength that lessen the risk of fracture beyond what is possible via the quality and quantity of bone itself.
在温带气候地区，对维生素D预防佝偻病的需求促使人们选择更浅的肤色。人类学家也知道，随着人类群体发展出更久坐的生活方式，这与骨量、骨质量以及抗骨折能力的下降同时发生。由于骨质疏松症在生育年龄之后出现，自然选择无法使我们的生物学特性适应以预防它。然而，通过优化体育活动以及与维生素D相关的环境和营养因素，骨质疏松症在很大程度上是可以预防的。从对四项关于每日20微克（800国际单位）效果的随机、安慰剂对照临床试验进行的非常简单的荟萃分析中，可以确凿地证实维生素D3在骨质疏松症中的作用。这些试验均表明，与安慰剂相比，该剂量可预防65岁以上成年人约30%的髋部或非椎骨骨折。从未发现低于此剂量有效。在任何显示骨折减少的研究中，平均血清25-羟基维生素D浓度的最低值为74纳摩尔/升。因此，老年人的25-羟基维生素D水平应超过这个量。补充维生素D的作用是为人类提供更接近我们物种生物学标准量的营养素。这个量的维生素D能使健康的许多方面达到最佳功能，包括平衡和肌肉力量，从而降低骨折风险，其降低幅度超过仅通过骨骼本身的质量和数量所能达到的程度。
