A new study has reported that dietary iron is not associated with risk of postmenopausal breast cancer regardless of whether the iron is primarily from meat or from plant sources. Intake of dietary iron and, in particular, heme iron (found in red meat, poultry and fish) has been hypothesized to increase risk of breast cancer by causing oxidative damage to DNA. The study included 116,674 postmenopausal participants in the National Institutes of Health-AARP Diet and Health Study who completed a detailed food questionnaire. This data was used to assess intakes of total dietary iron, iron from meat, iron from red meat, and heme iron. A total of 3,396 cases of invasive breast cancer were diagnosed during 6.5 years of follow-up. Study limitations included incomplete information on the women's intake of iron supplements and lack of data on iron consumption earlier in life, such as when breast tissue is developing.

Breast cancer risk was comparable among women in the highest and the lowest fifth of total intakes of iron, iron from meat, iron from red meat, and heme iron. In addition, no trend was observed with increasing iron intakes or when the analysis focused on hormone receptor status of the breast cancer. The analysis was adjusted for breast cancer risk factors such as age, obesity, family history, smoking, use of hormone replacement therapy and physical activity. The authors conclude that the results do not support an association between iron or heme-iron intakes and postmenopausal breast cancer. Based on these results, iron content is not likely to account for the observed association between consumption of red meat and breast cancer.