Breast feeding exclusively decreases overall estrogen secretion and this mechanism is one that may contribute to the lowered risk of ovarian and breast cancer. This relationship may also link to lowering the risk of endometrial cancer. To investigate this, researchers pooled data from 17 studies (3 cohort and 14 case-controlled), that totaled 8981 parous women with endometrial cancer and compared them to 17,241 controls. For women in both groups, about two thirds of them reported histories of breast feeding.
Having ever breast fed at all was associated with 11% lower risk for endometrial cancer. The lifetime cumulative breast-feeding of 3 months or less and the average breast-feeding duration per new born of 3 or less months was not associated with this lower risk for endometrial cancer. However, an average duration of breast feeding that was up to 9 months was associated with a consistently decreasing risk.
Commentary:
There is a robust list of the benefits of breast feeding including a lower risk for the child of gastroenteritis, respiratory illness, asthma, allergies, otitis media and urinary tract infections. For women, breast feeding lowers the risk of diabetes mellitus, breast and ovarian cancer. We can now add to this list, that breast feeding for greater than 3 months and at least up to 9 months, has a likely beneficial effect, although small, on lowering the risk of endometrial cancer.
Despite the increasing toxin load found in breast milk of women in the U.S., which is hugely bothersome, breast milk is still an optimal food because it contains unique oligosaccharides that promote healthy gut bacterial flora including the proliferation of Bifidobacterium infantis species, as well as the antimicrobial agents lactoferrin, secretory IgA.
Reference: Jordan S, et al. Breastfeeding and endometrial cancer risk: An analysis from the Epidemiology of Endometrial Cancer Consortium. Obstet Gynecol 2017; June; 129:1059
