The Effect of Genistein Supplementation on Vitamin D Levels and Bone Turnover Markers during the Summer in Healthy Postmenopausal Women: Role of Genotypes of Isoflavone Metabolism

Aims: The objective of this study was to determine whether vitamin D and genistein supplementation had an additive beneficial effect on levels of vitamin D and bone markers and whether this effect was mediated by genes regulating isoflavone metabolism. Materials and Methods: We carried out a prospective study in postmenopausal women randomized to calcium and vitamin D supplementation or calcium, vitamin D, and genistein supplementation. Vitamin D, parathyroid hormone (PTH), cross-linked C-telopeptide (CTX), and procollagen 1 N-terminal (P1NP) were determined by electrochemiluminescence. Three SNPs - rs2231142 (ABCG2), rs358231 (cytosolic β-glucosidase [CBG]), and rs2273697 (ABCC2) - were determined. Results: We included 102 women. The effects on bone remodeling were similar: rises in vitamin D were significantly associated with reductions in PTH, CTX, and P1NP. Pharmacogenomic analysis of the genotypes showed that, in AT heterozygotes of the CBG1368T>A polymorphism, CTX and P1NP were not reduced. Conclusion: Genistein added to calcium and vitamin D supplementation had no additional effect. The supplementation of individual AT heterozygotes of the CBG1368T>A polymorphism had no effect on markers of bone remodeling.