Simon J, Leboff M, Wright J, Glowacki J
Orthopedic Research, Brigham and Women's Hospital, Boston, MA 02115, USA.
J Nutr Health Aging. 2002;6(6):406-12.
Aging is associated with increased fracture risk. Among the many contributing factors, reduced bone mineral density is highly correlated with this risk. Nutritional factors, i.e. protein, calcium, and vitamin D intake, are essential for maintenance of the skeleton throughout the lifespan and are often compromised in the elderly. Vitamin D is also derived from conversion of precursors in the skin that is stimulated by sunlight. Decreased mobility and avoidance of the sun contribute to vitamin D deficiency in the elderly. The skeletal effects of vitamin D are two-fold: it ensures mineralization of the organic matrix of bone and it mediates mobilization of stored calcium and phosphate from bone to blood to achieve mineral homeostasis. Inadequate levels of vitamin D produce a secondary increase in release of parathyroid hormone that stimulates bone resorption and can result in osteoporosis. If coupled with insufficient intake of calcium, vitamin D deficiency results in osteomalacia. With aging, there is reduced absorption of the vitamin from the diet, reduced conversion to its active metabolites, and resistance to its action in the intestine and in bone. Correction of vitamin D deficiency is an inexpensive task and may require education of clinicians as well as the public. In sum, vitamin D deficiency is prevalent in the elderly and, to correct the adverse skeletal effects, it should be diagnosed, treated, and prevented.
衰老与骨折风险增加相关。在众多促成因素中，骨矿物质密度降低与这种风险高度相关。营养因素，即蛋白质、钙和维生素D的摄入，对于维持整个生命周期的骨骼至关重要，而在老年人中这些因素往往不足。维生素D也来源于皮肤中前体物质的转化，这种转化受阳光刺激。活动减少和避免日晒导致老年人维生素D缺乏。维生素D对骨骼的作用有两方面：它确保骨有机基质的矿化，并介导储存的钙和磷从骨骼向血液的转运以实现矿物质稳态。维生素D水平不足会导致甲状旁腺激素释放继发性增加，刺激骨吸收，并可能导致骨质疏松症。如果再加上钙摄入不足，维生素D缺乏会导致骨软化症。随着年龄增长，从饮食中吸收维生素的能力下降，转化为其活性代谢产物的能力降低，并且在肠道和骨骼中对其作用产生抵抗。纠正维生素D缺乏是一项成本低廉的工作，可能需要对临床医生以及公众进行教育。总之，维生素D缺乏在老年人中普遍存在，为纠正对骨骼的不良影响，应进行诊断、治疗和预防。
