Human Milk Oligosaccharides (HMO) are the third most abundant solid components in breast milk (next to fat and lactose), with a content of 5 ~ 15g/L. There are more than 200 kinds of oligosaccharides in human milk, among which 2′- fucosyl lactose (2′-FL) is the most abundant in HMO.

HMOs has the following functions:

 (1) Immunomodulation. HMOs can regulate the production of cytokines in lymphocytes and reduce the intercellular interaction mediated by selectin in the immune system, thus playing an immune role.

(2) Regulating the composition of intestinal flora of infants. HMOs is not easily digested and absorbed by the upper digestive tract, but can reach the colon completely, which can provide nutrition and energy for colon cells. In addition, the intestinal microenvironment with lower pH value is not conducive to the growth of harmful flora, thus playing a prebiotic role and regulating the intestinal flora of infants.

(3) Promote brain development. The rapid development of baby’s brain puts forward extremely high requirements for the supply of nutrients. Gangliosides containing sialyl groups and glycoproteins containing polysialyl groups are important components of brain tissue, so sialylated HMOs is related to nerve development and cognitive function, which is helpful to promote the development of baby’s brain.

(4) Prevent pathogens from adhering to the intestine. HMOs is similar to the sugar chain on the surface of mucosal cells, and can be used as a soluble ligand analog, which can occupy the binding site on the surface of host cells and block the combination of pathogens and epithelial cells. Unbound pathogens can’t attach to the cell surface, but will be excreted, reducing the infection rate.

(5) Antiviral activity. The first step of bacterial and viral infection is to recognize and bind the surface polysaccharides of specific cells on intestinal mucosa. Salivate and fucosylated oligosaccharides contain similar structural units to these polysaccharides. Therefore, HMOs can be used as a receptor analogue to inhibit the adhesion of pathogens, thus preventing infection.