Xylooligosaccharides (XOS)
Also called xylooligosaccharides, xylo-oligosaccharides, XOS, XOS prebiotic, xylooligosaccharide.
Best grade C across 6 graded outcomes Other Last checked
The short answer
From 8 sourcesXylooligosaccharides (XOS) are a prebiotic fibre that works at low doses. Small trials found 1.4 to 5 g a day raised gut bifidobacteria with few side effects, and 3 to 10 g a day eased functional constipation. A 26-person trial reported lower blood sugar in type 2 diabetes, but a prediabetes pilot found no glucose change.
Every graded outcome on this page
6 rows · line = participants- CGrade CFunctional constipation symptomsConstipationn 93
- DGrade DGut bacteria and butyrateGut bacterian 60
- DGrade DGut bifidobacteriaGut bacterian 32
- DGrade DSevere constipation in late pregnancyConstipationn 29
- DGrade DGlucose and insulin in prediabetesBlood sugarn 29
- DGrade DBlood sugar and cholesterol in type 2 diabetesBlood sugarn 26
- 3 more graded outcomes, in the evidence chapter
Key facts
- What it is
- Two to three xylose units with beta-1,4 links, made by breaking down grain hemicellulose7
- Bifidobacteria (32 adults)
- 1.4 and 2.8 g a day for 8 weeks raised bifidobacteria, more at 2.8 g1
- Constipation (93 adults)
- 3, 5 or 10 g a day for a month improved constipation without diarrhoea or flatulence6
What it is
Xylooligosaccharides (XOS) are short chains of xylose made from plant hemicellulose, used as a low-dose prebiotic fibre.
Forms
Form
| Form | Elemental % | Absorption (human data) | GI tolerance | Studied for |
|---|---|---|---|---|
| XOS powder | Varies7Not applicable; grams of XOS | Not absorbed in the small intestine; measured as changes in faecal bacteria.13 | 1.4 to 2.8 g a day caused no significant gut side effects, and 3 to 10 g a day caused no diarrhoea or flatulence in constipation.16 | Gut bacteria, constipation, blood sugar |
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
6 graded outcomes, largest study first6 graded outcomes: 5 improved, 1 no effect. The largest, a 2024 randomized trial of 93 people on functional constipation symptoms, found an improvement.
1Functional constipation symptoms
Improved · Grade C · RCT, 93 people, 2024
Adults with functional constipation (Rome IV)
Dose, result and source| Outcome | Found | People | Study | Who was studied |
|---|---|---|---|---|
| Functional constipation symptoms | Improved | 93 | Grade C · RCT, 2024 | Adults with functional constipation (Rome IV) |
| Gut bacteria and butyrate | Improved | 60 | Grade D · RCT, 2012 | Healthy volunteers on a high-fat diet |
| Gut bifidobacteria | Improved | 32 | Grade D · RCT, 2014 | Healthy adults |
| Glucose and insulin in prediabetes | No effect | 29 | Grade D · Pilot RCT, 2015 | Adults with prediabetes (13) and healthy adults (16) |
| Severe constipation in late pregnancy | Improved | 29 | Grade D · Open-label trial, 2005 | Pregnant women with severe constipation |
| Blood sugar and cholesterol in type 2 diabetes | Improved | 26 | Grade D · RCT, 2008 | Adults with type 2 diabetes (HbA1c 7.0 to 10.0%) |
Every graded row
6 rowsShowing 6 of 6 outcomes. Human trials only.
CGrade CFunctional constipation symptomsConstipationBetter bowel scoresRCT
n 93 · 2024
Improved XOS improved stool form, constipation scores and quality of life and enriched Bifidobacterium at lower doses than FOS (10 to 20 g), without diarrhoea or flatulence.
- Design
- RCT, n = 93, 2024
- Population
- Adults with functional constipation (Rome IV)
- Form
- XOS vs fructo-oligosaccharides vs placebo
- Dose
- 3, 5 or 10 g XOS a day
- Duration
- 1 month
- Source
- Reference 6 · PubMed 38370040 (opens PubMed)
DGrade DGut bacteria and butyrateGut bacteriaMore bifidobacteria, butyrateRCT
n 60 · 2012
Improved XOS alone raised faecal Bifidobacterium and butyrate and lowered acetate and p-cresol; only the inulin-XOS mix lowered blood LPS and inflammatory gene responses.
- Design
- RCT, n = 60, 2012
- Population
- Healthy volunteers on a high-fat diet
- Form
- XOS alone or inulin plus XOS
- Dose
- 5 g XOS a day (or 3 g inulin + 1 g XOS)
- Duration
- 4 weeks
- Source
- Reference 3 · PubMed 22264499 (opens PubMed)
DGrade DGut bifidobacteriaGut bacteriaMore bifidobacteriaRCT
n 32 · 2014
Improved Bifidobacteria rose in both XOS groups vs placebo, more at 2.8 g; lactobacilli, stool pH and short-chain fatty acids did not change, and XOS caused no significant gut side effects.
- Design
- RCT, n = 32, 2014
- Population
- Healthy adults
- Form
- XOS
- Dose
- 1.4 or 2.8 g a day
- Duration
- 8 weeks
- Source
- Reference 1 · PubMed 24513849 (opens PubMed)
DGrade DSevere constipation in late pregnancyConstipationMore bowel movementsOpen-label trial
n 29 · 2005
Improved Stools per week rose from 1.1 to 6.7 and 27 of 29 could pass stool spontaneously by the end; no side effects were seen.
- Design
- Open-label trial, n = 29, 2005
- Population
- Pregnant women with severe constipation
- Form
- XOS
- Dose
- 4.2 g a day
- Duration
- 4 weeks
- Source
- Reference 7 · PubMed 16521705 (opens PubMed)
DGrade DGlucose and insulin in prediabetesBlood sugarNo glucose changePilot RCT
n 29 · 2015
No effect XOS shifted several gut bacteria but did not change HOMA-IR, serum glucose, triglycerides, body composition or satiety hormones; 2-hour insulin tended lower (p = 0.13).
- Design
- Pilot RCT, n = 29, 2015
- Population
- Adults with prediabetes (13) and healthy adults (16)
- Form
- XOS
- Dose
- 2 g a day
- Duration
- 8 weeks
- Source
- Reference 5 · PubMed 26300782 (opens PubMed)
DGrade DBlood sugar and cholesterol in type 2 diabetesBlood sugarLower glucose, HbA1cRCT
n 26 · 2008
Improved Glucose, HbA1c, fructosamine, total and LDL cholesterol, oxidized LDL and apolipoprotein B fell vs placebo.
- Design
- RCT, n = 26, 2008
- Population
- Adults with type 2 diabetes (HbA1c 7.0 to 10.0%)
- Form
- XOS
- Dose
- 4 g a day
- Duration
- 8 weeks
- Source
- Reference 2 · PubMed 19001772 (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.
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
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.
What Xylooligosaccharides meets
1 cited row 1 tested togetherMedicines 1
Supplements and foods 1
- Measured in a human study
- Tested together in a graded trial
Choose a medicine or supplement above to read its cited rows here.
Also cited: 1 tested together
Diabetes medicines
RCTMeasured in a human study
Diabetes medicines, for example Insulin, sulfonylureas, metformin: In 26 people with type 2 diabetes, 4 g of XOS a day for 8 weeks lowered glucose and HbA1c; the effect could add to glucose-lowering drugs. No combination studies exist, and a 2 g a day prediabetes pilot found no glucose change.
Source 2, J Nutr Sci Vitaminol (Tokyo) (2008); Source 5, Front Physiol (2015)
InulinInulin page
Tested together
Gut bacteria and butyrate. Graded on the Xylooligosaccharides page; tested together is not a claim that they work better together.
Interactions
1 agent| Agent | What the source says | Evidence |
|---|---|---|
| Medicines1 | ||
| Diabetes medicinese.g. Insulin, sulfonylureas, metformin | In 26 people with type 2 diabetes, 4 g of XOS a day for 8 weeks lowered glucose and HbA1c; the effect could add to glucose-lowering drugs. No combination studies exist, and a 2 g a day prediabetes pilot found no glucose change.25 | RCT |
Check with what you take
Kept on this device onlyAdd what you take. We list every interaction our evidence profiles cite between Xylooligosaccharides and your picks, and between your picks.
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Add a supplement or medicine you take to check it against Xylooligosaccharides.
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
3 groups- Diabetes medicines
- One small trial found lower glucose and HbA1c with 4 g a day in type 2 diabetes; anyone on glucose-lowering drugs should tell their clinician before adding it.2
- Pregnancy and breastfeeding
- Only one uncontrolled study in 29 constipated pregnant women exists; it reported no side effects. We found no breastfeeding data and no LactMed record for XOS.7
- Medicines and surgery
- NCCIH advises telling your health care providers about every supplement you use.8
How to read the label
What to check on the Supplement Facts panel.
How to read the label
1 checksFrequently asked questions
Short answers to common questions; the numbers link to the sources below.
Common questions
7 answersDoes XOS help constipation?
In 93 adults with functional constipation, 3, 5 or 10 g a day for a month improved stool form and symptom scores without diarrhoea or flatulence, at lower doses than FOS.6
Does XOS lower blood sugar?
Does XOS increase bowel movements in healthy people?
In a crossover trial in healthy adults, XOS for 21 days increased bowel movements per day without more bloating, pain or flatulence than maltodextrin.4
Does XOS cause bloating?
Does XOS interact with medicines?
No interaction studies exist. Because 4 g a day lowered glucose and HbA1c in a small type 2 diabetes trial, its effect could add to glucose-lowering medicines.2
Is XOS safe in pregnancy?
Only one uncontrolled study exists: 29 constipated pregnant women took 4.2 g a day for 4 weeks, with better bowel habits and no reported side effects. There are no breastfeeding data.7
Sources
8 sources: trial abstracts, NIH fact sheets and reference databases. Numbers in the text link here.
Sources cited on this page
8 sources- 1Xylooligosaccharide increases bifidobacteria but not lactobacilli in human gut microbiota.RCT Food Funct, 2014 · PMID 24513849
- 2Effects of xylooligosaccharides in type 2 diabetes mellitus.RCT J Nutr Sci Vitaminol (Tokyo), 2008 · PMID 19001772
- 3Xylo-oligosaccharide (XOS) in combination with inulin modulates both the intestinal environment and immune status in healthy subjects, while XOS alone only shows prebiotic properties.RCT Br J Nutr, 2012 · PMID 22264499
- 4Xylo-oligosaccharides alone or in synbiotic combination with Bifidobacterium animalis subsp. lactis induce bifidogenesis and modulate markers of immune function in healthy adults: a double-blind, placebo-controlled, randomised, factorial cross-over study.Crossover RCT Br J Nutr, 2014 · PMID 24661576
- 5Xylooligosaccharide supplementation alters gut bacteria in both healthy and prediabetic adults: a pilot study.Pilot RCT Front Physiol, 2015 · PMID 26300782
- 6Xylo-oligosaccharides improve functional constipation by targeted enrichment of Bifidobacterium.RCT Food Sci Nutr, 2024 · PMID 38370040
- 7Effect of xylooligosaccharide intake on severe constipation in pregnant women.Open-label trial J Nutr Sci Vitaminol (Tokyo), 2005 · PMID 16521705
- 8Using Dietary Supplements WiselyFact sheet National Center for Complementary and Integrative Health (NCCIH), 2019 · nccih.nih.gov
What changed
Every dated change to this page: what changed, who made it and why.
Change log
2 entries| Date | Change | Who and why |
|---|---|---|
| interactions, who should be careful, FAQ | Searched PubMed for XOS meta-analyses and trials through 2026: nothing newer than the 2024 constipation trial tested XOS alone with reported numbers (a 2024 skin trial gave no participant count or dose in its abstract; other trials tested blends). Added the diabetes-medicine interaction from the existing type 2 diabetes trial, a breastfeeding note (no data, no LactMed record) and two FAQs. | Writer: Kymata Health EditorialTrigger: A–Z page audit |
| all | Initial editorial evidence review. Every PMID checked against NCBI E-utilities esummary (title, year, journal) and each cited abstract read; numbers taken from the abstracts, except the constipation trial's participant count, read from its full text on PMC (99 randomized, 6 left in run-in). The inulin-XOS immune effect is marked as a blend effect. Where to buy: we didn’t list a product; none of the stores we checked sells single-ingredient XOS. | Writer: Kymata Health EditorialTrigger: new page |
Supplement & Nutrient Encyclopedia. Educational information only; it is not medical advice and does not replace a clinician. Dietary supplements are not intended to diagnose, treat, cure or prevent any disease. Statements about supplements have not been evaluated by the FDA.