Insights & Discussion
Our dose-response analysis indicated that moderate green tea consumption (500–1000 mL/d) was associated with a 21% to 24% lower risk of stroke.
The meta-analysis aimed to clarify the inconsistent findings in epidemiologic studies regarding the link between green tea consumption and stroke risk. Five prospective cohort studies, involving 645,393 participants and 11,421 stroke cases, were analyzed. The summary relative risk (RR) revealed a substantial association, indicating a 26% reduction in stroke risk with the highest green tea consumption. The dose-response analysis indicated a nonlinear relationship, and compared with non-consumers, various levels of green tea intake showed progressively reduced RRs for stroke, emphasizing a potential protective effect.
The findings from the meta-analysis strongly suggest an inverse association between green tea consumption and stroke risk. Notably, the highest green tea consumption demonstrated a significant 26% risk reduction. The dose-response analysis further highlighted a nonlinear relationship, with moderate consumption levels (500–1000 mL/d) showing the most substantial risk reduction. These results provide support for recommending green tea consumption as a measure for the primary prevention of stroke.
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Higher daily tea consumption, especially green tea, is linked to a lower risk of cerebral hemorrhage in adults.
2022 Acta Neurologica Belgica Tea consumption and cerebral hemorrhage risk: a meta-analysis Cheng P, Zhang J, Liu W, Sun Q, Fu Z, Lin H, et al.
Systematic Review Cerebral Haemorrhage Green Tea Stroke
This meta-analysis uncovered evidence of a connection between tea consumption and cerebral hemorrhage risk, exploring databases including Web of Science, PubMed, Embase, and Scopus until December 2021. The synthesis utilized relative risks or odds ratios from observational studies. The pool of data included ten studies involving over 721,827 participants.
The evaluation revealed that a higher rate of tea consumption, and more specifically green tea, was significantly related to a lower risk of cerebral hemorrhage. Interestingly, this connection could be observed even when adjusted for key lifestyle factors such as alcohol consumption, fruit and vegetable intake, and physical activity. It is worth noting that the intake of tea on a daily basis demonstrated a protective effect against the risk of cerebral hemorrhage.
Higher coffee consumption, specifically 3-4 cups daily, is associated with a 21% lower risk of stroke, with no further reductions with increased intake.
2021 Journal of Stroke and Cerebrovascular Diseases Coffee Consumption and Stroke Risk: Evidence from a Systematic Review and Meta-Analysis of more than 2.4 Million Men and Women Shao C, Tang H, Wang X, He J
Systematic Review Coffee Stroke Stroke Risk
The research utilized a systematic review and meta-analysis approach to investigate the link between coffee consumption and stroke risk. Random-effects models were employed to compile relative risk estimates. The assessment was structured to compare the highest and lowest categories of coffee consumption and utilized a one-stage robust error meta-regression model for stroke risk assessment. The study incorporated 21 separate studies which in total included over 2.4 million participants.
The findings suggest a significant inverse connection between coffee consumption and the risk of stroke. According to the pooled relative risk analysis, the highest versus the lowest categories of coffee consumption showed a decrease in stroke risk. There seems to be a nonlinear (U-shaped) relationship between stroke risk and coffee consumption, with the lowest risk (21% lower) associated with consuming 3-4 cups of coffee per day. Sensitivity analysis suggested the influence of each individual data set on the overall result wasn't significant, and while some evidence of publication bias was witnessed, additional analysis established that potential bias didn't impact the findings noticeably.
The literature overall supports an inverse association between green tea and cardiovascular disease-related health outcomes, while the included meta-analyses generally suggested an inverse association between green tea and BMI-related and blood pressure outcomes.
2020 European Journal of Clinical Nutrition Green tea and cancer and cardiometabolic diseases: a review of the current epidemiological evidence Abe SK, Inoue M
Systematic Review Cancer Cardiovascular Disease Endometrial Cancer
The evidence on green tea consumption and health outcomes presented in this review suggests green tea may be favorable for cardiovascular disease, particularly stroke, and certain cancers such as endometrial, esophageal, lung, non-Hodgkins lymphoma, oral, and ovarian cancer. More evidence is needed to assess the impact of green tea on breast, gastric, and liver cancer risk. Additional studies could also help clarify the suggested null association with certain cancer sites: colorectal, pancreatic, and prostate cancer. Possible minor adverse events on health from green tea consumption were reported in one study, however these must be interpreted cautiously within the study context and possible finer dose-response implications. The findings for green tea and diabetes risk were inconclusive. For BMI the current evidence suggests a possible weak association, while the evidence is stronger supporting a decrease in blood pressure from green tea. More studies investigating a possible association between green tea consumption and other health outcomes such as cognition, injuries, respiratory disease would be informative to more completely assess the impact of green tea on human health.
In conclusion, our review suggests green tea may have health benefits especially for cardiovascular disease and certain cancer sites.