Elevated serum 25(OH)D concentrations, vitamin D, and calcium intakes are associated with reduced adipocyte size in women

Serum 25-hydroxyvitamin D3 and body composition in an elderly cohort from Germany: a cross-sectional study

Background

Emerging evidence indicates that there is an association between vitamin D and obesity. The aim of this study was to investigate whether the level of serum 25-hydroxyvitamin D₃ [25(OH)D₃] in the elderly is influenced by parameters of anthropometry and body composition independent of potential confounding lifestyle factors and the level of serum intact parathyroid hormone (iPTH).

Methods

Cross-sectional data of 131 independently living participants (90 women, 41 men; aged 66–96 years) of the longitudinal study on nutrition and health status in senior citizens of Giessen, Germany were analysed. Concentrations of 25(OH)D₃ and iPTH were ascertained by an electrochemiluminescence immunoassay. Body composition was measured by a bioelectrical impedance analysis. We performed univariate and multiple regression analyses to examine the influence of body composition on 25(OH)D₃ with adjustments for age, iPTH and lifestyle factors.

Results

In univariate regression analyses, 25(OH)D₃ was associated with body mass index (BMI), hip circumference and total body fat (TBF) in women, but not in men. Using multiple regression analyses, TBF was shown to be a negative predictor of 25(OH)D₃ levels in women even after controlling for age, lifestyle and iPTH (ß = −0.247; P = 0.016), whereas the associations between BMI, hip circumference and 25(OH)D₃ lost statistical significance after adjusting for iPTH. In men, 25(OH)D₃ was not affected by anthropometric or body composition variables.

Conclusions

The results indicate that 25(OH)D₃ levels are affected by TBF, especially in elderly women, independent of lifestyle factors and iPTH.

Genetic variants in vitamin D metabolism-related genes and body mass index: analysis of genome-wide scan data of approximately 7000 Chinese women

Vitamin D deficiency has been consistently associated with obesity. However, it is unclear whether vitamin D deficiency is the cause or consequence of obesity. We investigated this question by evaluating the association between genetic variants in vitamin D metabolism pathway genes and obesity-related traits. Using directly genotyped and imputed data from a genome-wide association study of 6922 women aged 25-70 years, we examined the association of 198 single-nucleotide polymorphisms (SNPs) in vitamin D pathway genes (CYP27A1, CYP27B1, CYP24A1, CYP2R1, group-specific component (GC) and vitamin D nuclear receptor (VDR)) with body mass index (BMI) and body weight. Per allele beta (β) estimates were calculated for this association using linear regression models, controlling for age, square of age, menopausal status and sample sets. Overall, only two SNPs (rs2248359 in CYP24A1 and rs10832313 in CYP2R1) had a nominally significant association with BMI and weight (P<0.05 for all), with no variation observed by menopausal status, physical activity or dietary energy intake. None of the SNPs examined in the VDR gene were associated with BMI or weight. Our findings suggest that common genetic variants in vitamin D pathway genes do not have a major role in obesity among Chinese women. This comprehensive evaluation of genetic polymorphisms in vitamin D metabolism-related genes and obesity-related traits did not provide strong evidence to support low vitamin D levels as a cause of obesity.