A Randomized Clinical Trial of Vitamin D Supplementation in Healthy Adolescents

Purpose: The most safe and effective dose of vitamin D supplementation for healthy adolescents is currently unknown. The aim of this study was to compare the efficacy of 200 IU versus 1,000 IU of daily vitamin D-3 for supplementation in healthy adolescents with baseline vitamin D sufficiency. Methods: We conducted a double-blind, randomized clinical trial. Fifty-six subjects, ages 11-19 years, with baseline vitamin D sufficiency received 1,000 IU or 200 IU of daily vitamin D-3 for 11 weeks. Compliance was assessed using MEMS6 Trackcaps and pill counts. Results: Fifty-three subjects completed the clinical trial. Subjects in the two treatment arms were similar in terms of age, race, gender, body mass index, and dietary calcium and vitamin D intake. Serum 25(OH)D level in the 200 IU treatment arm was 28.1 +/- 6.2 ng/mL at baseline (mean +/- SD) and 28.9 +/- 7.0 ng/mL at follow-up. In the 1,000 IU treatment arm, 25(OH)D levels were 29.0 +/- 7.3 and 30.1 +/- 6.6 at baseline and follow-up, respectively. Mean change in 25(OH)D level did not differ significantly between treatment arms (p = .87), nor did mean change in parathyroid hormone, calcium, phosphate, bone turnover markers, fasting glucose, or fasting insulin. Conclusions: In healthy adolescents with baseline vitamin D sufficiency, supplementation with vitamin D3 doses of 200 and 1,000 IU for 11 weeks did not increase serum 25(OH)D levels, with no significant difference observed between treatment arms. (C) 2013 Society for Adolescent Health and Medicine. All rights reserved.