Environment and Breast Cancer: Science Review

Evidence From Humans
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Intake of vitamins A, C, and E and postmenopausal breast cancer. The Iowa Women's Health Study
Kushi, L. H., Fee, R. M., Sellers, T. A., Zheng, W., Folsom, A. R. Am J Epidemiol. 1996. 144:2, 165-74.
Study design
Prospective cohort
Study Participants
Menopausal Status
The menopausal status of women included in this study is listed here.
Post menopausal
Number in Cohort
cohort: 34,387
Participant selection: Inclusion and exclusion criteria
Criteria used to select participants in the study.
In: Valid Iowa driver's license and between the ages of 55 and 69 years, participating in the Iowa women's health study Ex: Not postmenopausal, had a mastectomy or partial breast removal, had any cancer other than skin cancer at baseline, 30 or more items on the food questionnaire left blank, extreme energy intake (<600 kcal/day or >5,000 kcal/day)
Comment about participation selection
Good follow-up with biennial questionnaire and linkage with National Death Index Response rate for the first questionnaire was only 42%
Exposure Investigated
Exposures investigated
Vitamins A, C, and E
How exposure was measured
Questionnaire, self-administered, FFQ
Exposure assessment comment
Questionnaire correlation with 24-hour dietary recalls was only 0.14 for Vitamin A
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: race
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
RR with CI, highest versus lowest quintile of intake, stratified by supplemental intake of vitamins, latency of 2 years, follow-up 7 years
Strength of associations reported
Vitamin A:1.15 (0.85-1.56), carotenoid: 1.17 (0.87-1.56), vitamin C: 1.06 (0.77-1.47), vitamin E: 1.08 (0.74-1.58)
Results Comments
There was no suggestion of an appreciable association of any of the vitamins with breast cancer risk. Women who consumed doses of vitamin A greater than 10,000 IU/day had a modestly decreased age-adjusted risk of breast cancer compared with those who did not take vitamin A supplement.
Author address
Division of Epidemiology, University of Minnesota School of Public Health, Minneapolis 55454-1015, USA.