The effects of cinnamon supplementation on blood lipid concentrations: A systematic review and meta-analysis

BACKGROUND: Cinnamon is a rich botanical source of polyphenols, whose positive effects on blood lipid concentrations have been hypothesized, but have not been conclusively studied. OBJECTIVE: The objective of the study was to systematically review and evaluate the effect of administration of cinnamon on blood lipid concentrations. METHODS: We assessed 13 randomized controlled trials with 750 participants investigating the effect of cinnamon supplementation on blood lipid concentrations. A meta-analysis was performed using random effect models, with weighted mean differences (WMDs; with 95% confidence interval [CI]) for endpoints calculated using a random effects model. RESULTS: No statistically significant effect of cinnamon was observed on blood low-density lipoprotein cholesterol (LDL-C; WMD: -0.16 mmol/L [-6.19 mg/dL], 95% CI: -0.35, 0.03 [-13.53, 1.16], P = .10) and high-density lipoprotein cholesterol (HDL-C; WMD: 0.05 mmol/L [1.92 mg/dL], 95% CI: -0.03, 0.12 [-0.03, 4.64], P = .21) concentrations. However, a statistically significant reduction in blood triglycerides (WMD: -0.27 mmol/L [-23.91 mg/dL], 95% CI: -0.39, -0.14 [-34.54, -12.40], P < .01) and total cholesterol concentrations (WMD: -0.36 mmol/L [-13.92 mg/dL], 95% CI: -0.63, -0.09 [-24.36, -3.48], P < .01) was observed. HDL-C was significantly elevated after the omission of 1 study (WMD: 0.04 mmol/L [1.54 mg/dL], 95% CI: 0.03, 0.06 [1.16, 2.32], P < .01) during our sensitivity analysis. A meta-regression analysis was conducted, and no significant association was found between changes in lipid parameters and cinnamon dose. In contrast, changes in blood levels of total cholesterol (slope: 0.09; 95% CI: 0.02, 0.16; P < .01), LDL-C (slope: 0.05; 95% CI: 0.001, 0.10; P = .05) and triglycerides (slope: 0.06; 95% CI: 0.04, 0.09; P < .01) were significantly and positively associated with the duration of supplementation. No statistically significant association was found between blood HDL-C changes and duration of supplementation. CONCLUSION: Cinnamon supplementation significantly reduced blood triglycerides and total cholesterol concentrations without any significant effect on LDL-C and HDL-C. (C) 2017 National Lipid Association. All rights reserved.