The Therapeutic Effect of Garlic Supplements on the Metabolic Profile of Patients With Type 2 Diabetes: A Systematic Review and Meta-Analysis of Randomized Clinical Trials

Background: Garlic, as an additive, a spice, and an ancient herbal medicine, has been proposed as a potential treatment for type 2 diabetes mellitus (T2DM). This systematic review and meta-analysis provides a comprehensive evaluation of the effects of garlic supplementation on fasting blood sugar (FBS), hemoglobin A1c (HbA1c), and lipid profile in patients with T2DM. Methods: All articles published up to November 2024 were reviewed through the PubMed, SCOPUS, and Web of Science databases to gather all randomized clinical trials (RCTs) on T2DM patients in which garlic was used as a treatment. A random-effects model was used to measure pooled effect sizes. Weighted mean differences (WMDs) and 95% confidence intervals (CIs) were used to report pooled effect sizes. Subgroup analysis was utilized to investigate heterogeneity. Results: Finally, 8 studies were included in this systematic review and meta-analysis. Our pooled meta-analysis showed a significant decrease in FBS after garlic therapy based on 10 effect sizes (WMD: −12.41; 95% CI: −15.13 to −9.69; I ² = 99.2%) and in HbA1C based on 7 effect sizes (WMD: −0.5; 95% CI: −0.66 to −0.33; I ² = 96.4%). Also, total cholesterol (TC) was significantly reduced (WMD: −8.26; 95% CI: −14.65 to −1.88; I ² = 90.9%) based on 7 effect sizes, while changes in HDL-C, TG, and LDL-C were not significant overall. However, when garlic was combined with oral hypoglycemic agents, a significant reduction in LDL-C was observed (WMD: −8.64; 95% CI: −10.54 to −6.78; I ² = 95.6%) compared to garlic alone. Moreover, longer duration of garlic supplementation significantly improved all lipid profiles in patients with T2DM. Significant improvements in HDL-C, LDL-C, and TC were also noted in older patients after garlic therapy. Conclusions: The findings of this systematic review and meta-analysis support the potential effect of garlic therapy for the management of T2DM. However, due to the low quality of the studies included in this review, further high-quality RCTs should be conducted based on our findings. PROSPERO registration number: CRD42024628780.