Implications of a New Definition of Vitamin D Deficiency in a Multiracial US Adolescent Population: The National Health and Nutrition Examination Survey III

OBJECTIVE: In children, vitamin D deficiency can interfere with bone mineralization, leading to rickets. In adults, it is linked to cardiovascular disease, insulin resistance, and hypertension. Accurate estimates of the prevalence of vitamin D deficiency are complicated by the lack of consensus as to optimal vitamin D status. Currently, individuals with serum 25-hydroxyvitamin D levels of <11 ng/mL are classified as vitamin D deficient. Experts collectively have proposed that minimum levels be at least 20 ng/mL. Our objectives were to (1) determine the national prevalence of vitamin D deficiency in adolescents by using both the current and recommended cutoffs and (2) examine the implications of the new recommendation after adjustment for various factors. METHODS: Data were obtained from National Health and Nutrition Examination Survey III, a cross-sectional survey administered to a nationally representative sample of noninstitutionalized civilians aged 2 months and older. Analyses were restricted to 2955 participants aged 12 to 19 with serum 25-hydroxyvitamin D levels. Relationships between serum 25-hydroxyvitamin D levels and sociodemographic variables were evaluated by using logistic regression. RESULTS: Changing the definition of vitamin D deficiency from <11 to <20 ng/mL increased the prevalence from 2% to 14%. After adjustment for all covariates, non-Hispanic black adolescents had 20 times the risk of serum 25-hydroxyvitamin D <20 ng/mL compared with non-Hispanic white adolescents. The risk of deficiency was more than double for females compared with males. An inverse relationship between weight and serum 25-hydroxyvitamin D levels was found. Overweight adolescents had increased risk of deficiency compared with normal-weight adolescents. CONCLUSIONS: There was a disproportionate burden of vitamin D deficiency in the non-Hispanic black adolescent population. Routine supplementation and monitoring of serum levels should be considered. Females and overweight adolescents are at increased risk. The consequences of chronic vitamin D deficiency in adolescents should be prospectively investigated.