Abstract

Few studies on micronutrients and postmenopausal breast cancer have examined the association with breast cancer characteristics. The aim of this study was to investigate the associations between vitamin C, vitamin E, folate and beta-carotene from diet and supplements and risk of postmenopausal breast cancer subtypes defined by histology (ductal/lobular), estrogen receptor (ER) and progesterone receptor (PGR) status. In a prospective cohort study of 26,224 postmenopausal women information on diet, supplements and lifestyle was collected through questionnaires. One thousand seventy-two cases were identified during follow-up. Incidence rate ratios of total breast cancers and breast cancer subtypes related to micronutrient intake were calculated using Cox proportional hazard analyses. This study found no association between overall breast cancer and any micronutrients, while some effects were shown when stratifying by breast cancer subtypes: dietary but not supplemental beta-carotene showed a protective effect against lobular breast cancer [incidence rate ratio (IRR): 0.72; 95% confidence interval (CI): 0.57-0.91]. Dietary vitamin E was associated with decreased risk of ER and PGR positive breast cancer (IRR: 0.50; 95% CI: 0.25-0.98) and dietary folate was associated with increased risk of ER and PGR positive breast cancer (IRR: 1.27; 95% CI: 1.03-1.95). This study found no effect of micronutrients on overall risk of postmenopausal breast cancer, but indicated possible effects of micronutrients in subgroups of breast cancer, with a potential beneficial effect of dietary beta-carotene in lobular breast cancer and dietary vitamin E in ER + PGR+ breast cancer and a potential harmful effect of dietary folate in ER+ PGR+ breast cancer.