1.天津市住院医师规范化培训基地学员的教学工作。

2.发表文章

3.科研动态

Effects of vitamin D supplements on bone mineral density:a systematic review and meta-analysis

Ian R Reid, Mark J Bolland, Andrew Grey，

Summary

Background

Findings from recent meta-analyses of vitamin D supplementation without co-administration of calcium have not shown fracture prevention, possibly because of insuffcient power or inappropriate doses, or because the intervention was not targeted to deficient populations. Despite these data, almost half of older adults (older than 50 years) continue to use these supplements. Bone mineral density can be used to detect biologically significant effects in much smaller cohorts. We investigated whether vitamin D supplementation affects bone mineral density.

Methods

 We searched Web of Science, Embase, and the Cochrane Database, from inception to July 8, 2012, for trials assessing the effects of vitamin D (D3 or D2, but not vitamin D metabolites) on bone mineral density. We included all randomised trials comparing interventions that differed only in vitamin D content, and which included adults (average age >20 years) without other metabolic bone diseases. We pooled data with a random eff ects meta-analysis with weighted mean differences and 95%  CIs reported. To assess heterogeneity in results of individual studies, we used Cochran’s Q statistic and the I2 statistic. The primary endpoint was the percentage change in bone mineral  density from baseline.

Findings

 Of 3930 citations identified by the search strategy, 23 studies (mean duration 23·5 months, comprising 4082 participants, 92% women, average age 59 years) met the inclusion criteria. 19 studies had mainly white populations. Mean baseline serum 25-hydroxy  vitamin D concentration was less than 50 nmol/L  in eight studies (n=1791). In ten studies (n=2294), individuals were given vitamin D doses less than 800 IU per day. Bone mineral density was measured at one to fi ve sites (lumbar spine, femoral neck, total hip, trochanter, total body, or forearm) in each study, so 70 tests of statistical significance were done across the studies. There were six findings of significant benefit, two of significant detriment, and the rest were non-significant. Only one study showed benefi t at more than one site. Results of our meta-analysis showed a small benefi tat the femoral neck (weighted mean difference 0·8%, 95% CI 0·2–1·4) with heterogeneity among trials (I2=67%, p<0·00027). No eff ect at any other site was reported,including the total hip. We recorded a bias toward positive results at the femoral neck and total hip.

In Healthy Adults, Biological Activity of Vitamin D as Assessed by Serum PTH, Is Largely Independent of DBP Concentrations

ABSTRACT

Vitamin D insufficiency, as measured by 25‐hydroxy vitamin  D (25[OH]D) levels, has been associated with important health outcomes.The majority of vitamin D in circulation is bound to vitamin D–binding protein (DBP) and albumin, and recent genetic studies have demonstrated that serum DBP is a major determinant of 25(OH)D concentrations in adults. The impact of circulating DBP levels on vitamin D’s biologic action, is unclear, but is of particular relevance to vitamin D epidemiology, because a lack of control for DBP levels could strongly influence the association of vitamin D with disease. Serum parathyroid hormone (PTH) levels can act as a biological readout of 25(OH)D activity. We therefore assessed the relationship between serum total and free 25(OH)D and PTH with and without adjusting for DBP, in 2073 subjects of European descent. Total 25(OH)D levels correlated positively with DBP, whereas the free 25(OH)D correlated negatively . Total and free 25(OH)D levels correlated negatively with PTH . Including age, body mass index (BMI), sex, estimated glomerular filtration rate, calcium, and season of blood draw as covariates, total 25(OH)D levels were significantly associated with logtransformed  PTH (lnPTH) levels and this association was not changed by adjusting for DBP. These findings provide evidence that in a largely vitamin D–sufficient cohort, the biological effect of vitamin D on PTH levels is mainly independent of DBP concentration. Accordingly, this study may provide useful information for studies investigating the relationship between vitamin D, DBP, and disease.