Walsh Jennifer S, Bowles Simon, Evans Amy L
Mellanby Centre for Bone Research, University of Sheffield, Sheffield, UK.
Curr Opin Endocrinol Diabetes Obes. 2017 Dec;24(6):389-394. doi: 10.1097/MED.0000000000000371.
Vitamin D is essential for bone health, and may also have important functions in immunity and other systems. Vitamin D deficiency is common, and testing and supplementation is increasing. Serum vitamin D is lower in obese people; it is important to understand the mechanism of this effect and whether it indicates clinically significant deficiency.
Vitamin D is fat soluble, and distributed into fat, muscle, liver, and serum. All of these compartments are increased in volume in obesity, so the lower vitamin D likely reflects a volumetric dilution effect and whole body stores of vitamin D may be adequate. Despite lower serum vitamin D, obese adults do not have higher bone turnover or lower bone mineral density. Patients undergoing bariatric surgery do have bone loss, and ensuring vitamin D sufficiency in these patients may help to attenuate bone loss.
Lower vitamin D in obese people is a consistent finding across age, ethnicity, and geography. This may not always reflect a clinical problem. Obese people need higher loading doses of vitamin D to achieve the same serum 25-hydroxyvitamin D as normal weight.
维生素D对骨骼健康至关重要，在免疫及其他系统中可能也具有重要功能。维生素D缺乏很常见，检测及补充情况日益增多。肥胖人群的血清维生素D水平较低；了解这种效应的机制以及它是否表明存在具有临床意义的缺乏很重要。
维生素D是脂溶性的，分布于脂肪、肌肉、肝脏和血清中。肥胖时所有这些腔室的容积都会增加，因此较低的维生素D水平可能反映了容积稀释效应，且维生素D的全身储备可能充足。尽管血清维生素D水平较低，但肥胖成年人并无更高的骨转换或更低的骨密度。接受减肥手术的患者确实会出现骨质流失，确保这些患者的维生素D充足可能有助于减轻骨质流失。
肥胖人群中维生素D水平较低是一个在年龄、种族和地域上都一致的发现。这不一定总是反映临床问题。肥胖人群需要更高剂量的维生素D负荷量才能达到与正常体重者相同的血清25-羟维生素D水平。
