The influence of zinc supplementation on IGF-1 levels in humans: A systematic review and meta-analysis

Abstract

The effect of supplementation with zinc on levels of IGF-1 remains relatively unexplored, and many of previous studies have reported equivocal findings. Thus, the aim of this study was to elucidate the influence of zinc on IGF-1. A complete systematic search was executed in Scopus, Web of Science, Embase, and PubMed/MEDLINE, by reviewers, from database inception until June 2019. Weighted mean difference (WMD) with the 95% CI was used for assessing the effects of zinc on IGF-1. We evaluated between study heterogeneity using the I-squared and the Q-test statistic. Ten studies reported changes in plasma levels of IGF-1. Combined results ascertained an increase in IGF-1 levels following zinc administration (WMD: 8.620 ng/ml, 95% CI: 1.126, 16.113, I2 = 97.3%). Subgroup analyses demonstrated that zinc intake dosage ≤10 mg/day (WMD: 9.50 ng/ml, 95% CI: 1.47, 17.53) and intervention length ˃8 weeks (WMD: 10.08 ng/ml, 95% CI: 0.67, 19.48) significantly greater increased IGF-1 levels. The present study demonstrated that zinc supplementation can elicit significant increases in IGF-1 in humans. In addition, greater increments were observed when zinc intake dosage was ≤10 mg/day and intervention duration ˃8 weeks. Keywords: Zinc, IGF-1, Humans, Meta-analysis