Prebiotic Type Spotlight: Human Milk Oligosaccharides (HMOs)

Last Updated November 2026

Each edition of GPA’s Prebiotic Spotlight focuses on a specific prebiotic type to raise awareness around the prebiotic itself, its sources, any notable and/or recent research, and how it is used in the marketplace. This updated edition highlights human milk oligosaccharides (HMOs), which GPA’s Standards of Evidence classify as an Established prebiotic, the category reserved for ingredients supported by robust, repeatable human randomized controlled trials linking microbiota modulation to health benefits.

Overview

HMOs are complex, non-digestible carbohydrates and, after lactose and lipids, the third most abundant solid component of human milk (Wiciński et al., 2020; Zhang et al., 2021), present at roughly 5–15 g/L (Picaud et al., 2025). Human milk contains more than 200 distinct oligosaccharides (Jacobs et al., 2023). They are commonly grouped as fucosylated HMOs, such as 2′-fucosyllactose (2′-FL) and 3-fucosyllactose (3-FL); neutral, non-fucosylated HMOs, such as lacto-N-tetraose (LNT) and lacto-N-neotetraose (LNnT); and sialylated HMOs, such as 3′-sialyllactose (3′-SL) and 6′-sialyllactose (6′-SL). HMO profiles differ between mothers: milk from mothers with “secretor” status contains 2′-FL and more total HMOs, while milk from non-secretors largely lacks 2′-FL (Samarra et al., 2026).

Because infants cannot digest them, HMOs reach the colon largely intact, where they act as prebiotics that support the growth of beneficial bacteria, particularly Bifidobacterium (Zhang et al., 2021). Supplementation studies show the same bifidogenic effect in adults (Elison et al., 2016). HMOs also have anti-adhesive properties that help block pathogens from attaching to the gut lining, and they help modulate the developing immune system (Wiciński et al., 2020). Cow’s milk, the base of most infant formula, contains only about 0.05 g/L of oligosaccharides, a gap that has driven the commercial production of HMOs (Picaud et al., 2025). Manufactured HMOs are structurally identical to those in human milk and are now often called human-identical milk oligosaccharides (HiMOs) (Hojsak et al., 2026). They have been studied in infants, children and adults (Schönknecht et al., 2023).

Benefit Areas

Research on HMOs has expanded well beyond infant formula, with recent evidence highlighting benefits in the following areas:

• Infant gut microbiota: In a randomized clinical trial, infants fed a GOS/FOS-containing formula with added 2′-FL had Bifidobacterium levels similar to those of breastfed infants, and the authors reported a stronger bifidogenic effect than with the same formula without 2′-FL (Lazarini et al., 2025).

• Infant immune development: In a randomized controlled trial, a formula with six HMOs and two probiotics shifted immune cell networks and reduced the persistence of a T-helper 2 immune bias, following the pattern seen in breastfed infants (Rashid et al., 2026).

• Respiratory health in infancy: In a randomized multicenter trial, infants fed formula with 2′-FL and LNnT had fewer parent-reported cases of bronchitis and lower respiratory tract infection, and less antibiotic use, through 12 months (Puccio et al., 2017).

• Infant digestive comfort and skin: In an open-label study of 338 infants, rates of infantile colic and atopic dermatitis on 2′-FL-supplemented formula trended lower than on standard formula and closer to breastfed infants, although the colic difference was not statistically significant (Yang et al., 2025).

• Healthy aging: In a randomized controlled trial of older adults, 2′-FL increased Bifidobacterium and raised HDL cholesterol and the metabolic hormone FGF21 (Carter et al., 2025).

• Microbial resilience in adults: In a randomized controlled trial, 2′-FL taken after an antibiotic course temporarily improved gut microbiome recovery and lowered the inflammatory marker IL-6 (Vliex et al., 2025).

• Joint health: In a manufacturer-funded randomized pilot study, adults with knee osteoarthritis who took 3′-SL for 12 weeks reported less pain and better physical function than at the start of the study; comparisons with placebo were not reported in the abstract (Park et al., 2024).

• Gut barrier and infection (preclinical): In adult mice, 2′-FL increased Bifidobacterium and Lactobacillus and protected against colitis, partly through a metabolite produced by B. infantis (Schalich et al., 2024). In human intestinal tissue models from adults and children, 2′-FL reduced replication of a globally dominant norovirus strain (Patil et al., 2025).

Sources

HMOs occur naturally only in human milk; commercial HMOs are manufactured to be chemically and structurally identical to those found in breast milk. Microbial fermentation is the main production route, and engineered Escherichia coli has emerged as the preferred production platform (Palur et al., 2023). Researchers are also engineering yeasts such as Saccharomyces cerevisiae and Pichia pastoris to produce HMOs, including LNnT (Mund et al., 2025; Yang et al., 2024), and engineered plants have recently been shown to produce a range of HMOs, pointing to a possible photosynthetic production route (Barnum et al., 2024).

The number of HMOs cleared for use has grown since 2023. In the European Union, the European Food Safety Authority (EFSA) has concluded that 2′-FL and 3′-SL made with new production strains are safe as novel foods (EFSA NDA Panel, 2023a, 2023b), as are a lacto-N-fucopentaose I/2′-FL mixture (EFSA NDA Panel, 2023c), extended uses of 3-FL (EFSA NDA Panel, 2025) and lacto-N-triose II (EFSA NDA Panel, 2026). In China, the National Health Commission approved 2′-FL and LNnT as nutrition fortifiers in October 2023 (National Health Commission, 2023), and approved 3′-SL in February 2026 for infant formula, follow-on formula, children’s formulated milk powder and foods for special medical purposes for infants (National Health Commission, 2026; dsm-firmenich, 2026). HMO supplier dsm-firmenich has also announced approvals of 2′-FL/difucosyllactose, LNT, 3′-SL and 6′-SL for infant and children’s formulas in Malaysia and Thailand (dsm-firmenich, 2026).

Dose Range

The following dose ranges have been established through human clinical trials and scientific reviews:

• Adults: 5–20 g/day (Elison et al., 2016; Jacobs et al., 2023; Wiciński et al., 2020; Schönknecht et al., 2023).

• Infant formula: 1.0 g/L 2′-FL combined with 0.5 g/L LNnT, fed from the first two weeks of life to 6 months, was shown to be safe, well tolerated and supportive of age-appropriate growth in a randomized multicenter trial (Puccio et al., 2017).

Recent Research

HMO research has grown quickly since GPA’s last HMO spotlight in 2023. A PubMed search for HMO-related terms returns more than 1,000 publications from August 2023 to early November 2026 (PubMed, 2026). ClinicalTrials.gov lists roughly a dozen active interventional studies involving HMOs, testing them in infant and toddler formulas, in preterm infants, for respiratory and gastrointestinal infection prevention, alongside antibiotics, and in healthy adults (ClinicalTrials.gov, 2026). Below are six recent studies that show where the science stands.

2′-FL in Healthy Older Adults

Aging is linked to changes in the gut microbiome and immune function, and researchers tested whether 2′-FL could help. In this 6-week randomized controlled trial, 89 healthy older adults (average age 67) took 1 g/day of 2′-FL, 5 g/day of 2′-FL, or a placebo (Carter et al., 2025).

The main outcome, a change in immune cell responses, did not differ between groups. 2′-FL did increase Bifidobacterium in the gut and raised blood levels of insulin, HDL cholesterol and FGF21, a hormone involved in metabolism. Participants whose Bifidobacterium rose the most, the “responders,” showed further metabolic changes and scored better on a test of visual memory. Non-responders were more likely to have little or no Bifidobacterium at the start, a reminder that a person’s baseline microbiome shapes how they respond to a prebiotic. Several authors are employees of Abbott, which makes HMO-containing products.

Key Takeaways:

• In 89 older adults, 2′-FL increased Bifidobacterium and raised HDL cholesterol and FGF21, though it did not change the main immune measure.

• People whose Bifidobacterium responded saw added metabolic changes and better visual-memory scores.

• Starting levels of Bifidobacterium helped predict who responded.

2′-FL in Ulcerative Colitis

HMOs are well studied in infants but much less so in adults with gut disease. This crossover trial gave 38 adults with mild-to-moderate ulcerative colitis 5 g/day of 2′-FL and a maltodextrin placebo for 28 days each, in random order with a washout between (Kennedy et al., 2026).

Standard clinical disease scores did not change, but participants reported better control of their disease while taking 2′-FL. 2′-FL raised Bifidobacterium abundance (effect size 4.4%, p < 0.001) and shifted stool metabolites in ways consistent with increased microbial carbohydrate fermentation. Age and baseline microbiota appeared to influence who responded. The authors declared no competing interests.

Key Takeaways:

• In 38 adults with mild-to-moderate ulcerative colitis, 5 g/day of 2′-FL for 28 days sharply increased Bifidobacterium.

• Clinical scores did not change, but participants reported better disease control.

• Larger, longer trials are needed to test whether these microbial changes translate into clinical benefit.

2′-FL, Oligofructose and Mood in Working Adults

The EFFICAD trial tested whether prebiotics could ease stress-related mood symptoms in a working population (Jackson et al., 2023). For 5 weeks, 92 healthy adults with mild-to-moderate anxiety or depression took oligofructose (8 g/day), 2′-FL (2 g/day), the two combined, or a maltodextrin comparator.

Oligofructose and the combination increased Bifidobacterium, Bacteroides, Roseburia and Faecalibacterium prausnitzii, while 2′-FL alone produced more variable microbial changes. All three active groups improved on depression, anxiety and mood scores and on the cortisol awakening response, a marker of stress. The oligofructose-containing groups outperformed 2′-FL alone on several mood measures.

Key Takeaways:

• In 92 working adults with mild-to-moderate anxiety or depression, oligofructose, 2′-FL and their combination all improved mood and stress measures over 5 weeks.

• Oligofructose alone or combined with 2′-FL produced stronger microbiome and mood effects than 2′-FL alone.

• The results support further study of prebiotics, including HMOs, for the gut-brain axis in adults.

A 2′-FL Synbiotic for Toddlers

In this multicenter, double-blind trial in China, 390 healthy toddlers aged 1 to 3 were randomized to a synbiotic of 1.0 g/day 2′-FL with B. infantis R0033 and B. bifidum R0071 (1.5 billion CFU each), the same probiotics alone, or a placebo for 12 weeks, then followed for another 12 weeks (Chen et al., 2026). The three-arm design makes it possible to see what 2′-FL added beyond the probiotics.

Compared with placebo, the synbiotic reduced upper respiratory tract infections over 24 weeks from 85.4% to 55.4% of children, and also lowered rates of pneumonia, diarrhea and eczema. Probiotics alone reduced only eczema. The synbiotic enriched Bifidobacterium species able to use HMOs, lowered fecal calprotectin (a gut inflammation marker) and raised secretory IgA, an antibody that protects the gut lining. The effects are large for a nutritional intervention and need to be confirmed in other populations. A correction published in September 2026 fixed the reported probiotic dose; the 2′-FL dose and results were unchanged.

Key Takeaways:

• In 390 toddlers, 2′-FL with two Bifidobacterium strains reduced respiratory infections, pneumonia, diarrhea and eczema compared with placebo.

• Probiotics alone reduced only eczema, suggesting 2′-FL contributed to the broader benefits.

• The size of the effects calls for confirmation in independent trials.

A Six-HMO Formula and Infant Gut and Immune Development

This randomized trial tested a partially hydrolyzed infant formula containing six HMOs plus two probiotics (B. infantis LMG11588 and B. lactis CNCM I-3446) against the same formula without them, with a breastfed group as a reference (Picaud et al., 2025). Through 4 months, 313 infants were analyzed: 118 on the HMO formula, 114 on the control formula and 81 breastfed.

Weight gain with the HMO formula was non-inferior to the control formula, tolerance and stool patterns were similar, and Bifidobacterium abundance was significantly higher at 3 months. A companion analysis found that the formula changed infants’ immune cell networks and reduced the persistence of a T-helper 2 immune bias, bringing them closer to breastfed infants; in mouse models, the same synbiotic reduced the severity of respiratory infection (Rashid et al., 2026). The trial was sponsored by Nestlé.

Key Takeaways:

• In a randomized trial, a formula with six HMOs and two probiotics supported growth comparable to the control formula and was well tolerated.

• It increased Bifidobacterium and moved immune development toward the breastfed pattern.

• The trial is industry-sponsored and continues to 15 months, so longer-term results are still to come.

Where the Infant Evidence Stands

Independent reviews published in 2026 offer a measured view of the infant trials. Researchers reviewing 12 randomized trials of manufactured HMOs found that every trial in healthy infants showed growth and tolerability comparable to control formula, but results on illness were mixed and all were too small to test more serious illness outcomes (Shivakoti et al., 2026). A position paper from the European Society for Paediatric Gastroenterology, Hepatology and Nutrition (ESPGHAN) reached a similar conclusion: HMO-supplemented formulas raise no safety concerns, but the evidence is not yet strong enough for a recommendation on specific health outcomes (Dinleyici et al., 2026; Hojsak et al., 2026).

Key Takeaways:

• Manufactured HMOs in infant formula are consistently safe and support normal growth.

• Evidence for reduced illness is promising but mixed, and larger trials powered for health outcomes are needed.

• ESPGHAN notes that the lack of firm conclusions reflects differences between trials rather than evidence of no effect.