Focus on Alternative and Complementary Therapies
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Focus Alternat Complement Ther©2005 Pharmaceutical Press
Focus Altern Complement Ther 2003; 8: 127
Gastrointestinal cancer is one of the leading causes of cancer mortality in the world. Therefore, numerous efforts are being conducted to find chemoprotective substances able to reduce its incidence. Among these substances, green tea, one of the most popular beverages worldwide, has been reported to provide protective effects against gastrointestinal cancer. The purpose of this systematic review is to critically evaluate all the epidemiological studies of an association between green tea consumption and a risk reduction of gastrointestinal cancer.
Epidemiological studies of green tea consumption in relation to gastrointestinal cancer or preneoplastic lesions have been identified through computerised literature searches using the following databases: Medline (Pubmed), Embase, Amed, CISCOM, Phytobase and Cochrane Library. In addition, searches were performed on 20 websites related to the topic. No language restrictions were imposed. Data relating to number of subjects (sample size), study design, green tea consumption levels and results were extracted by the first author and validated by other authors.
Nineteen epidemiological investigations met our inclusion/exclusion criteria. Three cross-sectional studies, one population hospital-based case-control study, seven population-based case-control studies, four hospital-based case-control studies and four cohort studies were identified.
These studies seem to suggest a protective effect of green tea on adenomatous polyps, chronic gastritis and stomach cancer formation. In contrast, there is currently no clear epidemiological evidence to support the suggestion that green tea plays a role in the prevention of intestinal cancer.
