How Your Breasts ‘Eat Themselves’ When You Stop Breastfeeding

How Your Breasts 'Eat Themselves' When You Stop Breastfeeding

If you’re pregnant or currently breastfeeding, you may wonder what might happen to your breasts when you stop breastfeeding.

This might especially be the case if you’ve heard people say that breastfeeding can cause undesirable breast changes (e.g. saggy breasts) after weaning.

The good news is that this information is false.

The truth is that once weaning occurs, the milk-making cells in your breasts gradually shrink and fat cells get laid down again.

This process can take several months to complete. As it occurs, your breasts usually return to their pre-pregnancy size.

But, what actually happens to your breasts, on a cellular level, when you stop breastfeeding?

Your Breasts Start To Eat Themselves

During pregnancy, hormonal signals tell the cells lining the milk ducts (epithelial cells) to grow and multiply, and to form ball-like structures called alveoli where milk is made.

When women stop breastfeeding, the epithelial cells self-destruct, creating large amounts of cellular debris which needs to be cleaned up.

Typically, immune cells remove these dead cells through a process called phagocytosis.

But, here is where it gets interesting….

When breastfeeding stops, the amount of material that needs to be removed would be expected to cause significant inflammation, pain and tissue damage.

But, of course this doesn’t happen. So, the question is why?

The Rac1 Protein Removes Dead Cells Without Causing Inflammation

To investigate this, a team led by Nasreen Akhtar from the University of Sheffield in the UK studied on a protein called Rac1, which plays an important role in milk production and also phagocytosis.

The team bred mice that could not produce the Rac1 protein, and observed what happened when they had babies.

It was found that the first litter of pups were a lot smaller than normal, and all subsequent litters did not survive.

It was discovered that, without the Rac1 protein, the dead cells from the first pregnancy/lactation were not able to be cleared, but instead, clogged up the breast tissue leading to such significant inflammation that the mice were unable to make enough milk for subsequent litters.

But how does the Rac1 protein do this?

The Rac1 Protein Transforms Epithelial Cells From Milk Secretors Into Cellular Eaters

It appears that the Rac1 protein keeps dead or dying cells attached to the alveoli for longer which might encourage them to eat each other rather than leaving it to immune cells and hence keep inflammation at bay.

More importantly, this research could help scientists to discover why certain cells turn cancerous.

Breastfeeding Reduces The Risk Of Breast Cancer

It’s known that breastfeeding reduces a woman’s risk of breast cancer.

Currently, researchers are working on anti-cancer treatments based on the Rac1 protein. According to this recent research team’s leader Nasreen Akhtar, “Rac1 is over-expressed in various cancers including breast cancer and Rac1 inhibitors are currently being considered as anti-cancer therapies,” she says. “[But] given that sustained inflammation is linked to cancer progression, the findings show that blocking Rac1 might not be a good idea.”

It truly is remarkable how science is only beginning to unravel the complexities of breastmilk and the human breast and how these discoveries might impact future treatment of disease.

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Renee Kam IBCLC CONTRIBUTOR

Renee Kam is mother to Jessica and Lara, an International Board Certified Lactation Consultant (IBCLC), a physiotherapist, author of 'The Newborn Baby Manual' and an Australian Breastfeeding Association Counsellor. In her spare time, Renee enjoys spending time with family and friends, horse riding, running and reading.


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