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Soy isoflavone intake and breast cancer risk in Japan: From the Takayama study
Author(s) -
Wada Keiko,
Nakamura Kozue,
Tamai Yuya,
Tsuji Michiko,
Kawachi Toshiaki,
Hori Akihiro,
Takeyama Naoharu,
Tanabashi Shinobu,
Matsushita Shogen,
Tokimitsu Naoki,
Nagata Chisato
Publication year - 2013
Publication title -
international journal of cancer
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.475
H-Index - 234
eISSN - 1097-0215
pISSN - 0020-7136
DOI - 10.1002/ijc.28088
Subject(s) - medicine , breast cancer , hazard ratio , cancer , body mass index , population , hormone replacement therapy (female to male) , prospective cohort study , incidence (geometry) , lower risk , proportional hazards model , cohort study , menarche , physiology , gynecology , oncology , environmental health , confidence interval , optics , testosterone (patch) , physics
The effects of soy or isoflavone intake on breast cancer need to be examined further in epidemiologic studies. We assessed the associations of soy and isoflavone intake with breast cancer incidence in a population‐based prospective cohort study in Japan. Participants were members from the Takayama study, aged 35 years or older in 1992. The follow‐up was conducted from the time of the baseline study (September 1, 1992) to the end of March 2008. Cancer incidence was mainly confirmed through regional population‐based cancer registries. Breast cancer was defined as code C50 according to ICD‐10. Soy and isoflavone intakes were assessed with a validated food frequency questionnaire. Using the Cox proportional hazard models, the association of soy and isoflavone intake with breast cancer was assessed after adjustments for age, body mass index, physical activity, smoking, alcohol consumption, education, age at menarche, age at first delivery, menopausal status, number of children and history of hormone replacement therapy. Among the 15,607 women analyzed, 172 had developed breast cancer. The relative risks of postmenopausal breast cancer were lower among women with higher intakes of soy (trend p = 0.023) and isoflavone (trend p = 0.046), although the relative risks of premenopausal breast cancer were not associated with intakes of soy and isoflavone. Decreased risks of breast cancer were found even among women with a moderate intake of soy and isoflavone. These results suggested that soy and isoflavone intakes have a protective effect on postmenopausal breast cancer.