Cinnamon Use in Type 2 Diabetes

An Updated Systematic Review and Meta-analysis

Robert W. Allen, PharmD; Emmanuelle Schwartzman, PharmD; William L. Baker, PharmD, BCPS (AQ CV); Craig I. Coleman, PharmD; Olivia J. Phung, PharmD

Disclosures

Ann Fam Med. 2013;11(5):452-459. 

In This Article

Abstract and Introduction

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 (I2 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.

Introduction

Glycemic control presents a constant challenge for those with diabetes. Cardiovascular disease, one of the major complications of diabetes, is largely influenced by glycemic measures.[1] To date, strategies for modifying blood glucose include pharmacologic treatment, lifestyle modification, and dietary changes. Despite an increasing body of literature focused on the use of natural supplements in the treatment of diabetes, the American Diabetes Association (ADA) does not recommend their use because clinical evidence showing efficacy is insufficient, and they lack standardized formulations.[2]

Cinnamon has become a natural product of interest because it has been hypothesized to provide health benefits, such as the ability to lower serum lipids and blood glucose. It has been suggested that the modality in which cinnamon expresses its effect on blood glucose can be attributed to its active component cinnamaldehyde.[3] The insulinotropic effects of cinnnamaldehyde have been preliminarily investigated and are thought to be responsible for promoting insulin release, enhancing insulin sensitivity, increasing insulin disposal, and exerting activity in the regulation of protein-tyrosine phosphatase 1B (PTP1B) and insulin receptor kinase.[4] In animal studies, aqueous cinnamon extracts have been shown to increase the expression of peroxisome proliferator-activated receptors (PPARs), which are transcriptional factors involved in the regulation of insulin resistance and adipogenesis, resulting in improved lipid and glucose metabolism.[5] Several randomized controlled trials (RCTs) in humans have been conducted to explore cinnamon's efficacy; however, they report conflicting results.[6–15] A meta-analysis we conducted previously did not show any statistically significant effect on glucose or lipid parameters;[16] since that time, additional RCTs have been published investigating this effect.[11–15] To update our prior systematic review and meta-analysis, we added the newly published evidence to determine the effect of cinnamon in patients with type 2 diabetes on glycemic and serum lipid levels.

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