Black tea consumption and cancer risk: a prospective study

The Association between Tea Consumption and Bladder Cancer Risk Based on the Bladder Cancer Epidemiology and Nutritional Determinants (BLEND) International Consortium

OBJECTIVES

Evidence regarding the association between tea consumption and bladder cancer (BC) risk is inconsistent. This study aimed to increase our knowledge of the association by using international data from the Bladder Cancer Epidemiology and Nutritional Determinants Consortium.

METHODS

Individual data on 2,347 cases and 6,871 controls from 15 case-control studies with information on black, green, herbal, or general tea was pooled. The association was estimated using multilevel multivariable logistic regression analysis adjusted for multiple (non-)dietary factors.

RESULTS

Association between tea consumption and BC risk was observed (odds ratio, OR = 0.72, 95% confidence interval, 95% CI = 0.65-0.80) compared to non-tea drinkers. Stratified analyses based on gender and smoking status yielded similar results. Stratified analysis showed no significant association between black or green tea consumption and BC risk across models, while herbal tea consumption was linked to a reduced BC risk (OR = 0.59, 95% CI = 0.36-0.96). As daily tea consumption increased within a suitable range (<5.67 cups/day), BC risk decreased.

CONCLUSIONS

Camellia sinensis tea showed no association with BC risk, while herbal tea was inversely linked to BC incidence. Despite some significant findings in the selected strata, further studies are required to clarify the underlying mechanisms.

Association between tea consumption and colorectal cancer: a systematic review and meta-analysis of a population-based study

PURPOSE

A meta-analysis study was performed to systematically assess the association between tea consumption and CRC risk.

METHODS

Cochrane Library, Embase, PubMed, and Web of Science were retrieved to collect articles in English since 24 July 2023. Databases were searched and evaluated by two reviewers independently.We screened the literature based on inclusion and exclusion criteria. After determining the random effect model or fixed utility model based on a heterogeneity test, odds ratios (ORs) and 95% confidence intervals (CIs) were calculated.

RESULTS

We included fourteen articles in this meta-analysis. We analyzed the data using a random effect model to explore the association between tea consumption and CRC because of apparent heterogeneity (P < 0.001, I2 = 99.5%). The combined results of all tests showed that there is no statistically significant association between tea consumption and CRC risk (OR = 0.756, 95%CI = 0.470-1.215, P = 0.247). Subsequently, subgroup analysis and sensitivity analysis were performed. Excluding any single study, the overall results ranged from 0.73 (95%CI = 0.44-1.20) to 0.86 (95%CI = 0.53-1.40). It was determined that there was no significant publication bias between tea consumption and CRC risk (P = 0.064) by Egger's tests.

CONCLUSIONS

The results indicated that tea consumption may not be significantly associated with the development of CRC.

IMPLICATIONS OF KEY FINDINGS

Tea reduces colon cancer risk by 24%, but the estimate is uncertain. The actual effect on risk can range from a reduction of 51% to an increase of 18%, but regional and population differences may cause differences.

Green-synthesized gold nanoparticles from black tea extract enhance the chemosensitivity of doxorubicin in HCT116 cells via a ROS-dependent pathway

Green gold nanoparticles (GNPs) were prepared from black tea extract (BTE) and used to examine the chemosensitivity of doxorubicin in colon cancer cell line HCT116. BTE-GNPs were prepared by a single-step method and characterized by UV-Vis spectroscopy, FTIR spectroscopy, SEM, DLS and zeta-potential. The MTT assay was performed to determine the cytotoxicity of HCT116 cells and also normal kidney cells HEK293. Apoptosis and ROS generation were investigated by flow cytometry. The inhibition of ROS levels by the inhibitor NAC was determined by both spectrofluorimetry and confocal microscopy. Expression levels of pro- and anti-apoptotic proteins were determined by a western blot technique. BTE-GNPs significantly enhanced the cytotoxic effect of DOX with its co-treatment in HCT116 cells. The cytotoxic effect of BTE-GNP + DOX was involved in apoptosis via a ROS-dependent pathway by enhancing the pro-apoptotic protein expression. Therefore, our results indicated that green gold nanoparticles of black tea extract (BTE-GNP) may be potent chemosensitizers of doxorubicin.

Green gold nanoparticles (GNPs) were prepared from black tea extract (BTE) and used to examine the chemosensitivity of doxorubicin in colon cancer cell line HCT116.

Influence of Diet and Nutrition on Prostate Cancer

The incidence of prostate cancer (PCa) displays widespread regional differences, probably owing to differences in dietary habits. Nutrients, including fat, protein, carbohydrates, vitamins (vitamin A, D, and E), and polyphenols, potentially affect PCa pathogenesis and progression, as previously reported using animal models; however, clinical studies have reported controversial results for almost all nutrients. The effects of these nutrients may be manifested through various mechanisms including inflammation, antioxidant effects, and the action of sex hormones. Dietary patterns including the Western and Prudent patterns also influence the risk of PCa. Recent studies reported that the gut microbiota contribute to tumorigenesis in some organs. Diet composition and lifestyle have a direct and profound effect on the gut bacteria. Human studies reported an increase in the abundance of specific gut bacteria in PCa patients. Although there are few studies concerning their relationship, diet and nutrition could influence PCa, and this could be mediated by gut microbiota. An intervention of dietary patterns could contribute to the prevention of PCa. An intervention targeting dietary patterns may thus help prevent PCa.

Tea Consumption and Risk of Bladder Cancer: A Dose-Response Meta-Analysis

Background and Objective: Controversial results of the association between tea (black tea, green tea, mate, and oolong tea) consumption and risk of bladder cancer were reported among epidemiological studies. Thus, we performed a meta-analysis of observational studies to investigate the association. Methods: We searched the PubMed and Embase for studies of tea consumption and bladder cancer that were published in any language up to March, 2016. Cohort or case-control studies were included in the meta-analysis. All statistical analyses were performed in Stata 12.0 software. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to assess the relationship between tea consumption and risk of bladder cancer. Results: Totally, 25 case-control studies (15 643 cases and 30 795 controls) and seven prospective cohort studies (1807 cases and 443 076 participants) were included. The meta-analysis showed that tea consumption was not significantly associated with bladder cancer risk (OR = 0.96, 95% CI 0.86-1.06) (in a comparison of highest vs. lowest category). No non-linearity association was observed between tea consumption and bladder cancer risk (P = 0.51 for non-linearity). Specific analysis for black tea, green tea, and mate yielded similar results. The dose-response analysis showed the summary OR for an increment of 1 cup/day of tea consumption was 1.01 (95% CI 0.97-1.05). Conclusion: Results based on current meta-analysis indicated that no significant association was observed between tea consumption and risk of bladder cancer.

The consumption of coffee and black tea and the risk of lung cancer

PURPOSE

Coffee and black tea are among the most consumed beverages worldwide. Although their potential role in lung cancer occurrence has been investigated in several studies, results have been inconclusive. We investigated the associations between intake of coffee and black tea with lung cancer in a population-based case-control study in Montreal, Canada.

METHODS

These analyses included 1130 cases and 1483 controls. Adjusted odds ratios (ORs) were estimated between four metrics of coffee and black tea consumption (frequency, average daily amount, duration, and cumulative amount) and lung cancer, using unconditional logistic regression.

RESULTS

The adjusted ORs (95% confidence intervals) for lung cancer comparing daily to never consumers were 0.73 (0.49-1.10) for coffee and 1.05 (0.85-1.31) for black tea. Analyses of other metrics did not reveal any clear patterns of increasing or decreasing risk with increasing amounts or duration of consumption. There was no strong evidence of OR modification by sex or smoking level. The OR estimates did not materially differ by histological subtype for either of the beverages.

CONCLUSION

Our results do not provide strong support for associations between consumption of coffee and black tea and lung cancer.

Total, caffeinated and decaffeinated coffee and tea intake and gastric cancer risk: results from the EPIC cohort study

Prospective studies examining the association between coffee and tea consumption and gastric cancer risk have shown inconsistent results. We investigated the association between coffee (total, caffeinated and decaffeinated) and tea consumption and the risk of gastric cancer by anatomical site and histological type in the European Prospective Investigation into Cancer and Nutrition study. Coffee and tea consumption were assessed by dietary questionnaires at baseline. Adjusted hazard ratios (HRs) were calculated using Cox regression models. During 11.6 years of follow up, 683 gastric adenocarcinoma cases were identified among 477,312 participants. We found no significant association between overall gastric cancer risk and consumption of total coffee (HR 1.09, 95%-confidence intervals [CI]: 0.84-1.43; quartile 4 vs. non/quartile 1), caffeinated coffee (HR 1.14, 95%-CI: 0.82-1.59; quartile 4 vs. non/quartile 1), decaffeinated coffee (HR 1.07, 95%-CI: 0.75-1.53; tertile 3 vs. non/tertile 1) and tea (HR 0.81, 95%-CI: 0.59-1.09; quartile 4 vs. non/quartile 1). When stratified by anatomical site, we observed a significant positive association between gastric cardia cancer risk and total coffee consumption per increment of 100 mL/day (HR 1.06, 95%-CI: 1.03-1.11). Similarly, a significant positive association was observed between gastric cardia cancer risk and caffeinated coffee consumption (HR 1.98, 95%-CI: 1.16-3.36, p-trend=0.06; quartile 3 vs. non/quartile 1) and per increment of 100 mL/day (HR 1.09, 95%-CI: 1.04-1.14). In conclusion, consumption of total, caffeinated and decaffeinated coffee and tea is not associated with overall gastric cancer risk. However, total and caffeinated coffee consumption may be associated with an increased risk of gastric cardia cancer. Further prospective studies are needed to rule out chance or confounding.

Prospective study of the relationship between coffee and tea with colorectal cancer risk: the PLCO Cancer Screening Trial

Background:

Coffee and tea are commonly consumed and carry potential anticancer components that could reduce the risk of colorectal cancer; however, their relationships with colorectal cancer risk remain inconsistent.

Methods:

A prospective analysis was carried out to examine the relationships of coffee and tea intake with colorectal cancer risk in 57 398 men and women in the intervention arm of the National Cancer Institute-Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial, a national screening study that limits differential detection biases. Coffee and tea intakes were assessed by food frequency questionnaire.

Results:

Six hundred and eighty-one incident colorectal cancer cases were ascertained during a median follow-up of 11.4 years. Greater coffee intake was not associated with risk of colorectal cancer (relative risk (RR)=1.08, 95% confidence interval (CI)=0.79–1.48, P_trend=0.23). Stratifying by cancer site (P_{heterogeneity}=0.48) or stage (P_{heterogeneity}=0.83) did not alter the relationship. Associations remained unchanged in subsets of participants for either caffeinated or decaffeinated coffee or when stratifying by several colorectal cancer risk factors. Similarly, greater tea intake was not associated with colorectal cancer risk overall (RR=0.77, 95% CI=0.55–1.09, P_trend=0.17) or by cancer site (P_{heterogeneity}=0.14) or stage (P_{heterogeneity}=0.60). These associations were not modified by several colorectal cancer risk factors.

Conclusion:

The findings of this study do not provide evidence to suggest that drinking coffee or tea is beneficial in protecting against colorectal cancer.

A meta-analysis of tea consumption and the risk of bladder cancer

OBJECTIVE

Previous studies on the association between tea consumption and bladder cancer risk have only illustrated contradictory results. The role of tea in bladder carcinogenesis still remains conflicting. In order to illustrate the potential relationship between tea consumption and bladder cancer, a meta-analysis of case-control and cohort studies was conducted.

METHODS

Eligible studies were retrieved via both computerized searches and review of references. Stratified analyses on types of tea, gender, study design, ethnicity and smoking status were performed. Fixed- or random-effect models were used to summarize the estimates of OR with 95% CIs.

RESULTS

Seventeen studies were eligible for our analysis. No statistical significance was detected between tea consumption and bladder cancer risk when comparing the highest with the lowest intake of tea (OR = 0.825, 95% CI 0.652-1.043). In the subgroup of green tea, we observed it illustrated a protective effect on bladder cancer (OR = 0.814, 95% CI 0.678-0.976).

CONCLUSION

Our analysis indicated that green tea may have a protective effect on bladder cancer in Asian people. Further studies need to be conducted to better clarify the biological mechanisms.

Tea consumption and risk of bladder cancer: a meta-analysis

Background

Tea consumption has been reported to be associated with an decreased risk of several types of cancers. However, the results based on epidemiological studies on the association of tea consumption with bladder cancer were inconsistent. This meta-analysis was undertaken to evaluate the relationship between tea consumption and bladder cancer risk.

Methods

Eligible studies were retrieved via both computer searches and review of references. The summary relative risk (RR) with 95% confidence interval (CI) was calculated.

Results

Twenty three studies met the inclusion criteria of the meta-analysis. No association with bladder cancer was observed in either overall tea consumption group (OR =0.94, 95% CI 0.85-1.04) or subgroups stratified by sex, study design, geographical region or tea types.

Conclusions

Our findings did not support that tea consumption was related to the decreased risk of bladder cancer.

Green and black tea intake in relation to prostate cancer risk among Singapore Chinese

PURPOSE

Tea is one of the most commonly consumed beverages worldwide. To date, observational data from prospective cohort studies investigating the relationship between green and black tea intake and prostate cancer risk are sparse and equivocal. In a population-based, prospective cohort study of Chinese men in Singapore, we investigated the relationship between green and black tea intake and prostate cancer risk.

METHODS

Tea consumption data for 27,293 men were collected at baseline (between 1993 and 1998) using a validated food frequency questionnaire. After an average of 11.2 years of follow-up, 298 men had developed prostate cancer. Proportional hazards regression methods were used to assess the associations between tea intake and prostate cancer risk.

RESULTS

There was no association between daily green tea intake and prostate cancer risk, compared with no green tea intake [hazard ratio (HR) = 1.08; 95 % confidence interval (CI) 0.79, 1.47]. For black tea, a statistically significant positive association and trend were observed for daily intake compared with no black tea intake (HR = 1.41, 95 % CI 1.03, 1.92; p for trend <0.01)

CONCLUSIONS

Few prospective data are available from populations that have both a high level and wide range of black and green tea intake; this study represents a unique opportunity to evaluate their individual effects on prostate cancer risk. Our findings support the notion that green tea intake does not protect against prostate cancer and that black tea intake may increase prostate cancer risk.

Tea consumption and the risk of overall and grade specific prostate cancer: a large prospective cohort study of Scottish men

Tea may be a potentially modifiable and highly prevalent risk factor for the most common cancer in men, prostate cancer. However, associations between black tea consumption and prostate cancer in epidemiological studies have been inconsistent, limited to a small number of studies with small numbers of cases and short follow-up periods and without grade-specific information. We conducted a prospective cohort study of 6,016 men who were enrolled in the Collaborative Cohort Study between 1970 and 1973 and followed up to December 31, 2007. We used Cox proportional hazards models to investigate the association between tea consumption and overall as well as grade-specific risk of prostate cancer incidence. Three hundred and eighteen men developed prostate cancer in up to 37 years of follow-up. We found a positive association between consumption of tea and overall risk of prostate cancer incidence (P = 0.02). The association was greatest among men who drank ≥ 7 cups of tea per day (HR: 1.50, 95% CI: 1.06 to 2.12), compared with the baseline of 0-3 cups/day. However, we did not find any significant association between tea intake and low- (Gleason <7) or high-grade (Gleason 8-10) prostate cancer incidence. Men with higher intake of tea are at greater risk of developing prostate cancer, but there is no association with more aggressive disease. Further research is needed to determine the underlying biological mechanisms for the association.

Chemopreventive effects of tea in prostate cancer: green tea versus black tea

The polyphenol compositions of green tea (GT) and black tea (BT) are very different due to post-harvest processing. GT contains higher concentrations of monomeric polyphenols, which affect numerous intracellular signaling pathways involved in prostate cancer (CaP) development. BT polymers, on the other hand, are poorly absorbed and are converted to phenolic acids by the colonic microflora. Therefore, after consumption of GT, higher concentrations of polyphenols are found in the circulation, whereas after BT consumption the phenolic acid levels in the circulation are higher. The majority of in vitro cell culture, in vivo animal, and clinical intervention studies examine the effects of extracts of GT or purified (-)-epigallocatechin-3-gallate (EGCG) on prostate carcinogenesis. These studies provide strong evidence supporting a chemopreventive effect of GT, but results from epidemiological studies of GT consumption are mixed. While the evidence for a chemopreventive effect of BT is much weaker than the body of evidence with regard to GT, there are several animal BT intervention studies demonstrating inhibition of CaP growth. This article will review in detail the available epidemiological and human clinical studies, as well as animal and basic mechanistic studies on GT and BT supporting a chemopreventive role in CaP.

Tea and cancer prevention: epidemiological studies

Experimental studies have consistently shown the inhibitory activities of tea extracts on tumorigenesis in multiple model systems. Epidemiological studies, however, have produced inconclusive results in humans. A comprehensive review was conducted to assess the current knowledge on tea consumption and risk of cancers in humans. In general, consumption of black tea was not associated with lower risk of cancer. High intake of green tea was consistently associated with reduced risk of upper gastrointestinal tract cancers after sufficient control for confounders. Limited data support a protective effect of green tea on lung and hepatocellular carcinogenesis. Although observational studies do not support a beneficial role of tea intake on prostate cancer risk, phase II clinical trials have demonstrated an inhibitory effect of green tea extract against the progression of prostate pre-malignant lesions. Green tea may exert beneficial effects against mammary carcinogenesis in premenopausal women and recurrence of breast cancer. There is no sufficient evidence that supports a protective role of tea intake on the development of cancers of the colorectum, pancreas, urinary tract, glioma, lymphoma, and leukemia. Future prospective observational studies with biomarkers of exposure and phase III clinical trials are required to provide definitive evidence for the hypothesized beneficial effect of tea consumption on cancer formation in humans.

Cancer prevention with natural compounds

Botanical and nutritional compounds have been used for the treatment of cancer throughout history. These compounds also may be useful in the prevention of cancer. Population studies suggest that a reduced risk of cancer is associated with high consumption of vegetables and fruits. Thus, the cancer chemopreventive potential of naturally occurring phytochemicals is of great interest. There are numerous reports of cancer chemopreventive activity of dietary botanicals, including cruciferous vegetables such as cabbage and broccoli, Allium vegetables such as garlic and onion, green tea, Citrus fruits, soybeans, tomatoes, berries, and ginger, as well as medicinal plants. Several lead compounds, such as genistein (from soybeans), lycopene (from tomatoes), brassinin (from cruciferous vegetables), sulforaphane (from asparagus), indole-3-carbinol (from broccoli), and resveratrol (from grapes and peanuts) are in preclinical or clinical trials for cancer chemoprevention. Phytochemicals have great potential in cancer prevention because of their safety, low cost, and oral bioavailability. In this review, we discuss potential natural cancer preventive compounds and their mechanisms of action.

Risk of colon cancer and coffee, tea, and sugar-sweetened soft drink intake: pooled analysis of prospective cohort studies

BACKGROUND

The relationships between coffee, tea, and sugar-sweetened carbonated soft drink consumption and colon cancer risk remain unresolved.

METHODS

We investigated prospectively the association between coffee, tea, and sugar-sweetened carbonated soft drink consumption and colon cancer risk in a pooled analysis of primary data from 13 cohort studies. Among 731 441 participants followed for up to 6-20 years, 5604 incident colon cancer case patients were identified. Study-specific relative risks (RRs) and 95% confidence intervals (CIs) were estimated using Cox proportional hazards models and then pooled using a random-effects model. All statistical tests were two-sided.

RESULTS

Compared with nonconsumers, the pooled multivariable relative risks were 1.07 (95% CI = 0.89 to 1.30, P(trend) = .68) for coffee consumption greater than 1400 g/d (about six 8-oz cups) and 1.28 (95% CI = 1.02 to 1.61, P(trend) = .01) for tea consumption greater than 900 g/d (about four 8-oz cups). For sugar-sweetened carbonated soft drink consumption, the pooled multivariable relative risk comparing consumption greater than 550 g/d (about 18 oz) to nonconsumers was 0.94 (95% CI = 0.66 to 1.32, P(trend) = .91). No statistically significant between-studies heterogeneity was observed for the highest category of each beverage consumed (P > .20). The observed associations did not differ by sex, smoking status, alcohol consumption, body mass index, physical activity, or tumor site (P > .05).

CONCLUSIONS

Drinking coffee or sugar-sweetened carbonated soft drinks was not associated with colon cancer risk. However, a modest positive association with higher tea consumption is possible and requires further study.

Chemoprevention strategies for pancreatic cancer

Pancreatic cancer has a poor prognosis and is often diagnosed at an advanced stage, which makes it difficult to treat. The low survival rate of patients with pancreatic cancer points towards an increased need for novel therapeutic and chemopreventive strategies and also early detection of this disease. Increased consumption of fruits and vegetables has been associated with a reduced risk of pancreatic cancer. Synthetic and natural, diet-derived bioactive compounds have been evaluated as pancreatic cancer chemopreventive agents and have demonstrated various degrees of efficacy in cellular and in vivo animal models. Some chemopreventive agents (for example, curcumin or resveratrol) have also been reported to sensitize pancreatic cancer cells to standard chemotherapeutic drugs (for example, gemcitabine or erlotinib), which suggests that chemopreventive agents could potentially be used as potentiators of standard chemotherapy. Few clinical trials of pancreatic cancer chemopreventive agents have been completed and some are in early phases. Further development of pancreatic cancer chemopreventive agents may prove to be tremendously valuable for individuals at high risk of developing pancreatic cancer and patients who present with premalignant lesions. This Review discusses the current state of the pancreatic cancer chemoprevention field and highlights the challenges ahead.

Molecular mechanisms of green tea polyphenols

Tea, next to water, is the most popular beverage in the world. It has been suggested that tea consumption has the cancer-preventive effects. Epidemiological studies have indicated decreased cancer occurrence in people who regularly drink green tea. Research has also discovered numerous mechanisms of action to explain the biological effects of tea. The most abundant and popular compound studied in tea research is (-)-epigallocatechin-3-gallate or (-)-EGCG, which is a powerful antioxidant and can inhibit a number of tumor cell proliferation and survival pathways. Tea polyphenols are known to inhibit metaloproteonases, various protein kinases, and proteins that regulate DNA replication and transformation. We also reported that ester bond-containing tea polyphenols, for example, (-)-EGCG, potently and specifically inhibited the tumor proteasomal activity. We further demonstrated that methylation on green tea polyphenols under physiological conditions decreased their proteasome-inhibitory activity, contributing to decreased cancer-preventive effects of tea consumption. Since (-)-EGCG is unstable under physiological conditions, we also developed the peracetate-protected or prodrug form of (-)-EGCG, Pro-EGCG (1), and showed that Pro-EGCG (1) increases the bioavailability, stability, and proteasome-inhibitory and anticancer activities of (-)-EGCG in human breast cancer cells and tumors, demonstrating its potential use for cancer prevention and treatment.

Total fluid and specific beverage intake and risk of renal cell carcinoma in Canada

BACKGROUND

Intake of total fluids and specific beverages may be associated with the risk of renal cell carcinoma (RCC) through a diluting effect of carcinogens. However, total fluid consumption and RCC risk has not received sufficient examination. In this study, we assessed the roles of total fluid intake and type of beverage intake in the risk of RCC.

METHODS

Mailed questionnaires were completed by 1138 newly diagnosed, histologically confirmed RCC cases and 5039 population controls between 1994 and 1997 in 8 Canadian provinces. Data collection included information on socio-economic status, physical activity, smoking habits, alcoholic and non-alcoholic beverage use, diet, residential history and occupational history. Odds ratios (ORs) and 95% confidence intervals (CIs) were derived through unconditional logistic regression.

RESULTS

Higher total fluid intake was associated with risk of RCC; the OR for the highest versus the lowest quartile was 1.49 (95% CI 1.20-1.85). Intake of total juices and coffee was also related to the risk of RCC; for the highest versus the lowest quartile, the ORs were 1.53 (95% CI 1.18-1.99) and 1.33 (95% CI 1.07-1.66), respectively. These positive associations were stronger in men, but not in women. Higher coffee intake was more strongly associated with RCC in normal weight subjects. In contrast, total intake of alcohol was inversely associated with the risk of RCC. Intake of tap water (not in coffee or tea), bottled water, tea, soft drinks and milk was not related to RCC.

CONCLUSIONS

The risk of RCC for higher intake of total fluids, coffee and juices might involve gender differences.

Coffee intake is associated with lower rates of liver disease progression in chronic hepatitis C

Higher coffee consumption has been associated inversely with the incidence of chronic liver disease in population studies. We examined the relationship of coffee consumption with liver disease progression in individuals with advanced hepatitis C-related liver disease. Baseline coffee and tea intake were assessed in 766 participants of the Hepatitis C Antiviral Long-Term Treatment against Cirrhosis (HALT-C) trial who had hepatitis C-related bridging fibrosis or cirrhosis on liver biopsy and failed to achieve a sustained virological response to peginterferon plus ribavirin treatment. Participants were followed for 3.8 years for clinical outcomes and, for those without cirrhosis, a 2-point increase in Ishak fibrosis score on protocol biopsies. At baseline, higher coffee consumption was associated with less severe steatosis on biopsy, lower serum aspartate aminotransferase (AST)/alanine aminotransferase (ALT) ratio, alpha-fetoprotein, insulin, and homeostatic model assessment (HOMA2) score, and higher albumin (P < 0.05 for all). Two hundred thirty patients had outcomes. Outcome rates declined with increasing coffee intake: 11.1/100 person-years for none, 12.1 for less than 1 cup/day, 8.2 for 1 to fewer than 3 cups/day, and 6.3 for 3 or more cups/day (P-trend = 0.0011). Relative risks (95% confidence intervals) were 1.11 (0.76-1.61) for less than 1 cup/day; 0.70 (0.48-1.02) for 1 to fewer than 3 cups/day; and 0.47 (0.27-0.85) for 3 or more cups/day (P-trend = 0.0003) versus not drinking. Risk estimates did not vary by treatment assignment or cirrhosis status at baseline. Tea intake was not associated with outcomes.

CONCLUSION

In a large prospective study of participants with advanced hepatitis C-related liver disease, regular coffee consumption was associated with lower rates of disease progression.

Polyphenols from green tea and pomegranate for prevention of prostate cancer

Prostate cancer (PCa) is the most common non-cutaneous cancer diagnosed in North America with similar trends in many Western countries. Geographic, epidemiological and laboratory studies suggest a role for dietary constituents in the etiology as well as prevention of PCa. The rising incidence of PCa in several countries appears to be coincidental with adoption of western lifestyle. Increase in the incidence of PCa has also been found in Asian populations migrating to the west. These facts give numerous leads to explore testable PCa prevention strategies. There is growing evidence in support of use of dietary ingredients in prevention and treatment of PCa. While substantial data exists in favor of use of polyphenols from tea as PCa chemopreventive agent, interest in anti-cancer properties of polyphenols from pomegranate has recently emerged. This review summarizes current literature on the effects of polyphenols from green tea and pomegranate against PCa.

Green tea and prostate cancer: from bench to clinic

Green tea, the most popular beverage next to water, is a rich source of tea catechins and has potential to be developed as a chemopreventive agent for prostate cancer. For centuries it has been used in traditional medicine in Far-East countries. Male populations in these countries where large quantities of green tea are consumed on regular basis have the lowest incidence of prostate cancer. In this review, after a description of prostate cancer and several risk factors associated with the disease, we evaluated studies reported with green tea or its major constituent, (-)-epigallocatechin-3-gallate in inhibition of prostate cancer. This review provides an in-depth overview of various biochemical and signaling pathways affected by green tea in in vivo and in vitro models of prostate cancer. This is followed by a comprehensive discussion of the epidemiological studies and some ongoing clinical trials with green tea catechins. The review concludes with a brief discussion of the future direction and development of clinical trials employing green tea catechins which could be developed for prevention and/or intervention of prostate cancer.

Coffee, black tea and risk of gastric cancer

BACKGROUND

To provide information about the association of coffee, black tea with gastric cancer risk.

METHODS

Between 1985 and 2007, we conducted two case-control studies in northern Italy. Overall, cases were 999 subjects with incident, histologically confirmed gastric cancer and controls were 2,628 patients admitted to the same network of hospitals for acute non-neoplastic diseases. Odds ratios (OR) and the corresponding 95% confidence intervals (CI) for coffee (mostly espresso and mocha) and black tea consumption were estimated after allowance for socio-demographic data, smoking, and other major covariates of interest.

RESULTS

When compared with non-coffee drinkers, the OR was 0.94 (95% CI: 0.73-1.22) for drinkers of one cup of coffee per day, 1.03 (95% CI: 0.80-1.32) for two, 1.07 (95% CI: 0.82-1.40) for three, and 1.24 (95% CI: 0.94-1.65) for four or more cups per day. No association was found with reference to duration of coffee consumption, or consumption of decaffeinated coffee. When compared with non-black-tea drinkers, the OR was 0.89 (95% CI: 0.56-1.42) for drinkers of two or more cups of black tea per day.

CONCLUSIONS

Our investigation, based on a uniquely large dataset, provides convincing evidence that coffee and black tea consumption is unlikely to be strongly associated with gastric cancer risk.

Dietary intake of selected flavonols, flavones, and flavonoid-rich foods and risk of cancer in middle-aged and older women

BACKGROUND

Flavonoids may protect against cancer development through several biological mechanisms. However, epidemiologic studies on dietary flavonoids and cancer risk have yielded inconsistent results.

OBJECTIVE

We prospectively investigated the association between the intake of selected flavonoids and flavonoid-rich foods and risk of cancers in the Women's Health Study.

DESIGN

A total of 3234 incident cancer cases were identified during 11.5 y of follow-up among 38,408 women aged > or = 45 y. Intake of individual flavonols (quercetin, kaempferol, and myricetin) and flavones (apigenin and luteolin) was assessed from food-frequency questionnaires. Cox regression models were used to estimate the relative risk (RR) of total and site-specific cancer across increasing intakes of total and individual selected flavonoids and flavonoid-rich foods (tea, apple, broccoli, onion, and tofu).

RESULTS

The multivariate RRs of total cancer across increasing quintiles of total quantified flavonoid intake were 1.00, 1.00, 0.93, 0.94, and 0.97 (P for trend = 0.72). For site-specific cancers, the multivariate RRs in the highest quintile of total quantified flavonoid intake compared with the lowest quintile were 1.03 for breast cancer, 1.01 for colorectal cancer, 1.03 for lung cancer, 1.15 for endometrial cancer, and 1.09 for ovarian cancer (all P > 0.05). The associations for the individual flavonoid intakes were similar to those for the total intake. There was also no significant association between intake of flavonoid-rich foods and the incidence of total and site-specific cancers.

CONCLUSION

Our results do not support a major role of 5 common flavonols and flavones or selected flavonoid-rich foods in cancer prevention.

A review of the epidemiological evidence on tea, flavonoids, and lung cancer

Tea and its main bioactive ingredients, the flavonoids, have been associated with human cancer for several decades. In this article, an overview is provided of observational epidemiological studies of lung cancer incidence in relation to intake of green tea, black tea, flavonols/flavones, and catechins. A PubMed search was conducted in September 2007. Articles were selected if they provided risk ratios (relative risk or odds ratio) for lung cancer and were of observational design (cohort, case-control, or case-cohort). Three of 12 studies reported a significantly lower risk of lung cancer with a high intake of flavonoids, whereas 1 study reported a significantly increased risk. After stratification by type of flavonoid, catechin intake was no longer associated with lung cancer risk in 3 of 4 studies available. For tea, 4 of 20 studies reported significantly reduced risks with high intake. Two studies found significantly increased risk ratios, but both were older studies. Findings were similar for green and black tea but became more significant when only methodologically sounder cohort studies were considered. When tea intake and lung cancer were studied among never- or former smokers to eliminate the confounding effect of smoking, 4 of 7 reported associations were significantly protective. In general, the studies on tea, flavonoids, and lung cancer risk indicate a small beneficial association, particularly among never-smokers. More well-designed cohort studies, in particular for catechins, are needed to strengthen the evidence on effects of long-term exposure to physiological doses of dietary flavonoids.

Role of hormonal and other factors in human prostate cancer

American men have a lifetime risk of about 18% for prostate cancer diagnosis. Large international variations in prostate cancer risks and increased risks among migrants from low- to high-risk countries indicate important roles for environmental factors. Major known risk factors include age, family history, and country/ethnicity. Type 2 diabetes appears to reduce risk, while high birth weight and adult height are linked to increased risk of aggressive prostate cancer. Limited evidence supports an association with a history of sexually transmitted infections. A previous meta-analysis of eight cohort studies indicated no associations with plasma androgen, estrogen, or sex hormone binding globulin (SHBG) levels. However, there were dose-response relationships with baseline plasma testosterone levels in two studies that adjusted for other serum hormones and obesity. Finasteride (a drug that blocks testosterone activation) reduced prostate cancer risk by 25%. Low-frequency genes linked to familial prostate cancer only explain a small fraction of all cases. Sporadic cases were linked to relatively common polymorphisms of genes involved in (1) androgen synthesis, activation, inactivation and excretion, (2) hormone and vitamin D receptors, (3) carcinogen metabolism, and (4) DNA repair. Epidemiologic evidence supports protective roles for dietary selenium, vitamin E, pulses, tomatoes/lycopene, and soy foods, and high plasma 1,25-dihydroxyvitamin D levels. There is inadequate evidence that vegetables, fruit, carotenoids, and vitamins A and C reduce risk and that animal fat, alpha-linoleic acid, meat, coffee, and tea increase risk. Two major cohort studies found dose-response relationships with dietary calcium intake. Total dietary energy intake may enhance risk. Limited evidence supports a protective role for physical activity and elevated risk for farmers and other men with occupational pesticide exposure, particularly to organochlorine compounds and phenoxy herbicides. There is inadequate evidence for a relationship with alcohol or smoking. Most known or suspected external risk factors may act through hormonal mechanisms, but our review found little supporting evidence, and substantial further research is needed.

Tea or coffee? A case study on evidence for dietary advice

The present paper explores the level of evidence required to justify giving dietary advice to the public. There are important practical differences between the development of public health nutrition guidelines and guidelines for clinical practice. While the gold standard for evidence for clinical practice guidelines is a meta-analysis of a number of randomised controlled trials, this is often unrealistic and sometimes unethical for the evaluation of public health nutrition interventions. Hence, epidemiological studies make up the bulk of evidence for nutrition guidelines. Tea and coffee are an interesting case study in relation to this issue. They are two of the most commonly consumed beverages worldwide, yet there is little dietary advice on their use. The evidence for a relationship between coffee or tea consumption and several diseases is discussed. The available studies, predominantly epidemiological, together with animal and in vitro studies, indicate that coffee and tea are both safe beverages. However, tea is the healthier option because it has a possible role in the prevention of several cancers and CVD. While the evidence for such relationships is not strong, the public will continue to drink both tea and coffee, and will continue to ask nutritionists to make recommendations. It is therefore argued that advice should be given on the best available data, as waiting for complete data to become available could have severe consequences for public health.

Prospective cohort study of green tea consumption and colorectal cancer risk in women

Tea and its constituents have shown anticarcinogenic activities in in vitro and animal studies. Epidemiologic studies, however, have been inconsistent. We prospectively evaluated the association between green tea consumption and colorectal cancer (CRC) risk in a cohort of 69,710 Chinese women aged 40 to 70 years. Information on tea consumption was assessed through in-person interviews at baseline and reassessed 2 to 3 years later in a follow-up survey. During 6 years of follow-up, 256 incident cases of CRC were identified. The multivariate relative risk of CRC was 0.63 (95% confidence interval, 0.45-0.88) for women who reported drinking green tea regularly at baseline compared with nonregular tea drinkers. A significant dose-response relationship was found for both the amount of tea consumed (Ptrend = 0.01) and duration in years of lifetime tea consumption (Ptrend = 0.006). The reduction in risk was most evident among those who consistently reported to drink tea regularly at both the baseline and follow-up surveys (relative risk, 0.43; 95% confidence interval, 0.24-0.77). The inverse association with regular tea drinking was observed for both colon and rectal cancers. This study suggests that regular consumption of green tea may reduce CRC risk in women.

Tea beverage in chemoprevention and chemotherapy of prostate cancer

Prostate cancer (PCa) is the most frequently diagnosed malignancy and the second leading cause of cancer-related deaths in American males with similar trends in many western countries. The existing treatment approaches and surgical intervention have not been able to effectively cope with this dreaded disease. For these reasons, it is necessary to intensify our efforts for a better understanding of the disease process and for the development of novel approaches for its prevention and treatment. Based on considerable evidence from in vivo and in vitro data and epidemiological studies, in recent years the beverage tea has gained considerable attention for reducing the risk of several cancers. Much of the cancer preventive effects of tea, especially green tea appear to be mediated by the polyphenols present therein. Geographical evidence suggests that the incidence and occurrence of PCa is lower in populations that consume tea regularly. This evidence suggests that tea polyphenols could be extrapolated to optimize their chemopreventive properties against PCa. PCa represents an excellent candidate disease for chemoprevention because it is typically diagnosed in men over 50 years of age and therefore, even a modest delay in neoplastic development achieved through pharmacological or nutritional intervention could result in a substantial reduction in the incidence of clinically detectable disease. In this review we address the issue of possible use of tea, especially green tea, for the prevention as well as treatment of PCa.

Dietary supplements and nutraceuticals in the management of andrologic disorders

Dietary supplements and nutraceuticals are commonly used by men with erectile dysfunction, decreased libido, BPH, and concerns about developing prostate cancer. Many preparations do not contain the advertised dosages of the active ingredient or are contaminated. Dietary supplements and nutraceuticals, particularly those addressing erectile dysfunction and libido, need to undergo rigorous testing before they can be wholeheartedly recommended.

Prevention of prostate cancer through custom tailoring of chemopreventive regimen

One practical way to control cancer is through chemoprevention, which refers to the administration of synthetic or naturally occurring agents to block, reverse or delay the process of carcinogenesis. For a variety of reasons, the most important of which is human acceptance, for chemopreventive intervention naturally occurring diet-based agents are preferred over synthetic agents. For a long time, the prevailing mantra of cancer chemoprevention has been: "Find effective agents with acceptable or no toxicity and use them in preventing cancer in relatively healthy people or individuals at high risk for developing cancer". In pursuing this goal many naturally occurring phytochemicals capable of affording protection against carcinogenesis in preclinical settings in experimental animals have been described. However, clinical trials of single agents have yielded disappointing results. Since carcinogenesis is a multistage phenomenon in which many normal cellular pathways become aberrant, it is unlikely that one agent could prove effective in preventing cancer. This review underscores the need to build an armamentarium of naturally occurring chemopreventive substances that could prevent or slow down the development and progression of prostate cancer. Thus, the new effective approach for cancer prevention "building a customized mechanism-based chemoprevention cocktail of naturally occurring substances" is advocated.

Lessons learned from Art Pardee in cell cycle, science, and life

This essay is written to honor Dr Art Pardee's 85th birthday (July 13, 2006). In this essay, I have summarized the lessons I learned from Art and the cell-cycle research I performed in Art's laboratory during my postdoctoral training period. I have also summarized some research from my own laboratory that has been inspired by the lessons I learned from Art, including the interactions between cell cycle and cell death regulators and discovery of novel polyphenol- and copper-based proteasome inhibitors. Finally, I have discussed the potential use of these proteasome inhibitors in cancer prevention and treatment.

Protective effects of green tea against prostate cancer

Prostate cancer has the third highest incidence of all cancers in men worldwide with incidence and mortality being particularly high in affluent, developed countries. Tea, especially green tea, has demonstrated promise in the prevention of several cancers. Green tea contains several components including catechins, a category of polyphenols that have chemopreventive properties. Although evidence from epidemiological studies is not comprehensive, it is strengthened by animal and in vitro evidence suggesting that consumption of tea is associated with decreased risk or progression of prostate cancer. Emerging evidence and potential biological mechanisms for the role of green tea in prostate cancer prevention are presented in this review.

Green tea, black tea and colorectal cancer risk: a meta-analysis of epidemiologic studies

Experimental studies have supported tea as a chemopreventive agent for colorectal cancer. No quantitative summary of the epidemiologic evidence on tea and colorectal cancer risk has ever been performed. The current meta-analysis included 25 papers conducted in 11 countries across three continents (North America, Asia and Europe). Summary odds ratios (ORs) for highest versus non/lowest tea consumption levels were calculated based on fixed and random effects models. The meta-regression and stratified methods were used to examine heterogeneity across studies. For green tea, the combined results from eight studies indicated a reduced risk of colorectal cancer with intake [summary OR = 0.82, 95% confidence interval (CI) = 0.69-0.98]. The protective effect is mainly found among the three case-control studies of colon cancer (summary OR = 0.74, 95% CI = 0.60-0.93). Results from studies of rectal cancer irrespective of study design (case-control versus cohort) (summary OR = 0.99, 95% CI = 0.71-1.37) and cohort studies of colon cancer (summary OR = 0.99, 95% CI = 0.79-1.24) were compatible with the null hypothesis. For black tea, the summary OR derived from 20 studies was 0.99 (95% CI = 0.87-1.13). There is wide divergence in results across the 20 individual studies; formal tests for homogeneity across studies revealed statistically significant differences in findings across all studies (P < 0.001), amongst the 7 cohort studies (P = 0.002), and amongst the 13 case-control studies (P < 0.001). Despite the strong evidence from in vitro and non-human in vivo studies in support of green and black tea as potential chemopreventive agents against colorectal cancer, available epidemiologic data are insufficient to conclude that either tea type may protect against colorectal cancer in humans.

Beneficial effects of tea and its polyphenols against prostate cancer

Tea, next to water, is the most widely consumed beverage in the world. Depending upon the level of fermentation, tea can be categorized into three types: green (unfermented), oolong (partially fermented), and black (highly to fully fermented). In general, green tea has been found to be superior to black and oolong tea in terms of antioxidant and health promoting benefits owing to the higher content of (-)-epigallocatechin-3-gallate. Tea polyphenols comprise about one-third of the weight of the dried leaf, and they exhibit biochemical and pharmacological activities including antioxidant activities, inhibition of cell proliferation, induction of apoptosis, cell cycle arrest and modulation of carcinogen metabolism. Several studies demonstrate that most tea polyphenols exert their effects by scavenging reactive oxygen species (ROS) since excessive production of ROS has been implicated in the development of a variety of ailments including cancer of the prostate gland (CaP). Using cell culture and animal model systems, molecular targets for these remarkable beneficial effects of green tea drinking on CaP prevention and therapy have been defined. Geographical and case-control studies are showing that green tea drinking could afford CaP chemopreventive effects in human population. In this review we attempt to summarize the experimental as well as the epidemiological basis for the possible role of tea and its polyphenols for chemoprevention and chemotherapy of CaP.

Tea, hormone-related cancers and endogenous hormone levels

Tea is one of the most popular beverages consumed around the world, second only to water. There has been substantial interest in the potential role of tea in cancer prevention, particularly in respiratory and gastrointestinal tract cancers. Recent epidemiological data have linked tea intake to reduced risk of hormone-related cancers, including breast, ovarian and prostate cancers. Based on sparse data, there is suggestion that tea intake may influence circulating hormone levels, providing a plausible mechanism whereby tea intake may influence risk of hormone-related cancers. The major objectives of this paper are to review the epidemiological evidence on tea and risk of breast, ovarian, and prostate cancers as well as the human and non-human studies on tea and circulating hormone levels. We pay special attention to some of the limitations of the human studies and discuss future research needs.

Chemoprevention of lung cancer by tea

Tea is the second only to water as the most consumed beverage in the world. Both green and black teas have been studied for their health benefits for a variety of diseases, particularly cancer. Lung cancer is the predominant cause of cancer mortality in developed countries. Smokers' risk of lung cancer is 20 times that of persons who have never smoked. Epidemiological studies on the cancer-preventive effects of tea produce inconsistent results, which could in part be attributed to the lack of a universal standard for tea preparations. However, most animal studies indicate that tea has strong chemopreventive effects against lung tumorigenesis. The reported mechanisms for chemopreventive activity of green tea are antioxidation, induction of phase II enzymes, inhibition of TNFalpha expression and release, inhibition of cell proliferation, and induction of apoptosis. Cell cycle arrest and apoptosis induced by green tea are probably the two most significant factors. Future studies are needed to determine how green tea affects the genes associated with cell cycle regulation and apoptosis during the mouse lung carcinogenesis process.

Impact of diet on prostate cancer: a review

Epidemiological studies suggest that environmental factors may mediate the transformation of latent prostate cancer into clinically apparent tumors and that diet appears to influence this progression. Close correlations between average per capita fat intake and prostate cancer mortality internationally generated interest in underlying mechanisms for this link, such as through serum levels of androgens, free radicals, proinflammatory fatty acid metabolites, or insulin-like growth factor. Much interest currently lies in the potential of HMG-CoA reductase inhibitors (statins) to play a chemopreventative role in prostate cancer. Lycopene, a potent antioxidant found in tomatoes, may exert a protective effect in the prostate. Selenium and vitamin E have also been shown to decrease the risk of prostate cancer in some men. Calcium may support vitamin D-related antiproliferative effects in prostate cancer. Certain soy proteins, common in the Asian diet, have been shown to inhibit prostate cancer cell growth. Finally, green tea may also have a chemopreventive effect by inducing apoptosis. Despite confounding factors present in clinical studies assessing the effect of diet on cancer risk, the data remain compelling that a variety of nutrients may prevent the development and progression of prostate cancer.

Role of vitamins, minerals and supplements in the prevention and management of prostate cancer

The authors review the current literature on the complementary and alternative medicines most frequently utilized by prostate cancer patients and those at risk for the disease. Products covered are vitamin E, vitamin A, selenium, zinc, soy, lycopene, pomegranate juice, green tea and omega-3 fatty acids. There is no definitive proof that any of the nutritional supplements discussed can impact the course of prostate cancer or its development. The authors believe that simply taking a standard daily multivitamin should be sufficient to ensure that patients have the appropriate levels of vitamins and minerals without risking the over utilization of vitamins, minerals, and supplements which can lead to numerous negative side effects.

Associations Between Black Tea and Coffee Consumption and Risk of Lung Cancer Among Current and Former Smokers

Although cigarette smoking is a clear risk factor for lung cancer, the other determinants of lung cancer risk among smokers are less clear. Tea and coffee contain catechins and flavonoids, which have been shown to exhibit anticarcinogenic properties. Conversely, caffeine may elevate cancer risk through a variety of mechanisms. The current study investigated the effects of regular consumption of black tea and coffee on lung cancer risk among 993 current and former smokers with primary incident lung cancer and 986 age-, sex-, and smoking-matched hospital controls with non-neoplastic conditions. Results indicated that lung cancer risk was not different for those with the highest black tea consumption (>or=2 cups/day) compared with nondrinkers of tea [adjusted odds ratio (aOR)=0.90; 95% confidence interval (CI)=0.66-1.24]. However, elevated lung cancer risk was observed for participants who consumed 2-3 cups of regular coffee daily (aOR=1.34; 95% CI=0.99-1.82) or >or=4 cups of regular coffee daily (aOR=1.51, 95% CI=1.11-2.05). In contrast, decaffeinated coffee drinking was associated with decreased lung cancer risk for both participants who consumed <or=1 cup/day (aOR=0.67; 95% CI=0.54-0.84) and those who consumed >or=2 cups/day (aOR=0.64; 95% CI=0.51-0.80). These results suggest that any chemoprotective effects of phytochemicals in coffee and tea may be overshadowed by the elevated risk associated with caffeine in these beverages.

Tea beverage in chemoprevention of prostate cancer: a mini-review

Because prostate cancer has a long latency period and is typically diagnosed in elderly men, it represents an ideal candidate disease for chemoprevention. Therefore, even a modest delay achieved through intervention could have a significant impact on the outcome of this disease. Epidemiological and laboratory studies have provided convincing evidence that diet, genetic factors, and lifestyle are major causes of prostate cancer. Although surgery, radiotherapy, and hormone therapy are the most widely accepted curative options for a selected group of patients suffering from prostate cancer, the side effects of these treatments are many. In recent years, many dietary agents have been being described that show a wide range of chemopreventive effects in cell culture and selected animal model systems of prostate carcinogenesis. One such agent is the beverage tea, which, next to water, is the most popularly consumed beverage in the world. The epidemiological studies and recent data, amassed from various laboratories around the world, provide evidence that tea polyphenols such as epigallocatechin-3-gallate, epigallocatechin, and epicatechin-3-gallate may have the potential to lower the risk of prostate cancer in the human population. Recently, it has been shown that green tea polyphenols, when given to TRAMP, a transgenic mouse model that mimics progressive forms of human prostate cancer, exert remarkable preventive effects against prostate cancer development. Chemoprevention of prostate cancer by tea polyphenols appears to occur through the modulation of various molecular targets. This article attempts to address the issue of the possible use of tea, especially green tea, for the chemoprevention of prostate cancer.

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.

Effect of diet, life style, and other environmental/chemopreventive factors on colorectal cancer development, and assessment of the risks

This review presents a comprehensive, evenhanded evaluation of the evidence from experimental, in vitro and human studies associating environmental and therapeutic factors with risk of colorectal cancer. Life styles correlated with the greatest increase in colorectal cancer risk are the ones that typify a diet rich in fat and calories, alcohol drinking and tobacco smoking, and low intake of vegetable, fruits and fibers, referred to as a "western diet," as well as sedentary style (i.e., no- or low-exercise). This kind of life style has also been associated with other chronic diseases (other cancers, obesity, dyslipedemia, diabetes, hypertension cardiovascular, and hypertension). The evidence does not implicated red meat as a risk factor, and fiber has been shown to protect against colorectal adenomas and carcinomas. Calcium, vitamin D, folate, and some antioxidant vitamins and minerals (gamma-tocopherol and selenium) have protective effects, and daily exercise for > or =30 min results in a significant decrease in risk. Estrogen use (hormone replacement therapy) substantially reduces colorectal cancer risk in postmenopausal women. Nonsteroidal anti-inflammatory drugs (e.g., aspirin) in excessive doses is protective, especially in high risk populations, but the side effects of its use and cost incurred due to its continued intake over long periods must be carefully scrutinized before any recommendations are made for the general public.

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.

Dietary flavonoids and cancer risk in the Zutphen Elderly Study

Flavonoids are polyphenolic antioxidants naturally present in vegetable foods. Some flavonoids, such as quercetin, inhibit carcinogenesis in rodents, but their effect in humans is unknown. We measured the flavonoids quercetin, kaempferol, myricetin, apigenin, and luteolin in foods and assessed flavonoid intake in 1985 by dietary history in 738 men aged 65-84 years without a history of cancer, who were then followed for five years. Mean flavonoid intake was 25.9 mg/day. The major sources of flavonoid intake were tea at 61% and vegetables and fruits (mainly onions, kale, endive, and apples) at 38%. Between 1985 and 1990, 75 men developed cancer (all sites) and 34 men died from cancer. Flavonoid intake in 1985 was not associated with incidence of all-cause cancer (p for trend = 0.54) or with mortality from all-cause cancer (p for trend = 0.51). Flavonoid intake was also not associated with risk of cancers of the alimentary and respiratory tract (p for trend = 0.92). Adjustment for age, body mass index, smoking, physical activity, and vitamin C, vitamin E, beta-carotene, and dietary fiber intake did not change the relative risks. A high intake of flavonoids from vegetables and fruits only was inversely associated with risk of cancer of the alimentary and respiratory tract (relative risk of highest vs. lowest tertile = 0.51, 95% confidence interval 0.25-1.05); these results suggest the presence of other nonvitamin components with anticarcinogenic potential in these foods. We conclude that intake of flavonoids, mainly from tea, apples, and onions, does not predict a reduced risk of all-cause cancer or of cancer of the alimentary and respiratory tract in elderly men. The effect of flavonoids on risk of cancer at specific sites needs further investigation in prospective cohort studies.