How does breastfeeding influence breast cancer risk?

Mothers who breastfeed have a lower risk of developing breast cancer. That is one of the findings of a report of the American Institute of Cancer Research (AICR), which was released to mark World Breastfeeding Week in early August.

The 2017 report, Diet, Nutrition, Physical Activity and Breast Cancer, is a joint effort of AICR and the World Cancer Research Fund (WCRF), and is the result of systematic literature review on breast cancer. An independent panel of world-renowned experts evaluates and interprets the evidence and makes conclusions about what increases and decreases cancer risk.

One area of study in the report is lactation. It identified and reviewed 18 studies on lactation, 13 of which focused on duration, showing a 2% decreased risk of breast cancer per five-month increase in breastfeeding. While the lower risk is modest, it is one additional reason to breastfeed for moms who are able, researchers say.

Bender"It isn’t always possible for moms to breastfeed but for those who can, know that breastfeeding can offer cancer protection for both the mother and the child,” says AICR’s Director of Nutrition Programs Alice Bender, MS, RDN.

AICR recommends that new mothers breastfeed exclusively for up to six months and then add other liquids and foods. This advice is in line with recommendations of other health organizations, including the World Health Organization. Breastfeeding provides the nutrients babies need, helps protect them from infections and asthma, and boosts their immune system.

There are several possible reasons that breastfeeding may influence breast cancer risk, according to the report. Lactation may delay a new mother’s menstrual periods, reducing lifetime exposure to hormones such as estrogen, which is linked to breast cancer risk. Also, the shedding of breast tissue after lactation may help rid cells with potential DNA damage.

“With the many benefits of breastfeeding, it’s important that new moms get support to successfully breastfeed for longer than a few days or weeks,” Bender says. “I am a strong proponent that lactation, education and support should really be a normal part of pre- and postnatal care.”

Next: Known benefits

Breastfeeding provides health benefits now for the baby and later in life for both mom and baby, she adds.

“It’s also critical to know there are steps all women can take to lower the risk of this cancer,” Bender says. “For women who don’t have children, have not breastfed or are choosing not to breastfeed, I think it’s important to emphasize that there are other lifestyle factors that can reduce breast cancer risk, and they include avoiding alcohol, being a healthy weight and physical activity.”

The report finds that being overweight or obese in adulthood before menopause decreases the risk of premenopausal cancer. However, it increases the risk of postmenopausal breast cancer.

Achieving and staying at a healthy weight can be difficult, and getting help to do it is even more challenging as nutrition counseling is sporadically covered by health insurance plans.

“(Nutrition counseling) is often more therapeutic than for working with health behavior change,” Bender says. “So sometimes it’s covered in hospitals but not on an outpatient basis. We have 100,000 registered dieticians in this country all ready to help people make healthier diet changes,” she adds. “But oftentimes people do not have access to them because they don’t have insurance coverage for that kind of counseling and treatment.

“I think with any kind of preventive care, especially lifestyle, the benefits come later in life. That is especially true with many types of adult-onset cancers like postmenopausal cancer,” Bender says. “For the healthcare insurance industry, the payoff in investment may not be seen until years later.”