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Prebiotics

Prebiotics raised gut bifidobacteria in reviews. Short-chain fructans added about a third of a bowel movement a day. In IBS, a meta-analysis found no change in symptoms or quality of life, and inulin worsened flatulence. Pooled trials found small drops in blood glucose and LDL cholesterol. Fructans raised symptom scores in people with self-reported gluten sensitivity.

Add to Bio HackChecked 2026-11-09
Status
Sold as dietary supplements and added to foods and infant formula in the US.
Also called
inulin, chicory root fiber, fructooligosaccharides, FOS, oligofructose, short-chain FOS, scFOS, inulin-type fructans, beta-fructans, galactooligosaccharides, GOS, trans-galactooligosaccharides
Taken for
gut health, feeding gut bacteria, regularity, constipation, IBS, ulcerative colitis, Crohn's disease, blood sugar, cholesterol, appetite, weight loss, infant allergy prevention, mood

Strong several reviews agree · Moderate one review or consistent trials · Limited one or a few small studies · Untested no study in people, listed with what it rests on

Shown to help4

Reported risks3

What people take it for, and what was found

Shown to help4

Strong

Gut bifidobacteria

Shown to raise gut bifidobacteria in adults with IBS and in healthy adults. A change in bacteria is not a health outcome by itself.

The numbers and sources
Effect
In adults with IBS or other functional bowel disorders, prebiotics raised bifidobacteria by 1.16 log10 16S rRNA gene copies (95% CI 0.06 to 2.26) [1]. A systematic review of trials in healthy adults found inulin-type fructans raised Bifidobacterium, Lactobacillus and Faecalibacterium prausnitzii [2].
Population
11 trials, 729 patients [1]. Healthy adults [2].
Sources
[1], [2]
Caveats
A change in bacteria is not a health outcome by itself. [2] was funded by General Mills.
Moderate

Bowel movement frequency

Shown to raise bowel movements about 0.36 a day with short-chain fructans, while long-chain fructans did not. No change was found in children with constipation.

The numbers and sources
Effect
Across 47 publications, short-chain beta-fructans (chain length under 10) raised stool frequency by 0.36 bowel movements a day (p below 0.001) and slightly raised stool wet weight. Long-chain beta-fructans did not change frequency (-0.03 a day, p 0.82) [3]. In 39 adults with functional constipation, 12 g a day of chicory inulin for 4 weeks raised stool frequency and eased abdominal symptoms more than placebo [4]. In children with functional constipation, a network meta-analysis of 15 RCTs found no difference from placebo in weekly bowel movements for any probiotic, prebiotic or synbiotic [5].
Population
Healthy volunteers and patients [3]. Adults with functional constipation, crossover [4]. 1,087 children [5].
Sources
[3], [4], [5]
Caveats
Two authors of [3] were employees of Tereos, a fructan producer, which funded the other two authors and two unpublished studies that were included [3]. The inulin trial found a carry-over effect and confirmed the result by analyzing the first period alone [4]. Certainty in the pediatric review was low to very low [5].
Moderate

Blood glucose and cholesterol

Shown to lower LDL slightly, about 0.15 mmol/L, with fasting glucose and HbA1c falling in prediabetes and type 2 diabetes. Results for others disagreed.

The numbers and sources
Effect
In 20 trials (607 adults), inulin-type fructans lowered LDL cholesterol by 0.15 mmol/L (95% CI 0.02 to 0.29) and did not change other lipids, glucose or insulin overall. In type 2 diabetes, fasting insulin fell [6]. In 33 trials (1,346 participants), fasting glucose, HbA1c, fasting insulin and HOMA-IR fell. In prediabetes and type 2 diabetes, fasting glucose fell 0.60 mmol/L and HbA1c 0.58 percentage points [7].
Population
Adults with dyslipidemia, overweight or type 2 diabetes [6]. Adults including prediabetes and type 2 diabetes [7].
Sources
[6], [7]
Caveats
The two meta-analyses differ on glucose in the general population [6][7].
Limited

Allergy prevention in infants

Limited evidence: prebiotics lowered wheezing or asthma in infants against placebo, with no clear change in eczema, at very low certainty.

The numbers and sources
Effect
In infants, prebiotics compared with placebo gave risk ratios of 0.68 for eczema (95% CI 0.40 to 1.15), 0.37 for wheezing or asthma (95% CI 0.17 to 0.80) and 0.28 for food allergy (95% CI 0.08 to 1.00) [15].
Population
22 studies of infants. None tested prebiotics in pregnancy or breastfeeding [15].
Sources
[15]
Caveats
Certainty was very low, due to risk of bias and imprecision [15].

Mixed results1

Limited

Ulcerative colitis and Crohn's disease

Limited evidence: one prebiotic, kestose, brought ulcerative colitis remission more often in 40 patients, and none differed from control in Crohn's disease.

The numbers and sources
Effect
In 17 studies, the fructooligosaccharide kestose induced clinical remission of ulcerative colitis more often than control (RR 2.75, 95% CI 1.05 to 7.20, 40 patients). Oligofructose-enriched inulin and lactulose did not. Germinated barley foodstuff trended toward fewer relapses (RR 0.40, 95% CI 0.15 to 1.03, 59 patients), and oligofructose-enriched inulin, oat bran and Plantago ovata did not. In Crohn's disease, no prebiotic differed from control for inducing or keeping remission [13].
Population
Adults with ulcerative colitis or Crohn's disease, randomized and prospective observational studies [13].
Sources
[13]
Caveats
The overall certainty of evidence was very low, and each positive finding rests on a small number of patients [13].

Not shown to help3

Moderate

IBS and functional bowel symptoms

Not shown to improve IBS response, pain, bloating or quality of life over placebo, with flatulence easing only at 6 g a day or less.

The numbers and sources
Effect
In 11 trials (729 patients), response was 54% on prebiotics and 63% on placebo (OR 0.62, 95% CI 0.07 to 5.69). Abdominal pain, bloating, flatulence and quality of life did not differ. Flatulence improved at 6 g a day or less (SMD -0.35) and with non-inulin prebiotics (SMD -0.34) [1].
Population
Adults with IBS or other functional bowel disorders [1].
Sources
[1]
Caveats
No included trial was at low risk of bias in every category [1].
Limited

Depression and anxiety

Limited evidence: most reviews found no effect on depression or anxiety over placebo, and few trials tested prebiotics alone.

The numbers and sources
Effect
Pooled effects did not differ from placebo for depression (d -0.08) or anxiety (d 0.12) [8]. In 3 trials in people with clinical depression, prebiotics did not significantly lower symptoms (SMD -0.28, 95% CI -0.61 to 0.04) [9]. A 2026 review of 27 RCTs found no significant effect of prebiotics on depression [10]. A 2025 review of 72 RCTs reported that prebiotics alone reduced anxiety and depression in a subgroup analysis, without giving a prebiotic-only estimate in the abstract [11]. In 14 college students, 4.9 g a day of FOS inulin for 28 days did not change anxiety scores against no supplement [12].
Population
Controlled trials in clinical and general populations [8][9][10][11]. 14 college students [12].
Sources
[8], [9], [10], [11], [12]
Caveats
Few trials tested prebiotics alone, and heterogeneity was high across reviews [9][11].
Limited

Appetite and body weight

Limited evidence: most adult trials found no effect on appetite or intake, and one year-long trial slowed weight gain in adolescents.

The numbers and sources
Effect
In adults, 5 trials found no effect on appetite and 11 found no effect on energy intake. Two of 3 trials measuring weight found a reduction. In 97 adolescents, 8 g a day of oligofructose plus inulin for a year slowed weight gain compared with control [14].
Population
15 adult trials (545 people) and 4 pediatric trials (232) [14].
Sources
[14]
Caveats
The authors describe the weight data as limited [14].

Doses studied

In IBS trials, flatulence improved at 6 g a day or less [1]. The glucose meta-analysis found larger effects at 10 g a day for 6 weeks or more [7]. The adolescent weight trial used 8 g a day for a year [14]. The adult constipation trial used 12 g of chicory inulin a day for 4 weeks [4].

Risks

Reported risks2

Moderate

Flatulence and gut symptoms

Shown to worsen flatulence with inulin-type fructans in people with IBS, and flatulence and bloating with oligofructose-enriched inulin in bowel disease.

The numbers and sources
Effect
In IBS trials, inulin-type fructans worsened flatulence compared with placebo (SMD 0.85, 95% CI 0.23 to 1.47) [1]. In inflammatory bowel disease trials, flatulence and bloating were more common with oligofructose-enriched inulin [13].
Population
Adults with IBS or other functional bowel disorders [1]. Adults with inflammatory bowel disease [13].
Sources
[1], [13]
Caveats
Other prebiotic types and lower doses did not show this [1].
Limited

Symptoms in self-reported gluten sensitivity

One trial found 2.1 g a day of fructans raised gut symptom scores more than gluten or placebo in people with self-reported gluten sensitivity.

The numbers and sources
Effect
In 59 people on a self-started gluten-free diet, 7 days of 2.1 g a day of fructans raised gut symptom scores to 38.6, against 34.3 on placebo and 33.1 on gluten (p 0.04). Bloating scores were 11.6, 10.1 and 9.3 [16].
Population
Adults in Norway without celiac disease, crossover [16].
Sources
[16]
Caveats
One trial in a specific group.

Mixed results1

ModerateStudied in children

Adverse effects and growth in infants

Mixed results: side effects in infants were about as common as on placebo, while reviews disagreed on whether longer use slowed weight gain.

The numbers and sources
Effect
Across infant trials, adverse effects did not differ from placebo (RR 1.01, 95% CI 0.92 to 1.10). Growth rate was 0.92 g a day faster with prebiotics (95% CI 0 to 1.84) [15]. In 30 trials of formula with added prebiotics (5,290 infants up to 6 months), growth did not suffer, and weight-for-age favored prebiotic formula over breast milk in 2 trials (MD 0.23 z score, 95% CI 0.04 to 0.42) [17]. In 24 studies, weight, length and head growth did not differ overall. Infants given prebiotics for 3 months or more gained less weight than controls (SMD -0.479), and formulas with inulin-enriched oligofructose went with lower weight and length gain [18].
Population
Infants in 22 studies [15], 30 trials [17] and 24 studies [18].
Sources
[15], [17], [18]
Caveats
The reviews disagree on longer use. Certainty was very low in [15]. Prebiotic type mattered in [18].

Claims tested and not found

  1. That prebiotics improve IBS symptoms. Response, pain, bloating and quality of life did not differ from placebo [1].
  2. That inulin-type fructans curb appetite. Most adult trials found no effect on appetite or energy intake [14].

Sources

  1. Wilson B, Rossi M, Dimidi E, et al. Prebiotics in irritable bowel syndrome and other functional bowel disorders in adults: a systematic review and meta-analysis of randomized controlled trials. The American Journal of Clinical Nutrition. 2019. https://doi.org/10.1093/ajcn/nqy376
  2. Hughes RL, Alvarado DA, Swanson KS, et al. The Prebiotic Potential of Inulin-Type Fructans: A Systematic Review. Advances in Nutrition. 2022. https://doi.org/10.1093/advances/nmab119
  3. De Vries J, Le Bourgot C, Calame W, et al. Effects of β-Fructans Fiber on Bowel Function: A Systematic Review and Meta-Analysis. Nutrients. 2019. https://doi.org/10.3390/nu11010091
  4. Puhlmann ML, Wegh CAM, van der Zalm SCC, et al. Inulin-induced improvements on bowel habit and gut microbiota in adults with functional constipation: findings of a randomized, double-blind, placebo-controlled study. BMC Gastroenterology. 2025. https://doi.org/10.1186/s12876-025-04409-6
  5. Liang C, Deng X, Wang H, et al. Efficacy and Safety of Probiotics, Prebiotics and Synbiotics for the Treatment of Functional Constipation in Children: Systematic Review and Network Meta-analysis. Probiotics and Antimicrobial Proteins. 2026. https://doi.org/10.1007/s12602-026-10955-6
  6. Liu F, Prabhakar M, Ju J, et al. Effect of inulin-type fructans on blood lipid profile and glucose level: a systematic review and meta-analysis of randomized controlled trials. European Journal of Clinical Nutrition. 2017. https://doi.org/10.1038/ejcn.2016.156
  7. Wang L, Yang H, Huang H, et al. Inulin-type fructans supplementation improves glycemic control for the prediabetes and type 2 diabetes populations: results from a GRADE-assessed systematic review and dose-response meta-analysis of 33 randomized controlled trials. Journal of Translational Medicine. 2019. https://doi.org/10.1186/s12967-019-02159-0
  8. Liu RT, Walsh RF, Sheehan AE. Prebiotics and probiotics for depression and anxiety: A systematic review and meta-analysis of controlled clinical trials. Neuroscience & Biobehavioral Reviews. 2019. https://doi.org/10.1016/j.neubiorev.2019.03.023
  9. Asad A, Kirk M, Zhu S, et al. Effects of Prebiotics and Probiotics on Symptoms of Depression and Anxiety in Clinically Diagnosed Samples: Systematic Review and Meta-analysis of Randomized Controlled Trials. Nutrition Reviews. 2024. https://doi.org/10.1093/nutrit/nuae177
  10. Anjum N, Ahmed Z, Anjum F, et al. Efficacy of prebiotics, probiotics, and postbiotics on depression: a systematic review and meta-analysis of randomized controlled trials. Nutritional Neuroscience. 2026. https://doi.org/10.1080/1028415x.2026.2703621
  11. Zhang J, Zhu L, Meng Q, et al. The efficacy of probiotics, prebiotics, and synbiotics on anxiety, depression, and sleep: a systematic review and meta-analysis of randomized controlled trials. BMC Psychiatry. 2025. https://doi.org/10.1186/s12888-025-07644-z
  12. Herkes S, Lukaszuk JM, Walker DA, et al. Inulin, Containing Frutco-Oligosaccharides, and Generalized Anxiety Disorder 7-Item Scale Scores in College Students. Journal of Medicinal Food. 2026. https://doi.org/10.1177/1096620x261421081
  13. Limketkai BN, Godoy-Brewer G, Shah ND, et al. Prebiotics for Induction and Maintenance of Remission in Inflammatory Bowel Disease: Systematic Review and Meta-Analysis. Inflammatory Bowel Diseases. 2024. https://doi.org/10.1093/ibd/izae115
  14. Liber A, Szajewska H. Effects of Inulin-Type Fructans on Appetite, Energy Intake, and Body Weight in Children and Adults: Systematic Review of Randomized Controlled Trials. Annals of Nutrition and Metabolism. 2013. https://doi.org/10.1159/000350312
  15. Cuello-Garcia C, Fiocchi A, Pawankar R, et al. Prebiotics for the prevention of allergies: A systematic review and meta-analysis of randomized controlled trials. Clinical & Experimental Allergy. 2017. https://doi.org/10.1111/cea.13042
  16. Skodje GI, Sarna VK, Minelle IH, et al. Fructan, Rather Than Gluten, Induces Symptoms in Patients With Self-Reported Non-Celiac Gluten Sensitivity. Gastroenterology. 2018. https://doi.org/10.1053/j.gastro.2017.10.040
  17. Kebbe M, Leung K, Perrett B, et al. Effects of Infant Formula Supplemented With Prebiotics on the Gut Microbiome, Gut Environment, Growth Parameters, and Safety and Tolerance: A Systematic Review and Meta-Analysis. Nutrition Reviews. 2025. https://doi.org/10.1093/nutrit/nuae184
  18. Mirzohreh ST, Sohrabnavi A, Panahi P, et al. Effect of prebiotics on growth metrics in infants: A GRADE approach systematic review and meta-analysis of randomized clinical trials. Nutrition Research. 2025. https://doi.org/10.1016/j.nutres.2025.03.003

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