Vitamin D status is associated with total and regional fat mass in lactating adolescents

The aim of the present study was to investigate the association of serum concentrations of vitamin D (25OHD) and PTH with body composition in 28 lactating adolescents (15‐18y). Total bone mineral content (BMC), total lean mass, and total and regional (trunk, arms and legs) fat mass were assessed by DXA. Serum 25OHD and iPTH were determined by radioimmunoassay and chemiluminescent assay, respectively. Concentrations of 25OHD varied in a range (49‐75.5 nmol/L) below the proposed cutoff for adequacy (80 nmol/L). Serum 25OHD correlated negatively with serum iPTH (r=‐0.57, P <0.01) and positively with BMC (r=0.56, P <0.01) and total lean mass (r=0.56, P <0.01). In contrast to observations in other physiologic states, serum 25OHD was also positively associated with total body weight (r=0.61, P <0.001) and with fat mass in total body (r=0.57, P <0.05), trunk (r=0.55, P <0.01), arms (r=0.49, P <0.05) and legs (r=0.51, P <0.01). Serum iPTH was not associated with body composition measurements. Our results suggest that the influence of fat mass on vitamin D status may vary according to physiologic state. The mobilization of fat stores characteristic of lactation may contribute to increase circulating 25OHD levels, although this needs further investigation. Financial support: CNPq and FAPERJ (Brazil)