Vitamin D Deficiency in Relation to the Risk of Metabolic Syndrome in Middle-Aged and Elderly Patients with Type 2 Diabetes Mellitus.

Vitamin D deficiency is highly prevalent all over the world and dietary intakes of vitamin D are very low in China. In this study we aimed to determine whether vitamin D deficiency is associated with increased risk of metabolic syndrome (MetS) among Chinese type 2 diabetes mellitus (T2DM) patients aged over 50 y. Serum 25-hydroxyvitamin D [25(OH)D] concentrations were measured in a cross-sectional sample of 270 T2DM patients aged over 50 y from Zhejiang. Data on demographic characteristics, anthropometry and other variables were collected. The mean of serum 25(OH)D was 22.93 ng/mL, and percentages of vitamin D deficiency and insufficiency were 43.71% and 39.63%, respectively. Serum 25(OH)D concentrations were significantly lower in subjects with MetS than in those without MetS (21.74 vs 24.96 ng/mL, p=0.001), and the prevalence of MetS significantly increased according to tertiles of serum 25(OH)D concentrations. After adjusting for multivariate factors, the adverse effect of lower serum 25(OH)D concentrations was significant (OR: 3.26, 95% CI: 1.03-7.34; p=0.044) in the group with BMI≥24 kg/m2 while the change in OR of MetS for each 10 ng/mL decrease in the serum 25(OH)D concentrations was 2.03 (95% CI: 1.10-3.79). These results suggest that serum 25(OH)D deficiency may be a risk factor of MetS among Chinese type 2 diabetic patients, especially in the T2DM with BMI≥24 kg/m2. The challenge is determining the mechanisms of vitamin D action for recommendation of vitamin D supplementation that reduces the risks of MetS and progression to T2DM.

Vitamin D Deficiency Increases the Risk of Gestational Diabetes Mellitus: A Meta-Analysis of Observational Studies.

The results investigating the relationship between vitamin D levels and gestational diabetes mellitus (GDM) are inconsistent. Thus, we focused on evaluating the association of vitamin D deficiency with GDM by conducting a meta-analysis of observed studies. A systematic literature search was conducted via PubMed, MEDLINE, and Cochrane library to identify eligible studies before August 2015. The meta-analysis of 20 studies including 9209 participants showed that women with vitamin D deficiency experienced a significantly increased risk for developing GDM (odds ratio (OR) = 1.53; 95% confidence intervals (CI), 1.33, 1.75) with a little heterogeneity (I² = 16.20%, p = 0.252). A noteworthy decrease of 4.93 nmol/L (95% CI, -6.73, -3.14) in serum 25(OH)D was demonstrated in the participants with GDM, and moderate heterogeneity was observed (I² = 61.40%, p = 0.001). Subgroup analysis with study design showed that there were obvious heterogeneities in nested case-control studies (I² > 52.5%, p < 0.07). Sensitivity analysis showed that exclusion of any single study did not materially alter the overall combined effect. In summary, the evidence from this meta-analysis indicates a consistent association between vitamin D deficiency and an increased risk of GDM. However, well-designed randomized controlled trials are needed to elicit the clear effect of vitamin D supplementation on prevention of GDM.