In the first known study of the absorption and anti-tumor effects of green and black tea polyphenols in human tissue, researchers at the University of California at Los Angeles were able to detect tea polyphenols in prostate tissue after a very limited consumption of tea.
More importantly, the scientists found that prostate cancer cells grew more slowly when placed in a medium containing blood serum of men who had consumed either green or black tea for five days compared to serum collected before the men began their tea-drinking regimen. Serum from men who drank comparable amounts of diet or regular soda showed no such slowing in cancer cell proliferation.
The study was reported at Experimental Biology 2004, in Washington, D.C., as part of the scientific program of the American Society of Nutritional Sciences, one of the six sponsoring scientific societies of this large multi-disciplinary meeting.
Recent animal and epidemiological studies have suggested tea may have anti-tumor effects against carcinoma of the prostate, and many of the polyphenolic components of tea have been found in the prostate and many other tissues in rats and mice after chronic consumption of green tea polyphenols in drinking water.
Dr. Susanne Henning, UCLA Center for Human Nutrition, says the UCLA research team - a combination of nutrition scientists and urologists - focused on the possible effect of tea polyphenols on factors named polyamines and the enzymes responsible for the production of polyamines. Elevated levels of polyamines have been associated with malignancy in humans, including prostate cancer, and - since polyamines are present in prostate tissue in high concentration - are considered a logical target for chemoprevention of prostate cancer.
Five days before they were to undergo radical prostatectomy, 20 men with prostate cancer were randomly assigned to consume daily either five cups of green tea, five cups of black tea, or diet or regular soda containing no tea polyphenols. Their blood serum was then collected and added to prostate tissue samples from a commercially available prostate cancer cell line called LNCaP.
Analysis of the prostate tissue showed a large variation in tea polyphenol content between study participants. Tea polyphenols were found in six out of eight participants drinking green tea, seven out of seven drinking black tea, and two out of five drinking soda. The fact that two of the control participants showed polyphenols in the prostate sample might be because they were eating chocolate regularly or drinking tea before entering the study. Chocolate does contain the polyphenols epicatechin and epicatechingallate, and the turnover rate of these polyphenols - how long they might remain in tissue - is not known. They are water-soluble and are all excreted after eight hours. The maximum concentration in plasma is after two to three hours.
But two important factors were different in the men who drank tea and those who did not during the five-day study.
When the scientists compared the level of total polyamine to the total polyphenol content, the tea drinkers showed a significant negative correlation - the more tea components in the tissue, the less of the polyamines associated with malignancy.
And when the scientists measured the proliferation of prostate cancer cells, there was a significant decrease in how fast new cancer cells appeared for the men who had consumed either green or black tea. That was true even when no tea components could be detected in the serum, indicating, says Dr. Henning, that the inhibition of cell proliferation was caused by other compounds altered through tea consumption.
Prostate cancer is one of the common cancers among males in the United States, and more than a fourth of all those patients with prostate cancer are known to use alternative therapies, including green tea. This study suggests that both black and green tea are promising natural dietary supplements useful for chemoprevention of prostate cancer, according to Dr. Henning. She plans to investigate if this effect can be enhanced by consuming larger amounts of tea polyphenols in the form of green tea extract supplement capsules.
Dr. Henning's co-authors are Yantao Niu, Nicolas H. Lee, Francisco Conde, Pakshan Leun, Jenny Hong, George Csathy, Hossein Ziaee, Vay L. W. Go, David Heber, and William J. Aronson, of UCLA's Center for Human Nutrition, Department of Urology, and Department of Physiology.
Source: Eurekalert & othersLast reviewed: By John M. Grohol, Psy.D. on 21 Feb 2009
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