New research unravels why breast milk premiums are healthier than formula-fed infants

Human breast milk has long been considered “liquid gold” among clinicians treating premature babies in a newborn intensive care unit (NICU). Breast-fed “premiums” are, on average, healthier than those who are bottle-fed. Why that is true, however, has remained a mystery.

New research from the Institute for Genome Sciences (IGS) at the University of Maryland School of Medicine (UMSOM), published online in June in the journal mBio, found that it’s not just the content of breast milk that makes all the difference. It’s also the way the babies digest it.

The study, led by Bing Ma, PhD, Assistant Professor of Microbiology and Immunology at UMSOM and a researcher at IGS, discovered a strain of the Bifidobacterium breve bacterium or B. breve in the gut of breastfed babies who consumed higher amounts of breast milk. then got their counterparts. Those preemies had better nutrient absorption because they developed an intact intestinal wall a week after birth. B. breve was much less common in both bottle-fed and breastfed babies with ‘leaky gut’. Babies with leaky gut don’t develop a barrier to prevent bacteria and digested food from entering the bloodstream. For the first time, the team also found that the way B. breve metabolizes breast milk keeps breastfed babies healthier and allows them to gain weight by strengthening their underdeveloped gut barrier.

An immature or “leaky” gut can lead to necrotizing enterocolitis (NEC), the third leading cause of death in newborns in the United States and worldwide. In fact, NEC affects up to 10 percent of premature babies with a devastating death rate as high as 50 percent.

Our discovery could lead to promising and practical clinical interventions to fortify infants’ guts and thereby increase the survival rates of the most vulnerable preemies.”

dr. Bing Ma, PhD, Assistant Professor of Microbiology and Immunology at UMSOM

Bifidobacterium in the gut or microbiome has long been known to have health benefits. It includes a diverse range of species with very different traits. Some strains only occur in adults; some are usually in adolescence. One strain, Bifidobacterium infantis, has been observed primarily in term infants.

The researchers followed 113 premature babies born between 24 and 32 weeks of pregnancy. This study found Bifidobacterium breve (B. breve) only in preterm infants who had improved gut barrier function within one week of birth. dr. Ma and her colleagues found that Bifidobacterium breve is genetically equipped to digest nutrients within the cell membrane rather than the more typical external digestion process in which bacteria secrete digestive enzymes onto nutrients to break them down.

At the most basic level, the gut microbiome in these breastfed premiums metabolizes more B. breve carbohydrates differently than in the formula. The researchers say they hypothesize that this process of metabolism strengthens and matures the gut barrier more quickly, protecting vulnerable newborns from disease.

“We now know that it’s not just breast milk that helps premature babies develop their gut barrier faster,” said Dr. mom. “We will have to find the best way to prophylactically administer B. breve early in life, rather than relying on transmission of breast milk or even the maternal gut or vaginal microbiota during the birth process. This is especially critical in premature infants who are bottle-fed.”

dr. Ma said more studies are needed to determine whether the B. breve comes from breast milk, the gut, the mother’s vagina, or even the environment.

E. Albert Reece, MD, PhD, MBA, Executive Vice President for Medical Affairs, University of Maryland, Baltimore, the John Z. and Akiko K. Bowers Distinguished Professor and Dean at UMSOM said, “This research could have a lot of global impact. could ultimately save thousands of premature babies from permanent disability or death associated with an immature and permeable gut that lets in deadly bacteria.”


University of Maryland School of Medicine

Reference magazine:

in, B., et al. (2022) Highly specialized carbohydrate metabolism in Bifidobacterium strains associated with intestinal barrier maturation in preterm infants. mBio.

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