Breastmilk Protein May Shield Babies From Dangerous Lung Infections

Scientists have found strong clues about how a protein in breastmilk helps protect babies from serious respiratory infections. The protein is called osteopontin, and researchers say it helps start up a baby's immune system in the first weeks of life. The discovery was published in the science journal Cell and was led by immunologist Simon Phipps at the QIMR Berghofer Medical Research Institute in Australia. Researchers hope the findings will help make commercial infant formula better for babies who cannot be breastfed.

Scientists already knew that breastfeeding helps protect babies from respiratory infections, which are illnesses that affect breathing. They also knew that breastmilk contains high levels of osteopontin in the early weeks after a baby is born. But no one fully understood how the protein worked inside a baby's body — until now. Professor Phipps and his team spent five years studying the question with a large group of scientists from around the world.

The researchers tested their ideas on baby mice. They compared mice that were given osteopontin from cow's milk to mice that did not receive the protein. Both groups were then exposed to a respiratory tract infection. The mice that did not get osteopontin had fewer important immune cells to fight off the infection. The mice that did receive the protein were much better protected.

The scientists also found that osteopontin changed the baby mice's gut microbiome. The microbiome is the collection of tiny living organisms, like bacteria, that live in the digestive system. Osteopontin caused the bacteria to produce certain chemicals, called metabolites, that traveled to cells lining the lungs. Those chemicals switched on growth factors that helped the immune system develop. This chain of events — starting in the gut and ending in the lungs — surprised even the researchers.

The study also found something unexpected: a drug already used to treat type 2 diabetes could copy the effects of osteopontin. The drug activated the same immune processes in the mice. Professor Phipps said this was 'really exciting.' His lab is now talking with infant formula companies about using the research to improve their products so that babies who are not breastfed can still get some of the same benefits.

Not everyone involved in the study, though. Griffith University professor Ben Desbrow called it 'exceptional science.' He pointed out that the research was done in mice, not humans, which means scientists still need to do more studies. But he said it helps explain how early nutrition shapes the immune system. He also noted that the findings suggest lung conditions later in life might be connected to how lungs develop in the very first weeks after birth.

Researcher Lisa Stinson from the University of Western Australia agreed the study was strong foundational science. However, she said more research in human babies is needed before scientists can say for certain what osteopontin does in real infants. Associate Professor Valerie Slavin from Griffith University added that while every discovery about breastfeeding is exciting, the biggest improvement for mothers and babies would come from making breastfeeding support easier to access. She noted that many women stop breastfeeding earlier than they planned, often because they do not get the help they need in time.

One new mother, physiotherapist Bethany Kippen, said she found the research 'really interesting.' Kippen gave birth to her son Billy at Brisbane's Wesley Hospital and was breastfeeding when the study was published. She said her breastfeeding journey was hard at first but became rewarding once she and her baby found their rhythm. 'I don't see it as just him receiving food and nutrients. I see it as a bit of a bonding moment, too,' she said.