Vitamin D status in children and adolescents: A prospective cohort study

Background: The National Health and Nutritional Examination Survey III, 2009 reported that 48% of adolescents in the United States are vitamin D insufficient/deficient. Nutritional and environmental factors are implicated. The purpose of this study was to measure the prevalence of vitamin D insufficiency in orthopaedic patients and typical children and identify risk factors to aid in screening. Methods: This prospective study recruited 138 patients and 30 typical children ages 2 to <18 yr. Those with known problems with abnormal vitamin D metabolism or diminished ability to play outside were excluded. Height, weight, and serum 25-OH vitamin D levels were measured. Questionnaires assessed skin type, sunscreen use, diet, and physical activity. Results: Statistical analysis failed to detect any differences between patients and controls. Therefore, they were combined for statistical analysis (N=168). The mean age was 11.9 +/- 4.2 yr. The mean vitamin D level was 26.5 +/- 7.8 ng/mL, which was deficient (<20 ng/mL, n=33) or insufficient (>= 21 to <30 ng/mL, n=84) for 71% of participants. Children with sufficient vitamin D levels were younger than those with insufficient/deficient levels (P=0.02). Multivariate analysis showed that vitamin D levels were negatively affected in ethnic minority groups, those with higher body mass index, those with Medicaid or no insurance status, and those with outside playtime of less than 20 min/day (P=0.0006, P=0.001, P=0.0004, P=0.0005, respectively). Conclusions: Vitamin D insufficiency in 71% of our population is much greater than that being reported. The high rate of vitamin D insufficiency suggests that routine screening may be necessary to prevent long-term effects on bone growth and fragility. Characteristics of those at highest risk are ethnic minority, older age, obesity, time spent outdoors of less than 20 min per day, and no private health insurance.