BACKGROUND: Diabetes Mellitus, one of the leading causes of morbidity and mortality worldwide, is the 6th leading cause of mortality in the Philippines. It is multifactorial in nature but dietary components play an important role in its management. Cinnamon has been shown to have a potential role in improving lipid profile levels, increasing insulin sensitivity, and reducing fasting blood sugar and glycosylated hemoglobin (HbA1c) levels. Several studies have established cinnamon's hypoglycemic effect on fasting blood sugar levels. However, various data from randomized controlled trials showed conflicting results on its effects on HbA1c which is the most important long term predictor of complications arising from diabetes mellitus. Therefore, establishing its effect on HbA1c is critical in determining its clinical usefulness.
OBJECTIVES: This study aims to primarily determine the effectiveness of cinnamon in lowering HbA1c levels. It also aims to assess the effects of cinnamon on secondary outcomes such as fasting blood sugar level and lipid profile.
METHODOLOGY: A systematic search of local and international electronic databases (PubMed, Science Direct, Herdin, Sage, Biomed Central, Taylor and Francis Online, Cochrane library, Google Scholar, Medline, VHL Regional Portal, and Trove) of published blinded randomized controlled trials, which used cinnamon vs. placebo for 8-12 weeks to lower HbA1c levels of adults diagnosed with type 2 diabetes mellitus, was done. Assessment of articles was based on screening for title, abstract, and full text levels. Cochrane Risk of Bias Tool was used for critical appraisal. Data Extraction and Assessment Template from The Cochrane Public Health Group and Cochrane Training Practical Exercise: Data Collection was utilized for data collection while Review Manager 5 software was used for data analysis.
RESULTS: The total yield for the electronic searching was 37,066 articles. Seven articles passed the full text screening and were subsequently appraised and analyzed. Included articles generally had low risk for bias. Data analysis revealed that cinnamon doses of three grams for 8-12 weeks had a statistically significant overall effect in reducing levels of hemoglobin A1c (P=0.0004; MD=0.08%; 95% CI, 0.04% to 0.13%) and fasting blood sugar (P<0.00001; MD=4.79mg/dl; 95% CI, 3.65mg/dL to 5.93mg/dL). The mean difference was observed to be statistically significant for the values of HDL-c and triglyceride but was not statistically significant for total cholesterol and LDL-c. High degrees of heterogeneity were present for HbA1c, fasting blood sugar, total cholesterol, and triglyceride, while low degrees of heterogeneity was observed in HDL-c, and no degree of heterogeneity was detected in the analysis of LDL-c.
CONCLUSION: The results of this study showed that intake of cinnamon had a statistically significant effect in reducing HbA1c and fasting blood sugar levels but the effect of placebo was favored over cinnamon based on their forest plots. Moreover, the effects on lipid profile showed a mean difference that was observed to be statistically significant for HDL-c and triglyceride but not for total cholesterol and LDL-c levels. The individual baseline characteristics of the different studies may have contributed to the heterogeneity observed in the results of the studies.