Effects of green coffee bean extract on C-reactive protein levels: A systematic review and meta-analysis of randomized controlled trials

Background & objective: The effects of green coffee bean extract (GCBE) supplementation on inflammatory biomarkers have been widely spread. The purpose of this article was to assess the impact of GCBE supplementation on C-reactive protein (CRP) levels. Methods: The literature search was performed in four databases (Scopus, PubMed, the Cochrane Library, and Google Scholar) to identify studies that examined the influence of GCBE supplementation on CRP levels up to August 2019. Mean and standard deviation (SD) of the outcomes were used to estimate the weight mean difference (WMD) between intervention and control groups for the follow-up period. Results: Five (5) studies, with 6 arms, reported CRP as an outcome. Statistically, the use of GCBE supplements resulted in a significant change in CRP levels (WMD: -0.017 mg/dL, 95 % CI: - 0.032, - 0.003, p = 0.018), whose overall findings were obtained from random-effects model. In addition, a significantly greater reduction in CRP was noted for studies with doses of GCBE supplements >= 1000 mg/d (WMD: - 0.015 mg/dL, 95 % CI: - 0.020, - 0.010, p < 0.000), length of intervention < 4 weeks (WMD: -0.015 mg/dL, 95 % CI: - 0.020, - 0.010, p < 0.001), and for non-healthy subjects (WMD: -0.019 mg/dL, 95 % CI: - 0.027, - 0.011, p < 0.001). Dyslipidemia, hypertension and non-alcoholic fatty liver disease were the ailments of the studies that encompassed non-healthy patients. Conclusions: This meta-analysis shows that the use of GCBE supplements resulted in a statistical decrease in CRP levels, mainly for non-healthy subjects. However, due to the limited number of studies, further randomized clinical trials are crucial in this regard.