The effect of nettle (Urtica dioica) supplementation on the glycemic control of patients with type 2 diabetes mellitus: A systematic review and meta‐analysis

Type 2 diabetes mellitus (T2DM) is a major health problem, worldwide, that is associated with increased morbidity and mortality. Several randomized controlled clinical trials (RCTs) have investigated the effect of nettle (Urtica dioica) supplementation on markers of glycemic status in patients with T2DM, with conflicting results. Therefore, the present study assessed the effect of nettle on some glycemic parameters in patients with T2DM. A comprehensive search was conducted in PubMed, Scopus, Cochrane Library, and Web of Science, from database inception up to June 2019, to identify RCTs investigating the effect of nettle supplementation on glycemic markers, including fasting blood sugar (FBS) concentrations, insulin levels, homeostasis model assessment‐estimated insulin resistance index, and glycosylated hemoglobin percentage in adults with T2DM. The Cochrane Collaboration tool was used to assess the methodological quality of the included studies. Results of this meta‐analysis were reported based on the random effects model. Eight RCTs, comprising 401 participants, were included in the present systematic review and meta‐analysis. Based on the Cochrane Collaboration risk of bias tool, five studies were considered as good quality, one was fair, and two studies were poor, respectively. The results of the meta‐analysis revealed a significant reduction in FBS concentrations (weighted mean difference [WMD]: −18.01 mg/dl, 95% confidence interval [CI]: −30.04 to −5.97, p < .001, I² = 94.6%) following nettle supplementation. However, no significant reduction was observed in insulin levels (WMD: 0.83 Hedges' g, 95% CI: −0.26 to 1.92, p = .13, I² = 89.4%), homeostasis model assessment‐estimated insulin resistance index (WMD: −0.22, 95% CI: −0.83 to 0.40, p = .49, I² = 69.2%), or glycosylated hemoglobin percentage (WMD: −0.77%, 95% CI: −1.77 to 0.22, p = .12, I² = 83.0%). The findings of the present study suggest that nettle supplementation may be effective in controlling FBS for T2DM patients. However, further studies are needed to confirm the veracity of these results.