Tea Consumption and Risk of Cancer: An Umbrella Review and Meta-Analysis of Observational Studies

Public Health Nutrition, 2002

Objective:This study examines the relationship between tea consumption and colon cancer risk in the US population.Design:Data from the NHANES I Epidemiologic Follow-up study (NHEFS) were used to examine the hypothesis. Cox proportional hazard models were used to examine the hypothesis of a protective effect of frequent tea consumption on colon cancer occurrence.Setting:Due to differences in the precision of the exposure data, we analysed two cohort periods based on the NHEFS. Cohort I was based on the survey conducted at the NHEFS baseline and Cohort II began at the first follow-up.Subjects:After excluding non-incidence cases and cases lost to follow-ups, there were 2359 tea users and 6498 non-tea users at baseline and 7656 tea users and 4514 non-tea users at the first follow-up.Results:After adjusting for confounders, the relative risks of colon cancer are 0.57 (95% confidence interval (CI) 0.42, 0.78) and 0.59 (95% CI = 0.35, 1.00) for subjects who consumed ≤1.5 cups and ≥1.5 cups...

American Journal of Epidemiology, 1996

Carcinogenesis, 2006

Nutrition and Cancer, 2001

Background: Tea is derived from the leaf of Camellia sinensis, a natural beverage widely consumed around the world. Geological and botanical evidence suggests that the tea plant originated from China. Varying methods of processing tea leaves lead to green tea, black tea, or Oolong tea, which differ in their concentrations of polyphenols. Green tea polyphenols appear to have anti-tumorigenic properties, and form 30-40% of the dry weight of green tea compared with only 3-10% of black tea. Numerous studies in multiple animal models and different cancer cell lines have demonstrated the anti-tumorigenesis by green tea polyphenols. Despite the consistency of laboratory results, evidence of this effect occuring in humans has been inconclusive to date. Objective: To investigate if green tea consumption was associated with longer survival rates in ovarian cancer patients, and a lower risk of ovarian, breast, and colorectal cancer, in addition to adult leukemia Methods: We have conducted one prospective cohort study in ovarian cancer patients, and five case-control studies in ovarian, breast, and colorectal cancers, and leukemia over the past decade. Tea consumption was measured using a structured questionnaire by face-to-face interviews. The validity and reliability of the questionnaire was assessed in a preliminary study, and then evaluated by a test–retest. Cox proportional hazards regression models were used to obtain hazard ratios(HRs), 95% confidence intervals(95% CIs), and were adjusted for age at diagnosis, locality, body mass index(BMI), parity, International Federation of Gynecology and Obstetrics (IFGO) stage, histologic grade of differentiation, cytology of ascites, residual tumour, and chemotherapeutic status. Odds ratios(ORs) and 95% CIs were obtained using logistic regression analyses, which accounted for demographic, lifestyle, hormonal and family cancer factors, and potential confounders. Results: Higher green tea consumption was consistently observed as being associated with a lower risk of mortality due to ovarian cancer, and a decreased risk of ovarian, breast, and colorectal cancers, and adult leukemia occurrences in our observational studies. The adjusted HR and 95% CI for case mortality from ovarian cancer was 0.40(0.18-0.90) in the patients who consumed green tea at the highest level compared with non-tea drinkers. Compared with never or seldom tea drinkers, the adjusted ORs ranged from 0.07 to 0.61 for ovarian, breast, and colorectal cancers, and adult leukemia in those who consumed green tea at the highest level. Significant inverse dose-response relationships were also observed for quantity, duration, and frequency of green tea consumed. Conclusion: We concluded that regular consumption of green tea enhanced survival of ovarian cancer, and decreased risks of ovarian, breast, and colorectal cancers, and adult leukemia. Evidence from our observational studies supported the protective effect of green tea against cancers, and this evidence will provide a knowledge platform from which to launch interventional studies for cancer prevention in the next stage.

BMJ Open, 2020

ObjectiveTo examine the possible relationship between tea consumption and risk of gastric cancer (GC) among Japanese men and women included in a large Japanese population-based study titled the Japan Collaborative Cohort (JACC) Study.DesignProspective cohort study.SettingA population-based cohort included subjects who were recruited from 24 areas of JACC Study, in which data regarding the incidence of cancer were available.Participants63 848 participants (26 025 men and 37 823 women), aged 40–79, were included in the analyses and underwent follow-up (median 13.3 years) prospectively in research on cancer incidence.Primary and secondary outcome measuresThe primary outcome variable was the risk of GC according to the frequency intakes of total tea, green tea, black tea and oolong tea. The adjusted HRs for the risk of GC associated with tea consumption were calculated using the Cox proportional hazards model.Results1494 cases of GC were detected (960 men and 534 women) during the follo...

PLoS ONE, 2014

American Journal of Epidemiology, 2000

1994