RELATIONS BETWEEN CALCIUM INTAKE, CALCITRIOL, POLYMORPHISMS OF THE VITAMIN-D-RECEPTOR GENE, AND CALCIUM-ABSORPTION IN PREMENOPAUSAL WOMEN

The relations between calcium absorption, dietary calcium intake, 1,25 -dihydroxyvitamin D-3 (calcitriol), and vitamin D receptor (VDR) gene polymorphisms were evaluated in 99 healthy women who were approaching menopause (mean age: 47 y, range: 43-53 y). Dietary calcium was assess ed by food-frequency questionnaire and calcium absorption was measured by a single-isotope radiocalcium test. VDR alleles were classified ac cording to the presence (b, t, a) or absence (B, T, A) of the BsmI, Ta qI, and ApaI restriction enzyme cutting sites. Radiocalcium absorption was positively related to serum calcitriol (r = 0.23, P < 0.05) and i nversely related to dietary calcium intake (r = -0.26, P < 0.01). Ther e was, however, no significant relation (r = 0.10) between serum calci triol concentrations and dietary calcium. Radiocalcium absorption was higher in the bbaaTT haplotype (P < 0.05) and the aa genotype (P < 0.0 5), polymorphisms said to be associated with a higher bone density. We conclude that serum calcitriol and dietary calcium are independent de terminants of calcium absorption in premenopausal women and that VDR g ene polymorphisms influence calcium absorption.