Women who have a family history of breast cancer lowered their risk of developing premenopausal breast cancer by 59% if they breast fed, according to this study.
While some studies have shown that the rate of breast cancer in premenopausal women was lower in those who breast fed as compared to those who did not, other observational studies have failed to show an association.
This longitudinal study followed a large number of women prior to diagnosis to determine the relationship between breastfeeding and the development of premenopausal breast cancer.
Researchers from Brigham and Women’s Hospital and Harvard Medical School examined data from 60,075 women who had given birth at least once and participated in the Nurses Health Study II from 1997 to 2005†.
By the end of June 2005, 608 or about 1% of the participants developed premenopausal breast cancer. The average age at diagnosis was 46.
Overall, women who had breastfed for any length of time reduced their risk of developing premenopausal breast cancer by 25% compared with women who had never breastfed.
For women with a family history of breast cancer (mother, sister or other close relative), the beneficial effect was even greater. Their risk was reduced by 59% compared with women who had never breastfed.
The reduction of risk was about the same as that for women with a family history of the genetically-inherited form of the disease taking the medication tamoxifen to prevent breast cancer occurrence.
To obtain the benefit, women did not have to breastfeed exclusively; formula supplementation did not affect results. Additionally, women did not need to breastfeed for long periods of time. Alison Stuebe, M.D, lead author of the study, indicated that only about three months in total was required. This could have been three months with one child or one and a half months for two children.
Interestingly, for those women who used a medication to suppress lactation, their risk of developing breast cancer was reduced by 42% compared with women who neither breastfed nor suppressed lactation.
Researchers theorized that the lower incidence of breast cancer in women who breastfeed or use suppressive lactating medication may relate to how quickly breast tissue reverts back to its pre-pregnancy state.
In women who don’t breastfeed, the tissue abruptly engorges which often causes progressive inflammation. In women who breastfeed or use suppressive medications, this process occurs more slowly and as a result, prevents inflammation from occurring.
The Bottom Line
It is well established that breastfeeding brings numerous benefits to both baby and mother. Breastmilk is easy for babies to digest and contains antibodies that can protect infants from bacterial and viral infections.
Breastfeeding can save new mothers both time (don’t have to purchase, measure, and mix formula; no bottles to warm in the middle of the night) and money ($1,160 and $3,915 per year, depending on the brand of formula).
These latest findings provide additional motivation for women to breastfeed their young babies, even for a short time, regardless if breast cancer runs in their family or not.
†The Nurses’ Health Studies
The Nurses’ Health Studies are among the largest and longest running investigations of factors that influence women’s health.
The original Nurses’ Health Study was established in 1976. The study has followed 121,700 female registered nurses since the mid-1970s to assess risk factors for cancer and cardiovascular disease.
The Nurses’ Health Study II was established by Dr. Walter Willett and colleagues from Harvard Medical School in 1989 with funding from the National Institutes of Health. The primary motivation for developing the Nurses’ Health Study II was to study oral contraceptives, diet and lifestyle risk factors in a population younger than the original Nurses’ Health Study cohort.