Abstract

Abstract Purpose There is equivocality regarding the interaction between vitamin D and insulin-like growth factor-1 (IGF-1). Thus, the aim of this study was to elucidate the effect of vitamin D supplementation on serum levels of IGF-1 by conducting a systematic review and meta-analysis of randomized controlled trials (RCTs). Methods PubMed, Scopus, and ISI Web of Science databases were searched up to May 2019 for RCTs that evaluated the effect of vitamin D supplementation on IGF-1 levels. Mean and standard deviation changes of IGF-1 in each treatment group were considered for analysis and pooled using random-effect model. Risk of bias for included studies was assessed by the Cochrane scale and the NutriGrade approach was applied to evaluate the quality of evidence. Results Six trials (n = 773 participants) were included in the meta-analysis. Compared with control group, vitamin D supplementation had not significant effect on serum level of IGF-1 (weighted mean difference [WMD] =4.66 ng/ml, 95% CIs: -6.72 to 16.03, P = 0.42, I² = 74.8, P-heterogeneity = 0.001). Additionally, no meaningful changes were observed in subgroup analyses. Conclusion The evidence from the limited number of published trials does not convincingly show that vitamin D supplementation elicits any clinically relevant effects on IGF-1 levels. More high-quality studies are needed to reach a consensual conclusion in this area.