A new research has raised doubts about the effectiveness of green tea in preventing cancer.
Many individuals are incorporating small changes into their daily routine - such as drinking green tea - hoping that it will keep cancer risk at bay. However, a systematic review of studies has produced conflicting results.
"Despite the large number of included studies the jury still seems to be out on the question of whether green tea can in fact prevent the development of various cancer types," said lead review author Dr Katja Boehm.
"One thing is certain...green tea consumption can never account for cancer prevention alone," Boehm added.
Three types of tea - black, green and oolong - come from the plant Camellia sinensis, and all contain polyphenols. Catechins, a subgroup of the polyphenols, are powerful antioxidants that help prevent cancer.
While the review found that green tea had limited benefits for liver cancer, conflicting evidence were found for other gastrointestinal cancers, such as cancer of the esophagus, colon or pancreas.
One study showed a decreased risk of prostate cancer for men who consumed higher quantities of green tea or its extracts.
The review did not find any benefit for preventing death from gastric cancer, and found that green tea might even increase the risk of urinary bladder cancer.
But showed a positive association between green tea consumption, and a decreased risk of breast cancer.
Dr Nagi Kumar, director of Nutrition Research at Moffitt Cancer Centre in Tampa, Fla., is optimistic about the potential for green tea in cancer prevention.
"The substances found in green tea are certainly promising," Kumar said.
"The field now has progressed to where we [can]...test the effectiveness and safety of green tea polyphenols using a drug form similar to the constituents in tea to see if we can prevent cancer progression. Time will tell," Kumar added.
The review has been published in the latest issue of The Cochrane Library, which is a publication of The Cochrane Collaboration.