New research suggests that specific proteins found in breast milk can influence the abundance of gut microbes necessary for immune system development and overall health in infants.


The research, published in Frontiers in Microbiology, suggests that breast milk proteins play a vital role in an infant’s gut microbiome diversity — potentially influencing early immune system and metabolic development.

Scientists examined the breast milk protein composition of 23 Chinese mothers at 42 days and three months after delivery. Then, they identified the abundance and diversity of the gut microbiota in their baby’s stool samples.

The researchers focused on breast milk concentrations of nine different proteins, including osteopontin (OPN), α-lactoalbumin, serum albumin, immunoglobulin A, and κ-casein.

Proteins linked to microbes

After analyzing infant stool samples, the scientists found that specific proteins in human milk are significantly associated with the abundance of certain microbial species in the baby’s gut microbiome — particularly Clostridium butyricum and Parabacteroides distasonis. These bacterial species are rarely found in the gut microbiome of infants and are often included in probiotics supplements.

C. butyricum is known to regulate gut stability and combat inflammatory bowel disease (IBS), and P. distasonis may help inhibit diabetes, colorectal cancer, and IBS.

The scientists also observed that variations of κ-casein concentrations in a mother’s milk explained differences in the abundance of C. butyricum in the gut biome of their infants. Similarly, differences in OPN concentrations explained much of the variation in the abundance of P. distasonis.

Enzyme expression

The researchers also identified that some types of human milk proteins may influence the expression of certain enzymes, potentially leading to the regulation of compounds associated with sugar and fat metabolism.

“Here we show that the concentration of certain proteins in human breast milk predicts the abundance of specific gut microorganisms in infants, which are known to be important [and] necessary for health,” said joint senior author Ignatius Man-Yau Szeto from the Yili Maternal and Infant Nutrition Institute in Beijing.

Although more research is needed, Man-Yau Szeto concluded: “These findings suggest that maternal proteins play a role in the early immune and metabolic development of immunity of babies.”

The study authors suggest these findings may also explain the function of breast milk proteins in early immune development, add more evidence that breastfeeding is important for infant health, and support the use of functional proteins in infant formula.