How green tea might reduce prostate cancer risk

The incidence of many cancers seems to be related to lifestyle, especially to what we eat. For prostate cancer, Japanese men (living in Japan) have a much lower incidence than American men. However, when Japanese men move to the U.S., their risk of prostate cancer increases.

The question is why - and green tea might be part of the answer.

There is good laboratory data to suggest that green tea inhibits prostate cancer cell growth. However, the research in humans has been inconsistent. Some studies indicate green tea reduces the risk of prostate cancer while others show no real benefit. Complicating the data is one study illustrating that, in Hawaiian men of Japanese heritage, green tea consumption actually resulted in an increased risk of prostate cancer.

These studies, however, lack certain controls. Several studies included black tea as well as green tea, and perhaps the effects of black and green tea on prostate cancer are different. In addition, the stage of prostate cancer is often omitted. We know that localized and advanced prostate cancer respond very differently to medications - and possibly to green tea, too.

A large Japanese study, published in the American Journal of Epidemiology, controlled for a number of these variables and the results were very interesting. Almost 50,000 men were followed over a decade and their green tea consumption was regularly recorded over this time period. During this study, 404 men developed prostate cancer, of which 271 cases were localized, 114 were advanced and 19 were of an undetermined stage.

Drinking green tea did not reduce the risk of developing localized prostate cancer. However, the more green tea consumed, the lower the risk of developing the more serious advanced prostate cancer. Drinking five or more cups of green tea per day reduced the risk of advanced prostate cancer by almost 50 percent.

Whole green tea and its active constituents, like epigallocatechin, not only inhibit prostate cell growth but also actually promote prostate cancer cell death. In addition, substances in green tea prevent tumors from spreading and metastasizing by reducing tumor-specific enzymes called metalloproteases. Higher levels of metalloproteases are associated with more aggressive prostate cancer.

In a recent publication from the National Institutes of Health, the medical research on green tea and prostate cancer was reviewed. The findings are that epigallocatechin from green tea and green tea supplements can accumulate in the prostate gland to significant levels. Epigallocatechin reduces testosterone levels, and most prostate cancer is responsive to testosterone. Unfortunately, not all prostate cancers are testosterone responsive. Green tea does not seem to have benefit in hormone-resistant prostate cancers.

Although this was an excellent study, there are many questions to be answered regarding green tea and prostate cancer and further research is underway. Until then, drinking several cups of green tea each day remains a wonderful lifestyle choice.

• Patrick B. Massey, M.D., Ph.D is medical director for complementary and alternative medicine for the Alexian Brothers Hospital Network.