According to the American Institute for Cancer Research, new cases of breast cancer affect more than 1.2 women worldwide, annually. Over 220,000 women in the United States develop cancer of the breast and more than 40,000 die each year. Drugs, like tamoxifen, reduce the incidence of breast cancer in women prone to certain types of breast cancer. This does not eliminate all risk, and anti-estrogen therapies, like tamoxifen, do not impact the risk of developing estrogen receptor negative cancers. Alternatives to drug preventative therapies include changes in diet, physical activity, or lifestyle, including lactating. Consult a doctor before making any dietary or lifestyle changes.
Expert Report
The American Institute for Cancer Research conducted a systematic literature review on the effects of nutrition, food, and physical activity on cancer risk. Substantial evidence suggests that lactation reduces the risk of developing breast cancer at all ages. The report hypothesizes that lactation is beneficial for many reasons. First, lower hormones following breastfeeding reduce breast cancer risk. Secondly, exfoliation of breast tissue during breastfeeding may have a beneficial effect -- although research is inconclusive on this topic. Lastly, because the breasts reduce in size after termination of lactation, the breast tissue goes through a healthy controlled cell death. This provides an opportunity to eliminate any cells that developed errors during division, which may have potentially led to breast cancer.
Carolina Breast Cancer Study
More than 1,400 African-American and Caucasian mothers living in North Carolina provided information about their families, reproductive and lactation history, and lifestyle characteristics. H. Furberg and colleagues from the University of North Carolina, Chapel Hill, found that women of all ages had a 20 to 30 percent reduced risk of developing breast cancer if they breastfed. Additionally, those women who breastfed longer had the least chance of developing cancer of the breast.
Duration of Breastfeeding
As reported by the American Cancer Society, the protection from breast cancer that breastfeeding may provide arises only after 1.5 to two years of breastfeeding. The American Cancer Society believes that reduction in the number of menstrual cycles and the blood hormone, prolactin, are the reasons why lactation reduces the risk of breast cancer. The Carolina Breast Cancer Study also found that the length of breastfeeding reduced the women's risk of developing breast cancer. Women who breastfed for four to 12 months had a reduced risk compared to women who breastfed for one to three months. Breastfeeding for more than 12 months even further reduced the risk of developing breast cancer.
Conclusion
More evidence than not suggests lactation reduces the risk of developing breast cancer. Keep in mind, because not all research supports a role of lactation in reducing breast cancer risk, evidence is inconclusive.The total number of pregnancies, age at first pregnancy, and susceptibility to genetically based cancers are also factors to be considered regarding the issue of developing breast cancer.
References
- American Cancer Society: Learn About Cancer: Pregnancy and Breast
- National Cancer Institute: Summary Report: Early Reproductive Events and Breast Cancer Workshop
- "Cancer"; Higher Parity and Shorter Breastfeeding Duration: Association with Triple-Negative Phenotype of Breast Cancer; SS Shinde, MR Forman, HM Kuerer, et al.; Nov. 2010
- "International Journal of Epidemiology"; Lactation and Breast Cancer Risk; H. Furberg, et al.; Jun. 1999
