Association between serum 25-hydroxyvitamin D levels and body composition in postmenopausal women: the Postmenopausal Health Study

Objective: The present study examined the association between body composition measurements, using dual-energy x-ray absorptiometry and anthropometry, with serum 25-hydroxyvitamin D levels in nonosteoporotic, postmenopausal women. Methods: Serum 25-hydroxyvitamin D, intact parathyroid hormone, insulin-like growth factor I levels, dual-energy x-ray absorptiometry measurements of fat and fat-free mass, anthropometric and handgrip strength measurements, dietary intake estimations, ultraviolet B radiation exposure, and physical activity levels were collected from 112 nonosteoporotic, postmenopausal women (age, 60.3 +/- 5.0 y; body mass index, 29.5 +/- 4.8 kg/m(2)). Results: At a bivariate level, serum 25-hydroxyvitamin D levels were inversely associated with regional and total body fat mass (P < 0.05), whereas positive associations were observed with regional and total body fat-free mass (P < 0.05). After controlling for age, serum intact parathyroid hormone, insulin-like growth factor I levels, ultraviolet B radiation exposure, and physical activity levels, most of the associations observed at a bivariate level between serum 25-hydroxyvitamin D levels and body composition indices (as obtained by dual-energy x-ray absorptiometry) remained significant. No significant associations were observed between anthropometric indices of body mass and serum 25-hydroxyvitamin D levels. Conclusions: An independent inverse association between serum 25-hydroxyvitamin D levels and dual-energy x-ray absorptiometry measurements of total body and regional fat mass was observed in nonosteoporotic, overweight, postmenopausal women. Further clinical trials are required to come to safe conclusions on whether it is the fat mass that affects serum 25-hydroxyvitamin D levels or vice versa and whether there is a need to also take into account body composition when providing recommendations for vitamin D intake in postmenopausal women.