Vitamin D receptor alleles do not predict bone mineral density or bone loss in Danish perimenopausal women

A BsmI restriction enzyme polymorphism in the vitamin D receptor (VDR) gene has been reported to be associated with bone mineral density (BMD) and bone turnover. However, findings in other studies suggest the presence of considerable interaction by race, body size, and environmental factors. Therefore, we VDR BsmI genotyped 200 healthy perimenopausal Danish white women (mean age 50.8 years, mean calcium intake 900 mg/day) in a comprehensive, longitudinal, community-based population study. Bone loss was assessed by dual-energy X-ray absorptiometry (DXA) using cross-calibrated Hologic QDR-1000 W and QDR-2000 densitometers, with a mean follow-up period of 4 years (range 1-5 years). Despite a distribution of genotypes similar to that of other white populations (28% bb, 49% Bb, 23% BB), VDR genotypes were not associated with lumbar or femoral baseline BMD, subsequent bone loss rates, or biochemical markers of bone metabolism (bone-specific alkaline phosphatase, urinary hydroxyproline, and serum osteocalcin). Controlling for body size, calcium intake, and serum levels of 25-hydroxyvitamin D₃ [25(OH)D₃] did not alter this finding. The possible existence of a threshold effect was subsequently investigated by restricting analysis to women with low serum 25(OH)D₃ levels or low calcium intake, VDR BsmI genotypes showed no significant impact on bone density or bone loss in healthy Danish early postmenopausal women, even when allowance was made for calcium intake, serum 25(OH)D₃, and body size.