Efficacy of green tea in the prevention of cancers.

Understanding the literature about the efficacy of green tea consumption in preventing and slowing the progression of cancers is critical. A systematic review of the literature was conducted using an electronic search to identify studies from 2000 to 2008 in the following database: Alt HealthWatch, CINAHL, Medline, Health Source - Consumer Edition, Health Source: Nursing/Academic Edition, Web of Science (ISI), and the Cochrane Library. Although the evidence from this review suggested associations between green tea consumption and a decreased risk for some cancers, the findings were inconclusive. In selected cases, green tea was effective in slowing the progression of the earlier stages of cancer. However, contrary evidence is reported and the dose and duration of use is variable. Most evidence stems from self-reports. Research using more rigorous designs to investigate the efficacy of green tea in humans is needed.