Vitamin D–Binding Protein Levels Are Lower in Blacks Than in Whites

Compared with whites, blacks have lower 25-hydroxyvitamin D levels but higher bone- mineral density and lower risk for fragility fractures. How can we explain this apparent paradox? A new study of about 2000 middle-aged adults in Baltimore suggests that the answer might lie in vitamin D–binding protein. Black and white participants (about 1000 each) were closely matched for age, sex, and body-mass index.

Mean total 25-hydroxyvitamin D levels were substantially lower in blacks than in whites (16 vs. 26 ng/mL). However, the mean level of vitamin D–binding protein in blacks was half that in whites, resulting in similar levels of bioavailable, or free, 25-hydroxyvitamin D in blacks and whites. Polymorphisms in the vitamin D–binding protein gene …