Volume 32, Issue 10 p. 1855-1864
REVIEW

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

Mona Najaf Najafi

Mona Najaf Najafi

Clinical Research Unit, Mashhad University of Medical Sciences, Mashhad, Iran

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Maryam Salehi

Maryam Salehi

Clinical Research Unit, Mashhad University of Medical Sciences, Mashhad, Iran

Cancer Research Center, Mashhad University of Medical Sciences, Mashhad, Iran

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Masumeh Ghazanfarpour

Masumeh Ghazanfarpour

Evidence-Based Care Research Centre, Department of Midwifery, School of Nursing and Midwifery, Mashhad University of Medical Sciences, Mashhad, Iran

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Zeinab Sadat Hoseini

Zeinab Sadat Hoseini

Student Research Committee, Faculty of Medicine, Islamic Azad University of Mashhad, Mashhad, Iran

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Majid Khadem-Rezaiyan

Corresponding Author

Majid Khadem-Rezaiyan

Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran

Correspondence

Dr. Majid Khadem-Rezaiyan, Community Medicine Specialist, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran.

Email: [email protected]; [email protected]

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First published: 07 June 2018
Citations: 28

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, I2 = 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, I2 = 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.

CONFLICT OF INTEREST

Authors have no conflict of interest to declare.

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