The educational content in this post, elaborated in collaboration with Bromatech, was independently developed and approved by the GMFH publishing team and editorial board.

Early feeding type is a key factor in directing the development of the gut microbiome in neonates

Regardless of the current scientific debate on whether the story of a human’s gut microbes starts during pregnancy or at the moment of birth, what is more clear is that the diversity of the gut microbiome (that is, the number of different kinds of microorganisms and how they are distributed in the infant’s gut) and its functions during early infancy are affected by birth mode, feeding type, antibiotic use, geographical location and living in contact with siblings or furry pets.

A healthy baby first establishes a low-diversity gut microbiome that is dominated by bifidobacteria and its composition depends heavily on how the infant is fed.

Breastfeeding promotes an abundance of Lactobacillus and Bifidobacterium species, the latter specialized in degrading a type of sugar called human milk oligosaccharides, which are the third most abundant component in breastmilk. Those types of sugars, which have more than 200 different structures unique to each mother, are not digested in the infant’s upper digestive tract. Instead, they reach the colon, where they are fermented by bifidobacteria that contribute to protecting infants against infections and immune-related diseases.

In contrast, bottle-fed infants harbor a more diverse gut microbiome that resembles that of older children, with a higher abundance of potential bacterial pathogens (e.g., some Enterococcus and Streptococcus species) and gut bacteria that feed proteins, rather than carbohydrates, as a preferred fuel.

The early diet also affects gut microbiome metabolism. Breastfed infants have a higher abundance of the metabolites lactate and acetate compared to bottle-fed children, which might contribute to explaining the health benefits of breastfeeding. As the infant grows and genes involved in metabolizing sugars from breastmilk are needed less, the gut microbiome matures to digest starch found in solid food.


The origins and health effects of the microbiota in breast milk

The mother provides the first major seed for microbial colonization to the infant gut at birth upon vaginal delivery and possibly afterwards through breast milk.

Although it was initially thought that breast milk was a sterile liquid, recent research has shown that breast milk has its own microbiota that may have two origins. First, it is possible that the infant’s mouth or maternal skin may provide the milk with some bacteria. Secondly, scientists have suggested an internal route by which maternal bacterial strains are transferred from the maternal intestine to mammary ducts and milk through lymph/blood circulation.

Breast milk contains a rich and diverse microbial community that is as unique as a fingerprint and exquisitely tailored to meet the baby’s nutritional needs. Its composition is mainly made up of Staphylococcus and Streptococcus, followed by Lactobacillus and Bifidobacterium species.

Scientists are only just beginning to understand the countless benefits of human milk, from proper growth and development to a high performance in intelligence tests later in life, which depend on the breast milk microbiota but also on a wide range of nutrients and other compounds that have yet to be fully characterized.

It is also worth noting that maternal obesity, allergy and celiac disease, birth by cesarean section and receiving antibiotics during pregnancy and lactation can reduce the mother’s gut and breast milk colonization by protective bifidobacteria, which in turn could affect the infant immune system’s development, with a potential impact on later health.


What can bifidobacteria do for infant health?

The genus Bifidobacterium is the most abundant bacterium in the gut of healthy breastfed infants, although its levels decrease in adulthood, which suggests the important role of that bacterium in infant growth and development.

Bifidobacteria work alone and increase the presence of other health-related microbes (e.g., butyrate producers such as Faecalibacterium prausnitzii and Eubacterium species) on the journey toward the maturation of gut microbiome composition, resulting in a wealth of health benefits for the child, which include:

  • limiting the colonization of the infant gut by pathogen microbes,
  • strengthening the gut barrier function,
  • degrading dietary fiber and providing essential nutrients, and
  • having anti-inflammatory properties.

The role of bifidobacteria in shaping gut health and the immune system of newborns and children has been one of the most widely studied areas in gut microbiota research. Having the right balance of Bifidobacterium strains in the infant gut plays an important role in educating the immune system and preventing inadequate inflammatory responses that can lead to common conditions, including allergy, type 1 diabetes and inflammatory bowel diseases.

For instance, a recent study found that low abundance of bifidobacterial species and especially a lack in their capacity to metabolize human milk oligosaccharides is linked to intestinal inflammation. When infants were supplemented with B. infantis EVC001 strain, which can metabolize those substrates, the levels of inflammatory markers in feces decreased.


Some probiotics can help normalize the gut microbiome of babies who are born by cesarean section, bottle fed or exposed to antibiotics

Cesarean sections, bottle feeding and exposure to antibiotics are common situations in early life that can reduce the abundance of protective bifidobacteria in the infant gut, suggesting that such infants might benefit from probiotic supplementation.

Some studies have shown that probiotic supplementation with a mixture of B. lactis Bi-07, B. lactis HN019 and L. rhamnosus HN001 or L. rhamnosus KL53A and B. breve PB04 may help normalize the gut microbiome of babies born by cesarean section.

Another study found a multispecies probiotic consisting of B. breve Bb99, Propionibacterium freundenreichii subsp. shermanii JS, L. rhamnosus Lc705 and L. rhamnosus GG ameliorated most of the effects of cesarean birth and antibiotic treatment on the gut microbiome.

Likewise, the supplementation with fermented infant formula containing B. breve C50 and Streptococcus thermophilus 065 and prebiotic oligosaccharides or prebiotics alone has also been used to help fully bottle-fed infants or infants that had started the transition from breast to formula feeding achieve a fecal microbiota composition similar to that of breastfed infants.

Premature infants are also candidates for receiving a probiotic treatment due to the high likelihood of developing necrotizing enterocolitis. In that regard, the European Society for Paediatric Gastroenterology Hepatology and Nutrition has stated the recommendation, with low certainty of evidence, to provide either L. rhamnosus GG ATCC53103 or the combination of B. infantis Bb-02, B. lactis Bb-12 and Streptococcus thermophilus TH-4 to reduce necrotizing enterocolitis rates in preterm infants.

Although the extent to which the immune system is involved has not always been clarified, the findings suggest there is potential for selecting specific probiotics to ensure a healthy gut microbiome, aid the development of immune responses early in life and prevent some conditions related to an altered gut microbiome later in life.

Want to know more? Watch the interview with Prof. Diego Peroni, (University of Pisa).



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