Below is a selection of studies exploring the impact of breastfeeding on breast cancer risk. For more details on this, see our maternal health meta-analyses research section.
The fraction of cancer attributable to modifiable risk factors in England, Wales, Scotland, Northern Ireland, and the United Kingdom in 2015
This study explored the fraction of cancer cases attributable to modifiable risk factors in the UK, finding that nearly four in ten (37.7%) cancer cases in 2015 in the UK were attributable to known risk factors. Researchers identified not breastfeeding as one such risk factor; amongst women, not breastfeeding was attributed to 2,582 cancer cases in 2015.
Brown, K, et al, (2018). The fraction of cancer attributable to modifiable risk factors in England, Wales, Scotland, Northern Ireland, and the United Kingdom in 2015, British Journal of Cancer, doi:10.1038/s41416-018-0029-6.
World Cancer Research Fund (WCRF) International’s Continuous Update Project
WCRF International’s Continuous Update Project is an ongoing programme to analyse global research on how diet, nutrition, physical activity and weight affect cancer risk and survival. Its review of studies from around the world has found strong evidence that breastfeeding decreases breast cancer risk (type unspecified) in the mother.
Reproductive behaviors and risk of developing breast cancer according to tumor subtype: A systematic review and meta-analysis of epidemiological studies
This review of studies found that ever breastfeeding was associated with a reduced risk of developing both luminal and triple-negative subtypes of breast cancer.
Lambertini, M, et al (2016). Reproductive behaviors and risk of developing breast cancer according to tumor subtype: A systematic review and meta-analysis of epidemiological studies, Cancer Treatment Reviews, doi: 10.1016/j.ctrv.2016.07.006
Breastfeeding associated with reduced mortality in women with breast cancer
This study of 629 women with primary breast cancer found that pregnancy and a total breastfeeding history of more than 6 months were associated with both greater overall and breast cancer–specific survival for women diagnosed with breast cancer, having lived long enough for other causes of death to contribute substantially to mortality.
Cancers attributable to reproductive factors in the UK in 2010
This review of studies exploring the impact of reproductive factors (age at menarche, age at first birth, parity, age at menopause and duration of breastfeeding) found that breastfeeding reduces the risk of breast cancer, with the risk reducing by 4.3% for every 12 months of breastfeeding.