Chemopreventive effects of tea extracts on human pancreatic cancer cells
Lynn-Cook BD, Rogers T, Yan Y, Blann EB, Kadlubar FF & Hammons GJ, Nutrition & Cancer, 1999, 35(1): 80-86

Pancreatic and prostate cancers pose serious problems to human health. To determine the potential for chemopreventive intervention against pancreatic and prostate cancers, black and green tea extracts and components of these extracts were examined in vitro for their effect on tumour cell growth. Components included a mixture of polyphenols from green tea (GTP), mixtures of polyphenols (BTP) and of theaflavins (MF) from black tea, and the purified components epicatechin-3-gallate (ECG) and epigallocatechin-3-gallate (EGCG). Two human cell lines, pancreatic adenocarcinoma (HPAC) and prostate tumour (LNCaP), were exposed to these agents for 24 hours. Results showed inhibition (approx 90%) of cell growth in pancreatic tumour cells by black and green tea extracts (0.02%). GTP (10 mug/ml) and MF (100 mug/ml) significantly inhibited growth (approx. 90%); ECG and EGCG inhibited growth as well (approx. 95%). Black and green tea extracts, GTP, and EGCG decreased the expression of the K-ras gene, as determined by reverse transcription-polymerase chain reaction. Green and black tea extracts decreased the multidrug-resistant gene (malt-1), although GTP and EGCG increased expression. Similar data were obtained in the prostate cell line LNCaP. All agents significantly inhibited growth. These agents increased expression of the mdr-1 gene. This study suggests that components from black and green tea extracts can modulate the expression of genes known to play a role in the carcinogenesis process and, therefore, may be potential agents for chemoprevention against pancreatic cancer.

Tea and colorectal cancer

Tea compound may have preventive effect on colorectal cancer
Pan-H, Wu-J, Zheng-S. SO Chung-Hua-Yu-Fang-I-Hsueh-Tsa-Chih 1995 Nov, VOL: 29 (6), P: 356-9, ISSN: 0253-9624.

Colorectal cancer was induced by subcutaneous injection of 1,2- dimethylhydrazine (DMH) in mice, and the animals were administered orally with 0.4% of tea polyphenols (TP) simultaneously for 20 weeks to study its preventive effects. Results showed incidence of colorectal cancer in mice administered with TP was significantly lower than in positive controls (P < 0.05), and average number of tumour foci and proportion of adenocarcinoma were significantly fewer in TP group than in positive controls (P < 0.01). Level of cytochrome P450 (CP450) in liver microsome of the mice administered with TP was lower than that both in negative and positive controls (P < 0.01), and activities of superoxide dismutase (SOD) in liver tissue were higher than those in positive controls (P < 0.01), but lower than in negative controls (P < 0.01). Proliferative index of epithelial cells in mice was not obviously influenced by TP. It suggested that TP could have preventive effects on experimental colorectal cancer with a possible mechanism of lowering CP450 and increasing the activity of SOD in the liver.

Effect of black tea consumption on biomarkers of oxidative stress status and colorectal cancer risk in healthy older adults.
Dr Jeffrey Blumberg

Dr Blumberg intended to test the hypothesis that enhanced consumption of black tea for 9 weeks by healthy older adults would reduce measures of oxidative stress status and putative markers of cancer risk (particularly colorectal cancers) due to the antioxidant polyphenolic content of the tea. He carried out a trial of the hypothesis by running a randomised, double blind, placebo-controlled trial in a group of free-living healthy, older (65 years) adults. A substantial number of measures were made before and after the trial period in both the index and the placebo groups, e.g. plasma and urinary polyphenol content; vitamin C, E and Beta-carotene content in plasma, total anti-oxidant status, DNA methylation, fecal mutagens. In this experiment he did not demonstrate an effect of long-term tea consumption on plasma antioxidant and oxidative stress status and biomarkers of colorectal carcinogeneis. Dr Blumberg concluded that, to show the effects of tea upon the outcome variables he used samples must taken frequently during the trial to show changes above baseline. Long-term tea consumption in the amounts used in the study is not associated with ill effects such as decreased iron status.

Tea and Prostate Cancer

Research Shows Drinking Tea Reduces the Risk of Prostate Cancer
Professor David Forman, Centre for Cancer Research, University of Leeds.

A recent study published in the International Journal of Cancer indicates that the risk of prostate cancer decreases in people who drink two to three cups of tea a day. Excluding skin cancer, prostate cancer is now the second most common cancer affecting British men, with 14,000 new cases being diagnosed every year.

Researchers from the University of Toronto looked at the complete history of beverage intake amongst 617 men who were suffering from prostate cancer and compared them with 637 healthy men. The results of the study suggest that the benefits of drinking tea may be attributed to the high concentration of certain antioxidants called phytochemicals, which help the body fight harmful free radicals. Free radicals are a form of oxygen that can damage our bodies, including our cells. If not neutralised into "good oxygen," free radicals can advance ageing, work against the immune system and play a major role in the development of chronic and degenerative diseases. Tea also contains flavonoids which have been shown to help protect against lung, colon, digestive and breast cancer and substantially reduce the risk of heart attack in people who drink one or more cups of tea compared to those who drink no tea. In addition, tea is a good source of manganese, potassium, zinc and calcium when taken with milk (as 98% of people do).

"This study provides some further evidence concerning the anti-cancer properties of tea consumption. These new results are very preliminary, but if confirmed in other studies, it may provide an important new insight into the prevention of prostate cancer.