The effect of cinnamon supplementation on blood pressure in adults: A systematic review and meta-analysis of randomized controlled trials

Background & aims: Several clinical trials have shown that cinnamon can reduce blood pressure, but the results are controversial. Therefore, we conducted a systematic review and meta-analysis to provide a more precise estimate of the overall effects of cinnamon supplementation on blood pressure in adults. Methods: We searched PubMed, Scopus, Cochrane Library, ISI Web of Science, and Google Scholar databases through September 2019 to identify randomized clinical trials (RCTs) investigating the effect of cinnamon supplementation on blood pressure. Data were pooled by using the random-effects model, and weighted mean difference (WMD) was considered as the summary effect size. Sensitivity analysis was conducted using the leave-one-out method. Results: Meta-analysis of 9 RCTs with 641 participants showed significant reductions in both systolic (WMD: -5.17 mmHg, 95% CI: -9.35 to -0.99, P = 0.01) and diastolic blood pressure (WMD: -3.36 mmHg, 95% CI: -5.67 to - 1.04, P <= 0.001) after cinnamon supplementation. Subgroup analyses indicated that these results were significant only when cinnamon was administered at the dosages of <= 2 g/day, for a period longer than 8 weeks, and in participants with a baseline BMI of >= 30 kg/m(2). Conclusion: The present meta-analysis suggests that cinnamon supplementation can improve blood pressure by a modest degree. However, due to limited availability of studies with hypertensive cases and relatively small sample sizes of available studies, well designed trials with adequate sample sizes aimed at hypertensive populations are recommended. (C) 2020 European Society for Clinical Nutrition and Metabolism. Published by Elsevier Ltd. All rights reserved.