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 25O\HD level, less than or equal to15 ng/mL [less than or equal to37.5 nmol/L]), of whom 14 (4.6%) were severely vitamin D deficient (25OHD level, less than or equal to8 ng/mL [less than or equal to20 nmol/L]). By using a broader definition (25OHD level, less than or equal to20 ng/mL [less than or equal to50 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.