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.     

Green Tea Consumption and Risk of Esophageal Cancer: A Meta-Analysis of Published Epidemiological Studies

We performed a meta-analysis to analyze the association of various levels of green tea consumption with risk of esophageal cancer. We searched MEDLINE, EMBASE, and the Cochrane Library for studies of green tea consumption and esophageal cancer and identified 12 observational studies. For esophageal cancer, the pooled relative risk (RR) was 1.09 [95% confidence interval (CI), 0.76–1.55] for greatest vs. non/least green tea consumption; however, there was significant heterogeneity across studies (P = 0.00, I² = 75.5%). Compared with subjects who drank no/least green tea, the pooled RR was 1.14 (95% CI = 0.97–1.35) for moderate drinkers, 0.94 (95% CI = 0.77–1.13) for those who drank little, and 0.97 (95% CI = 0.77–1.22) for all subjects who had ever drunk green tea. Subgroup analysis showed that the RR was 0.46 (95% CI = 0.29–0.73) for female subjects. The results of the present meta-analysis are that any association between green tea and risk of esophageal cancer remains unclear. Subgroup analyses indicated that greater consumption of green tea might reduce the risk of esophageal cancer in female subjects. However, the results are based on limited research. Further research is needed to confirm the results and clarify the likely biological mechanisms.     

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.     

Dairy Product Consumption and Bladder Cancer Risk: A Meta-Analysis

Abstract

To explore the potential relationship between dairy product consumption and bladder cancer risk, we retrieved eligible studies published up to March 15, 2018, via online database search and manual review of the selected articles. Summary relative risk (RR) estimates were calculated using random-effects models based on high to low intake values. Inter-study heterogeneity was explored using stratified analyses of study design, geographic region, or whether studies adjusted for the confounders age, sex, body mass index, smoking, and education level. We extracted data from 16 studies on milk (5,193 subjects) and 10 studies on dairy products (20,434 subjects). The total study population included 220,952 individuals. Dairy product intake and bladder cancer risk were significantly associated, and milk intake and bladder cancer risk more so. Stratified analysis revealed that the trend was more pronounced in case–control studies, and in studies with impact factor <3 and in Asia. The relationship was confirmed after adjusting for sex and Newcastle–Ottawa Scale score of 7 and 8. Our study shows an inverse association between milk consumption and bladder cancer risk.     

Tetrachloroethylene Exposure and Bladder Cancer Risk: A Meta-Analysis of Dry-Cleaning-Worker Studies

Background: In 2012, the International Agency for Research on Cancer classified tetrachloroethylene, used in the production of chemicals and the primary solvent used in dry cleaning, as “probably carcinogenic to humans” based on limited evidence of an increased risk of bladder cancer in dry cleaners.Objectives: We assessed the epidemiological evidence for the association between tetrachloroethylene exposure and bladder cancer from published studies estimating occupational exposure to tetrachloroethylene or in workers in the dry-cleaning industry.Methods: Random-effects meta-analyses were carried out separately for occupational exposure to tetrachloroethylene and employment as a dry cleaner. We qualitatively summarized exposure–response data because of the limited number of studies available.Results: The meta-relative risk (mRR) among tetrachloroethylene-exposed workers was 1.08 (95% CI: 0.82, 1.42; three studies; 463 exposed cases). For employment as a dry cleaner, the overall mRR was 1.47 (95% CI: 1.16, 1.85; seven studies; 139 exposed cases), and for smoking-adjusted studies, the mRR was 1.50 (95% CI: 0.80, 2.84; 4 case–control studies).Conclusions: Our meta-analysis demonstrates an increased risk of bladder cancer in dry cleaners, reported in both cohort and case–control studies, and some evidence for an exposure–response relationship. Although dry cleaners incur mixed exposures, tetrachloroethylene could be responsible for the excess risk of bladder cancer because it is the primary solvent used and it is the only chemical commonly used by dry cleaners that is currently identified as a potential bladder carcinogen. Relatively crude approaches in exposure assessment in the studies of “tetrachloroethylene-exposed workers” may have attenuated the relative risks.Citation: Vlaanderen J, Straif K, Ruder A, Blair A, Hansen J, Lynge E, Charbotel B, Loomis D, Kauppinen T, Kyyronen P, Pukkala E, Weiderpass E, Guha N. 2014. Tetrachloroethylene exposure and bladder cancer risk: a meta-analysis of dry-cleaning-worker studies. Environ Health Perspect 122:661–666; http://dx.doi.org/10.1289/ehp.1307055     

Coffee Consumption and Prostate Cancer Risk: A Meta-Analysis of Cohort Studies

This meta-analysis was conducted to assess the association between coffee consumption and prostate cancer risk. Thirteen cohort studies with 34,105 cases and 539,577 participants were included in the meta-analysis. The summary relative risks (RRs) with 95% confidence intervals (CIs) for different coffee intake levels were calculated. Dose-response relationship was assessed using generalized least square trend estimation. The pooled RR for the highest vs. lowest coffee intake was 0.90 (95% CI: 0.85–0.95), with no significant heterogeneity across studies (P = 0.267; I²= 17.5%). The dose-response analysis showed a lower cancer risk decreased by 2.5% (RR = 0.975; 95% CI: 0.957–0.995) for every 2 cups/day increment in coffee consumption. Stratifying by geographic region, there was a statistically significant protective influence of coffee on prostate cancer risk among European populations. In subgroup analysis of prostate cancer grade, the summary RRs were 0.89 (95% CI: 0.83–0.96) for nonadvanced, 0.82 (95% CI: 0.61–1.10) for advanced and 0.76 (95% CI: 0.55–1.06) for fatal diseases. Our findings suggest that coffee consumption may be associated with a reduced risk of prostate cancer and it also has an inverse association with nonadvanced prostate cancer. Because of the limited number of studies, more prospective studies with large sample size are needed to confirm this association.     

Lycopene Consumption and Risk of Colorectal Cancer: A Meta-Analysis of Observational Studies

A number of epidemiological studies have explored the association between lycopene or lycopene-rich food intake and the risk of colorectal cancer, but the results of these studies have not been consistent. We conducted a systematic review and meta-analysis of studies published in the PubMed and EMBASE databases to quantitatively assess the association between lycopene consumption and the risk of colorectal cancer. A total of 15 studies were included in the meta-analysis, and the summary relative risk (RR) for highest versus lowest category indicated no significant association between lycopene consumption and the risk of colorectal cancer [RR = 0.94, 95% confidence interval (CI): 0.80–1.10]. However, a significant inverse association was observed between lycopene consumption and the site of cancer in the colon (RR = 0.88, 95% CI: 0.81–0.96). We also found that the incidence of colon cancer and lycopene intake did not exhibit dose-response relationships. The Grades of Recommendations Assessment, Development and Evaluation (GRADE) quality in our study was very low. In conclusion, this meta-analysis indicates that lycopene consumption is not associated with the risk of colorectal cancer. Further research will be needed in this area to provide conclusive evidence.     

Anthocyanin Consumption and Risk of Colorectal Cancer: A Meta-Analysis of Observational Studies

This meta-analysis aimed to summarize the association between anthocyanin consumption and the risk of colorectal cancer.

All relative articles were located on online databases, including PubMed, Embase, and the Cochrane Library as of June 11, 2018. Risk ratios (RRs) or odds ratio and their 95% confidence intervals (CIs) were calculated through the STATA 12.0 software package.

A total of seven studies were included in the meta-analysis. A significant inverse association was found between total anthocyanin consumption and colorectal cancer risk (RR?=?0.78; 95% CI, 0.64–0.95). Likewise, there was significant evidence of a relationship between anthocyanin intake and colorectal cancer in the colon site (RR?=?0.81; 95% CI, 0.71–0.92); men (RR?=?0.88; 95% CI, 0.81–0.95), and case-control studies (RR?=?0.69; 95% CI, 0.60–0.78). A dose–response relationship was not found in this meta-analysis. The Grades of Recommendations Assessment, Development, and Evaluation quality in our study was very low.

This meta-analysis indicates that anthocyanin consumption is inversely associated with the risk of colorectal cancer. Anthocyanins may play an active role in the prevention of colorectal cancer.

Key teaching points:

• Some epidemiological studies found an inverse correlation between the high consumption of anthocyanins and low risk of colorectal cancer.

• Because of this structure, anthocyanins/anthocyanidins have a powerful capability of donating electrons, which can be characterized as antioxidant properties.

• Anthocyanins can also inhibit colon cancer by interfering in the cell cycle and inducing the effect of anti-proliferation and apoptosis. The formation of cytoplasmic vacuoles in cells also indicates that anthocyanins may induce autophagy.

• From the findings of nonrandomized controlled trials, anthocyanins may play an active role in the prevention of colorectal cancer.

     

Soy Food Consumption and Risk of Prostate Cancer: A Meta-Analysis of Observational Studies

Soybean products have been suggested to have a chemo preventive effect against prostate cancer. The aim of this study was to provide a comprehensive meta-analysis on the extent of the possible association between soy-based food consumption and the risk of prostate cancer. Five cohort studies and 8 case-control studies were identified using MEDLINE, EMBASE, CINAHL, Korea Medical Database, KoreaMed, Korean studies Information Service System, Japana Centra Revuo Medicina, China National Knowledge Infrastructure, and a manual search. Summary odds ratios (ORs) comparing high versus low categories of soybean consumptions were calculated on the basis of the random effect model. We analyzed the associations based on the different types of soybean consumptions. The summary ORs (95% CI) for total soy foods were 0.69 (CI = 0.57–0.84) and 0.75 (CI = 0.62–0.89) for nonfermented soy foods. Among individual soy foods, only tofu yielded a significant value of 0.73 (CI = 0.57–0.92). Consumption of soybean milk, miso, or natto did not significantly reduce the risk of prostate cancer. Genistein and daidzein were associated with a lower risk of prostate cancer. This systematic review suggests that soy food consumption could lower the risk of prostate cancer. This conclusion, however, should be interpreted with caution because various biases can affect the results of a meta-analysis.     

Coffee Consumption and Risk of Gastric Cancer: A Large Updated Meta-Analysis of Prospective Studies

The potential role of coffee consumption in the development of various types of cancer has been extensively investigated in epidemiologic studies. How coffee consumption may modulate risk of gastric cancer, however, remains a subject open for investigation. To better quantify this relation, we quantitatively summarized evidence from prospective studies. Eligible studies were identified on PubMed databases. The summary risk estimates were obtained using the random-effects model. Subgroup, sensitivity and dose-response analyses were conducted. The present meta-analysis included 12 prospective cohort studies. A pooled analysis of these studies suggested that coffee consumption (highest vs. lowest consumption) was not associated with risk of gastric cancer (RR = 1.12, 95% CI = 0.93–1.36). In the subgroup analysis, significant increased risk was detected in the U.S. studies (RR = 1.36, 95% CI = 1.06–1.74) and in the studies with <10 years of follow-up (RR = 1.24, 95% CI = 1.00–1.54), and the greatest increase in risk was observed in those studies without adjustment for smoking (RR = 1.48, 95% CI = 1.13–1.93). There was some evidence of publication bias (P for Egger’s test = 0.03). Cumulative evidence from prospective studies suggests that coffee consumption is not associated with risk of gastric cancer. The observed positive results may be confounded by smoking and need further investigation.     

Milk Intake in Early Life and Later Cancer Risk: A Meta-Analysis

Dairy consumption in adulthood has been demonstrated to influence cancer risk. Although childhood and adolescence represent critical periods of rapid growth, the relationship between milk intake in early life and later cancer risk is unclear. Thus, we examined this relationship by conducting a meta-analysis of the observational studies. PubMed and Embase were searched for relevant articles that were published throughout December 2021. The summary relative risk (RR) and 95% confidence interval (CI) were estimated using the DerSimonian-Laird random-effects model. The summary RR for the highest vs. lowest milk intake was 0.83 (95% CI = 0.69–1.00; p = 0.05; I² = 60%; seven studies) for breast cancer, 0.98 (95% CI = 0.72–1.32; p = 0.88; I² = 51%; four studies) for prostate cancer, and 0.90 (95% CI = 0.42–1.93; p = 0.78; I² = 83%; three studies) for colorectal cancer. No evidence of an association emerged in subgroup analyses of menopausal status, cancer stage, fat content of milk, life stage of milk intake, or study design. Consistent results were observed in the meta-analyses using total dairy intake. In conclusion, milk intake during childhood and adolescence might not be associated with risks of breast, prostate, and colorectal cancer later in life. Given the small number of studies that were included in our meta-analysis, and the high heterogeneity, more studies are warranted for a definitive conclusion.     

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.     

Green Tea Consumption and the Risk of Liver Cancer: A Meta-Analysis

Green tea is a commonly consumed beverage in Asia and has been suggested to have anticarcinogenic properties. To date, epidemiological evidence of the effect of green tea consumption on liver cancer risk remains ambiguous. The aim of this meta-analysis is to evaluate the association between green tea consumption and the risk of liver cancer. The summary relative risk for the highest consumption (≥5 cups/day) of green tea on liver cancer incidence compared with nondrinkers was 0.62 (95% confidence interval: 0.49–0.79). We also found a trend that the incidence of liver cancer was reduced with the increasing years of green tea intake (significance at >20 yr). A significant dose–response association was found between green tea drinking and liver cancer risk. The downward trend was most obvious when the consumption of green tea increased up to about 4 cups/day. The results showed that the increasing green tea intake may have a preventive effect against liver cancer.     

Alcohol Consumption and Risk of Glioma: A Meta-Analysis of 19 Observational Studies

The relationship between risk of glioma and alcohol consumption has been widely studied, but results have been conflicting. We therefore conducted a meta-analysis of observational studies to systematically assess the relationship between alcohol drinking and risk of glioma. Two electronic databases (PubMed and EMBASE) were searched from inception to 8 August 2013 to identify pertinent studies that linked alcohol drinking with glioma risk. We used a random-effects model to calculate the overall relative risk (RR) with corresponding 95% confidence intervals (CIs). Fifteen case-control and four cohort studies were identified for this analysis. The combined RR for total alcohol drinkers versus non-drinkers was 0.96 (95% CI: 0.89–1.04). In the subgroup analysis by geographic area, a significant association was observed in North American studies (RR = 0.78, 95% CI: 0.65–0.93), but not in European or Asian/Australian studies. In the subgroup analysis by study design, a borderline significant association emerged in population-based case-control studies (RR = 0.82, 95% CI: 0.68–0.99), but not in hospital-based case-control studies (RR = 1.00, 95% CI: 0.99–1.01) or cohort group (RR = 1.03, 95% CI: 0.88–1.20). Our results show no material association between alcohol consumption and risk of glioma existed. Further prospective evidences are needed to confirm this association.     

Fish Consumption and Lung Cancer Risk: Systematic Review and Meta-Analysis

There is evidence pointing to a possible role of diet on cancer etiology. Prior studies evaluating the relationship between fish consumption and lung cancer risk reported inconclusive results. The aim of this study was to achieve a comprehensive assessment of the relationship between fish consumption and lung cancer risk through systematic review and meta-analysis. Case control and cohort studies up to September 1, 2012 about fish consumption and lung cancer risk were confirmed by an online search. Separate relative risk (RR) or odds ratio (OR) estimates with 95% confidence interval (CI) of the relationship between lung cancer risk and fish consumption level from the included articles were combined by Stata11.0 software. Publication bias was evaluated by Egger's linear regression test and funnel plot. Twenty articles (17 case-control and 3 cohort studies) comprising 8799 cases of lung cancer and 17,072 noncases were included in the final analysis. The pooled results from all studies indicated that high fish consumption was significantly associated with a decreased risk of lung cancer (pooled RR: 0.79; 95% CI: 0.69–0.92). There was heterogeneity among the studies (I² = 73%, P < 0.05). Pooled RR in case control and cohort studies were 0.76 (95% CI: 0.63–0.91) and 0.95 (95% CI: 0.73–1.24), respectively. Omission of any single study had little effect on the combined risk estimates. This article had no publication bias. This study identifies a significant association between fish consumption and lung cancer, confirming a protective role of fish in lung cancer. More well-designed prospective studies are required to further verify the effect of fish consumption on lung cancer.     

Higher Mushroom Consumption Is Associated with Lower Risk of Cancer: A Systematic Review and Meta-Analysis of Observational Studies

Mushrooms are rich in bioactive compounds. The potential health benefits associated with mushroom intake have gained recent research attention. We thus conducted a systematic review and meta-analysis to assess the association between mushroom intake and risk of cancer at any site. We searched MEDLINE, Web of Science, and Cochrane Library to identify relevant studies on mushroom intake and cancer published from 1 January, 1966, up to 31 October, 2020. Observational studies (n = 17) with RRs, HRs, or ORs and 95% CIs of cancer risk for ≥2 categories of mushroom intake were eligible for the present study. Random-effects meta-analyses were conducted. Higher mushroom consumption was associated with lower risk of total cancer (pooled RR for the highest compared with the lowest consumption groups: 0.66; 95% CI: 0.55, 0.78; n = 17). Higher mushroom consumption was also associated with lower risk of breast cancer (pooled RR for the highest compared with the lowest consumption groups: 0.65; 95% CI: 0.52, 0.81; n = 10) and nonbreast cancer (pooled RR for the highest compared with the lowest consumption groups: 0.80; 95% CI: 0.66, 0.97; n = 13). When site-specific cancers were examined, a significant association with mushroom consumption was only observed with breast cancer; this could be due to the small number of studies that were conducted with other cancers. There was evidence of a significant nonlinear dose–response association between mushroom consumption and the risk of total cancer (P-nonlinearity = 0.001; n = 7). Limitations included the potential for recall and selection bias in case-control designs, which comprised 11 out of the 17 studies included in this meta-analysis, and the large variation in the adjustment factors used in the final models from each study. The association between higher mushroom consumption and lower risk of cancer, particularly breast cancer, may indicate a potential protective role for mushrooms in the diet.     

Dietary Factors and Thyroid Cancer Risk: A Meta-Analysis of Observational Studies

To better understand the relationship between dietary factors and thyroid cancer risk, we summarized the published evidence on relationship between dietary factors and thyroid cancer incidence. Searching several databases for relevant studies published by March 2014 included a total of 19 studies. We calculated summary odds ratios (ORs) for each risk factor. Based on the highest level of total consumption vs. the lowest level, the summary OR [95% (confidence interval) CI] of thyroid cancer was 0.79 (0.66, 0.94) for fish; 0.95 (0.74, 1.23) for salt water fish; 0.86 (0.63, 1.16) for fresh water fish; 0.76 (0.58, 1.00) for vegetables; 0.88 (0.72, 1.08) for shellfish; 0.93 (0.66, 1.29) for cruciferous vegetables; 0.97 (0.78, 1.21) for fruits; 0.96 (0.70, 1.34) for meat; and 1.11 (0.86, 1.42) for grains. Subgroup analysis showed that fish (OR 0.74, 95%CI: 0.59, 0.92) and shellfish (OR 0.46, 95%CI: 0.27, 0.75) consumption have a protective effect in iodine deficiency areas, whereas the ORs were not statistically significant in iodine-rich areas. Our findings indicated that fish and shellfish consumption may decrease the risk of thyroid cancer in iodine deficiency areas, although no such effect was observed in iodine-rich areas.     

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.     

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.