Olifin, the breastcancer.org site might be more relevant on this, I posted this link earlier, check it out
www.breastcancer.org/risk/new_research/20090810.jsp
I'm reluctant to cut and paste particular sections of the article, at the risk of being accused of being somewhat selective, however,
"Breastfeeding May Cut Hereditary Breast Cancer Risk
This large study found that breastfeeding one baby even for as little as 3 months reduced the risk of breast cancer before menopause by 59% in women with higher-than-average risk compared to high-risk women who never breastfed.
Women in the study were considered high-risk if they had at least one first-degree relative (a mother or a sister) diagnosed with breast cancer.
Other research has shown clearly that women who have given birth to one or more babies have a lower risk of breast cancer than women who have never been pregnant. Other studies also have shown that breast cancer risk is lower among women who have breastfed one or more babies, but this link between breastfeeding and lower risk hasn't been found consistently in all studies.
In this study, the link between breastfeeding and lower pre-menopausal breast cancer risk was found only in women who were considered to have a higher-than-average risk. Breastfeeding didn't seem to lower pre-menopausal breast cancer risk in women who didn't have a first-degree relative diagnosed with breast cancer. The researchers aren't sure why this is."
I don't think anyone is actually disputing that medical research has shown that bf might/may/can reduce the risk of breast cancer.
FWIW my own issue with this thread and some of the posts is the assertion that only thick, uneducated, selfish or lazy mothers don't bf their children for 2 years, or that they simply didn't try hard enough. I'm assuming you've seen the posts I'm talking about?