From gut to brain:
the health benefits of HMOs

Human milk oligosaccharides are among the most studied bioactive carbohydrates in nutrition science, with a growing body of publicly available research pointing to benefits across four key health areas — gut health, immunity, metabolic health, and brain function.

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THE SCIENCE BEHIND THE BENEFITS

What makes HMOs uniquely bioactive?

HMOs are not simply prebiotics. They are structurally complex, multifunctional bioactive carbohydrates, each with a distinct mode of action that extends well beyond the gut. Their biological activity spans several interconnected systems: shaping the microbiome with precision, reinforcing the gut barrier, modulating immune responses, and interacting directly with host cells and pathogens. A single HMO structure may act as a precision prebiotic, a decoy receptor for pathogens, and an immune modulator, while also serving as a source of bioactive metabolites. Together, these mechanisms make HMOs one of the most scientifically compelling bioactive ingredient classes available to formulators today.

Health benefits for immunity

HMOs interact directly with the immune system through multiple complementary mechanisms, influencing the maturation, activity, and differentiation of a broad range of immune cells. Emerging evidence suggests they may help maintain a balanced immune response without over-stimulating the immune system, with potential implications extending to inflammatory conditions beyond the gut.

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HMOs have been shown to interact with innate and adaptive immune cells, including dendritic cells, natural killer cells, neutrophils, T cells, and B cells, by binding to lectin receptors on their surface 1. Preclinical research suggests that (fucosylated and sialylated) HMOs can stimulate dendritic cell cytokine secretion, influencing both pro- and anti-inflammatory immune responses 1,2. HMOs also appear to dampen the ability of neutrophils to migrate to sites of inflammation, while simultaneously increasing their phagocytic activity, suggesting a role in fine-tuning rather than broadly suppressing immune function 1.

In a pig model, a four-HMO blend was shown to double natural killer cell populations compared to formula without HMOs 3. HMOs have also been shown to increase immunoglobulin A secretion, further supporting mucosal immune defence 1. Clinical data confirm that HMO supplementation reduces the incidence of bronchitis and lower respiratory tract infections and otitis media 4. Extending this anti-inflammatory potential, preclinical studies and a human pilot study suggest that specific HMOs may help reduce joint inflammation and support bone health, pointing to a broader role in modulating systemic inflammatory processes 5,6.

  • 1 Slater A.S. (2025). Interactions of human milk oligosaccharides with the immune system. Frontiers in Immunology, 15:1523829. doi: 10.3389/fimmu.2024.1523829.
  • 2 Ayechu-Muruzabal V. et al. (2020). Exposure of intestinal epithelial cells to 2'-fucosyllactose and CpG enhances galectin release and instructs dendritic cells to drive Th1 and regulatory-type immune development. Biomolecules, 10(5), 784. doi: 10.3390/biom10050784.
  • 3 Comstock S.S. et al. (2017). Dietary human milk oligosaccharides but not prebiotic oligosaccharides increase circulating natural killer cell and mesenteric lymph node memory T cell populations in noninfected and rotavirus-infected neonatal piglets. Journal of Nutrition, 147(6), 1041-1047.
  • 4 Puccio G. et al. (2017). Effects of infant formula with human milk oligosaccharides on growth and morbidity. Journal of Pediatric Gastroenterology and Nutrition, 64(4), 624-631.
  • 5 Park E.J. et al. (2024). Effects of 3'-sialyllactose on symptom improvement in patients with knee osteoarthritis: a randomised pilot study. Nutrients, 16(19), 3410. doi: 10.3390/nu16193410.
  • 6 Baek A. et al. (2024). 3'-Sialyllactose alleviates bone loss by regulating bone homeostasis. Communications Biology, 7(1):110. doi: 10.1038/s42003-024-05796-4.

Health benefits
for metabolic balancing

The link between gut microbiome composition and metabolic health is increasingly well-established. Emerging evidence suggests that HMOs, through their prebiotic activity and the metabolites they generate, may play a role in supporting metabolic balance, weight management, and countering diet-induced metabolic inflammation.

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The gut microbiome is now widely recognised as a key regulator of host metabolism, influencing energy balance, fat storage, insulin sensitivity, and appetite regulation 1. Emerging evidence suggests that HMOs may support gut barrier integrity, the impairment of which is increasingly associated with systemic inflammation and obesity-related metabolic dysfunction, pointing to a possible indirect role in metabolic health through gut barrier modulation 2.

Emerging preclinical evidence further suggests that HMOs may help counteract diet-induced increases in metabolic inflammation, a key driver of obesity-related metabolic dysfunction, potentially through their immune-modulating properties 2. While breastfeeding has been associated with a reduced risk of childhood obesity, the specific contribution of HMOs to this effect has not yet been clearly established, yet their known mechanisms make them plausible modulators of metabolic health and obesity risk 2. HMO supplementation for metabolic health remains an emerging and under-explored area, with preclinical results yet to be consistently translated into clinical outcomes in humans.

  • 1 Kumari M., Kozyrskyj A.L. (2017). Gut microbial metabolism defines host metabolism: an emerging perspective in obesity and allergic inflammation. Obesity Reviews, 18(1), 18-31.
  • 2 Young K. et al. (2026). Human milk oligosaccharide supplementation for metabolic health and obesity: potential mechanisms, current evidence, and research priorities. World Journal of Pediatrics. doi: 10.1007/s12519-026-01025-6. PMID: 41874892.

Health benefits for gut health

The gut is where HMOs exert their most direct and best-documented biological activity. Largely resistant to upper gut digestion, HMOs arrive intact in the large intestine, where they act as precision prebiotics, selectively promoting beneficial microbes while not supporting the growth of pathogens.

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HMO degradation by Bifidobacterium indirectly supports other beneficial bacteria such as Lactobacillus species through cross-feeding mechanisms, amplifying the positive impact on overall microbiome composition. Fermentation of HMOs produces beneficial short-chain fatty acids, most notably acetate, propionate, and butyrate, which promote intestinal barrier integrity, limit inflammation, serve as energy substrates for intestinal epithelial cells, and modulate immune responses 1,2.

Clinical intervention trials have demonstrated that adding HMOs to infant formula brings the gut microbiota of formula-fed infants closer to that of breastfed infants 3. Beyond microbiome support, HMOs can enhance intestinal barrier function through multiple mechanisms, including promoting intestinal maturation, reducing intestinal permeability, and supporting the mucus layer 4,2. Preclinical studies demonstrate that HMOs positively influence gut maturation and reduce permeability by modulating glycocalyx components, inducing mucin expression, and suppressing pro-inflammatory cytokines 5.

  • 1 Fusco W. et al. (2023). Short-chain fatty-acid-producing bacteria: key components of the human gut microbiota. Nutrients, 15(9), 2211.
  • 2 Perdijk O. et al. (2019). Sialyllactose and Galactooligosaccharides Promote Epithelial Barrier Functioning and Distinctly Modulate Microbiota Composition and Short Chain Fatty Acid Production In Vitro. Frontiers in Immunology, 10, 94.
  • 3 Puccio G. et al. (2017). Effects of infant formula with human milk oligosaccharides on growth and morbidity. Journal of Pediatric Gastroenterology and Nutrition, 64(4), 624-631.
  • 4 Holscher H.D. et al. (2014). Human milk oligosaccharides influence maturation of human intestinal Caco-2Bbe and HT-29 cells. Journal of Nutrition, 144(5), 586-591.
  • 5 Kong et al. (2019). Modulation of intestinal epithelial glycocalyx development by human milk oligosaccharides and non-digestible carbohydrates. Molecular Nutrition & Food Research, 63(17), e1900303.

Health benefits for brain health

Of all HMO health benefit areas, brain and cognitive development is the most rapidly evolving in terms of new scientific evidence. Multiple mechanisms have been proposed through which HMOs may support early brain development, with promising findings from preclinical and observational research.

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Sialylated HMOs serve as a neonatal dietary source of sialic acid, a key building block of brain gangliosides — complex lipids critical for neuronal connectivity and brain function. Preclinical studies in piglets supplemented with sialylated HMOs found ganglioside sialic acid concentrations in key brain regions enriched by 10 to 15% compared to controls 1. Rodent studies further suggest that fucosylated HMOs such as 2'FL may support learning and memory through the gut-brain axis, with vagus nerve signalling identified as a key mediating pathway 2. Complementing these findings, a mouse cross-fostering study that selectively deprived pups of 6'SL during lactation, found that early-life 6'SL deficiency impaired attention, perseveration, and memory in adulthood, pointing to a specific and lactation-dependent role for this sialylated HMO in cognitive programming 3.

Observational studies in mother-infant pairs report positive associations between milk concentrations of specific HMOs and infant cognitive, language, and motor development scores 4,5. While this evidence is associational rather than causal, it is supported by a growing number of independent observational cohorts, though with some variation in findings, and underpinned by plausible biological mechanisms, making brain and cognitive development a compelling and active area of HMO research. Clinical intervention studies are currently underway to further investigate the role of HMOs in cognitive development.

  • 1 Jacobi S.K. et al. (2016). Dietary isomers of sialyllactose increase ganglioside sialic acid concentrations in the corpus callosum and cerebellum. Journal of Nutrition, 146(2), 200-208.
  • 2 Vazquez et al. (2016). Dietary 2'-Fucosyllactose Enhances Operant Conditioning and Long-Term Potentiation via Gut-Brain Communication through the Vagus Nerve in Rodents. PLOS ONE, 11(11), e0166070.
  • 3 Hauser J. et al. (2021). Sialylated human milk oligosaccharides program cognitive development through a non-genomic transmission mode. Molecular Psychiatry, 26(7), 2854-2871.
  • 4 Cho S. et al. (2021). Human milk 3'-sialyllactose is positively associated with language development during infancy. American Journal of Clinical Nutrition, 114(2), 588-597.
  • 5 Rajhans P. et al. (2023). The role of human milk oligosaccharides in myelination, socio-emotional and language development. Nutrients, 15(21), 4624.

Health benefits for sports nutrition

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Health benefits for women’s health

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Health benefits for microbiome support

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Innovation is at the heart of Inbiose. We continuously invest in advancing the science of bioactive carbohydrates, exploring new health applications, refining our understanding of mechanisms of action, and expanding the evidence base that supports our ingredients across nutritional markets.

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Inbiose offers more than ingredients. Our scientific team provides dedicated support across the full health application development journey, from experimental design through to data analysis and bioinformatics support. We support in building your evidence base for novel nutritional concepts.

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If you are exploring the health potential of milk oligosaccharides for a specific application, we invite you to start a conversation with our team. The most meaningful innovations are built in collaboration.

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