Does vitamin D receptor gene polymorphism affect bone mineral density and calcium absorption?

Decreased intestinal calcium absorption is considered one of the pathogenetic mechanisms of postmenopausal and age-dependent bone loss. Because vitamin D is the major regulator of intestinal calcium absorption, allelic polymorphism of the gene encoding the vitamin D receptor (VDR) has been proposed as a genetic component of osteoporosis. However, the plethora of studies attempting to link VDR polymorphism to bone mineral density have thus far generated very controversial and conflicting results. Although no definitive conclusion can be reached as yet on the role of VDR polymorphism on the postmenopausal bone loss, more consistent findings indicate that VDR allelic variants may discriminate subjects with low bone density among young populations of both genders. In elderly subjects, this distinction is lost, although VDR gene polymorphism may condition the response to calcium and/or vitamin D intake. On the other hand, intestinal calcium absorption is inconsistently associated with VDR allelic variants, and these differences are heavily dependent on calcium intake. These and other controversial issues must be resolved before VDR can be considered a reliable genetic marker for low bone density.