Human Milk Oligosaccharides
The building blocks of a healthy start
Hard to pronounce, easy to appreciate — Human Milk Oligosaccharides, or HMOs, are reshaping early-life nutrition. And beyond.
Not long ago, scientists discovered how dependent we are on the trillions of microbes that live in, on and all around us. And the gut microbiome is instrumental in supporting an infant’s development after birth.
Did you know the main function of human milk oligosaccharides (HMOs) is to nourish the child’s microbiome and guide its development? They’re the third largest component of breast milk, after lactose and fat. It’s a wonder that nature has evolved to optimize benefits from the microbiome.
While breast milk contains over 200 different HMOs, just five of them make up roughly 30–50% of the total volume — enough to make a measurable difference in gut health and beyond.
“Helping Microbiomes Optimally”
HMO could almost stand for “Helping Microbiomes Optimally.” They act as tiny gardeners tending the infant’s immature gut. Indigestible by the baby, HMOs travel intact through the digestive system, selectively feeding beneficial gut bacteria while keeping harmful microbes at bay. In essence, they act as prebiotics for probiotics — helping build and cultivate a balanced, resilient microbiome.
But there’s more. Studies increasingly show that the gut communicates directly with the brain through what scientists call the gut-brain axis, influencing cognition, behavior, and overall wellbeing. By supporting the growth of beneficial bacteria, HMOs help shape this early communication network, highlighting their impact on both gut and brain development.
In short, HMOs are multitasking behind the scenes to give infants a strong start in life.
Prebiotics and probiotics play different roles in gut health
Together, they help support digestion, metabolism and overall health.
Fibers that feed beneficial gut microbes.
Live beneficial microbes added through foods or supplements.
What is the gut-brain axis?
The gut (your gut microbiome) communicates with the brain, linking your physical and mental wellbeing. It’s why you can feel ‘butterflies’ when you’re excited or notice changes in digestion when you are nervous about an exam.
Eating a broad variety of foods supports a diverse group of microbes, helping them stay balanced and active to keep you healthy and happy.
Bringing infant formula closer to breast milk
Breast milk provides the best start in life, packed with so many important nutrients and other special components in a combination that no other food provides for the most precious and vulnerable - newborn infants and young children.
But not all infants can be breastfed and benefit from this. Globally, only 48% of babies under six months are exclusively breastfed. For these families, advances in science have made it possible to bring some of the unique benefits of human milk into infant formula, helping make it closer to nature’s own recipe in composition and benefits.
Through precision fermentation, a process where an engineered microorganism is used to manufacture the HMO, researchers can now produce the five most abundant HMOs that constitute up to 50% of all HMOs in breast milk. These five HMOs go by the names of 2’-FL, 3-FL, LNT, 3’-SL, and 6’-SL and each offers specific documented effects.
When added to infant formula, fermentation produced HMOs mirror their natural counterparts in structure and function, thus narrowing the gap between formula and nature’s blueprint.
Quick HMO facts
unique HMOs have been identified in breast milk
HMOs account for up to 50% of the total HMO content
HMOs are indigestible by the baby — they serve as prebiotics.
Why it matters
This advancement goes beyond science — it affects real-life choices, since parents aren’t just buying formula. They’re investing in early-life health and development.
Research increasingly shows that establishing a healthy gut microbiome in the first 1,000 days of life not only supports a strong start, but also shapes lifelong health outcomes – including reducing the risk of allergies, metabolic conditions, and even cognitive delays. HMOs are at the heart of this “first window” of opportunity.
This is evident in the penetration of HMOs in infant formula, which reached 29% globally in 2025 and continues to rise, both in terms of the number of products enriched and the concentration levels of HMOs added.
What the future holds
But the story doesn’t end there. We are at a remarkable moment in the history of HMOs and other human milk components. The science is advancing rapidly, revealing not only how these molecules work at a deep biological level but also how we can apply them across life stages and health outcomes.
An exciting area is synbiotics — synergistic formulations that pair beneficial bacteria (probiotics) with the HMOs that feed them (prebiotics), enhancing gut health, supporting immunity, and optimizing the gut microbiome.
With HMOs now produced at scale and increasingly accessible for research use, scientists can explore their effects in unprecedented ways. This enables detailed investigation of their concentrations, structures, and functional impacts—work that was previously unfeasible. Large datasets and advanced analytics, including AI, are accelerating these discoveries, helping to link specific HMOs to biological effects and uncover new opportunities for developing therapeutic solutions for people of all ages.
Before our very eyes, one of nature’s oldest systems is becoming a new frontier in human health.
HMO key functions
Start strong, stay strong
We’re at the forefront of human milk oligosaccharide exploration. Already, we know they support brain1, gut, immune2 and microbiome development3. Plus they protect from undesirable microbes.
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1 Olivero et al. Human Milk Levels of 2´-Fucosyllactose and 6´-Sialyllactose are Positively Associated with Infant Neurodevelopment and are Not Impacted by Maternal BMI or Diabetic Status. (2021). Nutrition & Food Science. Berger et al., Human milk oligosaccharide 2'-fucosyllactose links feedings at 1 month to cognitive development at 24 months in infants of normal and overweight mothers. PLoS One. 2020 Feb 12;15(2):e0228323.
2 Ayechu-Muruzabal et al., Diversity of Human Milk Oligosaccharides and Effects on Early Life Immune Development. Front Pediatr. 2018 Sep 10;6:239. Zuurveld et al, Immunomodulation by Human Milk Oligosaccharides: The Potential Role in Prevention of Allergic Diseases. Front Immunol. 2020 May 7;11:801.
3 Gotoh et al., Sharing of human milk oligosaccharides degradants within bifidobacterial communities in faecal cultures supplemented with Bifidobacterium bifidum. Sci Rep. 2018 Sep 18;8(1):13958. Kostopoulos et al., Akkermansia muciniphila uses human milk oligosaccharides to thrive in the early life conditions in vitro. Sci Rep. 2020 Aug 31;10(1):14330.