Green tea consumption and liver disease: a systematic review

Objectives: To present the effect of green tea consumption against liver disease. Data sources: Interventional and observational studies both in Western countries and in China and published between the years 1989 and December 2007. Review Methods: The articles were retrieved from Medline, Embase database, Chinese biomedicine web database and Chinese scientific journal's database using proper MESH headings and assessed by two independent investigators according to established inclusion criteria. The characteristics and outcomes of the chosen articles were displayed for further analysis and the quality of each study was also evaluated according to the widely acknowledged criteria. P < 0.05 was defined as statistically significant in all enrolled trials. Results: Ten qualified studies ( eight from China, one from Japan and the other from the USA) with various outcomes such as liver cancer, cirrhosis and fatty liver disease were finally chosen. Among them, study designs differed in that there were four randomized-controlled clinical trials, two cohort, one case-control and three cross-sectional studies. The heterogeneity in the study design, outcomes, cofounders and amount of tea consumption precluded further meta-analysis. Nevertheless, eight studies showed a significant protective role of green tea against various liver diseases as determined by relative risk/odds ratio or P-value and among them, four studies showed a positive correlation between green tea intake and attenuation of liver disease. Moreover, the other two studies also presented the protective tendency of green tea against liver disease. Conclusions: An increased consumption of green tea may reduce the risk of liver disease.