Tea and coffee consumption and the risk of digestive tract cancers: data from a comparative case-referent study in Japan

Botanical medicine and cancer: a review of the safety and efficacy

It is currently estimated that > 50% of all patients diagnosed with cancer explore complementary and alternative medicine - especially herbal medicine. We conducted a comprehensive review to assess the safety and efficacy of herbal medicines commonly used by patients in an attempt to: prevent cancer; treat cancer; and treat adverse effects associated with conventional cancer treatments. Current evidence suggests that Asian ginseng, garlic, green tea, tomatoes and soy intake as part of the diet may be useful in preventing various cancers; additional research is needed in order to determine the efficacy of essiac, evening primrose oil, mistletoe, reishi, shiitake and turmeric as cancer treatments; and ginger may be effective in treating chemotherapy-induced nausea and vomiting.

Science and ethics in epidemiology

This article is the summary of my Special Lecture at the 14th Annual Scientific Meeting of the Japan Epidemiological Association in 2004. Epidemiology is defined as the “science of investigating the distribution of diseases in human populations and their determinants.” Recent advances in study methodology, especially a widespread conduct of randomized controlled trials (RCTs), have strengthened the scientific basis of epidemiology. When a highly scientific method of investigation is applied to humans, the ethical aspects of the study also become an issue. However, it would also be unethical to use new drugs and vaccines without scientific evidence. The ethical aspects and the scientific aspects of epidemiologic research are thus both very important, but conflict with each other, often causing dilemmas. I would discuss how we could solve these dilemmas and thus contribute ourselves to health promotion and disease prevention of human populations. Finally, I would propose the new paradigm of changing epidemiology into a “neotype science” and transformation of EKIGAKU (epidemiology) into EKIGAKU (beneficial science).

Coffee bean extracts rich and poor in kahweol both give rise to elevation of liver enzymes in healthy volunteers

Background

Coffee oil potently raises serum cholesterol levels in humans. The diterpenes cafestol and kahweol are responsible for this elevation. Coffee oil also causes elevation of liver enzyme levels in serum. It has been suggested that cafestol is mainly responsible for the effect on serum cholesterol levels and that kahweol is mainly responsible for the effect on liver enzyme levels. The objective of this study was to investigate whether coffee oil that only contains a minute amount of kahweol indeed does not cause elevation of liver enzyme levels.

Methods

The response of serum alanine aminotransferase (ALAT) and aspartate aminotransferase (ASAT) to Robusta coffee oil (62 mg/day cafestol, 1.6 mg/day kahweol) was measured in 18 healthy volunteers.

Results

After nine days one subject was taken off Robusta oil treatment due to an ALAT level of 3.6 times the upper limit of normal (ULN). Another two subjects stopped treatment due to other reasons. After 16 days another two subjects were taken off Robusta oil treatment. One of those subjects had levels of 5.8 ULN for ALAT and 2.0 ULN for ASAT; the other subject had an ALAT level of 12.4 ULN and an ASAT level of 4.7 ULN. It was then decided to terminate the study. The median response of subjects to Robusta oil after 16 days was 0.27 ULN (n = 15, 25^th,75^th percentile: 0.09;0.53) for ALAT and 0.06 ULN (25^th,75^th percentile -0.06;0.22) for ASAT.

Conclusions

We conclude that the effect on liver enzyme levels of coffee oil containing hardly any kahweol is similar to that of coffee oil containing high amounts of kahweol. Therefore it is unlikely that kahweol is the component of coffee oil that is responsible for the effect. Furthermore, we conclude that otherwise unexplained elevation of liver enzyme levels observed in patients might be caused by a switch from consumption of filtered coffee to unfiltered coffee.

Suppressive effects of the kahweol and cafestol on cyclooxygenase-2 expression in macrophages

Inducible cyclooxygenase-2 (COX-2) has been suggested to play a role in the processes of inflammation and carcinogenesis. Recent studies have shown the chemoprotective effects of kahweol and cafestol, which are coffee-specific diterpenes. This study investigated the effects of kahweol and cafestol on the expression of COX-2 in lipopolysaccharide (LPS)-activated RAW 264.7 macrophages. Kahweol and cafestol significantly suppressed the LPS-induced production of prostaglandin E(2), COX-2 protein and mRNA expression, and COX-2 promoter activity in a dose-dependent manner. Furthermore, kahweol blocked the LPS-induced activation of NF-kappaB by preventing IkappaB degradation and inhibiting IkappaB kinase activity. These results will provide new insights into the anti-inflammatory and anti-carcinogenic properties of kahweol and cafestol.

Antioxidants of the beverage tea in promotion of human health

Tea that contains many antioxidants is a pleasant and safe drink that is enjoyed by people across the globe. Tea leaves are manufactured as black, green, or oolong. Black tea represents approximately 78% of total consumed tea in the world, whereas green tea accounts for approximately 20% of tea consumed. The concept of "use of tea for promotion of human health and prevention and cure of diseases" has become a subject of intense research in the last decade. Diseases for which tea drinkers appear to have lower risk are simple infections, like bacterial and viral, to chronic debilitating diseases, including cancer, coronary heart disease, stroke, and osteoporosis. Initial work on green tea suggested that it possesses human health-promoting effects. In recent years, the research efforts have been expanded to black tea as well. Research conducted in recent years reveals that both black and green tea have very similar beneficial attributes in lowering the risk of many human diseases, including several types of cancer and heart diseases. For cancer prevention, evidence is so overwhelming that the Chemoprevention Branch of the National Cancer Institute has initiated a plan for developing tea compounds as cancer-chemopreventive agents in human trials. Thus, modern medical research is confirming the ancient wisdom that therapy of many diseases may reside in an inexpensive beverage in a "teapot."

Chemopreventive potential of epigallocatechin gallate and genistein: evidence from epidemiological and laboratory studies

A wide array of antioxidative and anti-inflammatory substances derived from edible plants have been reported to possess chemopreventive and chemoprotective activities. Among the most extensively investigated and well-defined dietary chemopreventives are epigallocatechin gallate (EGCG), a principal antioxidant derived from green tea and genistein, a major pharmacologically active isoflavone widely present in soy products. Multiple lines evidence from epidemiologic studies indicate that frequent consumption of green tea is inversely associated with the risk of several types of human cancer, and studies with animal and in vitro cell culture models have revealed EGCG as a major chemopreventive ingredient of green tea. The lower frequencies of breast and prostate cancer in Asian population in general, compared to those in Western societies have been attributed to their consumption of relatively large amounts of soy products. Genistein, as a principal chemopreventive components of soy, exerts a wide array of chemopreventive activities in each stage of multistep carcinogenesis. The purpose of this review is to provide perspectives on the molecular basis of chemopreventive activities of EGCG and geneistein as representative functional food phytochemicals with emphasis on their ability to control intracellular signaling cascades responsible for regulating cell growth and differentiation.

Association of Fluids From Beverages With Risk of Rectal Cancer

Little information is available about how fluid intake from beverages and sources of fluid intake influence risk of rectal cancer. We examined these associations with risk of incident rectal cancer in a population-based case-control study of 952 cases and 1,205 controls living in northern California and Utah. We also determined if intake of fiber (soluble and insoluble), physical activity, and nonsteroidal anti-inflammatory medications (NSAIDs) or aspirin modified the associations between fluid intake and rectal cancer. We identified a modest inverse association of water intake (odds ratio, OR = 0.70; 95% confidence interval, CI = 0.48, 1.02) and total fluid intake (high vs. low OR = 0.70; 95% CI = 0.46, 1.06) with risk of rectal cancer in men and a positive association with juice among women (high vs. low OR = 1.56; 95% CI = 1.00, 2.41). Risk of rectal cancer increased nonsignificantly among men with beer consumption, among women with high white wine use, and among men and women with high long-term alcohol use. NSAIDs modified the association of alcohol consumption with rectal cancer: 1) risk associated with beer increased among men who did not take NSAIDs and had a high beer intake (OR = 1.60; 95% CI = 1.08, 2.39) and 2) risk associated with long-term alcohol intake increased in a linear fashion in women who did not use NSAIDs (OR = 1.98; 95% CI = 1.15, 3.40). Risk of rectal cancer increased among estrogen-negative women if they consumed any beer or white wine but decreased among estrogen-positive women with beer. In men, low intake of water and low insoluble fiber intake were associated with increased risk of rectal cancer beyond that of either factor alone (OR = 1.82; 95% CI = 1.11, 3.00). The interactions of fiber with water intake suggest that bowel motility may be the mechanism responsible for modification of rectal cancer risk for water. Associations of alcohol to risk for rectal cancer may be related to cellular hyperproliferation and may be modified by NSAID use.

Systematic review: green tea and gastrointestinal cancer risk

BACKGROUND

Gastrointestinal cancer is one of the leading causes of cancer mortality in the world. Therefore, numerous efforts are being made to find chemoprotective substances able to reduce its incidence. Amongst these, green tea, one of the most popular beverages world-wide, has been reported to provide protective effects against gastrointestinal cancer.

AIM

To critically evaluate all epidemiological studies reporting an association between green tea consumption and a reduced risk of gastrointestinal cancer.

METHODS

Epidemiological studies of green tea consumption in relation to gastrointestinal cancer or preneoplastic lesions were identified through computerized literature searches using the following databases: Medline (Pubmed), Embase, Amed, CISCOM, Phytobase and Cochrane Library. Only epidemiological studies indicating the type of tea (green tea) and the site of either cancer or precancerous lesions (stomach or intestine) were included. No language restrictions were imposed.

RESULTS

Twenty-one epidemiological investigations met our inclusion/exclusion criteria.

CONCLUSION

These studies seemed to suggest a protective effect of green tea on adenomatous polyps and chronic atrophic gastritis formations. By contrast, there was no clear epidemiological evidence to support the suggestion that green tea plays a role in the prevention of stomach and intestinal cancer.

Catechin content of 18 teas and a green tea extract supplement correlates with the antioxidant capacity

Our literature review of currently available data in the area of tea and cancer prevention demonstrated that there is more conclusive evidence for the chemopreventive effect of green tea compared with black tea. We suggest that this is due to a large variation of the flavanol content in tea, which is not taken into consideration in most of the epidemiological studies. It was the purpose of this study to determine the flavanol content of various teas and tea products and to correlate it with their radical scavenging activity. A modified oxygen radical absorbance capacity (ORAC) assay at pH 5.5 was utilized. The total flavavol content varied from 21.2 to 103.2 mg/g for regular teas and from 4.6 to 39.0 mg/g for decaffeinated teas. The ORAC value varied from 728 to 1686 trolox equivalents/g tea for regular teas and from 507 to 845 trolox equivalents/g for decaffeinated teas. There was a significant correlation of flavanol content to ORAC value (r = 0.79, P = 0.0001) for the teas and green tea extract. The large variation in flavanol content and ORAC value among various brands and types of tea provides critical information for investigators using tea in studies of nutrition and cancer prevention.

A nested case-control study of stomach cancer in relation to green tea consumption in Japan

To evaluate whether green tea consumption provides protection against stomach cancer, the relative risks (RRs) were calculated in the Japan Collaborative Study for Evaluation of Cancer Risk, sponsored by the Ministry of Health and Welfare (JACC Study). The study was based on 157 incident cases and 285 controls aged 40-79 years. Cox proportional hazards regression analysis was used to estimate the RRs for stomach cancer. It was found that green tea consumption had no protective effect against stomach cancer. After adjustment for age, smoking status, H. pylori infection, history of peptic ulcer, and family history of stomach cancer along with certain dietary elements, the risks associated with drinking one or two, three or four, five to nine, and 10 or more cups of green tea per day, relative to those of drinking less than one cup per day, were 1.3 (95% confidence interval (CI): 0.6-2.8), 1.0 (95% CI: 0.5-1.9), 0.8 (95% CI: 0.4-1.6), and 1.2 (95% CI: 0.6-2.5), respectively (P for trend=0.899). We found no inverse association between green tea consumption and the risk of stomach cancer.

Suppression of Helicobacter pylori-induced gastritis by green tea extract in Mongolian gerbils

Since urease of Helicobacter pylori is essential for its colonization, we focused attention on foodstuffs which inhibit the activity of this enzyme. Among plant-derived 77 foodstuff samples tested, some tea and rosemary extracts were found to clearly inhibit H. pylori urease in vitro. In particular, green tea extract (GTE) showed the strongest inhibition of H. pylori urease, with an IC(50) value of 13 microg/ml. Active principles were identified to be catechins, the hydroxyl group of 5(')-position appearing important for urease inhibition. Furthermore, when H. pylori-inoculated Mongolian gerbils were given GTE in drinking water at the concentrations of 500, 1000, and 2000 ppm for 6 weeks, gastritis and the prevalence of H. pylori-infected animals were suppressed in a dose-dependent manner. Since the acquisition by H. pylori of resistance to antibiotics has become a serious problem, tea and tea catechins may be very safe resources to control H. pylori-associated gastroduodenal diseases.

The epidemiology of tea consumption and colorectal cancer incidence

This manuscript provides a brief synopsis of 30 studies aimed at examining tea consumption as a factor in the incidence of colon and rectal cancers. The 30 papers examine populations in 12 countries and provide data on consumption of both black and green tea. These studies do not provide consistent evidence to support the theory from animal studies and basic research that tea is a potent chemopreventive agent. Details of the studies are presented, and the potential impact of measurement error, publication bias, the form of tea consumed, the appropriateness of the outcomes studied and the adjustment of confounders related to both tea consumption and risk of colorectal cancer or polyps in various countries are explored. In general, the data are not more consistent for green than for black tea. Particularly with green tea, the doses consumed do get into a perceived protective range in a significant subset of the population. A negative association is stronger in observational epidemiologic studies of rectal cancer than in colon cancer. There is no consistent adjustment for important potential confounders of any tea relationship, such as coffee and alcohol consumption and physical activity levels. Finally, the assessment of tea in most of these studies was based on a single question and therefore may have significant measurement error compared with more recent studies specifically aimed at assessing tea consumption.

Green tea catechins inhibit VEGF-induced angiogenesis in vitro through suppression of VE-cadherin phosphorylation and inactivation of Akt molecule

Studies have indicated that the consumption of green tea is associated with a reduced risk of developing certain forms of cancer and angiogenesis. The mechanism of inhibition of angiogenesis by green tea or its catechins, however, has not been well-established. Vascular endothelial (VE)-cadherin, an adhesive molecule located at the site of intercellular contact, is involved in cell-cell recognition during vascular morphogenesis. The extracellular domain of VE-cadherin mediates initial cell adhesion, whereas the cytosolic tail binding with beta-catenin is required for interaction with the cytoskeleton and junctional strength. Therefore, the cadherin-catenin adhesion system is implicated in cell recognition, differentiation, growth and migration of capillary endothelium. Using tube formation of human microvascular endothelial cells (HMVEC) in culture as an in vitro model of angiogenesis, we reported that vascular endothelial growth factor (VEGF)-induced tube formation is inhibited by anti-VE-cadherin antibody and dose-dependently by green tea catechins. We also demonstrated here that inhibition of tube formation by epigallocatechin gallate (EGCG), one of the green tea catechins, is in part mediated through suppression of VE-cadherin tyrosine phosphorylation and inhibition of Akt activation during VEGF-induced tube formation. These findings indicate that VE-cadherin and Akt, known downstream proteins in VEGFR-2-mediated cascade, are the new-targeted proteins by which green tea catechins inhibit angiogenesis.

Tea consumption, apoptosis, and colorectal adenomas

Induction of apoptosis has been suggested as a mechanism for the anti-carcinogenic effect of tea constituents in animals and in vitro studies. We addressed this hypothesis in a human study. Study participants were consecutive patients who underwent colonoscopy at the UNC Hospitals (August 1998 to March 2000). Biopsies were taken from normal rectal mucosa. Apoptosis was scored by the terminal deoxyribonucleotide transferase-mediated digoxigenin dUTP nick end labeling (TUNEL) method and by standard morphological criteria. The analysis included 171 patients with adenomas (cases) and 323 adenoma-free controls. After adjusting for sex, age, race, and BMI, apoptotic score was inversely associated with adenoma: the odds ratios (ORs) for linear trend associated with tertiles were 0.3 (0.3-0.5) for morphologic score and 0.5 (0.4-0.6) for the TUNEL score, respectively. Tea consumption (2-3 and >3 versus <2 servings/day) showed a weak negative association with adenoma: the ORs were 0.7 (0.3-1.4) and 0.5 (0.2-1.1), respectively. Neither measurement of apoptotic score changed by the level of tea consumption (P value for Kruskal-Wallis test > or =0.5). We did not find statistical interaction between apoptotic score and tea consumption. Tea exposure is not associated with apoptosis in normal rectal tissue in vivo.

Black tea consumption and risk of rectal cancer in Moscow population

PURPOSE

This population-based case-control study (663 cases and 323 controls) examined the effect of black tea intake on the risk of rectal cancer in Moscow residents. The Moscow population was selected for its wide range of black tea consumption.

METHODS

This study used three measures of tea consumption: the volume of beverage (l/month), zavarka (tea concentrate, l/month), and dry tea (g/month). We calculated the adjusted odds ratios (ORs) and 95% confidence intervals (CIs) for these three parameters of tea intake using logistic regression.

RESULTS

Greater use of dry tea was associated with lower risk of rectal cancer in women (high vs. low: OR = 0.40; 95% CI, 0.23-0.70) and in men (high vs. low: OR = 0.77; 95% CI, 0.42-1.43). The observed effect was weaker when tea was measured as zavarka (high vs. low in women: OR = 0.47; 95% CI, 0.26-0.83; in men: OR = 0.99; 95% CI, 0.52-1.96) and as beverage volume (high vs. low in women: OR = 0.68; 95% CI, 0.39-1.19; in men: OR = 1.03; 95% CI, 0.53-2.09).

CONCLUSIONS

These findings support the hypothesis that black tea consumption reduces the risk of rectal cancer. The attenuation of the effect across the three measures of tea intake can be explained by an increasing degree of exposure misclassification from dry tea to zavarka and beverage volume.

The effects of coffee on enzymes involved in metabolism of the dietary carcinogen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine in rats

The effects of coffee on the metabolism and genotoxicity of the dietary carcinogen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) were investigated. Coffee diminished the bacterial mutagenicity of PhIP in the Ames reversion assay through inhibition of cytochrome P450 1A2 (CYP1A2), a key enzyme involved in the metabolic activation of PhIP. When given as part of the diet (0, 1 or 5% w/w) to male Fischer-344 rats for 2 weeks, coffee affected the expression of hepatic enzymes involved in PhIP metabolism. Coffee increased the expression of CYP1A2 by 16-fold in the 5% coffee-treated group, and approximately half of this inductive effect was attributed to caffeine. Coffee also increased the expression of enzymes involved in the detoxication of PhIP. A 2-fold increase in expression of glutathione S-transferase alpha was observed, UDP-glucuronosyl transferase (UGTs) activities of p-nitrophenol increased 2-fold, while N(2)-and N3-glucuronidation of the genotoxic metabolite 2-hydroxyamino-1-methyl-6-phenylimidazo[4,5-b]pyridine (HONH-PhIP) increased by 1.3-fold in the 5% coffee-treated over the control group. The amount of PhIP (0.75 mg/kg, 24 h) eliminated in urine as the N(2)-and N3-glucuronide conjugates of HONH-PhIP increased by 1.8- and 2.5-fold, respectively, in the 5% coffee-treated group over control rats, suggesting either increased rates of N-oxidation of PhIP or N-glucuronidation of HONH-PhIP. Despite the strong induction of CYP1A2, there was no increase in PhIP-DNA adduct formation in colon and pancreas while liver adducts decreased by 50% over control animals. These data suggest that the effect of coffee on inhibition of PhIP N-oxidation and ensuing DNA damage is more important in vivo than its effect on induction of PhIP N-hydroxylation.

Effect of green tea in the prevention and reversal of fasting-induced intestinal mucosal damage

OBJECTIVE

Epidemiologic studies have suggested that high consumption of green tea protects against the development of chronic active gastritis and decreases the risk of stomach cancer. The effect of green tea on the intestinal mucosa was not studied previously, so we examined the effects of green tea on the intestinal mucosa of fasting rats in a controlled experimental setting.

METHODS

Two sets of experiments were performed. In the recovery set, rats were fasted for 3 d, after which they were allowed free access to water, black tea, green tea, or vitamin E for 7 d. On day 8, the animals were killed, and small bowels were removed for histologic examination. In the pretreatment set, rats were allowed a normal diet, but the water supply was replaced with green tea, black tea, or vitamin E for 14 d. They were subsequently fasted for 3 d. On day 4, the rats were killed, and small bowels were removed for histologic examination.

RESULTS

In the recovery set, fasting for 3 d caused shortening of villi, atrophy, and fragmentation of mucosal villous architecture, with a significant (P < 0.0001) reduction in the length and surface area of the villi. Ingestion of green tea and, to a lesser extent, vitamin E for 7 d helped in the recovery of villi to normal. In the pretreatment set, drinking green tea, black tea, or vitamin E for 14 d before fasting protected intestinal mucosa from damage.

CONCLUSION

The mucosal and villous atrophy induced by fasting was reverted to normal by the ingestion of green tea and, to a lesser extent, vitamin E. Black tea ingestion had no effect. In addition, ingestion of black tea, green tea, and vitamin E before fasting protected the intestinal mucosa against atrophy.

Validation of a food-frequency questionnaire for cohort studies in rural Japan

OBJECTIVES

To examine the validity and reproducibility of a self-administered food-frequency questionnaire (FFQ) used for two cohort studies in Japan.

DESIGN

Cross-sectional study.

SETTING

Two rural towns in the Miyagi Prefecture, in north-eastern Japan.

SUBJECTS

Fifty-five men and 58 women.

RESULTS

A 40-item FFQ was administered twice, 1 year apart. In the mean time, four 3-day diet records (DRs) were collected in four seasons within the year. We calculated daily consumption of total energy and 15 nutrients, 40 food items and nine food groups from the FFQs and the DRs. We computed Spearman correlation coefficients between the FFQs and the DRs. With adjustment for age, total energy and deattenuation for measurement error with the DRs, the correlation coefficients for nutrient intakes ranged from 0.25 to 0.58 in men and from 0.30 to 0.69 in women, with median of 0.43 and 0.43, respectively. Median (range) of the correlation coefficients was 0.35 (-0.30 to 0.72) in men and 0.34 (-0.06 to 0.75) in women for food items and 0.60 (-0.10 to 0.76) and 0.51 (0.28-0.70) for food groups, respectively. Median (range) of the correlation coefficients for the two FFQs administered 1 year apart was 0.49 (0.31-0.71) in men and 0.50 (0.40-0.64) in women for nutrients, 0.43 (0.14-0.76) and 0.45 (0.06-0.74) respectively for food items, and 0.50 (0.30-0.70) and 0.57 (0.39-0.66) respectively for food groups. Relatively higher agreement percentages for intakes of nutrients and food groups with high validity were obtained together with lower complete disagreement percentages.

CONCLUSIONS

The FFQ has a high reproducibility and a reasonably good validity, and is useful in assessing the usual intakes of nutrients, foods and food groups among a rural Japanese population.

Can teatime increase one's lifetime?

Lifestyle-related diseases, including cancer and cardiovascular disease, are also characterized as aging-related diseases, where aging may be the most potent causal factor. In light of this, prevention of lifestyle-related diseases will depend on slowing the aging process and avoiding the clinical appearance of the diseases. Green tea is now accepted as a cancer preventive on the basis of numerous in vitro, in vivo and epidemiological studies. In addition, green tea has also been reported to reduce the risk of cardiovascular disease. We found an apparent delay of cancer onset/death and all cause deaths associated with increased consumption of green tea, specifically in ages before 79 in a prospective cohort study of a Japanese population with 13-year follow-up data. This is consistent with analyses of age-specific cancer death rate and cumulative survival, indicating a significant slowing of the increase in cancer death and all cause death with aging. These results indicate that daily consumption of green tea in sufficient amounts will help to prolong life by avoiding pre-mature death, particularly death caused by cancer.

Determination of the ?avone tricin in human plasma by high-performance liquid chromatography

Tricin is a flavone constituent of brown rice and rice bran, which interferes potently with the survival of human-derived breast and colon cancer cells in vitro. A specific and simple high-performance liquid chromatographic (HPLC) method was developed for the determination of tricin in human plasma with UV-visible detection. HPLC separation on Hypersil-BDS C(18) (4.6 x 250 mm) was carried out with an isocratic mobile phase of 52% methanol in 0.1 m ammonium acetate, pH 5.10, containing 0.27 mm disodium ethylenediamine tetraacetic acid and detection at 355 nm. The retention times of tricin and quercetin (internal standard) were 14.2 and 7.8 min, respectively. The assay was linear in the range 1-100 microg/mL (r(2 ) > or = 0.995). Tricin in plasma was efficiently extracted with 0.1 m acetic acid in acetone, and the recoveries were in the range 92.6-102.8% (n = 6) with relative standard deviation below 10% for three concentrations of tricin, 5, 10 and 100 microg/mL. The lower limit of quantitation (relative standard deviation <20%) was 1 microg/mL.

Protective effect of green tea against prostate cancer: A case-control study in southeast China

To investigate whether green tea consumption has an etiological association with prostate cancer, a case-control study was conducted in Hangzhou, southeast China during 2001-2002. The cases were 130 incident patients with histologically confirmed adenocarcinoma of the prostate. The controls were 274 hospital inpatients without prostate cancer or any other malignant diseases, and matched to the age of cases. Information on duration, quantity and frequency of usual tea consumption, as well as the number of new batches brewed per day, were collected by face-to-face interview using a structured questionnaire. The risk of prostate cancer for tea consumption was assessed using multivariate logistic regression adjusting for age, locality, education, income, body mass index, physical activity, alcohol consumption, tobacco smoking, total fat intake, marital status, age at marriage, number of children, history of vasectomy and family history of prostate cancer. Among the cases, 55.4% were tea drinkers compared to 79.9% for the controls. Almost all the tea consumed was green tea. The prostate cancer risk declined with increasing frequency, duration and quantity of green tea consumption. The adjusted odds ratio (OR), relative to non-tea drinkers, were 0.28 (95% CI = 0.17-0.47) for tea drinking, 0.12 (95% CI = 0.06-0.26) for drinking tea over 40 years, 0.09 (95% CI = 0.04-0.21) for those consuming more than 1.5 kg of tea leaves yearly, and 0.27 (95% CI = 0.15-0.48) for those drinking more than 3 cups (1 litre) daily. The dose response relationships were also significant, suggesting that green tea is protective against prostate cancer.

Lack of inhibitory effects of green tea catechins in 1,2-dimetylhydrazine-induced rat intestinal carcinogenesis model: comparison of the different formulations, administration routes and doses

Differences in the modifying effects of green tea catechins (GTC) on intestinal carcinogenesis by different formulations, doses and administration routes were investigated in male rats pretreated with 1,2-dimethylhydrazine (DMH). One hundred and eighty nine F344 male rats received subcutaneous injections of DMH at 40 mg/kg body weight twice a week for 3 weeks. Three days after completion of the carcinogen treatment, they were divided into nine groups. Each was administered a different source of 0.1% or 0.01% of GTC (Mitsui Norin Co. (M) or Taiyo Kagaku Co. (T)) either in the diet (D) or the drinking water (W), or basal diet and tap water alone without GTC for 33 weeks and then killed for autopsy. The survival rate tended to be lower with 0.01% MGTC (W) group than in the other groups. In the large intestine, although the multiplicity and/or incidences of adenomas showed tendencies for dose-dependent decrease in all GTC groups, and the average volumes of tumors tended to be decrease dose-dependently in the MGTC (W) and TGTC (W) groups, the multiplicity of carcinomas did not show such a trend, rather being significantly increased in the 0.01% MGTC (D) and 0.1% TGTC (W) groups. In the small intestine, the incidence and the multiplicity of tumors in all GTC treated groups had a tendency to decrease. On the other hand, the volume of tumors was increased with statistical significance in the 0.01% MGTC (W) and 0.1% TGTC (W) groups. Thus it can be concluded that GTC does not exert chemopreventive effects on intestinal carcinogenesis irrespective of its formulation, dose or route of administration.

Primary prevention: phytoprevention and chemoprevention of colorectal cancer

Considering the various stages of carcinogenesis and the numerous tumor types and available chemoprevention agents, knowledge of the etiology and the type of cancer to be treated, or possibly prevented, and understanding of the mechanisms by which agents exert their chemoprevention benefits may provide for improved strategy in designing therapeutic regimens. Because cancer usually develops over a 10- to 20-year period, it may be necessary for some agents to be provided before or early in the initiation steps of carcinogenesis to have beneficial effects. On the other hand, some agents may be more suitable for CRC prevention if provided at a later stage of carcinogenesis. Gene array, genomics, and proteomics are useful tools in advancing our understanding of the molecular events involved in carcinogenesis and in identifying markers of risk and surrogate end-points for colorectal cancer progression. These techniques may also serve for screening, identifying, and providing treatment targets for high-risk patients populations. Treatment could be developed depending on a patient's individual needs and genomic tumor profile. Clinical markers and surrogate end-points should be considered, together with molecular measurements, to more accurately assess risk. NSAIDs and COXIBs are clinically recognized as chemoprevention agents, and clinical trials evaluating their efficacy are ongoing. Treatment protocols, including dose and timing, remain to be determined, however. DFMO may best be used in combination with other chemoprevention agents. Dietary fiber and calcium supplements, as part of an overall low-fat diet, may decrease CRC risk. Long-term compliance with this regimen may be necessary to effect a beneficial outcome. Folate holds promise but needs further investigation, especially because its beneficial effects may depend on cancer type. Phytochemicals have been identified as strong candidates for use as agents to prevent colorectal cancer in cell culture and in rodent models of carcinogenesis. Their potential as chemoprevention agents must be demonstrated in clinical trials. In vitro and animal studies indicated that combination therapy may be a promising strategy over the monotherapy approach; clinical trials addressing the safety and efficacy of some combinations (DFMO/sulindac, fiber/calcium) are underway. The gastrointestinal tract and other organs are constantly exposed to a mixture of potentially toxic compounds and molecules considered favorable to health. Homeostasis between stress-mediated by toxic compounds and defensive mechanisms, is key for the maintenance of health and the prevention of disease. Whereas aggressive pharmacologic treatment may be necessary for patients at high risk for cancer, dietary supplements may be useful for populations at normal risk. The message for cancer prevention in the general population may well remain: keep a balanced healthy diet, eating a variety from all food groups, as part of a healthy lifestyle that includes moderate exercise.

Cancer preventive effects of flavonoids--a review

A cancer protective effect from plant-derived foods has been found with uncommon consistency in epidemiologic studies. However, it has been difficult to identify specific components responsible for this effect. Many phytochemicals have been shown to be biologically active and they may interact to protect against cancer. In recent years, experimental studies have provided growing evidence for the beneficial action of flavonoids on multiple cancer-related biological pathways (carcinogen bioactivation, cell-signaling, cell cycle regulation, angiogenesis, oxidative stress, inflammation). Although the epidemiologic data on flavonoids and cancer are still limited and conflicting, some protective associations have been suggested for flavonoid-rich foods (soy and premenopausal breast cancer; green tea and stomach cancer; onion and lung cancer). This review focuses on the biological effects of the main flavonoids, as well as the epidemiologic evidence that support their potential cancer protective properties.

Mechanisms of chronic disease causation by nutritional factors and tobacco products and their prevention by tea polyphenols

The beverage tea, from the top leaves of the plant Camellia sinensis is one of the most widely used beverages in the world, second only to water. Black and green tea have mostly similar actions. The active components are polyphenols, mainly epigallocatechin gallate in green tea, and the tea leaf polyphenol oxidase mediated oxidation to oolong and black tea, yielding other polyphenols, theaflavin and thearubigins. There is 40-50 mg caffeine in a 160-ml cup of tea. The chemopreventive effects of tea depend on: (1) its action as an antioxidant; (2) the specific induction of detoxifying enzymes; (3) its molecular regulatory functions on cellular growth, development and apoptosis; and (4) a selective improvement in the function of the intestinal bacterial flora. The oxidation of LDL cholesterol, associated with a risk for atherosclerosis and heart disease, is inhibited by tea. Many of cancers are caused by lifestyle elements. One is cigarette and tobacco use, leading to cancer in the oral cavity, esophagus and lung, inhibited by tea. Mice administered a tobacco nitrosamine, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), developed significantly fewer lung tumors than controls when given green tea or its major polyphenol, epigallocatechin gallate (EGCG). Tea suppressed the formation of 8-hydroxydeoxyguanosine (8-OHdG), a marker of oxidative DNA damage, in the lung DNA of mice given NNK. Gastric cancer, caused by a combination of Helicobacter pylori and salted foods, is lower in tea drinkers. Western nutritionally-linked cancers of the breast, colon, prostate and pancreas can be inhibited by tea. The formation of genotoxic carcinogens for these target organs during the cooking of meats, heterocyclic amines, and their effects were decreased by tea. Tea inhibited the formation of reactive oxygen species and radicals and induced cytochromes P450 1A1, 1A2 and 2B1, and glucuronosyl transferase. The higher formation of glucuronides represents an important mechanism in detoxification. The developmental aspects and growth of cancers through promotion are decreased by tea. The regular use of a widely available, tasty, inexpensive beverage, tea, has displayed valuable preventive properties in chronic human diseases.

Cafestol and kahweol, two coffee specific diterpenes with anticarcinogenic activity

Epidemiological studies have found an inverse association between coffee consumption and the risk of certain types of cancers such as colorectal cancers. Animal data support such a chemopreventive effect of coffee. Substantial research has been devoted to the identification of coffee components that may be responsible for these beneficial effects. In animal models and cell culture systems, the coffee diterpenes cafestol and kahweol (C+K) were shown to produce a broad range of biochemical effects resulting in a reduction of the genotoxicity of several carcinogens including 7,12-dimethylbenz[a]anthracene (DMBA), aflatoxin B(1) (AFB(1)), benzo[a]pyrene (B[a]P) and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP). Different mechanisms appear to be involved in these chemoprotective effects: an induction of conjugating enzymes (e.g. glutathione S-transferases, glucuronosyl S-transferases), an increased expression of proteins involved in cellular antioxidant defense (e.g. gamma-glutamyl cysteine synthetase and heme oxygenase-1) and an inhibition of the expression and/or activity of cytochromes P450 involved in carcinogen activation (e.g. CYP2C11, CYP3A2). In animal models, the C+K-mediated induction of conjugating and antioxidant enzymes has been observed in hepatic, intestinal and kidney tissues. In the small intestine, these inductions were shown to be mediated by Nrf2-dependent transcriptional activation. In vitro investigations obtained in cell cultures of human origin indicate that the effects and mechanisms observed in animal test systems with C+K are likely to be of relevance for humans. In human liver epithelial cell lines transfected to express AFB(1)-activating P450s, C+K treatment resulted in a reduction of AFB(1)-DNA binding. This protection was correlated with an induction of GST-mu, an enzyme known to be involved in AFB(1) detoxification. In addition, C+K was found to inhibit P450 2B6, one of the human enzymes responsible for AFB(1) activation. Altogether, the data on the biological effects of C+K provide a plausible hypothesis to explain some of the anticarcinogenic effects of coffee observed in human epidemiological studies and in animal experiments.

A prospective study of stomach cancer death in relation to green tea consumption in Japan

To evaluate whether green tea consumption provides protection against stomach cancer death, relative risks were calculated using Cox proportional hazards regression analysis in the Japan Collaborative Study for Evaluation of Cancer Risk, sponsored by the Ministry of Health and Welfare (JACC Study). The study was based on 30 370 men and 42 481 women aged 40-79. After adjustment for age, smoking status, history of peptic ulcer, family history of stomach cancer along with certain dietary items, the risks associated with drinking one or two, three or four, five to nine, and 10 or more cups of green tea per day, relative to those of drinking less than one cup per day, were 1.6 (95% CI: 0.9-2.9), 1.1 (95% CI: 0.6-1.9), 1.0 (95% CI: 0.5-2.0), and 1.0 (95% CI: 0.5-2.0), respectively, in men (P for trend=0.669), and 1.1 (95% CI: 0.5-2.5), 1.0 (95% CI: 0.5-2.5), 0.8 (95% CI: 0.4-1.6), and 0.8 (95% CI: 0.3-2.1), respectively, in women (P for trend=0.488). We found no inverse association between green tea consumption and the risk of stomach cancer death.

A case-control study of stomach cancer in Mumbai, India

Stomach cancer incidence rates are much lower in India than elsewhere, but the stomach remains one of the 10 leading sites of cancer in both sexes in most of the metropolitan registries. This is an unmatched case-control study of stomach cancer carried out at Tata Memorial Hospital (TMH), Mumbai. Our purpose was to identify the association of tobacco and alcohol use, occupational hazards, diet, consumption of beverages like tea and coffee, the living environment, cooking media and literacy with stomach cancer. Our study included 170 stomach cancer cases and 2,184 hospital controls interviewed during the period 1988-1992. Tobacco chewing, bidi or cigarette smoking and alcohol drinking did not emerge as high risk factors for stomach cancer. Consumption of dry fish at least once a week compared to never or once a every 2 weeks showed a 12-fold excess risk (OR = 12.4, 95% CI 7.0-22.1, p < 0.0001) for stomach cancer among the nonvegetarian food items considered. A protective effect of tea consumption (OR = 0.4, 95% CI 0.2-0.9, p = 0.03), showing 59% reduction in risk, was identified, which could be of use for possible control and prevention of this cancer.

The glutathione biotransformation system and colorectal cancer risk in humans

Evidence for a protective role of the glutathione biotransformation system in carcinogenesis is growing. However, most data on this system in relation to colorectal cancer originate from animal studies. Here we review the human data. In humans, a significant association was found between glutathione S-transferase (GST) activity in the mucosa along the gastrointestinal tract and the corresponding tumour incidence. Low activity was correlated with high tumour incidence and vice versa. Also, in normal colonic mucosa, GST activity is lower in patients at risk of colon cancer than in healthy controls and therefore interventions which increase the glutathione detoxification capacity may reduce cancer incidence. Consumption of vegetables and fruit is associated with a lower risk of colorectal cancer. Human intervention studies showed that (components from) vegetables induced colonic glutathione detoxification capacity. Such an effect could contribute to a lower colon cancer risk, but further data are needed. The human GSTs consist of four main classes--alpha (A), mu (M), pi (P) and theta (T)--each of which is divided into one or more isoforms. Functional polymorphisms are known for the GST genes M1, P1 and T1 and they all lead to less active enzymes compared to the wild-type gene products. However, studies that compared these GST polymorphisms in relation to colon cancer risk were not conclusive with respect to an increased or decreased risk of a particular genotype. Diet or medication can also influence the expression levels of specific isoenzymes and the effect of such interventions on cancer risk deserves more attention.

The role of tea in human health: an update

Tea is an important dietary source of flavanols and flavonols. In vitro and animal studies provide strong evidence that tea polyphenols may possess the bioactivity to affect the pathogenesis of several chronic diseases, especially cardiovascular disease and cancer. However, the results from epidemiological and clinical studies of the relationship between tea and health are mixed. International correlations do not support this relationship although several, better controlled case-referent and cohort studies suggest an association with a moderate reduction in the risk of chronic disease. Conflicting results between human studies may arise, in part, from confounding by socioeconomic and lifestyle factors as well as by inadequate methodology to define tea preparation and intake. Clinical trials employing putative intermediary indicators of disease, particularly biomarkers of oxidative stress status, suggest tea polyphenols could play a role in the pathogenesis of cancer and heart disease.

Congou tea drinking and oesophageal cancer in South China

The study from a large hospital-based case-control for 1248 cases with oesophageal cancer and the same number of controls in South China showed that Congou, a grade of Chinese black tea, may protect against cancers of the oesophagus and reduce the risk of a combination of alcohol drinking and smoking (especially smoking), regardless of temperature when drinking.

Green tea catechins enhance tumor development in the colon without effects in the lung or thyroid after pretreatment with 1,2-Dimethylhydrazine or 2,2′-dihydroxy-di-n-propylnitrosamine in male F344 rats

Modifying effects of green tea catechins (GTCs) on the post-initiation stage of colon, lung and thyroid carcinogenesis were examined in F344 male rats. Groups of 20 animals were given subcutaneous injections of 40 mg/kg body wt of 1,2-dimethylhydrazine twice a week for 2 weeks or oral administration of 0.1% 2,2'-dihydroxy-di-n-propylnitrosamine (DHPN) in the drinking water for 2 weeks for initiation. They then received diet containing 1 or 0.1% green tea catechin or basal diet alone for 33 weeks. Histopathological examination after final sacrifice showed that although total incidence and multiplicity of colon tumors were not significantly different from controls, values for colon adenomas were decreased while those for carcinomas and the average size of tumors were significantly increased in the 0.1% GTC group. A similar tendency was observed for the 1% GTC group. Incidences and/or multiplicity of lung hyperplasia and tumors, and thyroid lesions did not significantly vary among the DHPN-treated groups. These results indicate that GTCs do not inhibit, but rather may enhance colon carcinogenesis, while not influencing lung and thyroid carcinogenesis under the present experimental conditions.

Hepatocarcinogenesis inhibition by caffeine in ACI rats treated with 2-acetylaminofluorene

The inhibitory effects of caffeine have been demonstrated on the development of various organs in animals. The purpose of the present study was to examine the inhibitory effect of caffeine on hepatocarcinogenesis and to determine the responsive dose of caffeine on hepatocarcinogenesis in young male ACI rats. Animals given a diet containing 2-acetylaminofluorene (2-AAF) for 12 weeks and then a basal diet and tap water containing caffeine for 18 weeks showed statistically significant decreases in the incidence, multiplicity (the number of hepatic tumors per rat) and histological grade compared with rats fed a diet containing carcinogen for 12 weeks followed by tap water alone. Dose-dependent inhibition of hepatocarcinogenesis by caffeine was also seen. The inhibitory effect of caffeine on hepatocarcinogenesis in rats was found when caffeine was administered during the initiation phase.

Protective effect of green tea on the risks of chronic gastritis and stomach cancer

Despite the declining trend, stomach cancer remains the second most common cancer worldwide. We examined the role of green tea consumption on chronic gastritis and stomach cancer risks. A population-based case-control study was conducted in Yangzhong, China, with 133 stomach cancer cases, 166 chronic gastritis cases, and 433 healthy controls. Epidemiologic data were collected by standard questionnaire and odds ratios (OR) and 95% confidence intervals (CI) were estimated using logistic regression models in SAS. Inverse association was observed between green tea drinking and chronic gastritis and stomach cancer risks. After adjusting for age, gender, education, body mass index, pack-years of smoking and alcohol drinking, ORs of green tea drinking were 0.52 (95% CI: 0.29-0.94) and 0.49 (95% CI: 0.31-0.77) for stomach cancer and chronic gastritis, respectively. In addition, dose-response relationships were observed with years of green tea drinking in both diseases. The results provide further support on the protective effect of green tea against stomach cancer. This is the first time that green tea drinking was found to be protective against chronic gastritis, which may be of importance when designing intervention strategies for stomach cancer and its pre-malignant lesions in the high-risk population.

Diet and cancer prevention

Research from several sources provides strong evidence that vegetables, fruits, and whole grains, dietary fibre, certain micronutrients, some fatty acids and physical activity protect against some cancers. In contrast, other factors, such as obesity, alcohol, some fatty acids and food preparation methods may increase risks. Unravelling the multitude of plausible mechanisms for the effects of dietary factors on cancer risk will likely necessitate that nutrition research moves beyond traditional epidemiological and metabolic studies. Nutritional sciences must build on recent advances in molecular biology and genetics to move the discipline from being largely 'observational' to focusing on 'cause and effect'. Such basic research is fundamental to cancer prevention strategies that incorporate effective dietary interventions for target populations.

Green tea and the risk of gastric cancer in Japan

BACKGROUND

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.

METHODS

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.

RESULTS

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).

CONCLUSIONS

In a population-based, prospective cohort study in Japan, we found no association between green-tea consumption and the risk of gastric cancer.

The effect of unfiltered coffee on potential biomarkers for colonic cancer risk in healthy volunteers: a randomized trial

BACKGROUND

Epidemiologic studies suggest that coffee use might protect against colorectal cancer. Inconsistencies as to the effect of coffee use and colorectal cancer between epidemiologic studies might be related to the type of coffee brew.

OBJECTIVE

We studied the effect of unfiltered coffee consumption on putative biomarkers for colonic cancer risk.

DESIGN

A total of 64 healthy volunteers (31 men and 33 women), with a mean age of 43 +/- 11 years were randomly assigned to two groups in a crossover design, with two intervention periods of 2 weeks separated by a washout period of 8 weeks. Treatments were 1 L of cafetière (French press) coffee daily or no coffee. At the end of each intervention period, fasting blood samples, colorectal biopsies and 48 h faeces were collected.

RESULTS

No effect of coffee on colorectal cell proliferation, assayed by estimating the Proliferating Cell Nuclear Antigen labelling index, was seen. Additionally, no effects were seen on the concentrations of faecal soluble bile acids and colorectal mucosal glutathione S-transferase activity. However, unfiltered coffee significantly increased the glutathione content in the colorectal mucosa by 8% and in plasma by 15%. Other aminothiols in plasma also increased on coffee.

CONCLUSION

Unfiltered coffee does not influence the colorectal mucosal proliferation rate, but might increase the detoxification capacity and anti-mutagenic properties in the colorectal mucosa through an increase in glutathione concentration. Whether this effect indeed contributes to a lower colon cancer risk remains to be established.

Coffee and cancer: a review of epidemiological studies, 1990-1999

Epidemiological studies on the relation between coffee consumption and cancer risk have been mainly focused on cancers of the urinary bladder, pancreas and colorectum. The relation between coffee and bladder cancer is controversial, despite a large number of studies published over the last three decades. In most studies, the risk tends to be higher in coffee drinkers than in those who do not drink coffee, but the excess risk is generally moderate and is neither dose- nor duration-related. Thus, a strong association between coffee drinking and bladder cancer can be excluded, although it is still unclear whether the weak association is causal or nonspecific and due to some bias or confounding. For pancreatic cancer, a possible association with coffee consumption has been postulated in a large case-control study published in 1981; since then, however, most studies have shown no substantial association, and overall evidence suggests that coffee is not materially related to pancreatic cancer risk. Overall evidence on the coffee-colorectal cancer relation suggests an inverse association, since most case-control studies found odds ratios below unity, particularly for colon cancer. The pattern of risk is less clear for cohort studies. A plausible biological explanation has been given in terms of coffee-related reduction of bile acids and neutral sterol secretion in the colon. For other cancer sites, including oral cavity, oesophagus, stomach, liver, breast, ovary, kidney and lymphoid neoplasms, the relation of coffee drinking with cancer risk has been less extensively investigated, but the evidence is largely reassuring.

Diet and stomach cancer: a case-control study in South India

A prospective case-control study was conducted in Trivandrum, India, to evaluate the dietary risk factors for stomach cancer. One hundred and ninety-four patients with stomach cancer registered at the Regional Cancer Centre (RCC), Trivandrum, Kerala, India, during the period 1988-1991 were considered as cases. A minimum of one control (n = 305), matched for age (+/- 5 years), sex, religion and residential area was selected from the visitors to RCC during the same period. Interviews were carried out using a predetermined structured food frequency questionnaire. The information collected also included socio-demographic/economic background, tobacco chewing, tobacco smoking and alcohol habits. Data were analysed using a multiple logistic regression model. Odds ratios for all dietary variables were estimated. Increased risks were observed with higher consumption of rice (OR 3.9; 95% CI 1.6-10.0). Risk was high for those consuming spicy food (OR 2.3; 95% CI 1.1-5.0), high consumption of chilli (OR 7.4; 95% CI 4.0-13.5) and consumption of high-temperature food (OR 7.0; 95% CI 3.7-12.9). On multivariate analysis, high consumption of rice, high consumption of chilli and consumption of high-temperature food were found to be independent risk factors.

Matrix metalloproteinase inhibition by green tea catechins

We have investigated the effects of different biologically active components from natural products, including green tea polyphenols (GTP), resveratrol, genistein and organosulfur compounds from garlic, on matrix metalloproteinase (MMP)-2, MMP-9 and MMP-12 activities. GTP caused the strongest inhibition of the three enzymes, as measured by fluorescence assays using gelatin or elastin as substrates. The inhibition of MMP-2 and MMP-9 caused by GTP was confirmed by gelatin zymography and was observed for MMPs associated with both various rat tissues and human brain tumors (glioblastoma and pituitary tumors). The activities of MMPs were also measured in the presence of various catechins isolated from green tea including (-)-epigallocatechin gallate (EGCG), (-)-epicatechin gallate(ECG), (-)-epigallocatechin (EGC), (-)-epicatechin (EC) and (+)-catechin (C). The most potent inhibitors of these activities, as measured by fluorescence and by gelatin or casein zymography, were EGCG and ECG. GTP and the different catechins had no effect on pancreatic elastase, suggesting that the effects of these molecules on MMP activities are specific. Furthermore, in vitro activation of proMMP-2 secreted from the glioblastomas cell line U-87 by the lectin concanavalin A was completely inhibited by GTP and specifically by EGCG. These results indicate that catechins from green tea inhibit MMP activities and proMMP-2 activation.

Green tea polyphenols induce apoptosis in vitro in peripheral blood T lymphocytes of adult T-cell leukemia patients

Green tea polyphenols (TEA) are known to exhibit antioxidative activity as well as tumor-suppressing activity. In order to examine the tumor-suppressing activity of TEA against adult T-cell leukemia (ATL), we cultivated peripheral blood T lymphocytes of ATL patients (ATL PBLs), an HTLV-I-infected T-cell line (KODV) and healthy controls (normal PBLs) for 3 days in the presence of TEA and its main constituent, epigallocatechin-3-gallate (EGCg), to measure cell proliferation and apoptosis, and to quantitate mRNAs of HTLV-I pX and beta-actin genes of the cultured cells. Growth of ATL PBLs was significantly inhibited by 9-27 microg/ml of TEA and EGCg, in contrast to minimal growth inhibition of T cells of normal PBLs. Inhibition of KODV was intermediate between ATL PBLs and normal PBLs. The ATL PBLs and KODV treated with 27 microg/ml of either TEA or EGCg induced apoptotic DNA fragmentation, producing terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL)-positive cells, while the normal PBLs treated with the same concentration of TEA or EGCg produced a negligibly small number of TUNEL-positive cells, in which apoptotic DNA fragmentation was not detectable. Expression of HTLV-I pX mRNA was suppressed more than 90% in ATL PBLs by treatment with 3-27 microg/ml of either TEA or EGCg, while expression of beta-actin mRNA was much less suppressed by treatment with the same concentration of TEA or EGCg. These results indicate that TEA and EGCg inhibit growth of ATL PBLs, as well as HTLV-I-infected T-cells, by suppressing HTLV-I pX gene expression and inducing apoptotic cell death.

Tea and health

Tea is a pleasant, popular, socially accepted, economical, and safe drink that is enjoyed every day by hundreds of millions of people across all continents. Tea also provides a dietary source of biologically active compounds that help prevent a wide variety of diseases. It is the richest source of a class of antioxidants called flavonoids and contains many other beneficial compounds such as vitamins and fluoride. A growing body of evidence suggests that moderate consumption of tea may protect against several forms of cancer, cardiovascular diseases, the formation of kidney stones, bacterial infections, and dental cavities. Future research needs to define the actual magnitude of health benefits, establish the safe range of tea consumption associated with these benefits, and elucidate potential mechanisms of action.

Molecular epidemiology, pathogenesis and prevention of gastric cancer

Cancer of the stomach is one of the most commonly diagnosed malignancies and remains an important cause of mortality world wide. This type of cancer is not uniformly distributed among populations but shows a marked variation in both incidence and mortality. Although gastric cancer is declining in many parts of the world, the reasons for this decline are not well understood and its etiology remains unclear. Several factors are suspected to play a role in gastric carcinogenesis, including the effects of diet, exogenous chemicals, intragastric synthesis of carcinogens, genetic factors, infectious agents and pathological conditions in the stomach (such as gastritis). A new look at the results of epidemiological and experimental studies is important for the establishment of strategies for control. Since cancer of the stomach has a very poor prognosis in its more advanced stages, such a control program must have its main focus on primary prevention. This review describes our knowledge about cancer of the stomach regarding epidemiology, pathogenesis and prevention.

Tea polyphenol intake and changes in serum pepsinogen levels

Following a phase I study, a phase II study was conducted to evaluate the effects of two different doses of tea polyphenols on serum pepsinogen levels. Subjects were patients aged 40 to 69 years who had undergone gastroscopy between 1995 and 1997 at Aichi Cancer Center Hospital, and had been found to have no disease requiring medication. Those with pepsinogen I < 70 ng/ml and pepsinogen I/II ratio < 6 were included in this study. Capsules containing 100 mg of tea polyphenols were administered for 1 year: 1 capsule per day for 101 patients (42 males and 59 females), and 6 capsules (equivalent to 10 cups) per day for 83 patients (30 males and 53 females). The enrollment of the 1 capsule group preceded that of the 6 capsule group, in which re-participation was allowed. Blood samples were obtained 1 year after participation from 86 participants of the 1 capsule group and 77 participants (43 new participants and 34 re-participants) of the 6 capsule group. The compliance in polyphenol capsule intake ranged from 11.4 to 105.7% (87.6% on average) of the scheduled amount for the 1 capsule group and 3.2 to 112.3% (77.8% on average) for the 6 capsule group. No serious polyphenol-related adverse effects were reported. The difference in pepsinogen I between before and after 1 year intake of the polyphenol was 3.1 ng/ml for the 43 participants of the 6 capsule group, but 3.5 ng/ml for the 1 capsule group. The mean pepsinogen I/II ratio for the 43 participants increased from 2.37 by 0.08. This increase was not larger than that for the 1 capsule group (from 2.61 by 0.11). Among 34 participants in both interventions, no significant increase in pepsinogen I and I/II ratio for the 6 capsule intervention was observed. This result suggests that additional polyphenol intake for 1 year in Japanese does not improve pepsinogen levels, which are considered to reflect stomach atrophy, a high-risk condition for stomach cancer.