Environment and Breast Cancer: Science Review

Evidence From Humans
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Dietary antioxidant vitamins, retinol, and breast cancer incidence in a cohort of Swedish women
Michels, K. B., Holmberg, L., Bergkvist, L., Ljung, H., Bruce, A., Wolk, A. Int J Cancer. 2001. 91:4, 563-7.
Topic area
Diet - Body size
Study design
Prospective cohort
Funding agency
Not reported
Study Participants
Number of Cases
1271 (invasive only)
Menopausal Status
The menopausal status of women included in this study is listed here.
Pre menopausal
Post menopausal
Number in Cohort
Cohort: 59,036
Cohort participation rate
> 70% (76% and 72% by county)
Participant selection: Inclusion and exclusion criteria
Criteria used to select participants in the study.
In: Swedish Mammography Screening Cohort; attended a population based mammography screening program in Vastmanland or Uppsala counties from 1987-1990; from the counties of Vastmanland born between 1917 and 1948 and Upssala born between 1914 and 1948. Ex: Women who did not fall within the age range of 40-76 years at mammography, women with missing or incorrect ID numbers, women with missing return date of the questionnaire, those who moved out of the study area at an unknown date and those who died during follow-up but for whom date of death was missing. Also excluded were women with self-reported energy intake estimates below or above 3 standard deviations of the mean Log e-transformed calories, women with a previous cancer diagnosis other than non-melanoma skin cancer at baseline, women with missing or unreasonable self-reported value for height, weight, BMI and age at first birth.
Comment about participation selection
Strengths: High participation rate, large cohort with over half a million person-years of follow-up, very specific exclusion criteria to define final participants, population based study.
Exposure Investigated
Exposures investigated
Beta-carotene, vitamin C and E, BMI
How exposure was measured
Questionnaire, self-administered, FFQ
Exposure assessment comment
Questionnaire included a FFQ that included 67 foods commonly consumed in Sweden. Limitations: anthropometric data self-reported; does not account for vitamin intake from supplements; inherent measurement error with questionnaire-based dietary assessment;
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.
Adequately controlled, Confounders: age, family history of breast cancer, height, BMI, education, parity, age at first birth, total caloric intake, alcohol intake, fiber intake, mono and poly-unsaturated fatty acid intake
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
Hazard Ratio and 95% CI, highest versus lowest quintile of intake, stratified by BMI, intake of linoleic acid, and BMI >25 with Linoleic acid>6g, follow-up 7-10 years. Body size analysis considered ascorbic acid intake as an effect modifier. Follow up: 19
Strength of associations reported
β carotene: 1.01 (0.84-1.22); vitamin C: 0.94 (0.78-1.14); vitamin E: 0.83 (0.6-1.14)
Association between breast cancer risk and ascorbic acid intake, 109.7 mg/day vs. 30.7 mg/day (median), in women with a BMI >25, HR=0.61 (0.45-0.82) trend p=0.004
Association between breast cancer risk and ascorbic acid intake, 109.7 mg/day vs. 30.7 mg/day (median), in women with a BMI <25, HR=1.27 (0.99-1.63) trend p=0.02
Results Comments
Overall intake of ascorbic acid, beta-carotene, vitamin E was not associated with incidence of invasive breast cancer. Inverse association between self-reported ascorbic acid intake and breast cancer incidence among women with high BMI and/or high intake of linoleic acid. A similar pattern was also present for vitamin E however not statistically significant. Analyzed breast cancer risk by ascorbic acid intake and BMI. Results are not stratified by menopausal status
Author address
Obstetrics and Gynecology Epidemiology Center, Brigham and Women's Hospital, Harvard Medical School, 221 Longwood Avenue, Boston, MA 02115, USA.