Green tea and black tea consumption and prostate cancer risk: an exploratory meta-analysis of observational studies

Observational studies on tea consumption and prostate cancer (PCa) risk are still inconsistent. The authors conducted a meta-analysis to investigate the association between green tea and black tea consumption with PCa risk. Thirteen studies providing data on green tea or black tea consumption were identified by searching PubMed and ISI Web of Science databases and secondary referencing qualified for inclusion. A random-effects model was used to calculate the summary odds ratios (OR) and their corresponding 95% confidence intervals (CIs). For green tea, the summary OR of PCa indicated a borderline significant association in Asian populations for highest green tea consumption vs. non/lowest (OR = 0.62; 95% CI: 0.38-1.01); and the pooled estimate reached statistically significant level for case-control studies (OR = 0.43; 95% CI: 0.25-0.73), but not for prospective cohort studies (OR = 1.00; 95% CI: 0.66-1.53). For black tea, no statistically significant association was observed for the highest vs. non/lowest black tea consumption (OR = 0.99; 95% CI: 0.82-1.20). In conclusion, this meta-analysis supported that green tea but not black tea may have a protective effect on PCa, especially in Asian populations. Further research regarding green tea consumption across different regions apart from Asia is needed.     

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.     

绿茶与子宫内膜癌关系的病例对照研究

目的探讨饮茶特别是绿茶与子宫内膜癌的关系。方法采用以人群为基础的病例对照研究,调查上海市1997年1月至2002年12月间已确诊年龄30～69岁的子宫内膜癌患者(n=995)和全人群对照(n=1087)的一般情况、月经生育史、饮食及营养素、个人生活习惯、激素相关因素、疾病及家族史等资料,采用非条件logistic回归模型分析饮茶与子宫内膜癌的关系。结果与从未饮茶者相比,有饮茶史者患子宫内膜癌的危险略降低(OR=0.82,P=0.0466)。饮茶主要对绝经前女性有保护作用(OR=0.74,95%CI:0.54～1.01);以从不饮茶者为参比组,饮淡茶、浓淡适中及浓茶者的OR值分别为0.72、0.88和0.44,趋势检验有统计学意义(P=0.0431)。在不吸烟不饮酒者中,饮绿茶对子宫内膜癌有保护作用(OR=0.77,P=0.0199);每周饮绿茶频率越高,患子宫内膜癌的危险性越低;以从未饮茶者为参比组,每周饮绿茶<7次及≥7次者OR值分别为0.90(95%CI:0.53～1.54)和0.76(95%CI:0.60～0.95),趋势检验P=0.0163;饮绿茶量越大危险性越低,每月饮绿茶≤100g、～200g及>200g者的OR值分别为0.76、0.87和0.74,趋势检验有统计学意义。结论饮茶特别是绿茶对子宫内膜癌可能有弱的保护作用,且该作用可能局限于绝经前女性。     

Smoking, alcohol drinking, green tea consumption and the risk of esophageal cancer in Japanese men

BACKGROUND: Although smoking and alcohol drinking are established risk factors of esophageal cancer, their public health impact is unclear. Furthermore, the effect of green tea is controversial. METHODS: The present study was based on a pooled analysis of two prospective cohort studies. A self-administered questionnaire about health habits was distributed to 9,008 men in Cohort 1 and 17,715 men in Cohort 2, aged 40 years or older, with no previous history of cancer. We identified 38 and 40 patient cases with esophageal cancer among the subjects in Cohort 1 (9.0 years of follow-up) and Cohort 2 (7.6 years of follow-up), respectively. Cox proportional hazards regression was used to estimate hazard ratios (HRs) of the risk of esophageal cancer incidence. RESULTS: Cigarette smoking, alcohol drinking and green tea consumption were significantly associated with an increased risk of esophageal cancer. Compared with men who had never smoked, never drunk alcohol or green tea, the pooled multivariate HRs (95% confidence intervals) were 5.09 (1.80-14.40) (p for trend <0.0001), 2.73 (1.55-4.81) (p for trend=0.0002), or 1.67 (0.89-3.16) (P for trend=0.04) for men who were currently smoking > or =20 cigarettes/day, drinking alcohol daily, or drinking > or =5 cups green tea/day, respectively. The population attributable fractions of esophageal cancer incidence that was attributable to smoking, alcohol drinking and green tea consumption were 72.0%, 48.6%, and 22.1%, respectively. CONCLUSIONS: Among the variables studied, smoking has the largest public health impact on esophageal cancer incidence in Japanese men, followed by alcohol drinking and green tea drinking.     

Diabetes and risk of prostate cancer in a prospective cohort of US men

One previous study has suggested that diabetes may decrease risk of prostate cancer but only several years after diagnosis of diabetes. The authors examined the role of timing of diabetes diagnosis in relation to risk of prostate cancer among men in the Cancer Prevention Study II Nutrition Cohort. Participants in the study completed a mailed questionnaire including information on diabetes at enrollment in 1992 and at follow-up questionnaires in 1997 and 1999. Historical information on diabetes was also available from a previous study in 1982. The authors documented 5,318 cases of incident prostate cancer through August 31, 2001, among 72,670 men. Results from Cox proportional hazards models showed that diabetes was associated with a lower incidence of prostate cancer (rate ratio (RR) = 0.67, 95% confidence interval (CI): 0.60, 0.75). This association differed significantly by time since diagnosis of diabetes (p < 0.0002); risk of prostate cancer was slightly increased during the first 3 years after diagnosis of diabetes (RR = 1.23, 95% CI: 0.92, 1.65) but was reduced among men diagnosed 4 or more years before (RR = 0.63, 95% CI: 0.56, 0.71). Study results are consistent with the hypothesis that diabetes is associated with reduced risk of prostate cancer but only several years after diagnosis of diabetes.     

Major dietary factors and prostate cancer risk: a prospective multicenter case-control study

The association between diet and prostate cancer (PC) risk, although suggestive, still remains largely elusive particularly in the Asian population. This study sought to further evaluate the possible effects of different dietary factors on risk of PC in Iran. Using data from a prospective hospital-based multicenter case-control study, dietary intakes of red meat, fat, garlic, and tomato/tomato products, as well as thorough demographic and medical characteristics, were determined in 194 cases with the newly diagnosed, clinicopathologically confirmed PC and 317 controls, without any malignant disease, admitted to the same network of hospitals. Odds ratios (ORs) and corresponding 95% confidence intervals (CIs) were obtained after adjustment for major potential confounders, including age, body mass index, smoking, alcohol, education, occupation, family history of PC, and total dietary calories. Comparing the highest with the lowest tertile, a significant trend of increasing risk with more frequent consumption was found for dietary fat (OR: 1.79, 95% CI: 1.71-4.51), whereas inverse association was observed for tomato/tomato products (OR: 0.33, 95% CI: 0.16-0.65). A nonsignificant increase in PC risk was revealed for dietary red meat (OR: 1.69, 95% CI: 0.93-3.06). For garlic consumption, a borderline reduction in risk was observed (OR: 0.58, 95% CI: 0.32-1.01; P = 0.05). In conclusion, our study supports the hypothesis that total fat may increase PC risk and tomatoes/tomato products and garlic may protect patients against PC.     

Green tea consumption and chronic atrophic gastritis: a cross-sectional study in a green tea production village

Chronic atrophic gastritis (CAG) is well known as a precancerous lesion of the stomach, and Helicobacter pylori (H. pylori) infection increases the risk of CAG. While recent studies have reported that green tea consumption decreases the risk of gastric cancer, there has been no study analyzing the relationship between green tea consumption and the both risks H. pylori infection and CAG. We conducted a cross-sectional study on 636 subjects living in a farming village in Japan to examine the relationship among green tea consumption, H. pylori infection, and CAG. Smoking, alcohol drinking, consumption of four beverages, including green tea, and of five foods were investigated as lifestyle factors that may affect H. pylori infection and CAG. The measurement of H. pylori-IgG antibodies was used to define H. pylori infection, and serum pepsinogens were used to define of CAG. The unconditional logistic regression model was used for analyzing each odds ratio (OR). H. pylori infection was positively associated with the risk of CAG (OR = 3.73; 95% confidence interval [CI], 2.59-5.36). High green tea consumption (more than 10 cups per day) was negatively associated with the risk of CAG, even after adjustment for H. pylori infection and lifestyle factors associated with green tea consumption (OR = 0.63; 95% CI, 0.43-0.93). These results support the hypothesis that high green tea consumption prevents CAG.     

Habitual tea consumption and risk of osteoporosis: a prospective study in the women's health initiative observational cohort

The purpose of this study was to prospectively investigate associations of habitual drinking of regular tea with bone mineral density and fracture risk. Study participants were a multiethnic postmenopausal cohort (n = 91,465) from the nationwide Women's Health Initiative Observational Study. These women were recruited in the United States and aged 50-79 years at the time of enrollment (1994-1998). The average follow-up time was 4.1 years. Habitual consumption of regular tea was assessed with a structured questionnaire at baseline. Clinical fractures during the follow-up were reported in questionnaires, and hip fractures were further confirmed by reviewing medical records. Bone mineral density measurements were conducted among a subgroup of women (n = 4,979) at three Women's Health Initiative bone mineral density centers using dual-energy x-ray absorptiometry. Multivariate analyses suggested a positive trend of increased total body bone mineral density with tea drinking (p < 0.05). However, results from the Cox proportional hazard models did not show any significant association between tea drinking and the risk of fractures at the hip and forearm/wrist. In conclusion, the results from this study indicate that the effect of habitual tea drinking on bone density is small and does not significantly alter the risk of fractures among the US postmenopausal population.     

A prospective study of occupation and prostate cancer risk

A wide variety of occupations has been associated with prostate cancer in previous retrospective studies. Most attention has been paid to farming, metal working, and the rubber industry. Today, these results cannot be affirmed with confidence, because many associations could be influenced by recall bias, have been inconsistent, or have not been confirmed satisfactory in subsequent studies. This study was conducted to investigate and confirm these important associations in a large prospective cohort study. The authors conducted a prospective cohort study among 58,279 men. In September 1986, the cohort members (55-69 years) completed a self-administered questionnaire on potential cancer risk factors, including job history. Related job codes were clustered in professional groups. These predefined clusters were investigated in 3 time windows: 1) profession ever performed, 2) longest profession ever held, and 3) last profession held at baseline. Follow up for incident prostate cancer was established by linkage to cancer registries until December 1993. A case-cohort approach was used based on 830 cases and 1525 subcohort members. To minimize false-positive results, 99% confidence intervals (99% CI) were calculated. Although moderately decreased prostate cancer risks were found for electricians, farmers, firefighters, woodworkers, textile workers, butchers, salesmen, teachers, and clerical workers, none of the relative risks (RR) were found to be statistically significant. For road transporters, metal workers, and managers, no association with prostate cancer risk was found. Although the RR for railway workers, mechanics, welders, chemists, painters, and cooks was moderately increased, these estimates were not statistically significant. For men who reported to have ever worked in the rubber industry, we found a substantially increased prostate cancer risk, but not statistically significant (RR, 4.18; 99% CI = 0.22-80.45). For policemen, we found a substantial and marginally statistically significant increased prostate cancer risk, especially for those who reported working as a policeman for most of their occupational life (RR, 3.91; 99% CI = 1.14-13.42) or as the last profession held at baseline (RR, 4.00; 99% CI = 1.19-13.37). Most of the previously investigated associations between occupation and prostate cancer risk could not be confirmed with confidence in this prospective study. The lack of statistical significance for rubber workers could be caused by the scarcity of rubber workers in this cohort and subsequent lack of power. The results for policemen were substantial and statistically significant, although a conservative value for significance level was used.     

Intake of coffee and tea and risk of ovarian cancer: a prospective cohort study

There is some evidence from case-control studies that coffee consumption might be positively associated with ovarian cancer risk, whereas the epidemiologic evidence regarding tea consumption and ovarian cancer is inconsistent. To date, there have been few prospective studies of these associations. Therefore, we examined ovarian cancer risk in association with both coffee and tea intake in a prospective cohort study of 49,613 Canadian women enrolled in the National Breast Screening Study (NBSS) who completed a self-administered food frequency questionnaire between 1980 and 1985. Linkages to national mortality and cancer databases yielded data on deaths and cancer incidence, with follow-up ending between 1998 and 2000. Data from the food frequency questionnaire were used to estimate daily intake of coffee and tea. Cox proportional hazards models were used to estimate hazard ratios (HR) and 95% confidence intervals (CI) for the association between categories of coffee and tea intake and ovarian cancer risk. During a mean 16.4 years of follow-up, we observed 264 incident ovarian cancer cases. Tea intake was not associated with ovarian cancer risk in our study population. In contrast, a borderline positive association was observed among women who drank > 4 cups coffee/day compared to women who did not drink coffee (HR = 1.62, 95% CI = 0.95-2.75, P(trend) = 0.06). Given the pervasive use of these beverages, the associations between coffee and tea consumption and ovarian cancer risk warrant investigation in further prospective studies.     

Fruit and vegetable consumption and risk of cholecystectomy: a prospective cohort study of women and men

Purpose

Epidemiologic data on whether consumption of fruit and vegetables (FVs) decreases the risk of gallstone disease are sparse. Therefore, we examined the association between FV consumption and the 14-year risk of symptomatic gallstone disease (defined as occurrence of cholecystectomy) in a large group of middle-aged and elderly persons.

Methods

Data from two population-based cohorts were used, which included 74,554 men and women (born 1914–1952). Participants filled in a food frequency questionnaire in the late fall of 1997 and were followed up for cholecystectomy between 1998 and 2011 via linkage to the Swedish Patient Register. Cox regression models were used to obtain hazard ratios (HRs).

Results

During 939,715 person-years of follow-up, 2120 participants underwent a cholecystectomy (1120 women and 1000 men). An inverse association between FV consumption and risk of cholecystectomy was observed in age- and sex-adjusted analyses (P _trend = .036) but not in confounder-adjusted analyses (P _trend = .43). The multivariable-adjusted HR was 0.95 (95 % CI 0.83–1.08) for the highest compared with the lowest sex-specific quartile of FV consumption. There was no evidence of interactions with age (P = .25) or sex (P = .72) in analyses pooled by sex. However, an age-by-FV consumption interaction was observed in separate analyses of women (P = .010), with decreased HRs of cholecystectomy for ages up to 60 years.

Conclusions

This study supports an inverse association between FV consumption and risk cholecystectomy in women, although the association was restricted to women aged 48–60 years. In contrast, the study does not support an association in men.

     

饮酒与男性肺癌发病关系的前瞻性队列研究

目的 研究我国男性饮酒与肺癌发病风险之间的关联。方法 对开滦集团队列（2006－2015年）男性人群每两年随访一次,收集饮酒相关信息及肺癌发病资料;此外,检索开滦附属医院医疗信息系统、开滦集团社保系统、唐山市医疗保险系统,补充收集随访过程中可能遗漏的肺癌新发病例。以不饮酒人群为参比组,利用Cox风险比例回归模型分别分析饮酒频率、饮酒类型与男性肺癌发病风险的关联,计算发病风险比（HR）及其95% CI。按照吸烟状况对研究人群分层,分别分析从不吸烟与既往吸烟/现在吸烟人群中饮酒与肺癌发病的关联。结果 共纳入101 751名男性,总随访808 146.56人年,中位随访时间8.88年,共收集肺癌新发病例913名。调整年龄、吸烟状态、吸烟量、文化程度、粉尘暴露、BMI等潜在的混杂因素后,既往饮酒、现在饮酒频率<1次/d、现在饮酒频率≥1次/d人群肺癌发病风险HR值（95% CI）分别为1.30（0.90～1.88）、0.80（0.64～1.01）和1.04（0.85～1.27）。饮用啤酒/红酒（HR=0.91,95% CI：0.69～1.20）和饮用白酒（HR=0.99,95% CI：0.83～1.19）与肺癌发病无统计学关联。依据吸烟状况分层分析,所得结果类似。结论 本研究结果尚不支持饮酒与男性肺癌发病风险存在关联。     

A prospective study of green tea consumption and oral cancer incidence in Japan

PURPOSE: To examine the relation of green tea consumption with oral carcinogenesis, we prospectively analyzed data from a nationwide large-scale cohort study in Japan. METHODS: A total of 20,550 men and 29,671 women aged 40-79 years, without any history of oral and pharyngeal cancer at baseline survey, were included in the present study. During a mean follow-up period of 10.3 years, 37 oral cancer cases were identified. The Cox proportional hazard model was used to estimate the hazard ratio (HR) and 95% confidence interval (95% CI) for oral cancer according to green tea consumption by sex, while adjusting for age, smoking, alcohol drinking, and other dietary factors. RESULTS: For women, the HRs of oral cancer for green tea consumption of 1-2, 3-4, and 5 or more cups per day were 0.51 (95% CI: 0.10-2.68), 0.60 (95% CI: 0.17-2.10), and 0.31 (95% CI: 0.09-1.07), respectively, compared with those who drank less than one cup per day (p for trend, 0.08). For men, no such trends were observed. CONCLUSIONS: Our findings did not suggest a prominent inverse association of green tea consumption with oral cancer, although there was a tendency for a reduced risk in women.     

Black tea consumption and risk of stroke in women and men

PurposeOur aim was examine the association between black tea consumption and risk of total stroke and stroke types in a prospective study.MethodsA total of 74,961 Swedish women and men who were free of cardiovascular disease and cancer at baseline in 1997 were followed up through December 2008. Tea consumption was assessed with a questionnaire at baseline. Stroke cases were ascertained from the Swedish Hospital Discharge Registry.ResultsDuring a mean follow-up of 10.2 years, we ascertained 4089 cases of first stroke, including 3159 cerebral infarctions, 435 intracerebral hemorrhages, 148 subarachnoid hemorrhages, and 347 unspecified strokes. After adjustment for other risk factors, high tea consumption was associated with a significantly lower risk of total stroke; however, there was no dose–response relation (P for trend = .36). Compared with no tea consumption, the multivariable relative risk for four or more cups per day (median, 5) was 0.79 (95% confidence interval [CI], 0.62–0.998). The corresponding relative risks were 0.80 (95% CI, 0.61–1.04) for cerebral infarction and 0.68 (95% CI, 0.35–1.30) for hemorrhagic stroke.ConclusionsThese findings suggest that daily consumption of four or more cups of black tea is inversely associated with risk of stroke.     

Green tea and the risk of colorectal cancer: pooled analysis of two prospective studies in Japan

BACKGROUND: Although laboratory experiments suggest protective effects of green tea against colorectal cancer, few prospective cohort studies have been conducted.METHODS: We conducted a pooled analysis of two prospective cohort studies among residents in Miyagi Prefecture in rural northern Japan. The first study started in 1984 and included 26,311 subjects. The second study started in 1990 and included 39,604 subjects. The subjects responded to a self-administered questionnaire including an item on green tea consumption. With 7 to 9 years of follow-up, 305 colon and 211 rectal cancers were identified in the two cohorts through record linkage to a regional cancer registry. We used Cox regression to estimate the hazard ratio (HR) of colorectal cancer according to the consumption of green tea with adjustment for potential confounders, and pooled the estimates obtained from each cohort by general variance-based method.RESULTS: Multivariate pooled HRs for colon cancer associated with drinking 1-2, 3-4, and 5 or more cups of green tea per day, as compared with less than 1 cup per day, were 1.06 (95% confidence interval [CI]=0.74-1.52), 1.10 (0.78-1.55), 0.97 (0.70-1.35), respectively (trend p=0.81). Corresponding HRs for rectal cancer were 0.85 (95% CI=0.56-1.29), 0.70 (0.45-1.08), 0.85 (0.58-1.23), respectively (trend p=0.31).CONCLUSIONS: Consumption of green tea was not associated with lower risk of colorectal cancer.