Previous Data: Studies by the investigators' lab and others have identified significant racial/ethnic differences in the frequency of variants in genes responsible for vitamin D metabolism (i.e., CYP2R1, CYP27B1 and CYP24A1). In collaboration with the Pike Laboratory (University of Wisconsin), the investigators' laboratory has identified several novel genetic variants in recently identified regulatory regions of the gene which encodes for the major vitamin D catabolic enzyme (CYP24A1).