Breastfeeding: Does baby ‘backwash’ trigger an immune response in the mother’s milk?

Quick summary: New animal study provides evidence to support the “backwash” hypothesis — that if a child is sick, saliva from the baby’s mouth is sucked into the nipple. The idea is this backflow of saliva can then trigger an immune response in the mother’s breast milk to fight the infection.

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New study: Does baby “backwash” create made-to-order immune response in breast milk? Ghosh S et al. Nature 2022. Find out more about this science at our virtual conference — featuring 20+ international speakers. Click this link to join the conference recordings waitlist >>> https://bit.ly/microbirth2023

I love this idea: the potential for “backwash” communication between a mum and her baby during breastfeeding.

The hypothesis is that during breastfeeding, there is a blackflow of saliva from the baby’s mouth. The saliva gets sucked into the nipple and into the milk ducts (called retrograde duct flow.)

If the baby is sick, the baby communicates information to the mum’s immune system about the infection.

In response, the composition of the mum’s milk changes — there’s an increase in antibodies to help the baby fight the infection.

Ingenius!

But what’s the evidence?

Does “backwash” actually trigger an immune response in the mum’s milk?

Previous studies have shown that immune components in the milk can increase if the baby is ill. This suggests the baby can communicate with the mother’s immune system — informing the mother about the baby’s health.

But previous studies fall short of saying definitively that saliva “backwash” is the source of this communication.

Now a new animal study adds an important piece of the puzzle — it tracks a signal from baby saliva TO the mammary gland TO the milk.

To summarise the study very simply: The mouse study suggests saliva from the infants mouth can transmit pathogens to the mother’s mammary gland during suckling.