Breastfeeding reduces breast cancer risk

By David Liu (davidl@foodconsumer.org)

A new study suggests that breastfeeding may reduce the risk for breast cancer in premenopausal women who are at high risk of the disease such as those with breast cancer in the family.

Overall, the results of the study do not show that breastfeeding was associated with a reduction in the risk for breast cancer in premenopausal women. But women whose mothers or sisters had breast cancer were at 59 percent reduced risk for premenopausal breast cancer if they chose to breastfed their children.

In other words, those at high risk for breast cancer if they breastfeed would be at the same risk for the disease as those who are not at the high risk due to their genetics.

The study led by Dr. Alison M. Stuebe, first author of the study, at the University of North Carolina, Chapel Hill and colleagues and published in The Archives of Internal Medicine examined data for 60,075 women in the second Harvard Nurses' Health Study from 1997 to 2005.

During the follow-up, 87 percent of the women had breastfed for some period. By June 2005, 608 women were diagnosed with breast cancer.

The researchers found that the women who had breast cancer in their families but opted to breastfeed developed 41 percent as many cancers as those who had an immediate family member like mother or sister with the disease but did not breastfeed.

However, the study found longer periods of breastfeeding did not render extra benefits in the reduction of the risk for breast cancer, meaning that breastfeeding for any short or long period would be beneficial.

Another study we reported in 2007 on foodconsumer.org suggests women who breastfeed their first baby can reduce their risk of breast cancer even if the first birth occurs later in life.

The study presented at the annual meeting of the American Association for Cancer Research held in Los Angeles was based on data from women aged 54 on average who participated in the Women’s Contraceptive and Reproductive Experiences (CARE) Study, which was published in 2003.  

The protective effect was found after researchers compared the history of breastfeeding and their age at first birth of 995 women with breast cancer and 1,498 women without the disease.  

Early studies showed that a first birth after 25 would increase a woman's risk of acquiring hormone-receptor positive breast cancer while having a baby earlier would decrease the risk.  

But the current study showed that breastfeeding offers a protection against breast cancer in the mothers regardless of their age or whether they are positive for hormone-receptors or not.  

It has been known for long that breastfeeding maturates the mother's breast tissue, which grows immaturely during puberty and pregnancy, increasing its resistance to carcinogenesis in breasts.  

Breast cancer is diagnosed in 190,000 American women each year and the disease skills about 50,000 a year.