Effect of cinnamon (Cinnamomum Zeylanicum) supplementation on serum C-reactive protein concentrations: A meta-analysis and systematic review

Objective: The effect of cinnamon (Cinnamomum Zeylanicum) on serum C-reactive protein (CRP), an acute phase protein commonly used as a marker of inflammation, is uncertain. Therefore, the objective of the present study was to conduct a systematic review and meta-analysis of published randomised controlled trials (RCTs) of cinnamon to determine the effect on levels of serum CRP, relative to controls. Design: Studies were identified by a search of electronic databases including PubMed, Cochrane Library, Google Scholar and Scopus before August 2018. Combined and stratified analyses were used. Weighted mean differences (WMD) and its 95% confidence interval were estimated for net change in serum CRP by using random-effects model. The heterogeneity of meta-analysis was assessed by chi(2) and I-2 test. Results: Six studies were identified, and data from 285 participants were included. Pooled analysis showed significant reductions in serum CRP (WMD: -0.81 mg/L, 95% CI: -1.36 to -0.26, p = 0.004), with significant heterogeneity between selected studies. Improvements in sub-group analysis were observed when baseline CRP levels were greater than 3 mg/dL, and in trials of > 12 weeks duration. Doses < 1500 mg/day and >= 1500 mg/day were effective in lowering serum CRP (WMD: -0.56 mg/dL, 95% CI: -1.01 to -0.10, p = 0.02 and WMD: -2.13 mg/dL, 95% CI: 4.08 to 0.19, p = 0.03), respectively, with significantly reduced heterogeneity in trials with lower doses of cinnamon < 1500 mg/day (test for heterogeneity: P = 0.22 and 12 = 33%). No changes were found in controls. Conclusion: Cinnamon supplementation improves levels of serum CRP, particularly in chronic conditions, where basal CRP levels are raised. Further well-designed studies are warranted to confirm or not the above mentioned findings.