A randomized clinical trial of vitamin D supplementation in healthy adolescents

Abstract

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 D3 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 D3 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.

Trial registration: ClinicalTrials.gov NCT01126671.

Conflict of interest statement

Disclosures: The authors have no conflicts of interest to disclose.

Copyright © 2013 Society for Adolescent Health and Medicine. Published by Elsevier Inc. All rights reserved.

Figures

Figure 1

Serum 25(OH) vitamin D in the 200 IU treatment arm (left) and 1000 IU treatment arm (right). Each subject’s 25(OH)D levels are represented by a grey line connecting baseline (BL) with follow-up (FU). Box plots illustrate the distribution of baseline and follow-up levels (upper panel) and within-subject changes from baseline to follow-up (lower panel). Top and bottom of the box indicate quartile boundaries (25th and 75th percentiles); center belt indicates median; cross (+) indicates mean. Individual points (●) indicate outliers, falling outside the box by at least 1.5 times its height. Vertical lines extend to position of farthest non-outlier above and below the box. P-value in the lower panel tests the hypothesis that the distribution of changes is equal in the two treatment arms.

Figure 2

Markers of bone metabolism in the 200 IU treatment arm and 1000 IU treatment arm: parathyroid hormone (upper left), osteocalcin (upper right), bone-specific alkaline phosphatase (lower left), C-telopeptides (lower right). Each subject’s marker levels are represented by a grey line connecting baseline (BL) with follow-up (FU). Box plots illustrate the distribution of baseline and follow-up levels (upper panel) and within-subject changes from baseline to follow-up (lower panel). Top and bottom of the box indicate quartile boundaries (25th and 75th percentiles); center belt indicates median; cross (+) indicates mean. Individual points (●) indicate outliers, falling outside the box by at least 1.5 times its height. Vertical lines extend to position of farthest non-outlier above and below the box. P-value in lower panel tests the hypothesis that the distribution of changes is equal in the two treatment arms.