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 D-3 [ 25(OH) D-3] 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) D-3 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) D-3 with adjustments for age, iPTH and lifestyle factors. Results: In univariate regression analyses, 25(OH) D-3 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) D-3 levels in women even after controlling for age, lifestyle and iPTH (beta = -0.247; P = 0.016), whereas the associations between BMI, hip circumference and 25(OH) D-3 lost statistical significance after adjusting for iPTH. In men, 25(OH) D-3 was not affected by anthropometric or body composition variables. Conclusions: The results indicate that 25(OH) D-3 levels are affected by TBF, especially in elderly women, independent of lifestyle factors and iPTH.