Results from observational studies looking at the relationship between breastfeeding and the development of premenopausal breast cancer have been inconsistent, so the results from a large prospective cohort study published recently in the Archives of Internal Medicine are welcome news.
The study looked at information from over 60,000 premenopausal women who had given birth and who had filled out detailed questionnaires over a period of time as a part of the Nurses’ Health Studies. Researchers concluded that women with a first-degree family history of breast cancer had a 59% reduction in risk for developing pre-menopausal breast cancer if they had ever breastfed. (A first-degree family member is a parent, sibling, or a child.) Information about breastfeeding history was collected before the diagnosis of breast cancer thus minimizing recall errors. Researchers did not find any relationship between the duration or intensity of breastfeeding and the risk of developing pre-menopausal breast cancer, or a reduction in risk for those women without a first-degree family member with breast cancer.
Researchers also found that mothers who never breastfed and who used medication to suppress lactation had a decreased risk for developing pre-menopausal breast cancer. Researchers theorize that the engorgement and inflammation that occur in new mothers who do not breastfeed and who do not take medication to suppress lactation may increase the risk for breast cancer.
Some young women who have lost close family members to breast cancer are choosing prophylactic mastectomies to reduce their own risk of developing breast cancer. Perhaps the results of this study and future studies will encourage them to keep their breasts and to breastfeed in order to reduce their risk.