Hi there, health reporter Olivia Willis here with your weekly dose of health news.
 

It's been known for some time that having children and breastfeeding is linked to a reduced risk of breast cancer — in fact, it was more than 300 years ago that this connection was first made.
 

Through historical studies of nuns, researchers observed that women who dedicated their life to religious service — most of whom never gave birth — had some of the highest rates of breast cancer.
 

Over time, evidence of the protective effect of childbearing and breastfeeding was confirmed, though the reasons behind it were not entirely clear, and thought to be largely the result of pregnancy-related hormonal shifts.
 

But this week, Australian research found another biological explanation, pointing to the lasting impact having kids and breastfeeding can have on a woman's immune system.
 

"Pregnancy and breastfeeding leave behind long-lived protective immune cells in the breast and the body," Sherene Loi, medical oncologist and clinician scientist at the Peter MacCallum Cancer Centre, said.
 

"These cells help to reduce risk and improve defence against breast cancer, particularly triple-negative breast cancer."
 

Professor Loi, who led the study, described the findings as a "paradigm shift" in how we understand immunity and breast cancer, and said it could lead to new approaches to prevention and treatment.
 

In other health news this week, two major pharmaceutical companies behind the weight-loss injectable drugs Wegovy and Mounjaro are under fire for "unethical" advertising.
 

As my colleague Jacinta Bowler reports, Novo Nordisk and Eli Lilly have both recently launched advertisements directing people towards their doctor for weight loss — but some experts warn these campaigns may distort public health messaging.
 

And finally, there are calls for Australia to follow Europe's push to ban PFAS "forever chemicals" because of potential health concerns and how they contaminate and stay in the environment.
 

And speaking of plastics, Dr Norman Swan has been looking at microplastics in the home — and some of the ways you might want to reduce your exposure as a precaution.
 

I'll catch you next week.
 

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