Vitamin D receptor polymorphisms predict greater decrease in calcium absorption (373.1)

Abstract

Genetic variation may account for more than 70% of the variance in Ca absorption, and several studies suggest that vitamin D receptor (VDR) gene polymorphisms influence absorption. Estrogen is also known to affect Ca absorption, yet only one study has examined the influence of estrogen‐α (ESR1) gene polymorphisms. Ca absorption is attenuated during caloric restriction (CR) and is increased by vitamin D supplementation (VitD). We therefore studied whether the ESR1 and VDR polymorphisms influence the Ca absorption response 6 weeks after either CR or VitD supplementation. True fractional calcium absorption (TFCA) was measured in 180 pre‐ and post‐menopausal women. Genotypes for the VDR (BsmI, ApaI, TaqI, and FokI) and the ESR1 (XbaI, PvuII) polymorphisms were determined through PCR‐RFLP analysis and the haplotypes were reconstructed using PHASE v2.1.1. Multiple linear regression and two‐way ANOVA analyses using dietary interventions and the dominant/recessive models as predictors showed that in the absence and presence of a dietary intervention, the BB genotype and the 2 copies of BAt allele predicted a greater decrease in TFCA. We found no association with the ESR1 polymorphisms. Our findings suggest that the VDR polymorphism improves the ability to predict Ca absorption under a variety of conditions and may influence dietary Ca requirements.Grant Funding Source: NIH‐AG12161