Vitamin D Status and Bone Health in Postmenopausal Women Working in Greenhouses

OBJECTIVES: Greenhouse workers synthesize less vitamin D because ultraviolet light is blocked by the vinyl that covers the greenhouses. This study aimed to investigate the vitamin D status and bone health of postmenopausal women working in greenhouses. METHODS: This observational study enrolled women living in urban (n = 70, group 1) and rural areas (n = 91, group 2) and those working in greenhouses (n = 112, group 3). Serum levels of total and bioavailable 25-hydroxy-vitamin D [25(OH)D] and vitamin D binding protein were measured. T-scores of the lumbar spine and femur neck were measured by dual-energy X-ray absorptionetry. RESULTS: Heights were shorter in group 2 and group 3 than in group 1. Bioavailable 25(OH)D levels were higher and T-scores of the spine and femur were lower in both group 2 and 3 than in group 1. T-scores of the femur in group 3 were lower than those in group 2. The linear regression analysis showed that levels of bioavailable 25(OH)D significantly correlated with the spine T-scores but not with the femur T-scores. The prevalence of spinal osteoporosis was higher in both groups 2 and 3 compared to group 1. Group 3 demonstrated greater femur osteoporosis compared to groups 1 and 2. CONCLUSIONS: Vitamin D plays an important role in spinal bone health. Moreover, working conditions are likely to play an important role in femur bone health. Therefore, appropriate working conditions and nutrition are paramount to improve bone health in postmenopausal women working in greenhouses.