Green tea associated with reduced risk of advanced prostate cancer

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Drinking green tea associated with reduced risk of advanced prostate

cancer

 

A report published online on September 29, 2007 in the American Journal

of Epidemiology described the finding of an association in Japanese men

between drinking green tea and a reduced risk developing advanced

prostate cancer.

Researchers at Japan & rsquo;s National Cancer Center in Tokyo utilized

data from the Japan Public Health Center-based Prospective Study, which

involved two cohorts enrolled in 1990 and 1993. The current analysis

included a total of 49,920 men aged 40 to 69 upon enrollment who were

followed until the end of 2004. Questionnaires completed by the cohorts

after enrollment were analyzed for amount and frequency of green tea

consumption, and participants were categorized according to their

intake.

 

By the end of the follow up period there were 404 cases of prostate

cancer diagnosed, of which 114 were advanced (having spread beyond the

prostate), 271 localized (confined to the prostate), and 19 were of an

undetermined stage. Although drinking green tea was not found to have an

effect on localized prostate cancer, it was dose-dependently associated

with a decrease in advanced prostate cancer risk. Men in the top

category of green tea intake, who consumed five or more cups per day,

had nearly half the risk of developing advanced prostate cancer compared

with those who consumed less than one cup per day.

 

The study is the first, to the authors & rsquo; knowledge, to examine the

association between green tea and prostate cancer according to stage,

and to determine the protective benefit of green tea on advanced

prostate cancer. They posit the induction of apoptosis, cell growth

inhibition, and cell cycle progression arrest as mechanisms for green

tea & rsquo;s effects, and add that EGCG, a compound believed to be

responsible for many of tea & rsquo;s benefits, has been found to prevent

tumor cell invasion as well as the expression of matrix metalloprotease,

an enzyme which is overexpressed in angiogenesis.

 

Although the researchers & rsquo; results are supported by a number of

animal studies, they recommend well-designed human trials to confirm

their findings.

 

Health Concern

Prostate cancer adjuvant therapy

 

Long-term consumption of tea catechins is common in China and Japan. The

frequency of the latent, localized type of prostate cancer (PC) does not

vary significantly between Eastern and Western cultures, but the

clinical incidence of metastatic PC is generally lower in Japan and

other Asian countries, in contrast to the common occurrence of

metastatic PC in Europe and the United States. One possible explanation

is that EGCG consumption in green tea in Asian countries prevents the

progression and metastasis of PC cells. This explains the lower

mortality rate due to PC and breast cancer in Asian countries as

compared to Western countries.

 

In regards to PC, there are now studies that show that vitamin E and

selenium use will decrease the incidence as well as the mortality from

PC. The ATBC study by Heinonen et al. (J. Natl. Cancer Inst., 1998)

demonstrated a 32% decrease in the incidence of PC and a 41% lower

mortality rate from PC in men taking alpha-tocopherol (vitamin E).

Another study by Fleshner et al. (J. Urol., 1998) showed a reduction in

growth rates of transplanted LNCaP cells in athymic mice induced by a

high-fat diet (40.5%) by dl-alpha tocopherol (synthetic vitamin E). The

landmark study by Clark et al. (JAMA, 1996) provided evidence that 200

mcg of selenium could reduce the incidence of PC by 63%. This is

consistent with the observation that selenium inhibited the growth of

DU-145-an androgen-independent human cell line of PC-by 50% at a

selenium dose of 1 × 10-6 M and by 98% at a dose of 10-4 M.

 

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