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Effect of cinnamon on glycaemic control? A meta-analysis of randomised control trials

Published online by Cambridge University Press:  14 October 2011

R. Akilen
Affiliation:
Faculty of Health and Human Science, Thames Valley University, Boston Manor Road, Brentford TE8 9GA, UK
A. Tsiami
Affiliation:
Faculty of Health and Human Science, Thames Valley University, Boston Manor Road, Brentford TE8 9GA, UK
D. Devendra
Affiliation:
Department of Investigative Sciences, Faculty of Medicine, Imperial College London & Brent NHS, London, UK
N. Robinson
Affiliation:
Faculty of Health and Human Science, Thames Valley University, Boston Manor Road, Brentford TE8 9GA, UK
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Abstract

Type
Abstract
Copyright
Copyright © The Authors 2011

Background: Cinnamon could be used as a dietary supplement to improve glycaemic control in people with diabetes. In the absence of strong supporting evidence from previous individual randomised controlled trials (RCT), a meta-analysis from all published RCT were carried out to identify the blood glucose lowering potential of cinnamon among patients with type 2 diabetes mellitus (T2DM).

Methods: The RCT using cinnamon for the treatment of T2DM were searched systematically from earliest possible date to November 2010. Searches included all EBM reviews, Cochrane library, MEDLINE, EMBASE, JAMA, BMJ and High wire press. RCT reporting the effect of cinnamon on glycated haemoglobin (HbA1c) and fasting plasma glucose (FPG) only were included in this study. Rev Man5.0 was used for meta-analysis (Cochrane collaboration). The mean change (baseline v. post intervention) was treated as a continuous variable, outcomes were analysed by weighted mean difference, as difference between the means in the control (placebo) and treatment (cinnamon) groups (fixed-effect model). Chi-square test (α=0.05) was used for heterogeneity test, and weighted mean difference was also calculated (95% CI).

Results: As a result, six RCT of cinnamon and T2DM were included for further review and analysis(Reference Akilen, Tsiami and Devendra1Reference Vanschoonbeek, Thomassen and Senden6). Meta-analysis of this six RCT(Reference Akilen, Tsiami and Devendra1Reference Vanschoonbeek, Thomassen and Senden6) demonstrated decrease in mean HbA1c (0.09%; 95% CI was 0.04–0.14) and mean FPG (0.84 mmol/l; 95% CI was 0.66–1.02).

Table 1. Randomised controlled trials reporting the blood glucose lowering effect of cinnamon in T2DM

Discussion: Meta-analysis based on a few small trials should be treated with caution. There are some limitations of the analysis that needs to be addressed. This meta-analysis only included six RCT (may be underpowered), the sample size is small and unpublished RCT were not included, and these factors may cause bias. We have done our utmost to include all published studies to avoid selection bias. Furthermore, this analysis only included short-term interventions (<4 months) of 1 g, 1.5 g, 2 g, 3 g or 6 g of cinnamon and placebo controlled trials, and this requires further long-term trials with different cinnamon dose levels.

Conclusion: Our meta-analysis demonstrated that short-term (<4 months) effects of the use of cinnamon on glycaemic control (both HbA1c and FPG) looks promising.

References

1.Akilen, R, Tsiami, A, Devendra, D et al. (2010) Glycated haemoglobin and blood pressure-lowering effect of cinnamon in multi-ethnic type 2 diabetic patients in the UK: a randomized, placebo-controlled, double blind clinical trial. Diabet Med 27, 11591167.CrossRefGoogle Scholar
2.Blevins, SM, Leyva, MJ, Brown, J et al. (2007) Effect of cinnamon on glucose and lipid levels in non insulin-dependent type 2 diabetes. Diabetes Care 30, 22362237.CrossRefGoogle ScholarPubMed
3.Crawford, P (2009) Effectiveness of cinnamon for lowering hemoglobin A1C in patients with type 2 diabetes: a randomized, controlled trial. J Am Board Fam Med 22, 507512.CrossRefGoogle ScholarPubMed
4.Khan, A, Safdar, M, Ali Khan, MM et al. (2003) Cinnamon improves glucose and lipids of people with type 2 diabetes. Diabetes Care 26, 32153218.CrossRefGoogle ScholarPubMed
5.Mang, B, Wolters, M, Schmitt, B et al. (2006) Effects of a cinnamon extract on plasma glucose, HbA, and serum lipids in diabetes mellitus type 2. Eur J Clin Invest 36, 340344.CrossRefGoogle ScholarPubMed
6.Vanschoonbeek, K, Thomassen, BJ, Senden, JM et al. (2006) Cinnamon supplementation does not improve glycemic control in postmenopausal type 2 diabetes patients. J Nutr 136, 977980.CrossRefGoogle Scholar
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Table 1. Randomised controlled trials reporting the blood glucose lowering effect of cinnamon in T2DM