Why breastfeeding reduces risk of breast cancer is unknown. The authors suspect that when women do not breastfeed, inflammation and engorgement shortly after birth causes changes in breast tissue that may increase risk for breast cancer. Breastfeeding followed by weaning may prevent this inflammation.
When the researchers compared data about women who breastfed and those who did not, there was a 25 percent total reduction in incidence of premenopausal breast cancer. But, Alison Stuebe, assistant professor of obstetrics and gynecology at the University of North Carolina at Chapel Hill School of Medicine and lead author of the study, says, that statistic was accounted for by women without a family history of the disease.
“We did not find an association between breastfeeding and premenopausal breast cancer among women without a family history of breast cancer,” Stuebe says. “This could be because there’s something about genetically caused breast cancer that’s affected by breastfeeding, or it could be because rates of breast cancer were so low in women without a family history that we couldn’t see an association in this data set.”
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