Whiting Susan J, Green Timothy J, Calvo Mona S
College of Pharmacy and Nutrition, University of Saskatchewan, 110 Science Place, Saskatoon, SK, Canada S7N 5C9.
J Steroid Biochem Mol Biol. 2007 Mar;103(3-5):626-30. doi: 10.1016/j.jsbmb.2006.12.067. Epub 2007 Jan 10.
Worldwide, vitamin D status is suboptimal relative to circulating levels of 25-hydroxyvitamin D (25OHD) needed to prevent a variety of chronic conditions, however, it has long been assumed that dietary intake is sufficient to meet needs when sun exposure is limited. In the USA, mean vitamin D intake from foods is close to 5 microg, the Dietary Reference Intake (DRI) recommendation for persons up to 50 years; however, the amount of vitamin D needed to maintain a sufficient 25OHD level during winter is >12.5 microg, and that needed for darkly pigmented, veiled, or sun protected persons is >50 microg. In the USA, most vitamin D intake from foods is provided by fortification. Canada and New Zealand have fewer fortified choices, and intakes are correspondingly lower. Supplement use can increase mean intake to >12.5 microg but does not always reach those who need it most. Serum 25OHD levels in New Zealand reveal much more insufficiency than expected, especially for Pacific people and Mäori; low serum 25OHD concentrations are seen throughout the Asia-Pacific region. Fortification and supplementation may be effective to achieve intakes of 12.5 microg vitamin D in some of the population, but for many achieving the amount needed in the absence of skin synthesis requires intakes above the current upper level for vitamin D of 50 microg.
在全球范围内,相对于预防多种慢性疾病所需的25-羟基维生素D(25OHD)循环水平而言,维生素D状况并不理想。然而,长期以来人们一直认为,在日照有限时,饮食摄入足以满足需求。在美国,食物中维生素D的平均摄入量接近5微克,这是50岁及以下人群的膳食参考摄入量(DRI)建议值;然而,冬季维持足够的25OHD水平所需的维生素D量超过12.5微克,而肤色较深、戴面纱或做好防晒措施的人群所需的维生素D量超过50微克。在美国,食物中大部分维生素D摄入量来自食品强化。加拿大和新西兰的强化食品选择较少,摄入量相应较低。使用补充剂可使平均摄入量增加至超过12.5微克,但并非总能惠及最需要的人群。新西兰的血清25OHD水平显示出比预期更多的不足,尤其是太平洋岛民和毛利人;在亚太地区普遍可见低血清25OHD浓度。强化和补充剂在某些人群中可能有效地实现12.5微克维生素D的摄入量,但对于许多人来说,在没有皮肤合成的情况下达到所需的量需要摄入量高于目前维生素D的每日最高摄入量50微克。