Breast milk contains essential nutrients, vitamins, and hormones that are important for newborn development.

Specifically, the proteins in breast milk help regulate the immune system. Since the gut microbiome also impacts immunity, a new study examined the association between breast milk and gut microbes related to immune system function.

The research, published in Frontiers in Microbiology on September 13, found that breast milk proteins regulate immune function.

The results demonstrate that the protein composition of breast milk helps diversify gut bacteria in newborns to better protect their immunity.

The study authors say that further understanding of the function of breast milk components will be helpful in designing infant formula that’s closer to breast milk.

Which proteins in breast milk benefit gut health?

For the study, researchers used ultra-performance liquid chromatography-mass spectrometry, a technique that helps to determine the individual components of complex solutions, to examine the protein composition of breast milk from 23 Chinese mothers. They also used sequencing technology to analyze gut microbes in their infants’ stools.

The aim was to look into the link between the protein composition of the mothers’ breast milk and the variation and quantity of gut microbes in their infants.

Researchers looked at nine milk proteins, which included osteopontin (OPN), lactalbumin, and κ-casein, to analyze its effects in infant gut microbiome regulation.

“To the best of our knowledge, we are the first group to report that the contents of certain proteins in human breast milk, such as OPN and κ-casein, affect the abundance of specific intestinal microorganisms in infants,” study author Ai Zhao, PhD, an assistant professor at the Vanke School of Public Health at Tsinghua University in Beijing, told Healthline. “Proteins in early breast milk had a more significant effect on the gut microbiota.”

“These findings explain the function of proteins in early immune development, indicate the potential extended function of breast milk protein and support the application of functional proteins used in infant formula,” Zhao continued.

How breast milk proteins affect infant gut microbiome

This study adds to the growing body of evidence showing the connection between breast milk and infant gut health and immune system development.

“The scientific community is constantly learning more about how nutrition can impact long-term health, particularly during the first months of life,” Dr. Devon Keuhn, board certified pediatrician and neonatologist and chief medical officer at ByHeart, an infant formula company, told Healthline.

“There is great research showing that the type and amount of microbes present in the gut, and importantly, how they behave, are critical to the development of the immune system and metabolic pathways through various mechanisms,” Keuhn added.

Keuhn noted that different proteins can impact the microbiome in different ways, as was noted by the study.

“Therefore, it is important to be thoughtful when choosing ingredients in infant formula, as we are learning that they can have an impact not only on the development of microbiome but also the associated body systems.”

Dr. Pamela Berens, professor and OB-GYN with UTHealth Houston, told Healthline: “We know that breast milk is more than nutrition. Part of breast milk is nutrition, but it’s also immunologic protection. This study adds to the growing evidence that demonstrates this.”

Breastfeeding provides vital nutrients, but isn’t always an option

Not all birthing parents can nurse their newborns for various reasons, whether due to latching difficulties or a parent’s return to work. Others may choose not to breast- or chestfeed, which is a personal decision.

“Breastfeeding is one of the first, and incredibly intimate, decisions women make as parents, and this choice is determined by many different personal circumstances,” said Keuhn.

Berens that some people may not be capable of nursing due to medical reasons.

“Occasionally, a woman can’t make enough milk due to insufficient glandular tissue. Also, certain chemotherapy drugs in the mother’s system could be unsafe for the baby to absorb, although it would depend on the specific drug. Another reason is HIV that isn’t well controlled,” Berens explained.

Latching difficulties can present a barrier to nursing, but Berens noted these issues are often resolved with assistance from a professional, such as a lactation consultant.

“It is true that not all babies can breastfeed,” said Dr. Arik Alper, assistant professor of pediatrics at Yale School of Medicine. “Most formulas try to mimic breast milk and have a great nutritional value. It is true that formula-fed babies have a different gut microbiome, but the clinical significance of this finding is still being investigated.”

What are the differences in breastmilk vs. formula?

As scientists discover more information about breast milk, they adjust the formula accordingly to meet any nutritional deficits.

“The proteins in breast milk are highly functional, providing benefits beyond filling tummies: they are key to supporting a strong immune system, healthy gut microbiome, and easy digestion; yet the protein blend is still the largest gap between breast milk and existing formula on the shelf,” said Keuhn.

Berens explained: “When we identify something the formula is lacking, we try to make changes to put that in formula or simulate it in formula, so the more we learn about breast milk the more the formula evolves.” It’s also important to note formula is static and breast milk is responsive. “The big difference between the breast milk and formula is that formula is predominantly nutrition, and breast milk is nutrition and immunology,” Berens said. “For example, when the mother gets ill and heals, the baby will absorb those antibodies. It is a dynamic liquid.”

Does baby formula benefit gut health?

Infant gut health is a growing area of interest among scientists and healthcare professionals, but researchTrusted Source on the effects of probiotics added to infant formulas is limited.

“Gut development is such an exciting and emerging area of research,” said Keuhn. “We know that nutrition can have a direct effect on not only how well a baby tolerates a feeding, but also the overall health of their gut.”

Not all ingredients in infant formula will have the same effects on gut health, so it’s important to read product labels carefully.

“Prebiotics, such as GOS, have been shown to directly impact babies’ stools (making them softer) for better formula tolerance, but also support gut health by promoting the growth of important bacteria,” Keuhn noted.

“Recently, researchers have been studying the impact of different carbohydrates used in infant formula, with some suggesting that replacements for lactose, such as maltodextrin or corn syrup solids, may have negative effects on the microbiome.” Parents and caregivers of formula-fed infants should seek guidance from their pediatrician before supplementing with infant probiotics.


According to a new study, breast milk proteins affect a newborn’s gut health by regulating the immune system.

This study supports prior research showing that breast milk benefits a baby’s nutrition and immunity.

Breast milk and formula both contain essential nutrients to promote an infant’s overall health. As scientists continue to discover more about breast milk, formulas are updated to fill any nutritional gaps.

By Kaitlin Vogel

Source: HealthLine Media

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