Dietary iron and heme iron intake and risk of breast cancer: a prospective cohort study.

Recent studies suggest that elevated body iron levels may contribute to breast carcinogenesis; however, epidemiologic evidence is lacking. We used data from a large cohort study of Canadian women to assess breast cancer in association with total iron and heme iron intake. Among 49,654 women ages 40 to 59 followed for an average of 16.4 years, we identified 2,545 incident breast cancer cases. Data from a food frequency questionnaire administered at baseline were used to calculate total dietary iron and heme iron intake. Using Cox proportional hazards models, we found no association of iron or heme iron intake with risk of breast cancer overall, in women consuming 30+ g of alcohol per day, or in women who had ever used hormone replacement therapy. The present study offers no support for an association of iron or heme iron intake with breast cancer risk or for a modification by iron of the effect of alcohol or estrogen. However, further cohort studies with repeated measurement of iron intake are warranted.