The power of human milk for infant health

Two open-access reviews by a renowned neonatal immunologist have highlighted the uniqueness of the developing infant immune system and how human milk provides a personalized and real-time approach to meeting the ever-changing needs of newborns.

Professor Verhasselt, Director of the Larsson-Rosenquist Foundation Center for Immunology and Breastfeeding at UWA Medical School and Head of Immunology and Feeding at The Kids Research Institute Australia, found human milk reflects the mother’s past and present environmental exposures.

It also protects infants from external threats such as pathogens and allergens and helps young immune system develop an appropriate and effective response for future challenges.

In the first study, published in Immunological Reviews, Professor Verhasselt explored food from the infant’s perspective, viewing breastmilk as the newborn’s natural food source.

She traced the origins of the uniquely mammalian food back to the secretions of skin glands in ancestors, which were initially produced to keep eggs moist and protect them with antimicrobial compounds.

“Breast milk has since evolved to not only to defend infants against pathogens but also to educate their immune systems about the external world,” Professor Verhasselt said.

“By pre-digesting food proteins and introducing these antigens—food proteins recognized by the immune system—in breast milk, the infant’s immune system is equipped to tolerate these foods.”

Contrary to common belief, Professor Verhasselt said infants were more prone to inflammatory reactions at their mucous membranes and skin barriers rather than developing tolerance, and so were very susceptible to allergy.

“Breast milk, with its thousands of bioactive compounds, has the potential to influence the development of the infant’s epithelial barriers and immune cells, both directly and indirectly, by shaping the gut microbiota, and hence promote an appropriate immune response to food allergens,” she said.

The research found looking at the immune response to food from the perspective of newborns should provide a new understanding of how the developing immune system sees and responds to food.

“Understanding how breast milk communicates with young immune systems provides clues to developing tailored approaches to allergy prevention by advising mothers on lifestyle, such as diet during breastfeeding, and by developing milk-inspired therapeutics for high-risk kids,” Professor Verhasselt said.

In the second review, also published in Immunological Reviews, Professor Verhasselt and her colleagues explored the impact of maternal breast milk antibodies on infant health.

The study examined how antibodies in breast milk protect newborns from environmental threats, help shape and guide their developing immune system, and promote transgenerational adaptation of the immune system to its environment.

“A newborn’s immune system is unprepared for the antigens it will encounter, such as pathogens, microbiota and food proteins, making it vulnerable to infection, intestinal inflammation or allergic reactions,” Professor Verhasselt said.

“Mothers help by passing on antibodies during pregnancy that provide protection in the first few months against infections they have previously encountered.

“Through an ingenious mammary immune system-mammary gland pathway, breast milk brings antibodies that reflect not only past, but also present, maternal exposure to pathogens.

“These antibodies coat the infant’s upper respiratory and digestive mucosa, perfectly positioned to control responses to environmental antigens, and may even reach the infant’s circulation.

“Breast milk antibodies therefore play a key role in the immune defense of the developing child and have a significant impact on the susceptibility to infectious diseases in both high and low-income countries, with up to one million lives potentially saved.

“Furthermore, new research is showing how important milk antibodies are in shaping the infant’s microbiota, and we know how important the microbiota is in regulating the immune system and susceptibility to disease,” she said.

Professor Verhasselt said the combined findings of the studies underscored the critical importance of breast milk in supporting infant health and in developing strategies to promote healthy immune responses.

“Further understanding of the bridge that maternal milk provides between the child and its environment should enable the best interventions to promote healthy development,” she said.