Breastfeeding is known for its protective effect against breast cancer. The exact reasons are not fully understood even though there are some excellent studies on pub med that show a strong correlation between prolonged breastfeeding and the incidence of breast cancer in women.
Studies have shown that women who breastfeed are statistically less likely to develop breast cancer than those who do not. The longer you breastfeed the less likely you are to develop breast cancer in your lifetime.
One of the studies can be accessed by clicking on this link; http://www.ncbi.nlm.nih.gov/pubmed/12133652
More than 100,000 women were part of this study which used data from 47 epidemiological studies in 30 different countries. The study concluded that breastfeeding could account for almost two-thirds of this estimated reduction in breast cancer incidence.
The lack of or short lifetime duration of breastfeeding makes a major contribution to the high incidence of breast cancer!
It is therefore vital for women to consider breastfeeding as the best way to protect themselves from breast cancer.