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Review
. Sep-Oct 2013;11(5):452-9.
doi: 10.1370/afm.1517.

Cinnamon Use in Type 2 Diabetes: An Updated Systematic Review and Meta-Analysis

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Free PMC article
Review

Cinnamon Use in Type 2 Diabetes: An Updated Systematic Review and Meta-Analysis

Robert W Allen et al. Ann Fam Med. .
Free PMC article

Abstract

Purpose: Cinnamon has been studied in randomized controlled trials (RCTs) for its glycemic-lowering effects, but studies have been small and show conflicting results. A prior meta-analysis did not show significant results, but several RCTs have been published since then. We conducted an updated systematic review and meta-analysis of RCTs evaluating cinnamon's effect on glycemia and lipid levels.

Methods: MEDLINE, Embase, and Cochrane Central Register of Controlled Trials (CENTRAL) were searched through February 2012. Included RCTs evaluated cinnamon compared with control in patients with type 2 diabetes and reported at least one of the following: glycated hemoglobin (A1c), fasting plasma glucose, total cholesterol, low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), or triglycerides. Weighted mean differences (with 95% confidence intervals) for endpoints were calculated using random-effects models.

Results: In a meta-analysis of 10 RCTs (n = 543 patients), cinnamon doses of 120 mg/d to 6 g/d for 4 to 18 weeks reduced levels of fasting plasma glucose (-24.59 mg/dL; 95% CI, -40.52 to -8.67 mg/dL), total cholesterol (-15.60 mg/dL; 95% CI, -29.76 to -1.44 mg/dL), LDL-C (-9.42 mg/dL; 95% CI, -17.21 to -1.63 mg/dL), and triglycerides (-29.59 mg/dL; 95% CI, -48.27 to -10.91 mg/dL). Cinnamon also increased levels of HDL-C (1.66 mg/dL; 95% CI, 1.09 to 2.24 mg/dL). No significant effect on hemoglobin A1c levels (-0.16%; 95%, CI -0.39% to 0.02%) was seen. High degrees of heterogeneity were present for all analyses except HDL-C (I(2) ranging from 66.5% to 94.72%).

Conclusions: The consumption of cinnamon is associated with a statistically significant decrease in levels of fasting plasma glucose, total cholesterol, LDL-C, and triglyceride levels, and an increase in HDL-C levels; however, no significant effect on hemoglobin A1c was found. The high degree of heterogeneity may limit the ability to apply these results to patient care, because the preferred dose and duration of therapy are unclear.

Keywords: cinnamon; lipids; meta-analysis; review; systematic; type 2 diabetes mellitus.

Figures

Figure 1
Figure 1
Preferred reporting items in systematic reviews and meta-analyses flow diagram of study selection, inclusion, and exclusion of randomized controlled trials evaluating cinnamon on glycemic and lipid parameters.
Figure 2
Figure 2
Forest plot depicting the meta-analyses results of randomized controlled trials evaluating cinnamon on serum levels of hemoglobin A1c and fasting blood glucose. Note: Squares represent individual studies, and size of the square represents the weight given to each study in the meta-analysis. Error bars represent 95% confidence intervals. The diamonds represent the pooled results. The solid vertical line extending upward from 0.00 is the null value.
Figure 2
Figure 2
Forest plot depicting the meta-analyses results of randomized controlled trials evaluating cinnamon on serum levels of hemoglobin A1c and fasting blood glucose. Note: Squares represent individual studies, and size of the square represents the weight given to each study in the meta-analysis. Error bars represent 95% confidence intervals. The diamonds represent the pooled results. The solid vertical line extending upward from 0.00 is the null value.
Figure 3
Figure 3
Forest plot depicting the meta-analysis results of randomized controlled trials evaluating cinnamon on serum levels of total cholesterol, LDL cholesterol, HDL cholesterol, and triglycerides. HDL=high-density lipoprotein; LDL=low-density lipoprotein. Note: Squares represent individual studies, and size of the square represents the weight given to each study in the meta-analysis. Error bars represent 95% confidence intervals. The diamonds represent the pooled results. The solid vertical line extending upward from 0.00 is the null value.
Figure 3
Figure 3
Forest plot depicting the meta-analysis results of randomized controlled trials evaluating cinnamon on serum levels of total cholesterol, LDL cholesterol, HDL cholesterol, and triglycerides. HDL=high-density lipoprotein; LDL=low-density lipoprotein. Note: Squares represent individual studies, and size of the square represents the weight given to each study in the meta-analysis. Error bars represent 95% confidence intervals. The diamonds represent the pooled results. The solid vertical line extending upward from 0.00 is the null value.
Figure 3
Figure 3
Forest plot depicting the meta-analysis results of randomized controlled trials evaluating cinnamon on serum levels of total cholesterol, LDL cholesterol, HDL cholesterol, and triglycerides. HDL=high-density lipoprotein; LDL=low-density lipoprotein. Note: Squares represent individual studies, and size of the square represents the weight given to each study in the meta-analysis. Error bars represent 95% confidence intervals. The diamonds represent the pooled results. The solid vertical line extending upward from 0.00 is the null value.
Figure 3
Figure 3
Forest plot depicting the meta-analysis results of randomized controlled trials evaluating cinnamon on serum levels of total cholesterol, LDL cholesterol, HDL cholesterol, and triglycerides. HDL=high-density lipoprotein; LDL=low-density lipoprotein. Note: Squares represent individual studies, and size of the square represents the weight given to each study in the meta-analysis. Error bars represent 95% confidence intervals. The diamonds represent the pooled results. The solid vertical line extending upward from 0.00 is the null value.

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