The special sugars in breast milk

Breast milk is often called nature’s superfood, but its abilities go far beyond nutrition. Hidden inside this liquid gold is a powerful collection of special sugars with secret superpowers that shape and strengthen a baby’s gut microbiome 

What exactly is a HMO? 

Breast milk contains an abundance of special sugars called human milk oligosaccharides (HMOs), which serve as food for beneficial gut bacteria. Unlike typical sugars, HMOs are largely indigestible by the baby and have little impact on energy. Instead, certain beneficial bacteria, such as strains of Bifidobacteria, can break them down. This unique relationship allows HMOs to play a functional role in infant health - strengthening the immune system, supporting the gut barrier and helping to prevent infections.

Within breast milk, there are over 200 structures of HMOs which can be broadly categorised into three main segments; neutral non-fucosylated, neutral fucosylated and sialylated (Jackson et al., 2022). The concentration of these structures can vary significantly depending on the genetic make-up of the mother and the lactation stage of the baby, with colostrum having the highest abundance of HMOs. 

What role do they play in gut health?

Inside the gut microbiome is a mixture of good and bad bacteria which contribute to our overall wellbeing, keeping these communities balanced helps fight disease and harmful bacteria. As adults, we can nourish our beneficial gut bacteria by eating fermented foods, maintaining a fibre-rich diet, or taking prebiotics. Babies, however, rely entirely on milk for nutrition during their first months of life. Fortunately, nature has adapted to give them the best possible start, with breast milk containing an abundance of special sugars with hidden superpowers, seeding the infant gut.

HMOs act as nature’s own prebiotic, entering the infant gut and seeking out the beneficial bacteria.

The beneficial bacteria consume these HMOs through a fermentation process, producing short-chain fatty acids which strengthen the gut barrier. When beneficial bacteria, such Bifidobacteria are nourished, they begin to flourish, outnumbering the harmful bacteria which ultimately creates a healthier gut environment. 

HMOs can also bind to harmful bacteria such as pathogens which prevents them from taking hold within the infant gut (Walsh et al., 2020). When harmful bacteria are unable to attach to the gut lining, they fail to colonise, thus acting as a preventative natural medicine for infection. HMOs also help train the infant immune system as this process of selective feeding trains the gut on how to identify and attack harmful infection-creating bacteria, creating a foundation for lifelong health (Castanys-Munaz et al., 2016). 

How do I ensure my baby gets all the HMOs they need? 

If you are breastfeeding your baby, they will automatically be provided with all of the special sugars that their developing gut needs. Breast milk is variable and many studies have shown its ability to adapt to your baby’s changing needs. If breastfeeding isn’t possible or is only partial, some infant formulas now include specific HMOs such as 2’-fucosyllactose (2’-FL) or lacto-N-neotetraose (LNnT), which are among the most common found in breast milk. These can help mimic some of breast milk’s prebiotic effects, though not its full complexity. You can also support your baby’s gut health by:

• Feeding expressed milk as soon as possible after pumping to preserve beneficial components.

• Avoiding unnecessary antibiotics early in life, when possible.

• Discussing with your healthcare provider whether HMO-enriched formulas or probiotic supplements are suitable for your baby.

  
  

Every baby’s situation is different - what matters most is finding a feeding approach that works for both you and your baby, while supporting their overall wellbeing.

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Further Reading: 

Castanys-Munaz, e., Martin, M & Vazquez, E. (2016). Building a beneficial microbiome from birth. Advances in Nutrition.

Jackson, P., Wijeyesekera, A & Rastall, R. (2022). Determining the metabolic fate of human milk oligosaccharides: it may just be more complex than you think? Gut Microbiome.

Walsh, C., Lane, J., Van Sinderen, D & Hickey, R. (2020). Human milk oligosaccharides: Shaping the infant gut microbiota and supporting health. J Funct Foods.