Human Milk Oligosaccharides (HMOs)

Also called HMOs, 2'-fucosyllactose, 2'-FL, lacto-N-neotetraose, LNnT, human-identical milk oligosaccharides.

Best grade C across 8 graded outcomes Other Last checked Oct 21, 2026

The short answer

From 12 sources

Human milk oligosaccharides such as 2'-FL feed bifidobacteria. In adult trials they mostly raised gut Bifidobacterium and were well tolerated up to 20 g/day, but did not improve IBS symptoms, and a trial in older adults missed its immune endpoint. In infant formula they supported normal growth; a 2026 review found limited evidence of further health benefits.

Every graded outcome on this page

8 rows · line = participants

Grade CInfant growth, tolerance and illness reportsInfant healthn 175
Grade CGut symptoms and stool bacteriaGut bacterian 100
Grade CImmune cytokine response (primary) and microbiomeAgingn 89
Grade CIBS symptom severity and stool bifidobacteriaIBSn 60
Grade DMood and anxiety scores in working adultsMoodn 92
Grade DBody fat and lean mass during a diet-and-walking weight-loss programBody compositionn 41
Grade DClinical indices and patient-reported control in ulcerative colitisColitisn 38
Grade DGut microbiome recovery after an antibiotic courseAfter antibioticsn 37
5 more graded outcomes, in the evidence chapter

Key facts

What they are: Complex sugars unique to human milk; supplements and formulas use lab-made versions, mainly 2'-FL and LNnT^1,6
Gut bacteria: Raised Bifidobacterium in healthy adults, older adults, IBS and ulcerative colitis trials^1,2,3,4
IBS: 5 or 10 g/day for 4 weeks did not change IBS symptom severity versus placebo²
Tolerance: Up to 20 g/day was well tolerated for 2 weeks in 100 healthy adults¹
Infant formula: A 2026 review of 12 trials found HMO formulas support normal growth, with mixed results for illness; a 2026 ESPGHAN technical review of 6 RCTs could draw no clear conclusion on infections and raised no safety concerns^6,11
Safety across trials: A 2023 systematic review of 26 trials of manufactured HMOs in infants, children and adults found them consistently safe and well tolerated (all authors employed by Chr. Hansen)¹²

What it is

Human milk oligosaccharides are sugars found in breast milk that feed infant gut bacteria; supplements use lab-made 2'-FL and LNnT.

How it works

Proposed

HMOs pass undigested to the colon, where bifidobacteria and some other bacteria ferment them. In human trials this consistently raised stool Bifidobacterium and changed fecal metabolites. Effects on immune function and the gut barrier come mainly from observational and mechanistic studies, as a 2026 review noted.^1,4,6

Forms, side by side

2 forms named in our sources. The rest show what our data holds, and say plainly where it holds nothing yet.

Human Milk Oligosaccharides (HMOs) forms compared

2 forms

Human Milk Oligosaccharides (HMOs) forms compared: 2 forms by 3 attributes. Empty cells are labelled No data yet, or Not graded in the evidence row.
2 forms	2'-fucosyllactose (2'-FL)	2'-FL with lacto-N-neotetraose (LNnT)
Absorption in people	Mostly reaches the colon, where gut bacteria use it; stool Bifidobacterium rose in adult trials.^1,3,4	No head-to-head human data on absorption; acts as a prebiotic in the gut.²
GI tolerance	Well tolerated at up to 20 g/day for 2 weeks in healthy adults.¹	10 g/day for 4 weeks did not worsen symptoms in IBS.²
Studied for	Gut bacteria, older adults, ulcerative colitis, infant formula	IBS and infant formula

2'-fucosyllactose (2'-FL)
Absorption in people
Mostly reaches the colon, where gut bacteria use it; stool Bifidobacterium rose in adult trials.^1,3,4
GI tolerance
Well tolerated at up to 20 g/day for 2 weeks in healthy adults.¹
Studied for
Gut bacteria, older adults, ulcerative colitis, infant formula
2'-FL with lacto-N-neotetraose (LNnT)
Absorption in people
No head-to-head human data on absorption; acts as a prebiotic in the gut.²
GI tolerance
10 g/day for 4 weeks did not worsen symptoms in IBS.²
Studied for
IBS and infant formula

What the human research says

Human trials only, one row per outcome. The form line shows what each trial actually tested. Grades follow our evidence-grading policy.

Trial map

8 graded outcomes, largest study first

8 graded outcomes: 3 improved, 5 mixed. The largest, a 2017 randomized trial of 175 people on infant growth, tolerance and illness reports, found an improvement.

By sizeTable

1Infant growth, tolerance and illness reports

Improved · Grade C · RCT, 175 people, 2017

Healthy formula-fed infants enrolled at 0 to 14 days (Italy and Belgium)

Dose, result and source

Every graded outcome on this page, largest study first
Outcome	Found	People	Study	Who was studied
Infant growth, tolerance and illness reports	Improved	175	Grade C · RCT, 2017	Healthy formula-fed infants enrolled at 0 to 14 days (Italy and Belgium)
Gut symptoms and stool bacteria	Improved	100	Grade C · RCT, 2016	Healthy adults (Denmark)
Mood and anxiety scores in working adults	Mixed	92	Grade D · RCT, 2023	Healthy working adults with mild-to-moderate anxiety and depression; 4 arms of 23
Immune cytokine response (primary) and microbiome	Mixed	89	Grade C · RCT, 2025	Healthy older adults, mean age 67 (USA)
IBS symptom severity and stool bifidobacteria	Mixed	60	Grade C · RCT, 2020	Adults with IBS (Rome IV), Sweden
Body fat and lean mass during a diet-and-walking weight-loss program	Improved	41	Grade D · RCT, 2024	Overweight, sedentary women and men starting a reduced-calorie diet and walking program
Clinical indices and patient-reported control in ulcerative colitis	Mixed	38	Grade D · Crossover RCT, 2026	Adults with mild-to-moderate ulcerative colitis (UK)
Gut microbiome recovery after an antibiotic course	Mixed	37	Grade D · RCT, 2025	Adults with overweight or obesity given oral vancomycin for 7 days before randomization

Every graded row

8 rows

Form tested

Showing 8 of 8 outcomes. Human trials only.

Grade CInfant growth, tolerance and illness reportsInfant healthImprovedRCT
n 175 · 2017

Improved Weight gain was non-inferior to standard formula. Parents reported less bronchitis (10.2% vs 27.6% by 12 months) and less antibiotic use (42.0% vs 60.9%) in the HMO group.

Design: RCT, n = 175, 2017
Population: Healthy formula-fed infants enrolled at 0 to 14 days (Italy and Belgium)
Form: Infant formula with 1.0 g/L 2'-FL and 0.5 g/L LNnT
Dose: In formula from birth to 6 months
Duration: 6 months, follow-up to 12 months
Source: Reference 5 · PubMed 28107288 (opens PubMed)

Grade CGut symptoms and stool bacteriaGut bacteriaImprovedRCT
n 100 · 2016

Improved Doses up to 20 g/day were well tolerated on a gastrointestinal symptom scale, with no dropouts. Bifidobacterium rose substantially in stool while Firmicutes and Proteobacteria fell.

Design: RCT, n = 100, 2016
Population: Healthy adults (Denmark)
Form: 2'-fucosyllactose (2'-FL) and/or lacto-N-neotetraose (LNnT), made by chemical synthesis
Dose: Various daily doses and mixes up to 20 g/day vs placebo
Duration: 2 weeks
Source: Reference 1 · PubMed 27719686 (opens PubMed)

Grade CImmune cytokine response (primary) and microbiomeAgingMixedRCT
n 89 · 2025

Mixed The primary endpoint, change in cytokine response, was not met. Gut Bifidobacterium rose, as did serum insulin, HDL cholesterol and FGF21; people whose Bifidobacterium rose did better on a visual memory test.

Design: RCT, n = 89, 2025
Population: Healthy older adults, mean age 67 (USA)
Form: 2'-fucosyllactose
Dose: Not stated in the abstract
Duration: 6 weeks
Source: Reference 3 · PubMed 40738103 (opens PubMed)

Grade CIBS symptom severity and stool bifidobacteriaIBSMixedRCT
n 60 · 2020

Mixed Symptom severity did not differ between groups at 4 or 8 weeks, and symptoms did not worsen. Stool bifidobacteria rose at 10 g/day at week 4 but not after stopping.

Design: RCT, n = 60, 2020
Population: Adults with IBS (Rome IV), Sweden
Form: 4:1 mix of 2'-FL and LNnT
Dose: 5 or 10 g/day vs glucose placebo
Duration: 4 weeks, then 4 weeks off
Source: Reference 2 · PubMed 32536023 (opens PubMed)

Grade DMood and anxiety scores in working adultsMoodMixedRCT
n 92 · 2023

Mixed Depression, anxiety and affect scores and the cortisol awakening response improved with oligofructose, 2'-FL and the combination, but oligofructose alone and the combination outperformed 2'-FL alone and maltodextrin on several mood measures. Bacterial changes with 2'-FL alone were highly variable.

Design: RCT, n = 92, 2023
Population: Healthy working adults with mild-to-moderate anxiety and depression; 4 arms of 23
Form: 2'-fucosyllactose alone or with oligofructose (inulin-type fructan)
Dose: 2 g/day 2'-FL (alone or with 8 g/day oligofructose) vs 10 g/day maltodextrin
Duration: 4 weeks after a 1-week run-in
Source: Reference 10 · PubMed 37657523 (opens PubMed)

Grade DBody fat and lean mass during a diet-and-walking weight-loss programBody compositionImprovedRCT
n 41 · 2024

Improved Weight fell similarly in both groups, but the 2'-FL group lost a larger share of body fat and less fat-free mass, with some favorable changes in fat oxidation and peak aerobic capacity. It was well tolerated, though bone mineral content fell slightly but significantly.

Design: RCT, n = 41, 2024
Population: Overweight, sedentary women and men starting a reduced-calorie diet and walking program
Form: 2'-fucosyllactose
Dose: 3 g/day vs placebo
Duration: 12 weeks
Source: Reference 7 · PubMed 39408354 (opens PubMed)

Grade DClinical indices and patient-reported control in ulcerative colitisColitisMixedCrossover RCT
n 38 · 2026

Mixed No clear effect on standard clinical indices; patient-reported disease control improved, and stool Bifidobacterium rose.

Design: Crossover RCT, n = 38, 2026
Population: Adults with mild-to-moderate ulcerative colitis (UK)
Form: 2'-fucosyllactose
Dose: Not stated in the abstract (vs maltodextrin)
Duration: 28 days per period
Source: Reference 4 · PubMed 42635599 (opens PubMed)

Grade DGut microbiome recovery after an antibiotic courseAfter antibioticsMixedRCT
n 37 · 2025

Mixed Microbial resilience improved more than with placebo after 2 weeks of 2'-FL, but the difference was gone by the end of the 8 weeks. Fasting IL-6 fell with 2'-FL; other metabolic effects were limited. 2'-FL did not increase gastrointestinal symptoms.

Design: RCT, n = 37, 2025
Population: Adults with overweight or obesity given oral vancomycin for 7 days before randomization
Form: 2'-fucosyllactose
Dose: 12 g/day (4 g three times daily, from the full text) vs maltodextrin
Duration: 8 weeks
Source: Reference 8 · PubMed 41243448 (opens PubMed)

What the numbers add up to

Each point is worked out from the data and the sources numbered on this page, with the arithmetic shown under it. It adds no new data and is not medical advice.

Bacteria change, symptoms mostly do not

The 2016 healthy-adult, 2020 IBS, 2025 older-adult and 2026 colitis trials each raised Bifidobacterium, but the IBS trial found no symptom change and the older-adult trial missed its immune endpoint.^1,2,3,4

Responders start with bifidobacteria

In older adults, people who lacked Bifidobacterium at the start were less likely to respond to 2'-FL.³

Studied doses

Doses used in research, shown against the official limits. They describe the studies, not a recommendation for you.

Studied doses in research, not advice. These are amounts used in research, not personal advice. Your clinician or pharmacist can say what fits you.

Doses studied in human trials

Doses studied in human trials ranged from 2 to 20 g/day in adults: 2 g/day of 2'-FL for 4 weeks (mood trial), 3 g/day for 12 weeks (weight-loss program), 5 or 10 g/day of a 2'-FL/LNnT mix for 4 weeks (IBS), 12 g/day of 2'-FL for 8 weeks (after antibiotics) and up to 20 g/day for 2 weeks (healthy adults). Infant formula trials added 1.0 g/L 2'-FL and 0.5 g/L LNnT for 6 months.^10,7,2,8,1,5

When trials measured an effect

2 outcomes

How long trials ran before effects were measured
Outcome	Measured at	Basis
Stool Bifidobacterium	Raised within 2 weeks in healthy adults; at week 4 (10 g/day) in IBS, but not 4 weeks after stopping	2-week dose trial (100 adults) and 4-week IBS trial (60 adults)^1,2
Gut microbiome recovery after antibiotics	Better than placebo after 2 weeks of 2'-FL, no longer different at 8 weeks	8-week RCT after a 7-day vancomycin course⁸

Interactions and safety

Published interactions only: each row cites a source. No row means none was found in our sources, not that a combination is safe.

Interactions

0 agents

None found in our sources.

Check with what you take

Kept on this device only

Add what you take. We list every interaction our evidence profiles cite between Human Milk Oligosaccharides and your picks, and between your picks.

Add a supplement or medicine

Most cited:

Add a supplement or medicine you take to check it against Human Milk Oligosaccharides.

Starting from one medicine? The interaction checker rates how serious each pair is, on a curated list of 19 entries for 11 medicines. This cabinet has no severity rating: it lists every interaction row our supplement pages cite.

Who should be careful

2 groups

Pregnancy and breastfeeding: No reliable data: LactMed has no entry for HMO supplements, and no cited trial tested them in pregnant or breastfeeding women. HMOs occur naturally in breast milk, but that does not show that added supplements are safe or useful in pregnancy.^1,2,3,6
Infants: For infants, HMOs were tested only as part of complete infant formulas, not as add-on supplements.^5,6

Reading the label, and the cost per dose

Compare any product you already have by the amount it delivers, not by capsule count or front-of-pack weight.

How to read the label

1 checks

Which HMO and how much

Adult trials used 5 to 20 g/day of 2'-FL alone or mixed with LNnT. Products providing much less have not been tested at those amounts.^1,2

Have the bottle? Photograph its Supplement Facts panel and see each line, human milk oligosaccharides (hmos) included, beside the doses and forms the trials used in Label X-Ray.

Cost per studied dose, without the sales pitch

Your numbers, no product data

Price paid ($)Servings per containerHMO per serving (mg)

Compare against

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Frequently asked questions

Short answers to common questions; the numbers link to the sources below.

Common questions

6 answers

Do HMO supplements help adults?

They raised gut Bifidobacterium in most adult trials here, but did not improve IBS symptoms, a 6-week trial in older adults missed its main immune outcome, and a benefit after antibiotics faded by 8 weeks. Small trials of body fat and mood are graded D.^1,2,3,8,7,10

Do HMOs help IBS?

In 60 people with IBS, 5 or 10 g/day for 4 weeks did not change symptom severity, though 10 g raised bifidobacteria without worsening symptoms.²

Is formula with HMOs as good as breast milk?

HMO formulas support normal growth, but a 2026 review of 12 trials found limited and mixed evidence for other health benefits, and a 2026 ESPGHAN technical review found no difference in colic and no clear conclusion on infections. Formula HMOs are manufactured to match the structure of milk HMOs but are not taken from breast milk.^5,6,11

Are HMOs safe?

Up to 20 g/day for 2 weeks was well tolerated in 100 healthy adults, and 10 g/day did not worsen IBS symptoms. A 2023 review of 26 trials, written by Chr. Hansen employees, found manufactured HMOs consistently safe and well tolerated; one 12-week trial noted a small fall in bone mineral content.^1,2,12,7

Do HMO supplements cause gas or bloating?

Not in the trials here. Doses up to 20 g/day for 2 weeks were well tolerated on a gastrointestinal symptom scale in healthy adults, 12 g/day for 8 weeks caused no more symptoms than placebo, and 5 or 10 g/day did not worsen symptoms in people with IBS.^1,8,2

What is 2'-FL?

2'-fucosyllactose is a lab-made copy of a sugar in human milk and the HMO most widely tested in infant trials, alone or with others such as LNnT.⁶

Sources

12 sources: trial abstracts, NIH fact sheets and reference databases. Numbers in the text link here.

Sources cited on this page

12 sources

1Oral supplementation of healthy adults with 2'-O-fucosyllactose and lacto-N-neotetraose is well tolerated and shifts the intestinal microbiota.RCT Br J Nutr, 2016 · PMID 27719686
2Human milk oligosaccharide supplementation in irritable bowel syndrome patients: A parallel, randomized, double-blind, placebo-controlled study.RCT Neurogastroenterol Motil, 2020 · PMID 32536023
3A human milk oligosaccharide alters the microbiome, circulating hormones, and metabolites in a randomized controlled trial of older adults.RCT Cell Rep Med, 2025 · PMID 40738103
42'-Fucosyllactose modulates gut microbiota and systemic metabolism in mild-to-moderate ulcerative colitis: a randomized crossover trial.Crossover RCT J Crohns Colitis, 2026 · PMID 42635599
5Effects of Infant Formula With Human Milk Oligosaccharides on Growth and Morbidity: A Randomized Multicenter Trial.RCT J Pediatr Gastroenterol Nutr, 2017 · PMID 28107288
6Limited Evidence of Benefits from Clinical Trials of Human-Identical Milk Oligosaccharides for Infants.Review Adv Nutr, 2026 · PMID 41544710
7Effects of Human Milk Oligosaccharide 2'-Fucosyllactose Ingestion on Weight Loss and Markers of Health.RCT Nutrients, 2024 · PMID 39408354
82'-Fucosyllactose supplementation results in a transient improvement in gut microbial resilience after vancomycin use in adults with overweight or obesity: a randomized, double-blind, placebo-controlled intervention.RCT Gut Microbes, 2025 · PMID 41243448
9Modulation of the gut microbiome and resistome by antibiotic use, but not by subsequent 2'-fucosyllactose intake, in adults with overweight or obesity.RCT Gut Microbes, 2026 · PMID 42878177
10Inulin-type fructans and 2'fucosyllactose alter both microbial composition and appear to alleviate stress-induced mood state in a working population compared to placebo (maltodextrin): the EFFICAD Trial, a randomized, controlled trial.RCT Am J Clin Nutr, 2023 · PMID 37657523
11Technical review by the ESPGHAN Special Interest Group on Gut Microbiota and Modifications on the health outcomes of infant formula supplemented with manufactured human milk oligosaccharides.Systematic review J Pediatr Gastroenterol Nutr, 2026 · PMID 40123480
12Clinical Studies on the Supplementation of Manufactured Human Milk Oligosaccharides: A Systematic Review.Systematic review Nutrients, 2023 · PMID 37630811

What changed

Every dated change to this page: what changed, who made it and why.

Change log

3 entries

Dated changes to this page
Date	Change	Who and why
Oct 21, 2026evidence, studied doses, time to effect, key facts, who should avoid, FAQ, questions, related	Added three graded rows (all D): 2'-FL after an antibiotic course (2025, with a 2026 follow-up analysis in its notes), 2'-FL during a weight-loss program (2024) and 2'-FL with or without oligofructose for mood (2023); added the 2026 ESPGHAN technical review on HMO infant formulas and a 2023 systematic review on safety; widened the studied dose range to 2–20 g/day; added time-to-effect rows; made the pregnancy and breastfeeding note an explicit 'no reliable data' (no LactMed entry); corrected 'every adult trial raised Bifidobacterium' (the 2023 trial found highly variable changes); added a FAQ on gas and bloating, page questions and links to inulin and the gut hub. Interactions checked: no LiverTox, LactMed, NCCIH or MedlinePlus entry and no human interaction study, so the list stays empty. Not added: a 19-person 6'-sialyllactose exercise trial (2026) and a 3'-sialyllactose knee pilot (2024) reporting only within-group changes.	Writer: Kymata Health EditorialTrigger: A–Z audit against docs/supplements/AUDIT-STANDARD.md
Oct 17, 2026all	First draft. Every PMID checked against NCBI E-utilities esummary (title and year taken from the record) and abstracts read for every cited row.	Writer: Kymata Health EditorialTrigger: new page
Oct 17, 2026all	Adversarial review pass: every evidence row's numbers machine-checked against its PubMed abstract, retraction and erratum flags checked for all PMIDs, unverified country and affiliation details removed, and claims not supported by the cited abstracts reworded or dropped.	Writer: Kymata Health EditorialTrigger: review

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