Potential Benefits of Green Tea on Cancer-Related Outcomes: The Impact of Dosage and BMI as Effect Modifiers

Introduction: Green tea, GT, catechins, epigallocatechin-3-gallate (EGCG) and its polyphenol extract called Polyphenon E have been studied as potential anticancer agents. This systematic review evaluates the effect of GT exposure on cancer outcomes while focusing on the influence of green tea dosage and body mass index (BMI) as effect modifiers. METHODS: A systematic review of studies among PubMed, Scopus, and Embase until June 2024, evaluating green tea or Polyphenon E among cancer patients was performed. Of 150 publications, five studies were included, comprising four RCTs and one single-center prospective cohort study. We evaluated the effects of green tea interventions on cancer biomarkers and survival outcomes, as well as the possible modifying role of BMI on such endpoints. RESULTS: The included studies have different types of cancers, dosages of green tea, and durations of intervention. High-dose green tea (≥800 mg EGCG) reduced certain biomarkers; for example, insulin-like growth factor-1 (IGF-1) and proliferating cell nuclear antigen (PCNA); there is not consistency across biomarkers or cancer types. Among the observational studies identified, only one reported a statistically significant dose-response association between green tea consumption and improved survival among ovarian cancer patients. BMI data varied little between the intervention and placebo arms across the studies; this certainly limits the ability to assess BMI as an effect modifier. CONCLUSION: While there was a trend towards a reduction of certain cancer biomarkers associated with green tea consumption, due to limitations in the data it is not possible to conclusively determine effect modification by dosage or BMI. Variability in study designs, dosages, and cancers limits generalizability. Future studies are warranted that are well-designed regarding dosage standardization, long-term effects, and identification of an interaction between green tea and standard cancer therapies. Keywords: Green tea, Catechins, Epigallocatechin-3-gallate (EGCG), Body Mass Index (BMI), Cancer