The role of vitamin D receptor gene polymorphisms in the bone mineral density of Greek postmenopausal women with low calcium intake

The aim of this study was to investigate the effect of common vitamin D receptor (VDR) gene polymorphisms on the bone mineral density (BMD) of Greek postmenopausal women. Healthy postmenopausal women (n=578) were recruited for the study. The BMD of the lumbar spine and hip was measured using dual-energy X-ray absorptiometry with the Lunar DPX-MD device. Assessment of dietary calcium intake was performed with multiple 24-h recalls. Genotyping was performed for the BsmI, TaqI and Cdx-2 polymorphisms of the VDR gene. The selected polymorphisms were not associated with BMD, osteoporosis or osteoporotic fractures. Stratification by calcium intake revealed that in the low calcium intake group (<680 mg/day), all polymorphisms were associated with the BMD of the lumbar spine (P<.05). After adjustment for potential covariates, BsmI and TaqI polymorphisms were associated with the presence of osteoporosis (P<.05), while the presence of the minor A allele of Cdx-2 polymorphism was associated with a lower spine BMD (P=.025). In the higher calcium intake group (>680 mg/day), no significant differences were observed within the genotypes for all polymorphisms. The VDR gene is shown to affect BMD in women with low calcium intake, while its effect is masked in women with higher calcium intake. This result underlines the significance of adequate calcium intake in postmenopausal women, given that it exerts a positive effect on BMD even in the presence of negative genetic predisposition.