DHCR7 and vitamin D deficiency: Although the two SNPs in DHCR7/NADSYN1 were not associated with 25OHD in Model 2 in the linear regression analysis, rs12800438 was significantly associated with vitamin D deficiency (P = 0.04, OR = 0.76, 95 % C.I.; 0.58–0.99) in AAs.