The influence of zinc supplementation on IGF-1 levels in humans: A systematic review and meta-analysis
Jian Guo, Jingbo Xie, Bo Zhou, Mihnea‐Alexandru Găman, Hamed Kord‐Varkaneh, Cain C. T. Clark, Ammar Salehi‐Sahlabadi, Yunkai Li, Xianzhang Han, Youguo Hao, Yimin Liang
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.