Most women know breast-feeding is good for their babies’ health. But doctors and midwives rarely tell moms-to-be that it’s also good for nursing mothers.
Nursing mothers reduce their relative risk of breast cancer by 4.3 percent for every 12 months they breast-feed, in addition to a relative decrease of 7 percent for each birth. Breast-feeding is particularly protective against some of the most aggressive tumors, called hormone receptor-negative or triple-negative tumors, which are more common among African-American women, studies show. It also lowers the risk by one-third for women who are prone to cancer because of an inherited BRCA1 mutation.
Women who breast-feed are also less likely to develop ovarian cancer, Type 2 diabetes and rheumatoid arthritis and may have improved cardiovascular health.
Yet only 16 percent — or fewer than one in five women surveyed — said their doctors had told them that breast-feeding is good for mother as well as baby, according to a new study published in Breastfeeding Medicine.
“We have an ounce of prevention that could save lives,” said Dr. Bhuvaneswari Ramaswamy, the paper’s senior author and an associate professor of medical oncology at Ohio State University in Columbus. “But are we fully educating the mothers when they make this difficult choice? Because it is not an easy choice.”
While companies market infant formula by claiming their products are effective substitutes for breast milk, Dr. Ramaswamy said, “formula is not going to help women live longer and be there for their families.”
The new study surveyed 724 women aged 18 to 50 who had given birth to at least one child. The vast majority of them had breast-fed.
Just over half knew before they gave birth that breast-feeding reduced the risk of breast cancer, and over a third of those said the information influenced their decision to breast-feed.
But only 120 of the women said that their health care providers had informed them about the implications for their own long-term health. Most of those who knew about the health advantages to nursing moms had gleaned the information from popular media or the internet. And these women tended to breast-feed for much longer — 13 months on average — than women who did not know about the health implications, who breast-fed for only nine months on average.
While 60 percent of white women surveyed knew breast-feeding could cut their breast cancer risk, only 47 percent of the African-American women knew, and 54 percent of women of other or unknown race knew.
Nationwide, among racial groups, African-American mothers have the lowest rates of breast-feeding and are least likely to nurse for at least six months, according to government health statistics. Sixty percent have “ever” breast-fed, and only 28 percent are still breast-feeding at six months.
In comparison, 77 percent of white mothers, 80 percent of Hispanic mothers and 86 percent of Asian mothers have “ever” breast-fed, with rates of breast-feeding at six months at 45 percent, 46 percent and 58 percent, respectively.
Scientists do not entirely understand why lactation helps prevent breast cancer, but say the breasts undergo changes during pregnancy as they develop more milk ducts in preparation for breast-feeding.
The breasts eventually go through a process called involution that returns them to their pre-pregnancy state and involves massive cell death and tissue remodeling. That transition can occur slowly through gradual weaning, or abruptly if there is no breast-feeding or only brief breast-feeding. When it happens abruptly, it creates an inflammatory condition that is conducive to cancer, Dr. Ramaswamy said.
Dr. Marisa Weiss, the founder of the website BreastCancer.org, who has done research in this area, often describes pregnancy and lactation as a “bat mitzvah” for the breasts, saying that breast-feeding “forces the breasts to finally grow up and get a job, and make milk, and show up for work every day, and stop fooling around.” That maturation process triggers changes in the milk ducts that make the breast more resistant to cancer.
Breast-feeding also appears to reset the body’s metabolism after pregnancy, improving glucose metabolism and insulin sensitivity, burning calories and mobilizing stores of fat that have accumulated during pregnancy, which may explain why women who breast-fed have lower rates of diabetes and other problems.