After a year's 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 don't 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.
