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.     

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.     

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.     

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.     

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.     

Green Tea Consumption and Esophageal Cancer Risk: A Meta-analysis

Abstract

Background: The protective role of green tea against cancer is still unknown.

Objectives: To investigate the association between green tea consumption and esophageal cancer risk through meta-analysis.

Methods: We searched MEDLINE, EMBASE, Web of Science and Cochrane Library for studies on the relationship between green tea and esophageal cancer risk. We assessed heterogeneity (I²) and publication bias (Begg’s and Egger’s tests). Pooled relative risks (RRs) or odds ratios (ORs) with 95% confidence intervals (CIs) were calculated using random effects models.

Results: A total of 20 studies were included. The RRs for all studies was 0.65 (95% CI: 0.57–0.73), with I² = 75.3% and P?=?0. In the subgroup analysis, the following variables showed marked heterogeneity: Asian (RR: 0.64; 95% CI: 0.56–0.73) and non-Asian countries (RR: 0.74; 95% CI: 0.45–1.03), female (RR: 0.55; 95% CI: 0.39–0.71) and male?+?female (RR: 0.64; 95% CI: 0.54–0.75), case–control study (RR: 0.62; 95% CI: 0.52–0.71), impact factor >3 (RR: 0.65; 95% CI: 0.56–0.75), impact factor <3 (RR: 0.64; 95% CI: 0.48–0.80), Newcastle–Ottawa Scale >7 (RR: 0.82; 95% CI: 0.66–0.97) and Newcastle–Ottawa Scale ≤7 (RR: 0.59; 95% CI: 0.49–0.68).

Conclusion: Green tea consumption could be a protective factor for esophageal cancer.     

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.     

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.     

Green Tea Consumption and Risk of Pancreatic Cancer: A Meta-analysis

Emerging laboratory and animal studies indicate that green tea inhibits development and progression of pancreatic cancer, but evidence from epidemiologic studies appears inconsistent and inconclusive. A meta-analysis summarizing published case-control and cohort studies was performed to evaluate the association of green tea consumption with risk of pancreatic cancer. Pertinent studies were identified by a search of PubMed and EMBASE up to April 2014. A random-effects model was assigned to compute summary risk estimates. A total of three case-control studies and five prospective studies were included, comprising 2317 incident cases and 288209 subjects. Of them, three studies were from China and the reminders were conducted in Japan. Overall, neither high vs. low green consumption (odds ratio (OR) = 0.99, 95% confidence interval [CI] = 0.78–1.25), nor an increase in green tea consumption of two cups/day (OR = 0.95, 95% CI = 0.85–1.06) was associated with risk of pancreatic cancer. The null association persisted when the analysis was stratified by sex or restricted to non-smokers. In the stratification by study location, the summary OR for the studies from China and for those from Japan was 0.77 (95% CI = 0.60–0.99) and 1.21 (95% CI = 0.94–1.54), respectively (P for differences = 0.04). Cumulative epidemiologic evidence suggests that green tea consumption is not associated with pancreatic cancer.     

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.

     

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.     

Tea Consumption and Risk of Cancer of the Colon and Rectum

The association between tea consumption and risk of colon and rectal cancers was investigated in a population-based case-control study conducted in Iowa (United States). Colon (n = 685) and rectal (n = 655) cancer cases age 40-85 yr were identified through the Iowa Surveillance, Epidemiology, and End Results (SEER) Cancer Registry (86% response rate); controls (n = 2,434) were frequency matched by sex and 5-yr age group (80% response rate). The usual adult consumption of tea (hot and iced), along with other information including dietary data, was self-reported using a mailed questionnaire. Total tea consumption (cups/day) was categorized as none (reference category), low (?3.1), medium (3.1-5.0), and high (?5.0), with cut points for tea consumers based on the 75th and 90th percentiles of use among controls. Unconditional logistic regression was used to estimate the odds ratios (ORs) and 95% confidence intervals. There was no association between total tea consumption and colon cancer (ORs = 1.0, 1.1, 1.3, and 0.7) or rectal cancer (ORs = 1.0, 0.9, 1.4, and 1.0) after adjustment for age, sex, education, physical activity, smoking history, and intake of coffee, fiber, and fruits and vegetables. Results were similar when hot tea and iced tea were evaluated individually. Further adjustment for other colorectal cancer risk factors did not alter these results. There was no association with proximal or distal colon cancer. There was also no interaction between tea consumption and any of the dietary variables or total fluid on risk of colon or rectal cancer, with the exception of a suggestive positive association between an increasing frequency of tea consumption and colon cancer risk among current smokers (multivariate ORs = 1.0, 1.4, 2.0, and 1.8; P for trend = 0.1), but not among never smokers (multivariate ORs = 1.0, 1.0, 1.1, and 0.4; P for trend = 0.3). These data do not support an overall association, either positive or negative, between tea consumption and risk of colon or rectal cancer in this Midwestern US population.     

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.     

Tea,Coffee, and Milk Consumption and Colorectal Cancer Risk

Background

Data regarding the effects of tea, coffee, and milk on the risk of colorectal cancer are inconsistent. We investigated associations of tea, coffee, and milk consumption with colorectal cancer risk and attempted to determine if these exposures were differentially associated with the risks of proximal colon, distal colon, and rectal cancers.

Methods

Data from 854 incident cases and 948 controls were analyzed in a case-control study of colorectal cancer in Western Australia during 2005–07. Multivariable logistic regression was used to analyze the associations of black tea (with and without milk), green tea, herbal tea, hot coffee, iced coffee, and milk with colorectal cancer.

Results

Consumption of 1 or more cups of herbal tea per week was associated with a significantly decreased risk of distal colon cancer (adjusted odds ratio, 0.37; 95% CI, 0.16–0.82; P_Trend = 0.044), and consumption of 1 or more cups of iced coffee per week was associated with increased risk of rectal cancer (adjusted odds ratio, 1.52; 95% CI, 0.91–2.54; P_Trend = 0.004). Neither herbal tea nor iced coffee was associated with the risk of proximal colon cancer. Hot coffee was associated with a possible increased risk of distal colon cancer. Black tea (with or without milk), green tea, decaffeinated coffee, and milk were not significantly associated with colorectal cancer risk.

Conclusions

Consumption of herbal tea was associated with reduced risk of distal colon cancer, and consumption of iced coffee was associated with increased rectal cancer risk.Key words: epidemiological, tea, coffee, milk, colorectal cancer, risk factors     

Effects of Serum Triglycerides on Prostate Cancer and Breast Cancer Risk: A Meta-Analysis of Prospective Studies

Epidemiological studies show conflicting results regarding the link between serum triglyceride and the risk of prostate cancer and breast cancer. Therefore, we performed a meta-analysis of prospective studies to clarify this association. We searched PubMed, EMBASE, the Chinese Biomedical Database (CBM), and the China National Knowledge Infrastructure (CNKI) database to identify relevant prospective studies of the relationship between serum triglyceride and prostate cancer and breast cancer risk. Study-specific estimates adjusting for potential confounders were combined to evaluate a summary relative risks (RRs) and 95% confidence intervals (95% CIs) using a fixed- or random-effects model. A total of 11 prospective studies (619,410 subjects and 15,691 incident prostate cancer patients) and 8 prospective studies (590,878 subjects and 12,177 incident breast cancer patients) were respectively included in our meta-analysis to assess the associations of serum triglyceride with prostate cancer and breast cancer risk. The pooled adjusted RR estimates for prostate cancer and breast cancer for the highest versus the lowest exposure levels of serum triglycerides were 0.95 (95% CI: 0.87–1.04) and 0.94 (95% CI: 0.87–1.00), respectively. Additionally, a dose–response analysis revealed that serum levels of triglycerides were not associated with the risk of prostate cancer and breast cancer. We found that serum triglyceride was not related to the risk of prostate cancer and breast cancer.     

Effects of Coffee,Black Tea and Green Tea Consumption on the Risk of Non-Hodgkin’s Lymphoma: A Systematic Review and Dose–Response Meta-Analysis of Observational Studies

Aim: Several studies have evaluated the association between coffee, black and green tea consumption and non-Hodgkin’s lymphoma (NHL) risk, while the results were inconsistent. We conducted a dose–response meta-analysis of available observational studies to assess the association among coffee, black and green tea intake and the risk of NHL in the general population.

Methods: Studies published up to August 2018 were identified on the basis of a literature search in PubMed, ISI Web of Science, Scopus and Cochrane databases using Mesh and non-Mesh relevant keywords. Relative risks (RRs) with 95% confidence intervals (CIs) and the dose–response relationships were calculated using random-effects models.

Results: In the meta-analysis of 19 effect sizes (315,972 participants with 4,914 cases of NHL), we found that higher green tea intake was associated with a 39% reduced risk of NHL (pooled RR?=?0.61; 95% CIs?=?0.38–0.99, I²=60.4%, p_{heterogeneity}=0.080) in high- versus low-intake meta-analysis. No association was observed between coffee intake (pooled RR?=?1.21; 95% CIs?=?0.97–1.50, I²=52.6%, p_{heterogeneity} < 0.05), black tea intake (pooled RR?=?1.01; 95% CI?=?0.82–1.24, I²=0%, p_{heterogeneity}=0.875) and risk of NHL in high- versus low-intake meta-analysis.

Conclusions: Findings from this dose–response meta-analysis suggest that green tea intake may be associated with reduced risk of NHL.     

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.     

Tea Consumption and Epithelial Ovarian Cancer Risk: A Systematic Review of Observational Studies

Ovarian cancer is the seventh most common type of cancer in the United States and is often not diagnosed until late stages. Thus, identifying potential risk factors and prevention strategies is particularly important. This systematic review analyzes existing evidence on the association between tea consumption and epithelial ovarian cancer risk in human observational studies. PubMed was searched through September 30, 2010 for eligible articles; 16 articles met the inclusion criteria for this systematic review. Five studies found overall tea intake to be associated with a decreased epithelial ovarian cancer risk, 1 found a borderline decreased risk, 9 found no association, and 1 found a borderline increased risk. Overall, it does not appear that tea consumption increases risk of ovarian cancer, but there is insufficient evidence at this point to conclude that it is protective against ovarian cancer. Many of the studies included in this review had important limitations, especially related to the lack of detailed data collected on tea consumption. Further research is needed and should focus on more detailed assessment of type of tea consumed, frequency, and duration of tea intake. Future studies should also explore potential differences in the association between tea intake and ovarian cancer risk among subpopulations.