Effects of Urtica dioica on Metabolic Profiles in Type 2 Diabetes: A Systematic Review and Meta-analysis of Clinical Trials

Background: Several studies have investigated the effect of Urtica dioica (UD) consumption on metabolic profiles in patients with type 2 diabetes mellitus (T2DM); however, the findings are inconsistent. This systematic review and meta-analysis of clinical trials were performed to summarize the evidence of the effects of UD consumption on metabolic profiles in patients with T2DM. Methods: Eligible studies were retrieved from searches of PubMed, Embase, Scopus, Web of Science, Cochrane Library, and Google Scholar databases until December 2019. Cochran (Q) and I-square statistics were used to examine heterogeneity across included clinical trials. Data were pooled using a fixed-effect or random-effects model and expressed as weighted mean difference (WMD) and 95% confidence interval (CI). Results: Among 1485 citations, thirteen clinical trials were found to be eligible for the current metaanalysis. UD consumption significantly decreased levels of fasting blood glucose (FBG) (WMD = 17.17 mg/dl, 95% CI: -26.60, -7.73, I-2 = 93.2%), hemoglobin A1c (HbA1c) (WMD = -0.93, 95% CI: 1.66, -0.17, I-2 = 75.0%), C-reactive protein (CRP) (WMD = -1.09 mg/dl, 95% CI: -1.64, -0.53, I-2 = 0.0%), triglycerides (WMD = -26.94 mg/dl, 95 % CI = [-52.07, -1.82], P = 0.03, I-2 = 90.0%), systolic blood pressure (SBP) (WMD = -5.03 mmHg, 95% CI = -8.15, -1.91, I-2 = 0.0%) in comparison to the control groups. UD consumption did not significantly change serum levels of insulin (WMD = 1.07 mu U/ml, 95% CI: - 1.59, 3.73, I-2 = 63.5%), total-cholesterol (WMD = -6.39 mg/dl, 95% CI: -13.84, 1.05, I-2 = 0.0%), LDL-cholesterol (LDL-C) (WMD = -1.30 mg/dl, 95% CI: -9.95, 7.35, I-2 = 66.1%), HDL-cholesterol (HDL- C) (WMD = 6.95 mg/dl, 95% CI: -0.14, 14.03, I-2 = 95.4%), body max index (BMI) (WMD = -0.16 kg/m(2), 95% CI: - 1.77, 1.44, I-2 = 0.0%), and diastolic blood pressure (DBP) (WMD = -1.35 mmHg, 95% CI: -2.86, 0.17, I-2= 0.0%) among patients with T2DM. Conclusion: UD consumption may result in an improvement in levels of FBS, HbA1c, CRP, triglycerides, and SBP, but did not affect levels of insulin, total-, LDL-, and HDL-cholesterol, BMI, and DBP in patients with T2DM.