The effect of green tea on C-reactive protein and biomarkers of oxidative stress in patients with type 2 diabetes mellitus: A systematic review and meta-analysis

Introduction The beneficial effects of green tea on regulating insulin sensitivity and preventing the development of type 2 diabetes mellitus (T2DM) have been identified. Objectives: We aimed to investigate the effect of green tea on serum levels of C-reactive protein (CRP) and biomarkers of oxidative stress in patients with T2DM. Methods: A systematic search was performed in the ISI Web of science, PubMed and Scopus to find articles related to the effect of the green tea on CRP, malondealdehyde (MDA) and total antioxidant capacity (TAC) in T2DM patients, up to June 2019. There was no language and time limitation. Meta-analyses were performed using both the random and fixed effects model where appropriate, and 12 index was used to evaluate the heterogeneity. Results: Initial search yielded 780 publications. Eight articles with 614 T2DM patients were eligible. Following green tea consumption, CRP levels significantly decreased (weighted mean difference (WMD): -5.51 mg/dl, 95% CI: -9.18 to -1.83, p = 0.003) compared with the controlled group. Green tea consumption had no significant effect on plasma levels of TAC and MDA (0.02 mg/dl, CI: -0.06 to 0.10; -0.14 mg/dl, CI: -0.40 to 0.12; respectively). Conclusion: This systematic review and meta-analysis indicated that green tea significantly reduced the circulating levels of CRP, whereas, it had no significant effect on MDA and TAC. Overall, green tea can be considered as a healthy drink to reduce CRP levels in T2DM patients.