Purpose: The purpose of this study was to estimate the incidence of low serum 25-hydroxyvitamin D [25(OH)D] levels in adolescent girls and across racial groups and seasons.
Methods: Healthy postmenarcheal girls (12-18 years of age) were recruited for the study. Serum samples were assayed for 25(OH)D with a competitive protein binding assay (CPB) (Nichols Institute, San Clemente, California).
Results: The study included 370 girls (mean age, 15.5 +/- 1.6 y), with a mean serum 25(OH)D level of 53.7(29.0) nmol/L. Seventeen percent of the girls were found to be vitamin D deficient (serum 25(OH)D <or= 27.5 nmol/L) and 54% were vitamin D insufficient (serum 25(OH)D <or= 50 nmol/L) using the CPB assay. There was a significant difference in mean serum 25(OH)D levels between the African-American girls (43.0 nmol/L) and non-African-American girls (72.2 nmol/L) (p < .0001). Mean vitamin D levels were higher in the spring/summer months (60.2 nmol/L) compared with those obtained during the fall/winter months (52.8 nmol/L) (p < .01), and weight was correlated negatively with vitamin D levels (r = -.19) (p = .0002).
Conclusions: For adolescent girls living in the northeastern United States, especially African-American girls, low 25(OH)D levels are a noteworthy concern because bone acquisition is crucial during this period of development.