Prevalence of vitamin D deficiency among healthy adolescents.

BACKGROUND: Although vitamin D deficiency has been documented as a frequent problem in studies of young adults, elderly persons, and children in other countries, there are limited data on the prevalence of this nutritional deficiency among healthy US teenagers.
OBJECTIVE: To determine the prevalence of vitamin D deficiency in healthy adolescents presenting for primary care.
DESIGN: A cross-sectional clinic-based sample.
SETTING: An urban hospital in Boston. PARTICIPANTS: Three hundred seven adolescents recruited at an annual physical examination to undergo a blood test and nutritional and activity assessments. MAIN OUTCOME MEASURES: Serum levels of 25-hydroxyvitamin D (25OHD) and parathyroid hormone, anthropometric data, nutritional intake, and weekly physical activity and lifestyle variables that were potential risk factors for hypovitaminosis D.
RESULTS: Seventy-four patients (24.1%) were vitamin D deficient (serum 25OHD level, </=15 ng/mL [</=37.5 nmol/L]), of whom 14 (4.6%) were severely vitamin D deficient (25OHD level, </=8 ng/mL [</=20 nmol/L]). By using a broader definition (25OHD level, </=20 ng/mL [</=50 nmol/L]), 129 patients (42.0%) were vitamin D insufficient. Serum 25OHD levels were inversely correlated with parathyroid hormone levels (r = -0.29), and were 24% lower during winter compared with summer. In a final multivariate model, season, ethnicity, milk and juice consumption, body mass index, and physical activity were significant independent predictors of hypovitaminosis D.
CONCLUSIONS: Vitamin D deficiency was present in many US adolescents in this urban clinic-based sample. The prevalence was highest in African American teenagers and during winter, although the problem seems to be common across sex, season, and ethnicity.