The Effect of Cinnamon on Glycolipid Metabolism: A Dose-Response Meta-Analysis of Randomized Controlled Trials

(1) Background: The effect of cinnamon on the regulation of glycolipid levels in type 2 diabetic patients is still controversial, and there is a lack of research on the dose-response relationship between cinnamon and glycolipid indicators in type 2 diabetic patients. (2) Methods: This dose-response meta-analysis was performed to explore the effect of the cinnamon intervention on glycolipid metabolism. We conducted a comprehensive database search for literature published before November 2022. Nonlinear models were used for dose-response relationship analysis. (3) Results: We identified that a cinnamon intervention was effective in controlling triglyceride (TG) levels (mean difference = -7.31; 95%CI: -12.37, -2.25, p = 0.005) and low-density lipoprotein cholesterol (LDL-C) levels (mean difference = -6.78; 95%CI: -11.35, -2.22, p = 0.004) in type 2 diabetic patients; however, it also was able to increase high-density lipoprotein cholesterol (HDL-C) levels in patients with type 2 diabetes (mean difference = 1.53; 95%CI: 1.01, 2.05, p < 0.001). However, the cinnamon intervention had no significant effect on the level of fasting blood glucose, glycated hemoglobin (HbA1c), or total cholesterol (TC) levels. We found a significant effect of the cinnamon intervention dose on the TG level (p-nonlinearity = 0.016) and LDL-C (p-nonlinearity = 0.019) in the nonlinear dose-response analysis. In the subgroup analysis, we found a hypoglycemic effect with the cinnamon dose ≤1200 mg (mean difference = -11.1, 95%CI: -14.64, -7.58, p < 0.001). (4) Conclusion: Cinnamon intervention may be beneficial in lowering TG and LDL-C levels while enhancing HDL-C levels, and the dosage of the intervention was an important factor in influencing the TG and LDL-C levels.