Breastfeeding Found to Lower Long-Term Breast Cancer Risk
23 Oct 2025
New Australian research provides fresh insight into why breastfeeding can reduce a woman’s risk of developing breast cancer. The study, published in Nature, shows that breastfeeding helps develop specialised immune cells in the breast that provide lasting protection against the disease.
Led by Professor Sherene Loi from the Peter MacCallum Cancer Centre, the research found that women who breastfeed have more CD8⁺ T cells — immune cells that remain in breast tissue for decades after childbirth. These cells act as “local guards,” ready to attack abnormal cells that could develop into cancer.
“Women who have breastfed have these specialised cells that can help lower the risk of breast cancer, particularly aggressive forms such as triple-negative breast cancer,” Professor Loi said.
The study showed that a full cycle of pregnancy, breastfeeding, and breast recovery encourages these T cells to accumulate in the breast. Experiments in models demonstrated that the presence of these cells slowed or stopped tumour growth. Analysis of data from over 1,000 breast cancer patients also found that women who had breastfed had higher numbers of protective T cells in their tumours and, in some cases, lived longer after diagnosis.
Further comparisons of breast tissue from 260 healthy women who had undergone preventive mastectomies or breast reductions showed that women who had children had more long-lived T cells, which could persist for up to 50 years after pregnancy.
While it has long been known that breastfeeding reduces breast cancer risk, this research provides a clear biological explanation for the protective effect and may help guide future prevention and treatment strategies.
Source: Peter MacCallum Cancer Centre / Nature – nature.com
