Osteoporos Int 20, 239–244.Īhn J, Yu K, Stolzenberg-Solomon R, Simon KC, McCullough ML, Gallicchio L et al.
Vitamin D status and response to treatment in post-menopausal osteoporosis. Genetic variation may have an effect on vitamin D blood levels and response to treatment with vitamin D.Īdami S, Giannini S, Bianchi G, Sinigaglia L, Di Munno O, Fiore CE et al. Vitamin D levels are maintained better in the presence of adequate calcium intakes, more exercise and less obesity. Adequate vitamin D may also allow for a normal innate immune response to pathogens, improve cardiovascular function and mortality and increase insulin responsiveness. There are vitamin D receptors in most nucleated cells and some evidence, although not consistent, that adequate vitamin D levels may be important in reducing the incidence of, or mortality from, some cancers and in reducing autoimmune disease.
On the basis of calcium control and musculoskeletal function, target levels for 25OHD in blood are at least 50–60 nmol/l and there may be a case for higher targets of 75–80 nmol/l. Vitamin D compounds appear to have direct effects to improve bone and muscle function, and there is good, although not entirely consistent, evidence that supplemental vitamin D and calcium together reduce falls and fractures in older individuals. This assists in building bone at younger ages and ensures that despite obligatory urinary losses, bone does not need to be resorbed to maintain blood calcium concentrations. The major function of vitamin D compounds is to enhance active absorption of ingested calcium (and phosphate). It is further metabolized to 25-hydroxyvitamin D (25OHD), the major circulating vitamin D compound, and then to 1,25-dihydroxyvitamin D, the hormonal form. Under normal circumstances, vitamin D is mainly obtained from skin through the action of ultraviolet B irradiation on 7-dehydrocholesterol.
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