Effects of cinnamon supplementation on serum levels of liver enzymes: A systematic review and meta-analysis of randomized controlled clinical trials

Objectives: A systematic review and meta-analysis of the effect of cinnamon supplementation on serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), and total bilirubin.Methods: PubMed, Scopus, Web of Science (ISI), Embase, Cochran, and Google Scholar were searched up to December 26, 2021, for relevant randomized controlled clinical trials (RCTs). The random-effects model was used to estimate the overall effects.Results: Eight trials with 10 treatment arms were included in the meta-analysis. The meta-analysis revealed no significant effect of cinnamon supplementation on ALT [weighted mean difference (WMD) = -3.74 U/L, 95 % CI: - 8.88, 1.40, P = 0.15], AST (WMD = -2.69 U/L, 95 % CI: -6.23, 0.84, P = 0.13), ALP (WMD = 4.79 U/L, 95 % CI: -0.22, 9.81, P = 0.06) and total bilirubin levels (WMD = 0.04 mg/dL, 95 % CI: -0.08, 0.17, P = 0.49). Subgroup analysis indicated the beneficial effect of > 2000 mg/day of cinnamon extract on serum ALT levels (P < 0.05). Moreover, cinnamon could be effective in reducing AST levels when taken before meals, and the treatment duration was longer than 12 weeks in studies done in T2DM (P < 0.05).Conclusion: Extracts of cinnamon remarkably decreased ALT and AST levels at a dosage of > 2000 mg/day, when consumed before meals in T2DM patients in trials lasting >= 12 weeks. Further large-scale high-quality RCTs assessing the efficacy of cinnamon on liver parameters as a primary outcome variable are recommended.