Environment and Breast Cancer: Science Review

Evidence From Humans
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Soya foods and breast cancer risk: a prospective study in Hiroshima and Nagasaki, Japan
Key, T. J., Sharp, G. B., Appleby, P. N., Beral, V., Goodman, M. T., Soda, M., Mabuchi, K. Br J Cancer. 1999. 81:7, 1248-56.
Topic area
Diet - Ionizing radiation
Study design
Prospective cohort
Funding agency
Other: Japanese Ministry of Health and Wellfare an
Study Participants
Menopausal Status
The menopausal status of women included in this study is listed here.
Postmenopausal and premenopausal combined
Number in Cohort
Cohort: 34,759
Cohort participation rate
Survey 1 <70%; survey 2 >70%
Participant selection: Inclusion and exclusion criteria
Criteria used to select participants in the study.
In: Participants of the Radiation Effects Research Foundation's Life Span Study; women living in Hiroshima and Nagasaki present during the bombing and resident during the census in 1950. Women who were residents but not present in either city at the time of the bombing were identified through a special census between 1950 and 1953 and were included in survey 1, but not in survey 2. Ex: Women who were registered with cancer before the start of follow-up were excluded.
Comment about participation selection
Large cohort, long follow-up; 2 surveys
Exposure Investigated
Exposures investigated
Soy food, miso soup, milk, fruits, green tea
How exposure was measured
Questionnaire, self-administered
Exposure assessment comment
19 food items, questionnaire was not validated
Early life exposures considered
One third of the women were less than 15 at the time of bombing
Statistical Analysis
Ethnic groups with separate analysis
If this study provided a separate analysis by ethnic or racial group, the groups are listed here.
Confounders considered
Other breast cancer risk factors, such as family history, age at first birth, and hormone replacement therapy use, that were taken into account in the study.
Not considered: BMI, race, parity, menopausal status, alcohol consumption, family history of breast cancer
Genetic characterization included
If the study analyzed relationships between environmental factors and inherited genetic variations, this field will be marked “Yes.” “No”, if not.
Description of major analysis
Adjusted RR with 95% CI; higher versus lower tertile of intake, stratified by age < 50y or ³50y, and by dose of radiation; follow up 24 years for first survey, 14 years for second survey
Strength of associations reported
Tofu: 1.19 (0.62-2.29); miso soup 0.74 (0.43-1.28); milk 0.87 (0.66 - 1.16); fruits 0.95 (0.71 - 1.27); green tea 0.86 (0.62 - 1.21)
Results Comments
No significant associations between reported consumption of tofu and breast cancer risk; relatively high consumption of tofu was associated with a small increase in risk whereas relatively high consumption of miso soup was associated with a small decrease risk. Adjusting for risk factors for breast cancer did not materially alter the results.
Author address
Imperial Cancer Research Fund Cancer Epidemiology Unit, Radcliffe Infirmary, Oxford, UK.