A Systematic Review Evaluating Cinnamon's Effects on Glucose Utilizing a Ranking System to Assess Bias and Study Quality.

In the context of diabetes, the use of cinnamon continues to be among the most popular supplements taken by patients for glucose control. To strategically evaluate the available literature comparing various cinnamon species and statistically significant glucose effects after ranking studies based on two tools to assess bias and overall study quality, to clarify cinnamon's role in glucose control. The authors performed a systematic search based upon PRISMA guidelines. The search was conducted utilizing PubMed, AMED, CINAHL, EMBASE, Cochrane, and Medline databases, with the final search performed in September 2022 with restrictions to human subjects and English language. Electronic searches were conducted utilizing the keywords "diabetes mellitus" combined with // combined with blood glucose (BG). A second search utilized "cinnamomum zeylanicum/cinnamomum cassia/cinnamomum verum" combined with "blood glucose," and a final search utilized "diabetes mellitus" combined with "cinnamon." Data extraction and ranking of included studies utilizing the risk of bias 2 tool and modified Heyland Methodological Quality Scoring tool were performed independently by two review authors. These authors compared their results and reconciled any differences in scoring to generate a final ranking of studies. A third author was available for any discrepancies that could not be resolved but was not needed. Forty-five studies were included in the review and were scored for bias and quality. Overall 62% demonstrated statistical significance for positive effects in at least one parameter around BG control. Applying the ranking systems reduced the percentage closer to 50%. Safety was extremely well documented across studies with few adverse effects. Results are limited by heterogeneity of glucose parameters, leading to studies being ranked individually and not synthesized. Cinnamon supplementation likely has a modest positive effect on BG. Based upon the strong safety profile, utilization of this spice as an adjunct to pharmacologic therapy is reasonable.