Monday, June 22, 2009
Green Tea: A New Weapon Against Prostate Cancer?
Many medical “discoveries” have occurred quite by happenstance. For instance, consider the story of Green Tea which began some 5,000 years ago when, as Chinese legend has it, leaves from a nearby Camellia sinensis tree fell into an emperor’s boiling pot of water. The leaves turned the water a light-brown color and gave off a delightful aroma. The emperor, upon taking a sip, found it also had an excellent taste and proclaimed it as “heaven sent.” Since then, the delectable brew has been considered a health-promoting beverage in China; used to treat everything from headaches to depression.
Today, a wealth of studies has provided hard evidence for its positive effects on health. Drinking green tea is reputed to promote heart health, lower high cholesterol levels, lessen free radical damage to cells, fight obesity, inhibit the abnormal formation of blood clots, and slow the progression of age-related cognitive impairment and Alzheimer’s disease. Researchers now say that certain compounds in green tea may actually slow the progression of prostate cancer, a disease that kills more men each year in the United States than any cancer other than lung cancer.
Previous studies have shown that green tea may be linked to a reduced incidence of prostate cancer, and its polyphenols have been regarded as a potential cancer therapy. But last year, the FDA announced that the evidence for green tea benefits was inconclusive, because people consume relatively small quantities. So, Dr. James Cardelli, and his colleagues at Louisiana State University Health Sciences Center in Shreveport, carried out a clinical trial to determine the effects of short-term supplementation with increased amounts of the active compounds in green tea on the progression of prostate cancer.
The small study consisted of 26 men between 41 and 68 years of age who had been diagnosed with prostate cancer and were scheduled for radical prostatectomy. The men were put on a daily dose of four capsules containing a total of 1.3 grams of polyphenon E, equivalent to about 12 cups of normally brewed concentrated green tea, for 12 to 73 days (with an average time of 34.5 days), until the day before surgery. Blood tests showed a significant reduction in serum levels of three biomarkers associated with the growth and spread of prostate cancer: hepatocyte growth factor (HGF), vascular endothelial growth factor (VEGF), and prostate specific antigen (PSA).
On an average, HGF decreased 18.9 percent, VEGF decreased by 9.9 percent and PSA dropped by 10.4 percent. Some patients demonstrated reductions of more than 30 percent. The researchers said that in vitro, EGCG (the main catechin in polyphenon E) swiftly blocked the production of HGF, and the block “seems to be at the level of transcription.” EGCG also blocked the production of VEGF, which plays a critical role in the angiogenic process in cancer-associated fibroblasts, they noted. Age, race, and time on the drug did not have a significant effect on the changes in serum biomarkers.
Previous studies have suggested that high levels of EGCG may have adverse effects on liver function, but in this study the liver function of the patients remained normal. “Our results show a significant reduction in serum levels of PSA, HGF, and VEGF in men with prostate cancer after brief treatment with EGCG (Polyphenon E), with no elevation of liver enzymes. These findings support a potential role for Polyphenon E in the treatment or prevention of prostate cancer,” the researchers concluded.
Dr. Cardelli admits that the study is still in an early stage and that the findings need to be verified by larger, placebo-controlled trials. “Green tea can keep cancer from growing very fast, but it may not be able to shrink tumors,” he said. “But it can be a good addition to traditional therapies, like chemotherapy or radiation.”
“We think that the use of tea polyphenols alone or in combination with other compounds currently used for cancer therapy should be explored as an approach to prevent cancer progression and recurrence," Dr. Cardelli said. “There is reasonably good evidence that many cancers are preventable, and our studies using plant-derived substances support the idea that plant compounds found in a healthy diet can play a role in preventing cancer development and progression.”
John Neate, chief executive of the Prostate Cancer Charity, says though there have been a number of studies into the potential benefits of green tea, there is no conclusive evidence. “The results of this study do suggest that there is merit in further research into the effects of extracts of green tea, both in relation to its impact on the prevention of prostate cancer and in controlling progression in men already diagnosed with the disease, as was investigated in this instance,” he said. “These initial positive findings could indicate that green tea could have a place in ‘active surveillance’, where a slow-growing, low risk tumor is monitored for changes and men want to take something which could help keep progression at bay.”
“Potentially, this could mean completely avoiding, in some cases, any of the more usual medical interventions and their associated side effects,” Neate said.
Prostate cancer is the second leading cause of cancer death among American men. According to the American Cancer Society, prostate cancer will be diagnosed in 192,280 men and will kill 27,360 in 2009. Men over 50 are urged to get tested for the disease annually, however very few do, putting them at risk of being diagnosed at a later stage rather than earlier in the cancer process.
The study is published in the journal Cancer Prevention Research.
By: Madeline Ellis
Published: Monday, 22 June 2009