Research Highlights Green Tea's Chemopreventive Effects

LONDON--The European Journal of Cancer Prevention ran several studies regarding green tea in its October issue. The studies covered cervical and colorectal cancers, as well as explored a possible mechanism of action.

Researchers from the Catholic University of Korea found green tea extracts--polyphenon E (poly E) and (-)-epigallocatechin-3-gallate (EGCG)--in ointment and capsule form are effective for treating cervical lesions, which are a risk factor for cervical cancer (12, 5:383-90, 2003). They randomly assigned 51 patients with cervical lesions caused by the human papilloma virus (HPV) to various treatment groups and compared the responses with those of 39 controls. Results indicated 20 out of 27 patients (74 percent) using topical poly E ointment twice weekly showed a response. In addition, six out of eight (75 percent) subjects using poly E ointment plus 200 mg/d of oral poly E showed a response, and three out of six subjects using oral poly E alone showed a response. As for EGCG, six out of 10 subjects taking 200 mg/d of EGCG for eight to 12 weeks showed a response. Researchers concluded an overall 69-percent response rate was seen with green tea extract therapy compared with a 10-percent response rate seen in controls.

Green tea consumption also seems to have a slight protective effect against colorectal tumors, according to researchers at Wake Forest University School of Medicine, Winston-Salem, N.C. (12, 5:439-43, 2003). They took biopsies from the rectal mucosal of 171 patients with adenomas (a benign tumor) and 323 adenoma-free controls. Tea consumption showed a weak negative association with adenoma occurrence, although consumption was not associated with an increase in apoptosis (cell death) of normal rectal tissue.

Animal research conducted out of the Seoul National University College of Medicine in Korea indicated green tea may prevent cancer via a different mechanism than its polyphenols (12, 5:391-5, 2003). Green tea polyphenols have been shown to inhibit an enzyme known as CYP1A that specifically activates carcinogens, according to the researchers. In their study, however, they found green tea consumption induced rather than inhibited CYP1A activity. Additional evidence from their research suggested green tea may work to biotransform CYP1A-inducing carcinogens into non-carcinogenic metabolites by modulating enzymatic activity.