The Effect of Nigella sativa Supplementation on Cardiometabolic Health in Patients With Metabolic Diseases: A GRADE ‐Assessed Systematic Review and Meta‐Analysis

Background Metabolic diseases, including type 2 diabetes and obesity, are primary drivers of cardiovascular disease (CVD) through the exacerbation of intermediate risk factors such as dysglycemia, hypertension, and central adiposity. Nigella sativa supplementation has been studied for its potential cardiometabolic benefits, but evidence from clinical trials remains inconsistent. In relation to this matter, a meta‐analysis was undertaken to present a more precise evaluation of the effect of N. sativa supplementation on cardiovascular risk factors in patients with metabolic diseases. Methods The review was conducted in accordance with PRISMA guidelines. A random‐effects meta‐analysis was performed to calculate weighted mean differences (WMDs) with 95% confidence intervals. Heterogeneity was assessed using the I 2 statistic, and sensitivity analyses were conducted to examine the robustness of pooled estimates. Primary outcomes included obesity and glycemic indices, while blood pressure outcomes were considered secondary. Results Meta‐analysis of 31 trials with 2145 participants revealed significant reductions in weight (WMD: −1.59 kg; 95% CI: −3.03 to −0.15), and BMI (WMD: −0.51 kg/m 2 ; 95% CI: −0.85 to −0.18), SBP (WMD = −3.25 mmHg; 95% CI: −4.44, −2.06), and DBP (WMD = −2.75 mmHg; 95% CI: −4.62, −0.89), FBS (WMD = −18.62 mg/dL; 95% CI: −23.30, −13.95), and HbA1c (WMD = −0.56; 95% CI: −0.79, −0.33) following N. sativa supplementation. Also, N. sativa had no effect on other indices such as WC, HC, WHR, HOMA‐IR, and insulin. Conclusion This meta‐analysis suggests that N. sativa supplementation is associated with modest improvements in several cardiovascular risk factors. However, no significant effects were observed for measures of insulin resistance or central adiposity, and the findings should be interpreted cautiously given variability in study quality and outcomes. Further well‐designed trials are needed to clarify its clinical relevance.