Human milk banks improve infant health but can’t fully replace mother’s milk

In a recent Nutrients journal study, scientists explore the practices of human milk banks (HMBs) and the health outcomes of infants fed with donated human milk.

Study: Personalized Nutrition with Banked Human Milk for Early Gut Microbiota Development: In Pursuit of the Perfect Match. Image Credit: Evgenyrychko / Shutterstock.com

Early microbiota establishment and human health

Millions of microorganisms reside in the human and animal gut and influence hosts’ physiology, immunity, and metabolic function. Several studies have indicated the importance of initial microbial colonization, as this process significantly shapes an individual’s health throughout their lifespan.

Babies born vaginally are exposed to maternal vaginal and fecal microbiota composed mainly of Prevotella, Escherichia/Shigella Lactobacillus, Bacteroides, Atopobium, and Bifidobacterium genera members. Comparatively, babies born through Cesarean section will be exposed to the microbiota of the mother’s skin and hospital environment, which has been attributed to higher levels of Staphylococcus spp., Klebsiella spp., and Escherichia coli that will subsequently colonize the gut microbiota, as well as lower levels of Bacteroides and Bifidobacterium.

Breast milk intake is the most crucial factor for optimal colonization and establishment of the infant gut microbiota. Oligosaccharides are a key component of breast milk that supports the growth of beneficial bacteria such as Lactobacillus, Bifidobacterium, and Bacteroides. Feeding mode is also crucial for early microbiota colonization, as beneficial bacteria like Lactobacillus and Bifidobacterium present on the mother’s nipple are also transferred during breastfeeding.

Breastfeeding may not be possible in the case of premature birth or early pathology. Although these babies are often provided infant formula milk, the official nutritional and health international guidelines recommend the use of donated human milk (DHM) from human milk banks.

Some studies have indicated that DHM does not fully match maternal breast milk regarding infant growth and development. In fact, the differential composition of the gut microbiota has been observed in infants fed DHM and own-mother milk (OMM), which could be attributed to the milk processing, including pasteurization, at the milk bank.

Comparison of the main nutritional and bioactive components between different infant’s feeding sources: mother’s own milk, pasteurized donor human milk and commercial infant formula.

Hospital practices for milk donation, safety, and quality

Any healthy woman leading a healthy lifestyle can become a human milk donor. During the donation process, the European Milk Bank Association (EMBA) recommends serologically testing donors, conducting an oral interview, obtaining prior consent regarding the use of the milk, training donors on hygiene issues, and providing appropriate ongoing support.

EMBA exclusion criteria include smokers, users of recreational drugs, human immunodeficiency virus (HIV) infection, syphilis or human T-lymphotropic virus, hepatitis B or C, users of drugs not on the EMBA-approved medication list, having a tattoo or piercing, and following a vegan diet without B12 supplementation.

Milk obtained through HMBs should be pasteurized, which subsequently inactivates bacterial and viral agents, in an effort to retain the beneficial nutrients of human milk, such as fatty acids, lactose, and most minerals. However, heat interventions may also lead to a decline in bioactive compounds, such as immune cells, hormones, cytokines, immunoglobulins, and water-soluble vitamins.

Multiple proteins and enzymes, including lipase, amylase, lactoferrin, and amylase, decrease in activity due to heat interventions. Notably, human milk oligosaccharides (HMOs) are resistant to pasteurization and remain available in donated breast milk. Furthermore, HMBs perform standard fortification based on the micronutrient content of milk.

Since heat treatments alter milk composition, many alternative techniques, including high-temperature short-time pasteurization (HTST), ultraviolet-C irradiation (UV-C), high-pressure processing (HPP), and thermo-ultrasonication have also been used. The HPP method causes less harm to exosomes and their microribonucleic acid (miRNA) content, whereas UV-C treatment successfully retains the important bioactive components of fresh human milk.

The EMBA considers the holder pasteurization (HoP) method to be the safest method for treating DHM despite the elimination of beneficial bacteria from milk through this process. Thus, technological improvements are needed to minimize the degradation of beneficial components.

Health outcomes in breastfed and formula-fed infants

Breastfed infants have higher levels of beneficial gut bacteria like Bifidobacterium as compared to formula-fed infants. In fact, the gut microbial profile of full-term babies fed with human milk significantly differs from those fed with bovine-derived formula.

For example, lower levels of Clostridium and higher levels of Veillonella, Bifidobacterium, and Propionibacterium have been observed in the gut microbiome profile of breastfed infants. These microorganisms produce anti-inflammatory short-chain fatty acids (SCFAs).

Several studies have shown that early-life breastfeeding optimally shapes the development of intestinal microbiota in infants. Human milk reduces the risk of necrotizing enterocolitis (NEC), a gastrointestinal tract disease that generally affects premature infants and is associated with delayed maturation of the gut microbiota. Studies have also shown that human milk immunoglobulin A (IgA) plays a key role in preventing NEC in both full-term and preterm infants.

Formula feeding could lead to rapid weight gain during childhood, as opposed to breastfeeding, which prevents childhood obesity. In the first three to six months of an infant’s life, breastfeeding reduces the risk of developing atopic diseases like asthma. Breast milk also improves the neurocognitive development of preterm babies.

Conclusions

Although donor milk does not exactly match OMM, particularly its microbial composition, DHM is the best alternative when breast milk is unavailable. Nevertheless, additional research is needed to assess the short- and long-term health effects of DHM on premature babies.