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

Abstract

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.