• Posted September 14, 2023

Breast Milk Brings Babies a Healthier Microbiome

Breast milk supplies many benefits for babies and their moms, and a new study highlights another one: Mother's milk provides proteins that are important for a newborn's gut health.

“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 co-author Dr. Ignatius Man-Yau Szeto from the Yili Maternal and Infant Nutrition Institute in Beijing, China.

The results were published Sept. 13 in Frontiers in Microbiology.

“These findings suggest that maternal proteins play a role in the early immune and metabolic development of immunity of babies,” Szeto said in a journal news release.

The immune-boosting function of breast milk proteins might be two-pronged, the researchers said. They may stimulate the immune system directly, but also indirectly, by regulating the abundance of microbes in the gut's microbiome, which in turn affect immunity.

Researchers looked at the protein composition of breast milk from 23 Chinese mothers, using ultra-performance liquid chromatography-mass spectrometry.

They also looked at the diversity and abundance of beneficial gut microbes in the stools of their infants.

“We focused on nine milk proteins, including osteopontin, lactalbumin and K-casein, because these were recently found to benefit the early development of infants. Their function and mechanisms haven't yet been fully discovered, so we wanted to examine their potential role in regulating the microbiome of infants,” said co-author Dr. Ai Zhao from Tsinghua University.

Researchers found that the concentration of proteins in breast milk was 1.6% at 42 days after delivery and 1.2% at three months after delivery.

The most abundant proteins were casein, α-lactalbumin and lactoferrin. The concentration of most of the studied proteins decreased from 42 days to three months postpartum, with the exception of immunoglobulin A, which is an antibody important for the immune function of mucous membranes.

The gut microbiome of the babies was mainly composed of the bacterial genera Bifidobacterium, Escherichia, Streptococcus and Enterobacter.

The research team found the strongest associations between the concentrations of breast milk proteins and two beneficial bacteria that were relatively rare within the gut microbiome of the babies. These were Clostridium butyricum and Parabacteroides distasonis. Both are used as probiotics for humans and domestic animals.

Variations in the concentration of certain proteins explained variations in certain bacteria that can regulate the gut, combat inflammatory bowel disease and counter diabetes and colon cancer.

“The results of this study suggest that specific proteins in breast milk can influence the abundance of certain gut microbes in infants, playing an important role in early immune and metabolic development,” the authors concluded.

More research is necessary, however. “Our findings are based on correlations, which are not enough to establish a direct causal effect," Szeto said.

More information

The U.S. National Human Genome Research Institute has more on the microbiome.

SOURCE: Frontiers in Microbiology, news release, Sept. 12, 2023