This study investigates the relationship between vitamin D-binding protein and vitamin D status in black and white Americans. The researchers measured levels of total 25-hydroxyvitamin D, vitamin D-binding protein, and parathyroid hormone, as well as bone mineral density (BMD), in 2085 participants from the Healthy Aging in Neighborhoods of Diversity across the Life Span (HANDLS) cohort. They also genotyped participants for two common polymorphisms in the vitamin D-binding protein gene (rs7041 and rs4588). Key findings include: - Total 25-hydroxyvitamin D and vitamin D-binding protein levels were lower in blacks than in whites. - Genetic polymorphisms explained a significant portion of the variation in vitamin D-binding protein levels. - Blacks had higher BMD and calcium levels but slightly higher parathyroid hormone levels compared to whites. - Among homozygous participants, blacks and whites had similar levels of bioavailable 25-hydroxyvitamin D. - Genetic variants in the vitamin D-binding protein gene may explain the lower levels of total 25-hydroxyvitamin D in blacks, despite their higher BMD and calcium levels. The study suggests that low levels of total 25-hydroxyvitamin D do not uniformly indicate vitamin D deficiency, especially when vitamin D-binding protein levels are also low. The measurement of vitamin D-binding protein may be necessary to accurately assess vitamin D status in diverse populations.This study investigates the relationship between vitamin D-binding protein and vitamin D status in black and white Americans. The researchers measured levels of total 25-hydroxyvitamin D, vitamin D-binding protein, and parathyroid hormone, as well as bone mineral density (BMD), in 2085 participants from the Healthy Aging in Neighborhoods of Diversity across the Life Span (HANDLS) cohort. They also genotyped participants for two common polymorphisms in the vitamin D-binding protein gene (rs7041 and rs4588). Key findings include: - Total 25-hydroxyvitamin D and vitamin D-binding protein levels were lower in blacks than in whites. - Genetic polymorphisms explained a significant portion of the variation in vitamin D-binding protein levels. - Blacks had higher BMD and calcium levels but slightly higher parathyroid hormone levels compared to whites. - Among homozygous participants, blacks and whites had similar levels of bioavailable 25-hydroxyvitamin D. - Genetic variants in the vitamin D-binding protein gene may explain the lower levels of total 25-hydroxyvitamin D in blacks, despite their higher BMD and calcium levels. The study suggests that low levels of total 25-hydroxyvitamin D do not uniformly indicate vitamin D deficiency, especially when vitamin D-binding protein levels are also low. The measurement of vitamin D-binding protein may be necessary to accurately assess vitamin D status in diverse populations.