Ascorbic acid supplementation in type 2 diabetes mellitus: A protocol for systematic review and meta-analysis

BACKGROUND: Diabetes is one of the most common chronic diseases in the world. In recent years, with the continuous improvement of people's living standards and changes in dietary structure, the incidence of diabetes is gradually increasing. Studies have shown that ascorbic acid supplementation can reduce blood glucose, increase insulin synthesis and secretion, improve insulin resistance, and reduce the occurrence and development of complications of type 2 diabetes mellitus (T2DM). However, relevant studies have common problems such as the lack of large sample studies and low quality of included studies. Therefore, it is needed that we meta-analyze the clinical trials with high quality to elucidate the efficacy and safety of ascorbic acid supplementation in patients with T2DM. METHODS: We will search randomized controlled trials published by PubMed, Embase, the Cochrane Library, Web of Science, and the Clinical Trials.gov website from inception to August 2020 on the effects of ascorbic acid supplementation on blood glucose, glycosylated hemoglobin, serum insulin, insulin resistance and other variables in T2DM patients with no language restrictions. The retrieval adopts the combination of medical subject headings and random words, and traces the references of the included literature to supplement the acquisition of relevant literature. Two researchers will independently screen the retrieved literature, extract the data and cross-check, and the Review Manage software V5.3.0 will be utilized for meta-analysis. RESULTS: Our study will provide a high-quality and in-depth comprehensive analysis of the effects of ascorbic acid supplementation on blood glucose control, glycosylated hemoglobin and insulin resistance in type 2 diabetic patients. CONCLUSION: This systematic review and meta-analysis concerning randomized controlled trials of ascorbic acid supplementation for type 2 diabetic patients will provide a new direction and strong evidence to evaluate whether ascorbic acid supplementation is of benefit to glucose control and insulin resistance in T2DM. PROSPERO REGISTRATION NUMBER: CRD 42019146826