Green tea and the risk of gastric cancer in Japan.
ABSTRACT Although laboratory experiments and case-control studies have suggested that the consumption of green tea provides protection against gastric cancer, few prospective studies have been performed.
In January 1984, a total of 26,311 residents in three municipalities of Miyagi Prefecture, in northern Japan (11,902 men and 14,409 women 40 years of age or older), completed a self-administered questionnaire that included questions about the frequency of consumption of green tea. During 199,748 person-years of follow-up, through December 1992, we identified 419 cases of gastric cancer (in 296 men and 123 women). We used Cox regression to estimate the relative risk of gastric cancer according to the consumption of green tea.
Green-tea consumption was not associated with the risk of gastric cancer. After adjustment for sex, age, presence or absence of a history of peptic ulcer smoking status, alcohol consumption, other dietary elements, and type of health insurance, the relative risks associated with drinking one or two, three or four, and five or more cups of green tea per day, as compared with less than one cup per day, were 1.1 (95 percent confidence interval, 0.8 to 1.6), 1.0 (95 percent confidence interval, 0.7 to 1.4), and 1.2 (95 percent confidence interval, 0.9 to 1.6), respectively (P for trend=0.13). The results were similar after the 117 cases of gastric cancer that were diagnosed in the first three years of follow-up had been excluded, with respective relative risks of 1.2 (95 percent confidence interval, 0.8 to 1.8) 1.0 (95 percent confidence interval, 0.7 to 1.5), and 1.4 (95 percent confidence interval, 1.0 to 1.9) (P for trend=0.07).
In a population-based, prospective cohort study in Japan, we found no association between green-tea consumption and the risk of gastric cancer.
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ABSTRACT: The aim of the research was to analyze the composition of biologically active compounds, to determine the correlation between the concentration of biologically active compounds and antioxidant activity, the dependence of extractive compounds on the extraction time, the quality of different tea preparation forms (daily tea, infusions, decoctions) of those teas found in Lithuanian market. Four specimens of green tea from different regions of the world have been chosen as the object of analysis. Quality criteria's have been analyzed by using gravimetric and spectrophotometric methods. Detailed analysis has been performed using high performance liquid chromatography (HPLC) technique. With reference to analysis results it can be stated that in the aspect of relation to antioxidant activity/phenolic compounds, the teas with highest numbers in these dimensions were those from China region. The least numbers in antioxidant activity, dry residue and phenolic compounds were of teas from Sri Lanka. We tested the hypothesis that all green teas have phenolic compounds as their biological active compounds and because of this group of active compounds they distinguish antioxidant activity. The study gave strong evidence that green tea as a daily preparation and as well as pharmaceutical form (infusions, decoctions, capsules of green tea extract) may be used as preventive measures for cancerogenous processes, prostate cancer, renal or liver diseases because of it's antioxidant and free radical binding properties.
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ABSTRACT: Tea made from the leaves of the plant Camellia sinensis is a popular beverage. The possible cancer-preventive activity of tea and tea polyphenols has been studied extensively. This article briefly reviews studies in animal models, cell lines, and possible relevance of these studies to the prevention of human cancer. The cancer-preventive activity of tea constituents have been demonstrated in many animal models including cancer of the skin, lung, oral cavity, esophagus, stomach, liver, pancreas, small intestine, colon, bladder, prostate, and mammary gland. The major active constituents are polyphenols, of which (-)-epigallocatechin-3-gallate (EGCG) is most abundant, most active, and most studied, and caffeine. The molecular mechanisms of the cancer-preventive action, however, are just beginning to be understood. Studies in cell lines led to the proposal of many mechanisms on the action of EGCG. However, mechanisms based on studies with very high concentrations of EGCG may not be relevant to cancer prevention in vivo. The autooxidation of EGCG in cell culture may also produce activities that do not occur in many internal organs. In contrast to the cancer prevention activity demonstrated in different animal models, no such conclusion can be convincingly drawn from epidemiological studies on tea consumption and human cancers. Even though the human data are inconclusive, tea constituents may still be used for the prevention of cancer at selected organ sites if sufficient concentrations of the agent can be delivered to these organs. Some interesting examples in this area are discussed.Toxicology and Applied Pharmacology 12/2007; 224(3):265-73. DOI:10.1016/j.taap.2006.11.024 · 3.63 Impact Factor
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ABSTRACT: Gastric cancer in Japan, previously the top killer cancer, has recently shown decreased incidence and mortality rates. Epidemiological studies have demonstrated that environmental factors are closely associated with stomach oncogenesis, as evident from the geographical differences seen throughout Japan in both incidence and mortality. Moreover, Japanese immigrant populations gradually exhibit the lower incidence and mortality rates of gastric cancer in their chosen country. Likewise, younger generations in Japan have lower mortality rates than older generations at the same age, which may be accounted by the dramatic lifestyle changes in Japan after World War II. In addition to exploring and learning from the impact of these environmental factors, deliberate strategies to further lower the incidence and mortality rates of gastric cancer must include aggressive eradication programs for Helicobacter pylori and dietary education in both school curricula and for the general adult population to lower the intake of causative agents such as salt and increase the intake of beneficial agents such as fruits, vegetables and seaweeds. The dietary education should be coupled with better motivation for the general population to undergo regular screening with improved techniques. In the future, changes in these environmental factors and progresses in the diagnosis of and therapeutic strategies for gastric cancer will lead to further decrease in the incidence and mortality rates of this disease in Japan.The Tohoku Journal of Experimental Medicine 08/2007; 212(3):207-19. DOI:10.1620/tjem.212.207 · 1.28 Impact Factor