Dietary calcium intake and serum vitamin D are major determinants of bone mass variations in women. A longitudinal study

BACKGROUND AND AIMS: Bone mineral density (BMD) is one of the main determinants in the pathogenesis of fractures. However, data on factors predicting longitudinal variations in BMD are still limited and incomplete. Such data would be of great importance in order to better focus prevention strategies in both the clinical setting and at the population level. The aim of the study was to investigate the predictive value of both serological and questionnaire variables for bone mass variations in healthy women participating in a population-based longitudinal study carried out in Napoli, Italy. METHODS: High completion rate (85.2%) and adequate sample size were obtained: 139 women (45 to 79 years of age) were examined at study entry and then again after two years (24 +/- 2 months) following the same protocol. They underwent medical examination, questionnaire, anthropometric measurements, blood sampling and urine collection. BMD was measured by dual energy X-ray absorptiometry (DEXA) at the lumbar spine (L1-L4) and femoral neck. Data analysis included calculation of the percent variation in BMD in the 2-year period. Longitudinal data underwent stepwise analysis for a global evaluation of mutual interactions between independent variables. RESULTS AND CONCLUSIONS: Our findings indicate that dietary and serum calcium, and serum 25(OH)vitamin D are the only independent determinants of BMD variations at the lumbar and femoral level, respectively. While the pharmacological significance of calcium and vitamin D in the therapy of established osteoporosis is still controversial, the present longitudinal data evidence their role as essential nutrients in determining the natural history of BMD variations.