Consumption of soy foods and the risk of breast cancer: findings from the Japan Collaborative Cohort (JACC) Study.
OBJECTIVE
The association between a lower incidence of breast cancer within the Asian population and the consumption of a diet high in soy has recently been the subject of much attention. To examine whether soy foods really have protective effects against breast cancer and how their influence on breast cancer is modified according to menopausal status, we conducted a population-based, prospective cohort study in Japan.


METHODS
We analyzed the data from the Japan Collaborative Cohort (JACC) Study. From 1988 to 1990, 30,454 women aged 40-79 years, completed a questionnaire on diet and other lifestyle features. Hazard ratios (HRs) were computed to examine the association between soy intake and the risk of breast cancer.


RESULTS
During the mean follow-up of 7.6 years, 145 cases of breast cancer were documented. We found no significant association between the risk of breast cancer and consumption of tofu, boiled beans, and miso soup; the multivariate HRs (95% CI) in the highest category of consumption were 1.14 (0.74-1.77), 0.77 (0.47-1.27) and 1.01 (0.65-1.56), respectively. Only among postmenopausal women, we found no significant associations between soy foods and the risk of breast cancer.


CONCLUSIONS
This prospective study suggests that consumption of soy food has no protective effects against breast cancer. Further large-scale investigations eliciting genetic factors may clarify different roles of various soybean-ingredient foods on the risk of breast cancer.
Nishio
Kazuko
K
Department of Preventive Medicine/Biostatistics and Medical Decision Making, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya 466-8550, Japan. kaz-n@med.nagoya-u.ac.jp
Niwa
Yoshimitsu
Y
Toyoshima
Hideaki
H
Tamakoshi
Koji
K
Kondo
Takaaki
T
Yatsuya
Hiroshi
H
Yamamoto
Akio
A
Suzuki
Sadao
S
Tokudome
Shinkan
S
Lin
Yingsong
Y
Wakai
Kenji
K
Hamajima
Nobuyuki
N
Tamakoshi
Akiko
A
D000328:Adult; D001943:Breast Neoplasms / Q000453:epidemiology* / Q000517:prevention & control; D015331:Cohort Studies; D005247:Feeding Behavior; D005260:Female; D006801:Humans; D007564:Japan / Q000453:epidemiology; D008593:Menopause; D008875:Middle Aged; D011446:Prospective Studies; D018570:Risk Assessment; D045730:Soy Foods; D011795:Surveys and Questionnaires