Women with a history of breast cancer in the family should breastfeed.
A woman with a mother or sister with breast cancer should "strongly" consider breastfeeding her baby, doctors advise in a report released today.
In a long-term study of more than 60,000 women, researchers found that women with a close family history of breast cancer had significantly lower risk of developing breast cancer before menopause themselves if they breastfed their babies, compared to women who did not breastfeed.
"Breastfeeding is good for mothers and for babies," study chief Dr. Alison M. Stuebe, of University of North Carolina at Chapel Hill, told Reuters Health by email.
The findings stem from data on 60,075 nurses who had given birth and who participated in the long-running Nurses' Health Study between 1997 and 2005.
By the end of June 2005, 608 women - about 1% - had developed breast cancer when they were an average of 46 years old, Stuebe and her associates from Brigham and Women's Hospital and Harvard Medical School, Boston, report in the latest issue of Archives of Internal Medicine.
They also report that women who had a mother, sister or other close relative with breast cancer had a 59% lower risk of developing the disease if they had ever breastfed than if they had never breastfed.
That amount of risk reduction "compared favorably" to that seen by women at very high risk for breast cancer who take the hormone therapy tamoxifen to prevent breast cancer, the investigators note.
There was no association between breastfeeding and breast cancer among women without a family history of the disease.
However, Stuebe's team also found that women who did not breastfeed but used medication to suppress production of breast milk had a 42% lower risk of developing breast cancer than women who neither breastfed nor used medication to suppress breast milk production.
This association could be related to a problem with the process by which breast tissue returns to its pre-pregnant state. If a woman does not breastfeed, she experiences abrupt engorgement, and breast tissue may become progressively inflamed, they explain in their report. That inflammation may be linked to breast cancer.
"We hypothesize that both breastfeeding and use of suppressive medications prevent this inflammation," the authors write.
In the current study, about 70% of women who chose not to breastfeed their babies said they took medication to suppress breast milk production.
Clearly, the researchers conclude, breastfeeding is associated with "multiple health benefits" for both mother and child.
"That's why we need supportive hospital policies, paid maternity leave, and workplace accommodations so that women can meet their breastfeeding goals," Stuebe said.