Protective immune cells in breastfeeding women identified as guard against breast cancer, new research finds

An illustration of a T-cells attack dividing breast cancer cell. Modern data has confirmed a centuries-old observation that child-bearing and breastfeeding could protect against breast cancer but until now the biological reasons have remained unclear. Photograph: Nemes Laszlo/Alamy

In the 18th century, physicians noticed nuns had some of the highest rates of breast cancer. It was one of the earliest clues that led scientists to suspect that child-bearing and breastfeeding could protect against the disease.

Modern data has confirmed the centuries-old observation but the biological reasons behind it have remained unclear. Explanations have often focused on pregnancy-related hormonal changes, but research published Tuesday in Nature has found breastfeeding provides long-lasting immune protection.