Vitamin D binding protein polymorphisms significantly impact vitamin D status in children

BACKGROUND: Polymorphic alleles of the vitamin D (vitD)-binding protein (VDBP) gene are associated with discriminatory differences in circulating concentrations of 25-hydroxyvitamin D (25-D), the indicator of vitD status (sufficiency defined by the Endocrine Society as >= 75 nmol/L). Within a diverse group of children, we hypothesized that reaching recommended daily allowance (RDA) of vitD intake would have differential impact on vitD status depending on VDBP variability. METHODS: VDBP alleles (Gc1S, Gc1F, Gc2) in 123 children (1-4 annual visits/child; ages 1-8 years) were compared for relationships with serum 25-D concentrations and daily vitD intake. RESULTS: In African-American children, reaching the vitD RDA was associated with significantly higher mean serum 25-D concentrations for the 20% carrying the VDBP 1S allele than for the large majority without this allele (77 vs. 61 nmol/L 25-D; p = 0.038). Children with the Gc1S/1S homozygous genotype (30% Caucasians, 24% Hispanics, 2% African-Americans) who met RDA had 51% (39 nmol/L) greater mean serum 25-D than those below RDA (p < 0.0001). CONCLUSIONS: VDBP genetic variability was a significant factor affecting childhood vitD status when following RDA guidelines. This study may inform public health policy of uniformity in recommended childhood vitD dosage, especially regarding racially/ ethnically associated disparities.