Effect of Nigella sativa Consumption on Lipid Profile and Glycemic Index in Patients with Metabolic Syndrome: A Systematic Review and Meta-analysis of Randomized Controlled Trials

Background: Metabolic syndrome is a multifactorial disorder and genetics, lifestyle, and aging play important roles in its prevalence. Nigella sativa has several pharmacological benefits, including anti-inflammatory, antitumor, anti-diabetic, antioxidant, and hypolipidemic effects. This meta-analysis of randomized controlled trials assesses the effect of N. sativa consumption on lipid profile and glycemic indices in patients with metabolic syndrome. Methods: We systematically researched Cochrane Library, PubMed, Scopus, and Web of Science databases. The literature research identified 171 studies with duplication. Of those, 73 articles were screened for titles and abstracts, and 7 studies were finally selected for the meta-analysis. Because of the high degree of heterogeneity, we performed subgroup analyses based on the dose of N. sativa (<=500 mg/day or >500 mg/day). Results: The results revealed that N. sativa intake significantly decreased total cholesterol (SMD: -0.71; 95% CI, -1.44 to -0.38; p = 0.00), LDL-C (SMD: -1.06; 95% CI, -1.45 to -0.66; p = 0.00) and HDL-C (SMD: -0.31; 95% CI, 0.09 to 0.53; p = 0.01) concentrations. In addition, N. sativa significantly decreased FBS (SMD: -0.8; 95% CI, -1.21 to -0.39; p = 0.00) and HbA1c (SMD: -0.37; 95% CI, -0.66 to -0.09; p = 0.01) concentrations. No publication bias was observed, and sensitivity analysis showed stable results. Conclusion: The current systematic review and meta-analysis indicates that N. sativa could improve lipid profile and glycemic index in patients with metabolic syndrome.