A study of 504 breast cancer patients indicates breastfeeding for six months or longer can delay the onset or reduce the risk of early breast cancer even when early breast cancer runs in the family. The benefit of breastfeeding for 6+ months had no effect, however, in female smokers.

Estimates cited in the study indicate as many as 720,000 women around the world will be diagnosed with breast cancer in any given year. That number represents approximately 20% of all cancers diagnosed each year. Of the women who will be diagnosed with breast cancer, 17% to 36% of them will be younger than 40.
Dr. Emilio González-Jiménez and his team of researchers at the University of Granada, Spain, analyzed the medical records of 504 female breast cancer patients whose ages ranged from 19 to 91. All the women had been treated for cancer at one of the hospitals in the city.

In addition to a woman's breast cancer diagnosis, the researchers also evaluated a woman's:


  • Age at cancer diagnosis
  • Alcohol consumption
  • Duration of breastfeeding
  • The family history of cancer
  • Smoking habits
  • Weight, particularly obesity

In spite of the significant impact a family history of cancer plays on the development of cancer in an individual, family history proved to be of no relevance when an individual breastfed a child for a minimum of six months at some point during her life.

Cancer patients who breastfed did not get breast cancer, on average, until 10 years later than those who did not breastfeed. The nursing mothers enjoyed 10 cancer-free years in spite of all other factors except smoking. Smoking seemed to cancel out all breast cancer-related benefits of breastfeeding.

González-Jiménez explains that his study did not attempt to establish a cause-and-effect relationship between breastfeeding and breast cancer but he suggests hormonal changes during pregnancy and lactation may play a preventive role. He writes that prolonged breastfeeding "not only provides children with numerous health benefits but also protects the mother from serious diseases such as breast cancer. Breastfeeding is a potential ally in the fight against breast tumors."

The Spanish research team recognizes the "crucial role" of nurses in encouraging women to nurse their babies. Nurses who explain how breastfeeding affects breast cancer risks may provide additional incentive to new mothers to do so.

In the United States, breastfeeding has become more popular in recent years, according to the Centers for Disease Control and Prevention. The centers' data indicates 71% of mothers chose to breastfeed in 2000 but 77% did so in 2010.

Source: González-Jiménez, Emilio. "Breastfeeding and the prevention of breast cancer: a retrospective review of clinical histories." PubMed.gov. National Center for Biotechnology Information / US National Library of Medicine. Aug 13, 2014. Web. Apr 23, 2014.