The effect of zinc supplementation in pre-diabetes: A protocol for systematic review and meta-analysis

BACKGROUND: The number of people with diabetes and pre-diabetes is growing exponentially. Human studies have shown that zinc supplementation is beneficial for pre-diabetes. However, owing to the low quality, small sample size, and methodological heterogeneity of these studies, this conclusion is not convincing. Consequently, in order to determine whether zinc supplementation is effective and safe in pre-diabetic patients, it is necessary to conduct a meta-analysis of high-quality clinical trials. METHODS: We will retrieve MEDLINE (PubMed), EMBASE, the Web of Science, Cochrane Library, and the ClinicalTrials.gov website without restriction on language. Randomized controlled trials (RCTs) of Zinc supplementation for adult patients with pre-diabetes will be searched in multiple databases from inception to October 2020. The primary outcome of the meta-analysis is the HbA1c. The secondary outcomes include the fasting blood glucose (FBG), fasting insulin (FINS), homeostasis model assessment of insulin resistance (HOMA-IR), and quantitative insulin sensitivity check index (QUICKI). Two assessors will utilize the Cochrane Collaboration's risk of bias tool to evaluate the RCTs and all statistical data will be analyzed by using the Review Manage software V5.3.0. RESULTS: This study will provide high-quality synthesis of effectiveness and safety of zinc supplementation for pre-diabetes. CONCLUSION: This systematic review and meta-analysis will provide the available evidence to assess whether the zinc supplementation is beneficial to glucose control and insulin resistance in patients with pre-diabetes. PROSPERO REGISTRATION NUMBER: CRD 42018095724