Serum 25(OH)D response to vitamin D-3 supplementation: A meta-regression analysis

Abstract

Objective: The aim of this study was to review factors that influence serum 25(OH)D when patients are given vitamin D supplements. Methods: From a comprehensive search of all randomized controlled clinical trials with vitamin D-3 supplementation available on PubMed up to November 2011, we selected 33 with 43 treatment arms that included at least 30 adult participants. The achieved pooled mean difference (PMD) and 95% confidence intervals (CIs) were calculated using the random-effects models. Meta-regression and subgroup analyses were performed for prespecified factors, including dose, duration, baseline serum 25(OH)D, and age. Results: With a mean baseline serum 25(OH)D of 50.4 nmol/L, PMD was 37 nmol/L (95% CI, 33-41) with significant heterogeneity among studies. Dose (slope: 0.006; P < 0.001), trial duration (slope: 0.21; P < 0.001), baseline serum 25(OH)D (slope: -0.19; P < 0.001), and age (slope: 0.42; P < 0.001) independently influenced vitamin D response. Similar results were found in studies with a mean baseline serum 25(OH)D <50 nmol/L. In subgroup analyses, the PMD was higher with doses >= 800 IU/d (39.3 nmol/L) after 6 to 12 mo (41.7 nmol/L), with baseline 25(OH)D <50 nmol/L (39.6 nmol/L), and in adults aged >80 y (40.5 nmol/L). Conclusion: This meta regression indicates that a higher increase in serum levels of 25(OH)D in adults is found with a dose of >800 IU/d, after at least 6 to 12 mo, and even when baseline 25(OH)D is low and in adults >80 y. (C) 2014 Elsevier Inc. All rights reserved.