A concentrated extract consumed daily for an average of 34 days was associated with significant reductions in the blood levels of hepatocyte growth factor (HGF), vascular endothelial growth factor (VEGF) and prostate specific antigen (PSA), say the new results from Louisiana State University (LSU).
The new study, published online in Cancer Prevention Research, reports the effects of green tea extracts in the form of Mitsui Norin's commercial Polyphenon E (PE). The extract contained 800 mg of EGCG (epigallocatechin-3-gallate) and lesser amounts of epicatechin, epigallocatechin, and epicatechin-3-gallate. The total tea polyphenol dose was 1.3 grams.
"The investigational agent used in the trial, Polyphenon E may have the potential to lower the incidence and slow the progression of prostate cancer," said lead researcher, Professor James Cardelli.
The LSU researchers recruited 26 men, aged between 41 and 72. The men all had diagnosed prostate cancer and were scheduled for radical prostatectomy. The men consumed four capsules per day of the green tea extract, equivalent to 12 cups of tea, until the day before surgery. The average supplementation period was 34.5 days.
Findings showed a significant reduction in serum levels of HGF, VEGF and PSA after treatment, with some patients demonstrating reductions in levels of greater than 30 percent, according to the researchers.
“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,” wrote the researchers. “These findings support a potential role for Polyphenon E in the treatment or prevention of prostate cancer,” they concluded.
The researchers are reportedly continuing their study in this area with an investigation into why some patients responded better than others. Cardelli suggested that additional controlled clinical trials should be done to see if combinations of different plant polyphenols were more effective than Polyphenon E alone.
"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," said Cardelli.
Commenting on the findings, William Nelson, professor of oncology, urology and pharmacology at the Johns Hopkins Kimmel Cancer Center, said: "Unfortunately, this trial was not a randomized trial, which would have been needed to be more sure that the observed changes were truly attributable to the green tea components and not to some other lifestyle change (better diet, taking vitamins, etc.) men undertook in preparation for surgery.
“[However,] this trial is provocative enough to consider a more substantial randomized trial,” he added.
Global tea market
The global tea market is worth about €790 (£540, $941) million, with green tea accounting for about 20 per cent of total global production, while black tea accounts for about 78 per cent.
Green tea is said to contain over four times the concentration of antioxidant catechins than black tea (green tea leaves that have been oxidized by fermentation), about 70 mg catechins per 100 mL compared to 15 mg per 100 mL for black tea.
Consumer awareness of the benefits of green tea and green tea extracts continues to rise with growing numbers of studies, from 430 papers in 2000 to almost 1500 in 2003, reporting benefits of the main compounds, catechins.
This has seen European demand surge, having reached 500 metric tonnes in 2003. Companies such as DSM, with its Teavigo boasting 95 per cent purity of epigallocatechin gallate (EGCG), and Taiyo International, with its Sunphenon claiming more than 90 per cent purity, position themselves firmly in specific catechin markets.
Source: Cancer Prevention ResearchPublished online ahead of print, doi: 10.1158/1940-6207.CAPR-08-0167v1“Tea Polyphenols Decrease Serum Levels of Prostate-Specific Antigen, Hepatocyte Growth Factor, and Vascular Endothelial Growth Factor in Prostate Cancer Patients and Inhibit Production of Hepatocyte Growth Factor and Vascular Endothelial Growth Factor In vitro”Authors: J. McLarty, R.L.H. Bigelow, M. Smith, D. Elmajian, M. Ankem, J.A. Cardelli