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Green Tea and Prostate Cancer
Each year
in the U.S. more than 220,000 men receive the unwelcome news that
they've developed prostate cancer and, unfortunately, 31,000 men die of
the disease. Yet in Asian countries, the rates of prostate cancer are
surprisingly low. How did the Asians get to be so lucky? Many
researchers think it may have to do with their tea consumption.
At least two studies of large populations have shown that men who
regularly consume tea (black or green) have a lower incidence of
prostate cancer.1,2 And as the frequency, duration and
quantity of green tea consumption goes up, the risk of developing
prostate cancer goes down.3 This was dramatically illustrated
in a study of men with pre-cancerous prostate lesions, which made them
particularly likely to develop prostate cancer. Those who received daily
doses of green tea catechins were found to be 90 percent less likely to
develop full-blown prostate cancer than those who didn't receive
catechins.4
Why would
green tea have an effect on prostate cancer? Well, for starters, once
green tea is ingested, its catechins make their way through the
bloodstream and settle right there inside the prostate tissue. From this
fortunate position, the catechins appear to fight prostate cancer by:
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Slowing the growth and speeding the death of
cancer cells - In "test tube" studies, green tea's EGCg not
only slowed the growth of human prostate cancer cells but promoted
cancer cell “suicide.”5
-
Stopping cancer before it starts -Animal
studies have shown that green tea catechins reduce the activity of an
enzyme called ornithine decarboxylase (ODC), which is believed to play
a part in the start-up of prostate cancer.6
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Inhibiting COX-2 - The enzyme COX-2,
which is found in large quantities in prostate cancer tissue, appears
to play a role in the cancer process. Studies have shown that
medications that inhibit COX-2, like the arthritis drug celecoxib,
slow prostate cancer growth in animals. Green tea's EGCg has also
been found to inhibit COX-2 in prostate cancer cells7
indicating that it, too, may be helpful in combating the disease.
But an even
better idea may be combining EGCg with celecoxib to deliver a double
whammy to prostate cancer. In mice bred to
develop the disease, prostate tumor growth was slowed 42 percent by EGCg
and 57 percent by celecoxib. But when the two were combined, the growth
of prostate tumors was slowed by an astounding 81 percent! 8
This finding is especially important since
taking too much celecoxib carries with it an increased risk of heart
attacks. But when combined with green tea's EGCg, lower doses of the
medication may be even more effective than the higher “stand-alone”
doses.
Click here for a
simplified look at the studies on
green tea's effect
on prostate cancer.
Footnotes:
1)
Heilbrun LK, Nomura A, Stemmermann GN. Black tea consumption and cancer
risk: a prospective study. British Journal of Cancer
1986;54:677-83.
2)
Jain
MG, Hislop GT, Howe GR, et al. Alcohol and other beverage use and
prostate cancer risk among Canadian Men. International Journal of
Cancer 1998;78(6):707-11.
3)
Jian L, Xie LLP, Lee AH, Binns CW. Protective effect of green tea
against prostate cancer: a case-control study in southeast China.
International Journal of Cancer 2004;108(1):130-35.
4)
Bettuzzi S, Brausi M, Rizzi F, et al. Chemoprevention of human prostate
cancer by oral administration of green tea catechins in volunteers with
high-grade prostate intraepithelial
neoplasia: a preliminary report from a one-year proof-of-principle
study. Cancer Research 2006;66(2):1234-40.
5)
Gupta S, Ahmad N, Nieminen AL, Mukhtar H. Growth inhibition, cell-cycle
dysregulation, and induction of apoptosis by green tea constituent
(-)-epigallocatechin-3-gallate in androgen-sensitive
and androgen-insensitive human prostate carcinoma cells. Toxicology &
Applied Pharmacology 2000;164(1):82-90.
6)
Gupta S, Ahmad N, Mohan RR, et al. Prostate cancer chemoprevention by
green tea: in vitro and in vivo inhibition of testosterone-mediated
induction of ornithine decarboxylase. Cancer Research
1999;59(9):2115-20
7)
Hussain T, Gupta S, Adhami VM, Mukhtar H. Green tea constituent
epigallocatechin-3-gallate selectively inhibits COX-2 without affecting
COX-1 expression in human prostate carcinoma cells. International
Journal of Cancer 2005;113(4):660-69
8)
Adhami VM, Malik A, Zaman N, et al. Combined inhibitory effects of green
tea polyphenols and selective cyclooxygenase-2 inhibitors on the growth
of human prostate cancer cells both in vitro and in vivo. Clinical
Cancer Research 2007;13:1611-19.
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Nadine Taylor, M.S., R.D. presents
GreenTeaLibrary.com,
the most comprehensive collection of scientific information
describing the health benefits of green tea.
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