Breastfeeding is one Lowers Cancer Risk. A total of one year or more have a lower risk of breast cancer the women who breast feed for. Because breast feeding can cause changes in hormones and in breast tissue that help protect the cells from becoming cancerous. A history of breast-feeding may decrease the risk of breast cancer.
To date, virtually all epidemiologic data regarding breast-feeding and breast cancer risk are derived from case-control studies, which vary according to classification of breast-feeding history. Original data for inclusion were identified through a MEDLINE® search of the English language literature from 1966 through 1998. Overall, the evidence with respect to “ever” breast-feeding remains inconclusive, with results indicating either no association or a rather weak protective effect against breast cancer. An inverse association between increasing cumulative duration of breast-feeding and breast cancer risk among parous women has been reported in some, but not all, studies; the failure to detect an association in some Western populations may be due to the low prevalence of prolonged breast-feeding.
The biology underlying a protective effect of breast-feeding and why this should be restricted to premenopausal women remain unknown, although several mechanisms have been postulated (hormonal changes, such as reduced estrogen; removal of estrogens through breast fluid; excretion of carcinogens from breast tissue through breast-feeding; physical changes in the mammary epithelial cells, reflecting maximal differentiation; and delay of the re-establishment of ovulation). It appears that the protective effect, if any, of long-term breast-feeding is stronger among, or confined to, premenopausal women. It has been hypothesized that an apparently protective effect of breast-feeding may be due to elevated breast cancer risk among women who discontinue breast-feeding or who take medication to suppress lactation; however, the evidence is limited and should be interpreted with caution.
While breast-feeding is a potentially modifiable behavior, the practical implication of reduced breast cancer risk among premenopausal women with prolonged durations of breast-feeding may be of marginal importance, particularly in Western societies.