Green tea shown to prevent prostate cancer
First clinical study shows 90 percent efficacy in men with pre-malignant lesions
After a years oral administration of green tea catechins (GTCs), only one man in a group of 32 at high risk for prostate cancer developed the disease, compared to nine out of 30 in a control, according to a team of Italian researchers from the University of Parma and University of Modena and Reggio Emilia led by Saverio Bettuzzi, Ph.D.
Their results were reported here today at the 96th Annual Meeting of the American Association for Cancer Research.
"Numerous earlier studies, including ours, have demonstrated that green tea catechins, or pure EGCG (a major component of GTCs), inhibited cancer cell growth in laboratory models," Bettuzzi explained. "We wanted to conduct a clinical trial to find out whether catechins could prevent cancer in men. The answer clearly is yes."
Earlier research demonstrated primarily that green tea catechins were safe for use in humans. Bettuzzi and his colleagues had found that EGCG targets prostate cancer cells specifically for death, without damaging the benign controls. They identified Clusterin, the most important gene involved in apoptosis, or programmed cell death in the prostate, as a possible mediator of catechins action. "EGCG induced death in cancer cells, not normal cells, inducing Clusterin expression" said Bettuzzi.
To gauge susceptibility for prostate cancer among their research subjects, the team of Italian scientists recruited men with high-grade prostatic intraepithelial neoplasia – premalignant lesions that presage invasive prostate cancer within one year in nearly a third of cases and for which no treatment was given.
Eligible men were between 45 and 75 years of age. Vegetarians and men consuming green tea or derived products, or those taking anti-oxidants or following anti-androgenic therapy were excluded.
Of the 62 volunteers, 32 received three tablets per day of 200 mg each GTCs; the remainder were given a placebo. Follow-up biopsies were administered after six months and again at one year. Only one case of prostate cancer was diagnosed among those receiving 600 mg daily of GTCs, while nine cases were found in the untreated group. The 30 percent incidence rate among controls is consistent with previous findings, as was the absence of significant side effects or adverse reactions.
The interest in green tea catechins and other polyphenols – antioxidants found in many plants that give some flowers, fruits and vegetables their coloring – derives from traditional Chinese medicine, and the observation of lower cancer rates among Asian populations.
Bettuzzi observed that the Mediterranean diet is rich in vegetables, and lower rates of prostate cancer are found in that region, as well.
The 600 mg-per-day dosage of caffeine-free, total catechins (50 percent of which is EGCG) given to participants in the Italian study is one or two times the amount of green tea consumed daily in China, where ten to 20 cups a day is normal.
"We still dont know enough about the biological processes leading to prostate cancer," Bettuzzi noted. "The only thing we know for sure is that prostate cancer is diffuse, related to age and more prevalent in the West. Thus, prevention could be the best way to fight it. Although our follow-up will continue for up to five years, a larger, confirmatory study is needed."
Even so, Bettuzzi hints at the exciting prospect of using green tea catechins as a prophylactic against prostate cancer in men believed to be at higher risk, such as the elderly, African-Americans, and those with a family history of prostate cancer.
Warren R. Froelich | EurekAlert!