The association between green tea consumption and breast cancer risk: A systematic review and meta‐analysis

Abstract

This systematic review and meta-analysis aimed to critically evaluate the relation between green tea (GT) consumption and the risk of breast cancer. Popular electronic databases were systematically searched for papers in English language. All case-control and cohort studies in addition to randomized clinical trials were included if they assessed the chemopreventive effects of GT on breast cancer. The quality of included studies was assessed using the Newcastle-Ottawa and Jadad scale. This systematic review comprised 14 studies: 9 case-control studies, 4 cohort studies, and 1 clinical trial. Odds ratio (OR) in case-control studies suggested that women in the group receiving the highest level of GT had 19% reduction in breast cancer risk compared with those who received the lowest level of GT (summary OR = 0.81, p = .031; 95% CI [0.66, 0.981]; heterogeneity, I = 71.53, p < .001, random effect model; 9 studies). OR in cohort studies also showed no significant difference (OR = 0.99, p = .94; 95% CI [0.81, 1.138]; heterogeneity, I = 19.06, p = .29; fixed-effect model; 4 studies). According to the only clinical trial, treatment with GT could not alter the mammographic density compared with placebo (26% vs. 25%). It cannot be concluded that GT consumption may decrease the risk of breast cancer. Due to high heterogeneity, a pooled analysis of case-control and cohort studies was not performed.

Healthy Effects of Plant Polyphenols: Molecular Mechanisms

“…The results indicated that resveratrol altered glucose homeostasis only slightly except in a small group of Caucasians, where it improved insulin resistance and glucose homeostasis [81]. The beneficial effects of green tea, particularly of epigallocatechins, have been largely investigated even in clinical trials addressing their anti-cancer properties; however, the reported data do not permit to draw solid conclusions indicating a decreased risk of breast cancer by green tea consumption, due to the high heterogeneity of case-control and cohort studies (reviewed in [82]). Recently it has been suggested that green tea and/or green tea extracts inhibit the progression of cardiac amyloidoses [83]; however, currently, reduced information is available in humans on the protection against amyloidoses and amyloid-associated neurodegeneration specifically attributable to EGCG.…”

Natural Product Interventions for Chemotherapy and Radiotherapy-Induced Side Effects

“…A systematic review of preclinical studies demonstrate that grape seed extract can treat chemotherapy and radiotherapy-induced neurotoxicity (Olaku et al, 2015 ). Clinical trial demonstrates that green tea consumption with neuroprotective effect has anticancer action via regulation of intra-tumoural lymph-angiogenesis and COX-2 expression (Najaf Najafi et al, 2018 ). These diet supplements may be effective in the prevention or treatment of chemotherapy and radiotherapy-induced neurotoxicity.…”

Medicinal Herbs Used in Traditional Management of Breast Cancer: Mechanisms of Action

“…Other reported systematic and meta-analysis reviews of studies showed an inverse relationship between increased green tea consumption (>3 cups/day) and risk of breast cancer recurrence [ 161 ]; no significant relationship between consumption of ≥ cups of green tea/day and developing breast cancer in cohort studies (RR = 0.89, 95% CI: 0.71–1.10, p > 0.05) [ 162 ] and the analysis of nine case-control studies, four cohort studies revealed that green tea consumption may not reduce breast cancer risk (overall OR = 0.81, 95% CI: 0.66–0.98, p = 0.031) [ 163 ].…”