New research shows that mother’s own milk (moreso than the type of milk fortifier) is key to developing a healthy gut microbiome for premature babies

Milk fortifiers help to meet the unique nutritional needs of premature babies by providing extra nutrients, protein, and energy. Milk fortifiers have traditionally been made from cow milk, but fortifiers made from human milk are now available.

A new randomized clinical trial was recently conducted by scientists from the Children’s Hospital Research Institute of Manitoba (CHRIM) to compare how the different milk fortifiers impact the gut microbiome (the trillions of bacteria found in our intestines), which play a key role in the health and development of premature babies.

The study, published in Cell Reports Medicine and co-led by Dr. Meghan Azad, Associate Professor of Pediatrics and Child Health at the University of Manitoba, alongside Dr. Michael Narvey, Section Head of Neonatology at the University of Manitoba, compared 30 premature babies with very low birth weight that were given either the cow milk fortifier or the human-derived fortifier.

They found that the fortifier type does not have much impact on the overall microbiome, although the babies who received the human-derived fortifier were less often colonized by one particular type of bacteria (a member of the Clostridiales Family). In contrast, strong associations were seen between the babies’ microbiome profiles and the proportion of mother’s own milk (as opposed to donor breast milk) they received. Additionally, the analyses also showed that babies receiving more of their mother’s own milk had better weight gain and reduced gut inflammation.

“We were surprised by the results because we expected that human-derived fortifiers would benefit the microbiome, but they didn’t seem to make much difference.” said Dr. Meghan Azad, Tier 2 Canada Research Chair in Developmental Origins of Chronic Disease, “Instead, we found that the source of breast milk (rather than the type of fortifier) was very important. Feeding mothers’ own breast milk was very strongly linked to microbiome composition.”

The study’s lead author, Dr. Shreyas Kumbhare, who completed his post-doctoral fellowship at CHRIM and the University of Manitoba, believes the results reflect the special properties of mother’s milk, which is uniquely “personalized” for her own baby, and contains hundreds of compounds that support optimal infant growth and development. “Donor breast milk has many benefits compared to synthetic baby formulas, but there is no perfect replacement for a mother’s own milk,” he said.

In a published commentary about the new study, Dr. Paula Meier, director for clinical research and lactation in the neonatal intensive care unit and professor of women, children and family nursing and pediatrics at Rush University Medical Center in Chicago, remarked that ‘These findings have important implications for future research, clinical quality improvement initiatives, and efforts to prioritize the availability of mother’s own milk in the NICU.

Overall, the study provides new evidence that the source of human milk (mother vs. donor) is more important than the type of milk fortifier (human vs. cow) in shaping the gut microbiota in premature infants.

“This research highlights the importance of supporting new mothers to produce, pump and feed their own breast milk in the Neonatal Intensive Care Unit,” says Dr. Narvey. “While the results suggest fortifier type does not have a great deal of influence over the development of the microbiome, there is still much to be learned with respect to the clinical impacts of exclusive human milk diets.”

The study was partially funded by an operating grant from CHRIM with additional researchers who worked on the project from Canada’s National Microbiology Laboratory.