Tea and Tea Polyphenols in Cancer Prevention
Chung Yang, Jee Chung, Guang-yu Yang, Saranjit Chhabra & Mao-Jung Lee
2000 American Society for Nutritional Sciences

The inhibitory action of tea (Camellia sinensis) and tea components against cancer formation has been demonstrated in different animal models involving different organ sites in many laboratories. The possible preventive activity of tea against cancer in humans, however, is not clear.

A critical question is whether the information obtained from animal studies is applicable to humans because of possible species differences or the difference in the quantity of the tea used in animal studies and that consumed by humans.

This article will discuss the results from animal studies and possible cancer inhibitory mechanisms that might be applicable to human cancer prevention. To provide a basis for more quantitative analyses of the effect of tea on carcinogenesis, the levels of tea polyphenols in blood, urine and tissue samples have been analyzed, and the pharmacokinetic properties of tea polyphenols studied.

Studies with cell lines have demonstrated that tea polyphenols effect signal transduction pathways, inhibit cell proliferation and induce apoptosis, but the effective concentrations are usually much higher than those observed in blood and tissues. More mechanistic studies in these areas will help us to understand the inhibitory action of tea against carcinogenesis and provide background for evaluating the effects of tea consumption on human carcinogenesis.

Tea and Pancreatic Cancer

Lifetime consumption of tea not associated with risk of pancreas cancer
Bueno de Mesquita H B, Maisonneuve P, Moerman C J, Runia S and Boyle P.
International Journal of Cancer Vol. 50 514-522 1992.

From 1984 to 1988 a population-based case-control study was carried out in The Netherlands, in collaboration with the International Agency for Research on Cancer, to examine the possible relationship between the habitual lifetime consumption of alcohol, coffee and tea and exocrine pancreatic carcinoma in 176 cases and 487 controls.

An interviewer-administered questionnaire was used to ascertain major life events and obtain estimates of consumption (ever-never) and frequency of consumption throughout life. Logistic regression analyses yielded odds ratios adjusted for age, sex, response status, smoking, dietary intake of energy and vegetables and of alcoholic or non-alcoholic drinks.

When compared with data from non-drinkers, the cumulative lifetime consumption of all types of alcohol in grams of ethanol (ORs 1.00, 0.97, 0.93, 1.25, p trend 0.55), beer, spirits, red wine and fortified wine was not related to risk. The consumption of white wine was inversely associated with risk (OR 0.41, 95% CI 0.24-0.70). The uniformly reduced risk estimates for the lifetime number of drinks of white wine were based on small numbers (ORs 1.00, 0.44, 0.25, 0.40, p trend 0.001). When compared with data from non-drinkers, our findings suggest an inverse dose-response relationship for the lifetime consumption of coffee (ORs 1.00, 0.72, 0.37, 0.58, p trend 0.06), whereas lifetime consumption of tea and of ground, instant and decaffeinated coffee was not associated with risk.

The absence of an effect of lifetime consumption of decaffeinated coffee may be due to the small numbers of subjects. These results further strengthen existing evidence against a positive association between consumption as well as lifetime consumption of (sources of) alcohol, tea or coffee and the development of exocrine pancreatic cancer.

Lifetime consumption of tea does not increase risk of pancreas cancer
Zatonski W A, Boyle P, Przewozniak K, Maisonneuve P, Drosik K and Walker A M. International journal of Cancer Vol. 53 601-607 1993.

A population-based, case-control study of pancreas cancer was undertaken in Opole, Poland, within the framework of the SEARCH Programme of the International Agency for Research on Cancer: this is the first aetiological study of pancreas cancer reported from Poland where the reported mortality rate has doubled since 1963.

This study of pancreas cancer has provided some further supporting evidence of an association between increased pancreas risk with increasing levels of cigarette smoking. The risk rose with increasing lifetime cigarette consumption with a trend which was weakly significant (p = 0.061). Findings regarding lifetime tea and coffee consumption were not consistent with intake of either beverage increasing the risk of this disease. There was a strongly significant trend of decreasing risk with increasing lifetime consumption of tea (p < 0.001), which was also apparent when the analysis was restricted to subjects who were interviewed directly.

For coffee consumption, which is low in Poland, there was also a negative association apparent in the data, which was not statistically significant among the sub-set of subjects who were directly interviewed. The findings regarding alcoholic beverages were overall null, although the weakly positive trend in risk with spirits consumption (p = 0.71) may deserve further investigation in view of the special nature of the source of spirits (vodka) in Poland.

Tea consumption reduces risk of pancreatic cancer
Shibata A, Mack T M, Paganini-Hill A, Ross R K and Henderson B E., International Journal of Cancer Vol. 58 46-49 1994.

Risk factor for pancreatic cancer were examined in a cohort study of 13,979 residents of a retirement community. After 9 years of follow-up, 65 incident cases of pancreatic cancer were identified. An increased risk of pancreatic cancer was associated with a history of diabetes and cholecystectomy. Higher intake of vegetables, fruits, dietary beta-carotene, and vitamin C were each associated with a reduced risk of pancreatic cancer, although none of these associations was statistically significant. Risk of pancreatic cancer decreased with increasing tea consumption but was unrelated to coffee consumption. No strong or consistent association was seen between either smoking or alcohol consumption and risk of pancreatic cancer, but a consistent and significant increase in risk followed cholecystectomy.