HMOs have a multifunctional action on neonatal immunity. As the immune system of the newborn in naive, human milk confers multiple layers of protection against pathogenic infection, facilitates intestinal and immune development and support healthy gut and microbes. To this day, HMOs represent the largest group of bioactive components found in human milk in terms of concentration and complexity.
There are different places where HMOs may affect the infant’s immune function. They can have an influence on innate immunity through the epithelial barrier, the intraluminal prebiotic and anti-infective activities as well as the mucosal and systemic immunity.
Many observational studies have been done and most focus on the effect of 2-FL, one of the major HMO found in the milk of mothers and one of the only two HMOs that have been added to commercial infant formulas. It has been seen that moderate to severe diarrhea occurred less often in infants fed with milk high in 2-FL showing some protective effect.
In human intervention trials, HMOs were added to infant formula and no difference in weight, length or head circumference growth was observed showing that HMOs do not influence growth significantly. These studies have revealed that similarly to children that are breastfed, infants fed a formula with 2-FL’ have lower inflammatory cytokines. 2-FL’ and/or LNnT have been shown to be safe, well tolerated and supports age appropriate growth. Furthermore, 2FL+LNnT reduces parents reported morbidity as well as shifted the microbiome composition to be more similar to BF infant vs. control formula and increased bifidobacterium.