New research shows that breastfeeding is not only beneficial for babies, but also for mothers who are diagnosed with breast cancer later in life.
Women who had previously breastfed had a 30 percent overall decrease in the risk of recurring breast cancer, and they had a 28 percent decrease in the risk of dying from cancer, according to a new Kaiser Permanente study published in the Journal of the National Cancer Institute. 
The study focused on the medical histories of 1,636 women with breast cancer. Researchers found that women who had breastfed had 30 percent less of a chance of the cancer recurring with effective treatment. They also were less likely to develop aggressive types of tumors than those who did had not breastfed, as reported by SF Gate.
Lead author of the study and research scientist with Kaiser Permanente Division of Research Marilyn L. Kwan said that this study is the first “we’re aware of” that focuses on the “role of breastfeeding history in cancer recurrence, and by tumor subtype.”
Researchers discovered that women diagnosed with the breast cancer subtype luminal A received benefits of breastfeeding, while there were no significant associations with other subtypes. Kwan said that women who breastfeed are more likely to get the less-aggressive luminal A subtype of breast cancer.
The answer as to why women who breastfeed get less aggressive tumors is unclear. Senior research scientist with Kaiser Permanente Division of Research Bette J. Caan explained that breastfeeding could make ductal cells in the breast “less susceptible to carcinogens by increasing their maturation or it could “facilitate the excretion” of them. Caan said that leads to slower growing tumors, according to Science Daily.
Kwan added that a woman reduces her risk of developing breast cancer 5 to 10 percent by breastfeeding, although other factors–like how many children a woman has–“come into play,” as reported by Web MD. She said that overall, their study ensures that breastfeeding is not only good for the baby, but it “has potential health benefits for the mom.”
