Human Milk Oligosaccharides: Frequently Asked Questions

Human Milk Oligosaccharides are a group of unique prebiotics that are the third most abundant solid component of human milk after fats and lactose. Preclinical and clinical research show HMOs may provide unique benefits to infants’ immune and digestive health, in addition to a possible role in cognitive development.

It is not clear whether a mother can impact HMO composition. Maternal genetics, diet, and exercise are thought to play a role.

2′-FL HMO is the most abundant HMO in most mothers’ milk and has been shown to have unique benefits to infants’ immune and digestive health, in addition to a possible role in cognitive development.

Approximately 30% of total HMOs in most mothers' milk is 2′-FL.

Acetylated (uh·see·tuh·lay·tid)

• LNT: lacto-N-tetraose

Fucosylated (few·cose·uh·lay·tid)

• 2'-FL: 2'-fucosyllactose
• 3-FL: 3-fucosyllactose
  

Sialylated (sigh·a·lay·tid)

• 3'-SL: 3'-sialyllactose
• 6'-SL: 6'-sialyllactose

There are over 150 HMOs found in human milk, and they fall into 3 categories. Each HMO is unique in structure, and they have different functions. Preclinical and clinical research show that HMOs may provide unique benefits to the immune and digestive systems, in addition to a possible role in cognitive development. Additionally, HMOs act as receptor decoys for different pathogens in cell culture studies. 

3-FL HMO represents the fucosylated category of HMOs. Emerging research shows that 3-FL may help support the infant’s immune system by acting as a receptor decoy for various intestinal pathogens in cell culture studies (Weichert, 2013; Weichert, 2016) and supporting growth of beneficial bacteria in the gut.

3′-SL HMO represents the sialylated category of HMOs. 3′-SL contains sialic acid, which is an important building block for the developing brain. Furthermore, emerging research shows that 3′-SL may help support the infant’s immune system by acting as a receptor decoy for various intestinal pathogens in cell culture studies (Angeloni, 2005; Idota, 1995; Simon, 1997; Mysore, 1999; Kim, 2019; Hester, 2013; Laucirica, 2017) and supporting growth of beneficial bacteria in the gut.

6′-SL HMO represents the sialylated category of HMOs. 6′-SL contains sialic acid, which is an important building block for the developing brain. Furthermore, emerging research shows that 6′-SL may help support the infant’s immune system by acting as a receptor decoy for various intestinal pathogens in cell culture studies (Facinelli, 2019; Simon, 1997; Kim, 2019; Duska-McEwen, 2014; Hester, 2013; Laucirica, 2017) and supporting growth of beneficial bacteria in the gut.

LNT HMO represents the acetylated category of HMOs. Emerging research shows that LNT may help support the infant’s immune system by acting as a receptor decoy for various intestinal pathogens in cell culture studies (El-Hawiet, 2015; Lin, 2017; Jantscher-Krenn, 2012) and supporting growth of beneficial bacteria in the gut.

Three of the 5 HMOs are thought to benefit brain development. 3′-SL and 6′-SL contain sialic acid, which is an important building block for the developing brain (Lis-Kuberka, 2019). Clinical evidence from breastfeeding studies shows positive associations between 2′-FL and cognitive development through 24 months of age (Oliveros, 2021; Berger, 2020).

Emerging research shows that all 5 HMOs may help support the infant’s immune system by acting as a receptor decoy for various intestinal pathogens in cell culture studies and supporting growth of beneficial bacteria in the gut. Additionally, HMOs play a role in balancing the immune response.

Preclinical research shows that the 5 HMOs help support growth of beneficial gut bacteria. Having a variety of HMOs that support the growth of beneficial bacteria may help support a healthy immune system.

Both represent the acetylated category of HMOs. However, in human breast milk, LNT is more widely represented.

HMOs that are available in infant formula are not organic.

Preterm infants consume breast milk that contains HMOs; however, 2′-FL, 3-FL, LNT, 3′-SL, and 6′-SL HMOs are currently not available in preterm formulas. There are many benefits associated with HMOs; therefore, this will remain an active area of research.

HMOs are immune-nourishing prebiotics, and HMOs added to infant formula are structurally identical to those in human milk. Other prebiotics such as GOS and FOS are not structurally identical to those in human milk. Research indicates these other prebiotics do not function the same way as HMOs due to their structures. Only HMOs have been found in the circulation of infants. Fucose from 2'-FL and 3-FL and sialic acid from 3'-SL and 6'-SL may play a role in brain development.