Objective: The influence of the vitamins A, C, and E on breast cancer development has not been clarified. An effect of a vitamin per se implicates similar patterns for the effects of the vitamin from dietary and supplemental sources. We examined how the breast cancer incidence rate among postmenopausal women was related to intake of vitamins A, C, and E from diet and supplements.
Methods: Data was sampled as case-control nested within the Danish 'Diet, Cancer and Health' cohort. Data on vitamin intakes were collected at entry into the cohort by means of self-administered questionnaires. Women eligible for the nested case-control study were postmenopausal at entry into the cohort. The analyses were based on 418 cases of incident breast cancer and 394 controls (including two cases).
Results: Breast cancer was not significantly related to the intakes of vitamin A or E, whereas a monotonic dose-response relation was seen for the intake of vitamin C. The estimated rate ratio per 100 mg vitamin C was: 2.06 (95% CI: 1.45-2.91) for dietary intake and 1.06 (95% CI: 1.01-1.13) for supplemental intake.
Conclusions: We found no evidence of an association between breast cancer and intake of vitamin A or E for postmenopausal women. For vitamin C we found an increase in breast cancer rate with increasing intake.