Milk consumption and bladder cancer risk: a meta-analysis of published epidemiological studies

Studies investigating the association of milk consumption with bladder cancer risk have reported inconsistent findings. We conducted a meta-analysis of published cohort and case-control studies to pool the risk estimates of the association between milk intake and bladder cancer. We quantified associations with bladder cancer using meta-analysis of odds ratio (OR) associated with the highest vs. the lowest category of milk intake using fixed- or random-effect models depending on the heterogeneity of effects among studies. Nineteen cohort and case-control studies were eligible for inclusion. High milk intake was significantly associated with decreased risk of bladder cancer (OR, 0.84; 95% CI, 0.71-0.97) when comparing the highest with the lowest category of milk intake. The inverse association was stronger in Asia (OR, 0.60; 95% CI, 0.40-0.81) than North America (OR, 0.89; 95% CI, 0.76-1.03), and no association was observed in Europe (OR, 1.05; 95% CI, 0.85-1.26). This relationship also varied significantly by specific dairy products. Our results suggest that milk may be related to the reduction of bladder cancer risk. Further studies need to clarify the biological mechanisms.     

Folate intake and risk of bladder cancer: a meta-analysis of epidemiological studies

Epidemiological studies have reported conflicting results between folate intake and bladder cancer risk. We conducted a meta-analysis of epidemiological studies published between 1996 and June 2013 on the relationship between folate intake and bladder cancer. We quantified associations with bladder cancer using meta-analysis of risk estimates (REs) associated to the highest versus the lowest category of folate intake using random effect models. Seven cohort and six case-control studies were eligible for inclusion. A significantly decreased risk with bladder cancer was observed in overall folate intake group (RE?=?0.84; 95% CI, 0.72–0.96) and subgroup of case-control studies (RE?=?0.73; 95% CI, 0.57–0.89), but not in cohort studies (RE?=?0.96; 95% CI, 0.81–1.10) when comparing the highest with the lowest category of folate intake. No heterogeneity and publication bias were observed across studies. Although the current evidence, mainly based on data from case-control studies, supports an inverse association between folate intake and bladder cancer, additional large and well-designed cohort studies are needed before definitive conclusions can be drawn.     

Dairy Consumption and Gastric Cancer Risk: A Meta-Analysis of Epidemiological Studies

Studies investigating the association of dairy consumption with gastric cancer risk have reported inconsistent findings. We conducted this systematic review and meta-analysis to review and summarize the epidemiologic evidence on the relation of total dairy and milk consumption with risk of gastric cancer. We summarized the available literature on this topic using meta-analysis of relative risks (RR) associated with total dairy and milk intake. The total of 17 case-control and 6 cohort studies (3256 cases) were eligible for inclusion. When comparing the highest with the lowest category of total dairy intake, the results of cohort studies indicated that increased consumption of total dairy food was associated with a reduced risk of gastric cancer (RR = 0.76; 95% CI: 0.64–0.91), whereas case-control studies provided no association. In subgroup analysis, significantly inverse associations between total diary food consumption and gastric cancer risk were observed in Europe subgroup (RR = 0.73; 95% CI: 0.54–0.99), U.S. subgroup (RR = 0.78; 95% CI: 0.63–0.98) but not in Asia subgroup. However, milk consumption was not associated with gastric cancer risk no matter in main or subgroup analysis. The results of cohort studies, but not case-control studies, suggested that total dairy might be related to the reduction of gastric cancer risk. Milk consumption was not associated with gastric cancer risk.     

Dietary Carbohydrate and Prostate Cancer Risk: A Meta-Analysis

Carbohydrate intake has been inconsistently associated with risk of prostate cancer. We review and quantitatively summarize the evidence from observational studies in a meta-analysis. We searched the PubMed database for observational studies related to the association of carbohydrate intake and prostate cancer risk up to December 25, 2013. Summary relative risks (RRs) were estimated by the use of a random effects model. We included 13 case-control studies with 4,367 cases and 6,205 controls, and 5 cohort studies with 3,679 cases and 74,115 participants in this meta-analysis. The summary RR of prostate cancer for the highest vs. the lowest carbohydrate intake was 1.06 [95% confidence interval (CI): 0.93–1.20, I² = 46.8%] for all included studies. In the subgroup analyses stratified by study design, the summary RRs for the highest vs. the lowest carbohydrate intake were 1.04 (95% CI: 0.87–1.23) for case-control studies and 1.06 (95% CI: 0.88–1.28) for cohort studies. For the 5 studies that reported results for advanced prostate cancer, the summary RR was 0.92 (95% CI: 0.71–1.20). This meta-analysis of observational studies indicates that there is no association between carbohydrate intake and prostate cancer risk. Further studies are needed to confirm our findings.     

Dietary Magnesium Intake and Risk of Cancer: A Meta-Analysis of Epidemiologic Studies

The aim of this study was to investigate the association between dietary magnesium and the risk of overall cancer using a meta-analysis. We searched PubMed, SCOPUS, and the Cochrane Review through November 2012. All the articles searched were independently reviewed by 3 authors based on predetermined selection criterion. A total of 13 epidemiologic studies, 6 case-control studies, and 7 prospective cohort studies involving 1,236,004 participants were included in the final analysis. When all studies were pooled, the relative risk (RR) of overall cancer for the highest level of dietary magnesium intake was 0.801 [95% confidence interval (CI): 0.664–0.966) compared with the lowest level of dietary magnesium intake. In subgroup meta-analyses by study design, there was a significant inverse association between dietary magnesium and the risk of cancer in case-control studies (RR = 0.663, 95% CI: 0.475–0.925), whereas there was no significant association in prospective cohort studies (RR = 0.888, 95% CI: 0.745–1.060). Furthermore, there was a significant preventive effect of dietary magnesium for colorectal cancer (RR = 0.775, 95% CI: 0.655–0.919), but not for other cancer. Our meta-analysis showed that higher dietary magnesium intake seems to have a protective effect for cancer, especially colorectal cancer and in females.     

Cultured milk, yogurt, and dairy intake in relation to bladder cancer risk in a prospective study of Swedish women and men

BACKGROUND: Findings from epidemiologic studies of the effect of dairy foods (mainly milk) on the risk of bladder cancer have been inconsistent. OBJECTIVE: We aimed to examine the association between the intake of cultured milk and other dairy foods and the incidence of bladder cancer in a prospective, population-based cohort. DESIGN: We prospectively followed 82,002 Swedish women and men who were cancer-free and who completed a 96-item food-frequency questionnaire in 1997. Incident cases of bladder cancer were identified in the Swedish cancer registries. RESULTS: During a mean follow-up of 9.4 y, 485 participants (76 women and 409 men) were diagnosed with bladder cancer. Total dairy intake was not significantly associated with risk of bladder cancer [> or =7.0 servings/d compared with < 3.5 servings/d: multivariate rate ratio (RR) = 0.87; 95% CI: 0.66, 1.15; P for trend = 0.33]. However, a statistically significant inverse association was observed for the intake of cultured milk (sour milk and yogurt). The multivariate RRs for the highest category of cultured milk intake (> or =2 servings/d) compared with the lowest category (0 serving/d) were 0.62 (95% CI: 0.46, 0.85; P for trend = 0.006) in women and men combined, 0.55 (95% CI: 0.25, 1.22; P for trend = 0.06) in women, and 0.64 (95% CI: 0.46, 0.89; P for trend = 0.03) in men. The intake of milk or cheese was not associated with bladder cancer risk. CONCLUSION: These findings suggest that a high intake of cultured milk may lower the risk of developing bladder cancer.     

Consumption of Tea and Risk for Pancreatic Cancer: A Meta-Analysis of Published Epidemiological Studies

Epidemiologic studies on the relationship between tea consumption and pancreatic cancer are inconsistent. Therefore, we conducted a systematic search of databases and performed a meta-analysis to analyze the association between tea consumption and risk of pancreatic cancer. We searched Medline, EMBASE, ISI Web of Science, and the Cochrane library for studies of tea consumption and pancreatic cancer published up to December 2012. Subgroup analysis was conducted by study type, study region, sex, type of tea, without or with adjustment for smoking, and body mass index. We performed a meta-analysis of 8 case-control studies and 6 cohort studies. For pancreatic cancer, the summary odds ratio (OR) for highest vs. lowest was 0.95 (95% confidence interval (CI), 0.84–1.08). The summary OR for moderate vs. lowest was 1.07 (95% CI, 0.86–1.35). The summary OR for ever vs. lowest was 1.00 (95% CI, 0.86–1.16). The results of this meta-analysis suggested tea consumption is not related to pancreatic cancer risk, even at high doses. Because of the small number of studies, further prospective studies are needed.     

Coffee Drinking and the Risk of Endometrial Cancer: An Updated Meta-Analysis of Observational Studies

Background: Several compounds contained in coffee have been found to suppress carcinogenesis in experimental studies. We conducted a dose–response meta-analysis to assess the impact of coffee consumption on the risk of endometrial cancer. Materials and methods: We searched MEDLINE and EMBASE databases for studies published up to August 2016. Using random effects models, we estimated summary relative risks (RR) for cohort studies and odds ratios (OR) for case-control studies with 95% confidence intervals (CI). Dose–response analyses were conducted by using generalized least square trend estimation. Results: We identified 12 cohort studies and 8 case-control studies eligible for inclusion, contributing with 11,663 and 2,746 endometrial cancer cases, respectively. The summary RR for highest compared with lowest coffee intake was 0.74 (95% CI: 0.68–0.81; p_{heterogeneity} = 0.09, I² = 32%). The corresponding summary RR among cohort studies was 0.78 (95% CI: 0.71–0.85; p_{heterogeneity} = 0.14, I² = 31.9%) and 0.63 (95% CI: 0.53–0.76; p_{heterogeneity} = 0.57, I² = 0%) for case-control studies. One-cup increment per day was associated with 3% risk reduction (95% CI: 2–4%) in cohort studies and 12% (95% CI: 5–18%) in case-control studies. After pooling the results from 5 cohort studies, the association remained significant only in women with body mass index over 30 (RR = 0.71, 95% CI: 0.61–0.81). Conclusion: The results from our meta-analysis strengthen the evidence of a protective effect of coffee consumption on the risk of EC and further suggest that increased coffee intake might be particularly beneficial for women with obesity.     

Citrus fruit intake and bladder cancer risk: a meta-analysis of observational studies

Epidemiological studies have investigated the association between citrus fruit and bladder cancer risk; however, the results are inconsistent. To assess these issues, we conducted a meta-analysis of currently available studies. We identified relevant articles by searching the MEDLINE and EMBASE databases. We calculated the summary relative risk (RR) with 95% confidence interval (95% CI) using a random effect model. We included eight case–control studies and six cohort studies in the meta-analysis. There was a significant inverse association between citrus fruit intake and bladder cancer risk in all pooled studies (RR: 0.85; 95% CI, 0.76–0.94) and case–control studies (RR: 0.77; 95% CI, 0.64–0.92), but not in the cohort studies (RR: 0.96; 95% CI, 0.87–1.07). Our results suggest that citrus fruit intake is related to decreased bladder cancer risk. Subsequent well-designed, large prospective studies are needed to obtain better understanding of this relationship.     

Processed Meat and Risk of Renal Cell and Bladder Cancers

We assessed the association of processed meat intake with the risk of renal cell carcinoma (RCC) and bladder cancer. We used data from two Italian hospital-based case-control studies, including 1,115 RCC cases and 2,582 controls, and 1,417 bladder cancer cases and 1,732 controls. We calculated odds ratios (ORs) and 95% confidence intervals (CIs) with unconditional logistic regression models, adjusted for major confounders. The median consumption of processed meat in cases and controls was around 2 portions/week (50 g/portion). The ORs for a daily 10 g increment of processed meat was 0.89 (95% CI 0.84–0.94) for RCC and 1.00 (95% CI 0.94–1.06) for bladder cancer. The OR for the highest vs. the lowest consumption was 0.80 (95% CI 0.66–0.96) for RCC and 0.98 (95% CI 0.80–1.21) for bladder cancer. The ORs were consistent in strata of various covariates. For bladder cancer, however, a significant 23% excess risk was found in women (95% CI 1.03–1.47) for a daily increase of 10 g, significantly heterogeneous from the risk recorded in men (OR 0.96, 95% CI 0.90–1.02). The inconsistent results between men and women and the absence of association in both sexes combined indicate that the apparent association between processed meat and bladder cancer in women is unlikely to be causal.     

Glycemic index, glycemic load and endometrial cancer risk: results from the Australian National Endometrial Cancer study and an updated systematic review and meta-analysis

Purpose

The relationship between habitual consumption of foods with a high glycemic index (GI) and/or a diet with a high glycemic load (GL) and risk of endometrial cancer is uncertain, and relatively few studies have investigated these associations. The objectives of this study were to examine the association between GI/GL and risk of endometrial cancer using data from an Australian population-based case–control study and systematically review all the available evidence to quantify the magnitude of the association using meta-analysis.

Methods

The case–control study included 1,290 women aged 18–79 years with newly diagnosed, histologically confirmed endometrial cancer and 1,436 population controls. Controls were selected to match the expected Australian state of residence and age distribution (in 5-year bands) of cases. For the systematic review, relevant studies were identified by searching PubMed and Embase databases through to July 2011. Random-effects models were used to calculate the summary risk estimates, overall and dose–response.

Results

In our case–control study, we observed a modest positive association between high dietary GI (OR 1.43, 95 % CI 1.11–1.83) and risk of endometrial cancer, but no association with high dietary GL (OR 1.15, 95 % CI 0.90–1.48). For the meta-analysis, we collated information from six cohort and two case–control studies, involving a total of 5,569 cases. The pooled OR for the highest versus the lowest intake category of GI was 1.15 (0.95–1.40); however, there was significant heterogeneity (p 0.004) by study design (RR 1.00 [95 % CI 0.87–1.14] for cohort studies and 1.56 [95 % CI 1.21–2.02] for case–control studies). There was no association in the dose–response meta-analysis of GI (RR per 5 unit/day increment of GI 1.00, 95 % CI 0.97–1.03). GL was positively associated with endometrial cancer. The pooled RR for the highest versus the lowest GL intake was 1.21 (95 % CI 1.09–1.33) and 1.06 (95 % CI 1.01–1.11) per 50 unit/day increment of GL in the dose–response meta-analysis.

Conclusion

The pooled results from observational studies, including our case–control results, provide evidence of a modest positive association between high GL, but not GI, and endometrial cancer risk.     

Total fluid and water consumption and the joint effect of exposure to disinfection by-products on risk of bladder cancer

BACKGROUND: Findings on water and total fluid intake and bladder cancer are inconsistent; this may, in part, be due to different levels of carcinogens in drinking water. High levels of arsenic and chlorinated by-products in drinking water have been associated with elevated bladder cancer risk in most studies. A pooled analysis based on six case-control studies observed a positive association between tap water and bladder cancer but none for nontap fluid intake, suggesting that contaminants in tap water may be responsible for the excess risk. OBJECTIVES: We examined the association between total fluid and water consumption and bladder cancer risk, as well as the interaction between water intake and trihalomethane (THM) exposure, in a large case-control study in Spain. METHODS: A total of 397 bladder cancer cases and 664 matched controls were available for this analysis. Odds ratios (OR) were estimated using unconditional logistic regression, controlling for potential confounders. RESULTS: Total fluid intake was associated with a decrease in bladder cancer risk [OR = 0.62; 95% confidence interval (CI), 0.40-0.95 for highest vs. lowest quintile comparison]. A significant inverse association was observed for water intake (for > 1,399 vs. < 400 mL/day, OR = 0.47; 95% CI, 0.33-0.66; p for trend < 0.0001), but not for other individual beverages. The inverse association between water intake and bladder cancer persisted within each level of THM exposure; we found no statistical interaction (p for interaction = 0.13). CONCLUSION: Findings from this study suggest that water intake is inversely associated with bladder cancer risk, regardless of THM exposure level.     

Citrus fruits intake and prostate cancer risk: a quantitative systematic review

OBJECTIVES: The purpose of this systematic review was to investigate the association between dietary intake of citrus fruits and prostate cancer risk. METHODS: Authors searched electronic databases and the reference lists of publications of diet and prostate cancer studies until August 2007. All of the epidemiological studies that obtained individual data on dietary intake of citrus fruits and presented risk estimates of the association between intake of citrus fruits and risk of prostate cancer were identified and included. Using general variance-based methods, study-specific odds ratios (OR)/ relative risk (RR) and associated confidence interval (CI)/ standard error (SE) for highest versus lowest intake of citrus fruits level were extracted from each paper. RESULTS: Eleven articles including six case-control studies, one nested case-control study and four cohort studies, proved eligible. Overall summary OR using random effect model did not show an association in risk of prostate cancer with intake of citrus fruits (summary OR=1.03, 95% CI=0.89-1.19) with large heterogeneity across studies that we were unable to explain (I(2)=67.88%). The summary ORs in case-control studies and cohort studies were 1.10 (95% CI=0.97-1.22) and 1.05 (95% CI=0.96-1.14), respectively. CONCLUSIONS: Pooled results from observational studies did not show an association between intake of citrus fruits and the risk of prostate cancer, although results vary substantially across studies.     

Dietary Fat Intake and the Risk of Skin Cancer: A Systematic Review and Meta-Analysis of Observational Studies

Abstract

We conducted a meta-analysis to evaluate the association between fat intake and the risk of three major types of skin cancer including basal cell carcinoma (BCC), squamous cell carcinoma (SCC) and cutaneous malignant melanoma (CMM). A comprehensive search of PubMed and EMBASE was performed to identify all relevant observational studies published up to December 1, 2018. Specific odds ratio (OR) or relative risk (RR) estimates for the highest versus the lowest intake of dietary fat and 95% confidence intervals (CI) from the included studies were pooled using random effect model. Three prospective cohort studies (175,675 participants and 30,915 BCC cases, 4,106 SCC cases and 1,638 CMM cases) and nine case-control studies (328 BCC cases, 493 SCC cases, 1,547 CMM cases and 2,660 controls) were identified. The pooled results indicated that dietary consumption of total fat and saturated fat were not associated with three major types of skin cancer. High consumption of monounsaturated fat was significantly associated with a decreased risk of BCC (RR: 0.90, 95% CI: 0.85–0.96) and high level of polyunsaturated fat intake was potentially positively associated with SCC (RR: 1.19, 95% CI: 1.06–1.33). Our findings should be confirmed by further evidence from well-designed and large-scale prospective cohort studies.     

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.     

大豆食品摄入与乳腺癌发病关系的Meta分析

目的探讨大豆食品摄入与乳腺癌发病的关系。方法检索1991年到2011年4月公开发表的关于大豆食品摄入与乳腺癌关系的流行病学研究进行Meta分析,结果报告合并比值比(OR)及95%可信区间(95%CI)。结果 28个研究纳入Meta分析,其中有23个病例对照研究,5个队列研究。总体分析,大豆食品摄入对乳腺癌具有保护作用(合并OR=0.86,95%CI 0.78～0.94),但按设计类型分层后,只有病例对照研究的结果显示大豆食品对乳腺癌具有保护作用(合并OR=0.86,95%CI 0.77～0.95)。在不同国家和地区人群中开展的研究结果显示,在亚洲地区人群中,合并OR=0.76(95%CI 0.67～0.87),而欧美地区人群的研究合并OR=1.01(95%CI 0.93～1.09)。对在亚洲地区人群中开展的病例对照研究和队列研究分别进行合并分析,结果显示大豆食品摄入对乳腺癌均具有保护作用,合并OR分别为0.76(95%CI 0.65～0.89)和0.81(95%CI 0.70～0.92)。但在欧美地区人群中开展的两类研究均未发现大豆食品摄入对乳腺癌有保护作用。根据绝经前后的亚组分析结果显示,仅在绝经后女性中大豆食品摄入对乳腺癌起保护作用。结论根据亚洲地区人群中开展的研究,尤其是病例对照研究结果的合并分析,提示大豆食品摄入对亚洲地区女性乳腺癌具有保护作用。     

Soy Food Consumption and Lung Cancer Risk: A Meta-Analysis Using a Common Measure Across Studies

A published meta-analysis pooled individual studies by using the study-specific odds ratio (OR) or relative risk (RR) for the highest vs. lowest category of soy or isoflavone intake from each study, but it should be problematic to make comparison between studies/populations for lung cancer risk as the quantiles are so different from different studies/populations. Therefore, we conducted a meta-analysis to explore the association between exposure of estimated daily soy protein intake in grams and lung cancer risk. We extracted ORs or RRs and 95% confidence intervals (CIs), converted them to the estimated ones for daily soy protein intake and pooled them using fixed or random effects models from 11 epidemiologic studies. Overall, the inverse association between daily grams of soy protein intake and risk of lung cancer was borderline statistically significant (OR = 0.98, 95% CI = 0.96 to 1.00); the inverse association was statistically significant in nonsmokers (OR = 0.96; 95% CI = 0.93 to 0.99) and stronger than in smokers (P for difference <0.05). No statistical significance for the associations was observed between genders, the origin of the participants, study design and types of soy intake. This study suggests a borderline reduction in risk of lung cancer with daily soy protein intake in grams, and a significant inverse association in nonsmokers.     

Dietary Vitamin D and Calcium Intake and Premenopausal Breast Cancer Risk in a German Case-Control Study

Epidemiological studies and laboratory data suggest that vitamin D may protect against the development of cancer, including breast cancer. Vitamin D supply affects the bioavailability of dietary calcium, which might also have anticarcinogenic effects. However, few studies considered them jointly. We used a population-based case-control study in Germany to examine the independent and joint effects of dietary vitamin D and calcium on premenopausal breast cancer risk. Dietary information was assessed using a validated food frequency questionnaire from 278 premenopausal cases and 666 age-matched controls. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated using multivariate models adjusting vitamin D models for calcium intake and vice versa. Breast cancer risk was significantly inversely associated with vitamin D intake. The OR and 95% CI for the highest intake category (≥ 5 μ g/day) was 0.50 (95% CI = 0.26–0.96) compared with the lowest (< 2 μ g/day; P_trend = 0.02). Dietary calcium intake was not associated with breast cancer (OR = 0.73, 95% CI = 0.41–1.29) for the highest (≥ 1,300 mg/day) versus the lowest category (< 700 mg/day), P_trend = 0.29). No statistically significant interaction between the 2 nutrients was observed. Our data support a protective effect of dietary vitamin D on premenopausal breast cancer risk independent of dietary calcium intake.     

Coffee and gastric cancer: systematic review and meta-analysis

We systematically reviewed the literature on the association between coffee consumption and gastric cancer and performed a meta-analysis of the results. Published cohort and case-control studies were identified in PubMed and reference lists. Random effects meta-analysis was used to pool effects from 23 studies, and heterogeneity was explored by stratification and meta-regression. The odds ratio (OR) for the overall association between coffee and gastric cancer (highest vs. lowest category of exposure) was 0.97 (95%CI: 0.86-1.09), similar for cohort (OR = 1.02; 95%CI: 0.76-1.37) and case-control studies (population-based: OR = 0.90; 95%CI: 0.70-1.15; hospital-based: OR = 0.97; 95%CI: 0.83-1.13). The OR was 1.26 (95%CI: 1.02-1.57) when considering five studies conducted in the USA, 0.97 (95%CI: 0.82-1.14) for the five Japanese studies, 0.98 (95%CI: 0.81-1.17) for the six studies from Europe, and 0.64 (95%CI: 0.47-0.86) for the two studies from South America. In this meta-analysis we found no adverse effect of coffee associated with gastric cancer. Knowledge on the level of exposure to different coffee constituents may provide a deeper understanding of this reassuring result and the real role of coffee on cancer risk.     

Meta-Analysis of Black Tea Consumption and Breast Cancer Risk: Update 2013

Black tea is a commonly consumed beverage in the world, comprising approximately 80% of all tea consumed. We sought to examine the association between black tea consumption and risk of breast cancer, using all available epidemiologic evidence to date. PubMed, EMBASE, ISI Web of Science, Chinese National Knowledge Infrastructure Database, and China Biological Medicine Database were used to search for citations using the MeSH terms as “breast neoplasm” AND “black tea.” Then we performed a meta-analysis of studies of breast cancer risk published between 1985 and 2013 by using RevMan 5.0 software. The results showed that no association between black tea consumption and breast cancer risk in overall [odds ratio (OR) = 0.97; 95% confidence interval (CI) = 0.89–1.05]. We further performed a stratified analysis according to region (United States/Europe). Black tea consumption did not decrease breast cancer risk in the United States (OR = 0.91; 95% CI = 0.78–1.07) and in Europe (OR = 0.99; 95% CI = 0.93–1.06). In addition, the summary OR from all cohort studies (OR = 1.04, 95% CI = 0.91–1.18) or all case-control studies (OR = 0.95, 95% CI = 0.88–1.02) showed black tea intake has no effects on breast cancer risk. However, the association between black tea consumption and breast cancer incidence remains unclear based on the current evidence. Further well-designed large studies are needed to confirm our result.