Prebiotics

Which prebiotic has the best evidence: inulin, FOS or GOS?

Updated 4 Nov 2026

Short answer

It depends on the goal, and no type leads for everything. Low-dose GOS has the better results for gas and bloating, though from small trials.[1][2] Chicory inulin has the EFSA opinion on stool frequency.[3] Inulin-type fructans, which include FOS, have large reviews for blood sugar, cholesterol and weight.[4][5] They also made flatulence worse in a 2019 review.[6]

The main types

The main groups are fructans (inulin and fructo-oligosaccharides, or FOS), galacto-oligosaccharides (GOS), lactulose, resistant starch, polydextrose and pectin oligosaccharides.[7] Oligofructose is a shorter form of inulin.[8] Most comparisons below come from subgroups in reviews. They do not come from trials that tested one type against another.[6]

For bloating and gas

GOS at low doses looks best, and the evidence is small. Two trials found less bloating at 2.75 g and 3.5 g a day.[1][2] In a 2019 review, prebiotics other than inulin-type fructans improved flatulence, and inulin-type fructans made it worse.[6] One crossover trial tested both in the same people with inflammatory bowel disease. In that trial, 12 g a day of fructans made symptoms worse, and 6 g a day of GOS did not.[9]

For constipation

Inulin has the strongest official support, and the newest guideline is less positive:[3][10][11][12][13]

  • EFSA, the European food safety agency, concluded that 12 g a day of native chicory inulin raises stool frequency, based on 6 studies with 86 people.[3]
  • A 2025 British guideline found that inulin-type fructans softened stools a little but did not raise stool frequency in chronic constipation. It found no effect on either measure for GOS or polydextrose.[10]
  • Single trials of GOS were more positive. 11 g a day showed a trend overall and raised stool frequency in the subgroup with 3 bowel movements a week or fewer. Five of the authors were employees of FrieslandCampina.[11] Another trial in 63 people with functional constipation found more bowel movements after 4 weeks.[12]
  • In a 2024 network review of 37 trials, lactulose raised stool frequency by 3.39 a week, with moderate certainty.[13]

For blood markers of inflammation

No type clearly leads. A 2020 review in type 2 diabetes found the strongest evidence for resistant starch, resistant dextrin and oligofructose-enriched inulin.[14] A 2017 review in overweight and obese adults listed drops in CRP with GOS, inulin and synbiotics, and asked for more trials.[15]

For blood sugar, cholesterol and weight

The large reviews here are on inulin-type fructans. A 2019 review of 33 trials found lower blood sugar in people with prediabetes or type 2 diabetes.[4] A 2024 review of 55 trials found small drops in LDL cholesterol, triglycerides and weight, with low or very low certainty.[5]

For calcium and iron

Inulin-type fructans raised calcium absorption in adolescents, and GOS raised iron absorption from ferrous fumarate in women with low iron stores.[16][17] The two types have been tested for different minerals, so these results do not compare them.[16][17]

What is still unknown

Even inside one group, chain length may change the effect. A 2022 review said that the lack of direct comparisons limits any conclusion.[18] Which type suits a person may also depend on that person's gut, and on the dose they tolerate.[19]

Sources (19)

  1. Effect of a prebiotic galactooligosaccharide mixture (B-GOS®) on gastrointestinal symptoms in adults selected from a general population who suffer with bloating, abdominal pain, or flatulence. Vulevic J, Tzortzis G, Juric A, Gibson GR Neurogastroenterol Motil, 2018. PMID 30109908
  2. Clinical trial: the effects of a trans-galactooligosaccharide prebiotic on faecal microbiota and symptoms in irritable bowel syndrome. Silk DB, Davis A, Vulevic J, Tzortzis G, Gibson GR Aliment Pharmacol Ther, 2009. PMID 19053980
  3. Scientific Opinion on the substantiation of a health claim related to "native chicory inulin" and maintenance of normal defecation by increasing stool frequency. European Food Safety Authority, 2015. www.efsa.europa.eu
  4. 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. Wang L, Yang H, Huang H, Zhang C, Zuo HX, Xu P, et al. J Transl Med, 2019. PMID 31805963
  5. The effects of inulin-type fructans on cardiovascular disease risk factors: systematic review and meta-analysis of randomized controlled trials. Talukdar JR, Cooper M, Lyutvyn L, Zeraatkar D, Ali R, Berbrier R, et al. Am J Clin Nutr, 2024. PMID 38309832
  6. Prebiotics in irritable bowel syndrome and other functional bowel disorders in adults: a systematic review and meta-analysis of randomized controlled trials. Wilson B, Rossi M, Dimidi E, Whelan K Am J Clin Nutr, 2019. PMID 30949662
  7. Prebiotics and Probiotics for Gastrointestinal Disorders. Rau S, Gregg A, Yaceczko S, Limketkai B Nutrients, 2024. PMID 38542689
  8. Gastrointestinal tolerance of chicory inulin products. Bonnema AL, Kolberg LW, Thomas W, Slavin JL J Am Diet Assoc, 2010. PMID 20497775
  9. Fermentable Carbohydrates [FODMAPs] Exacerbate Functional Gastrointestinal Symptoms in Patients With Inflammatory Bowel Disease: A Randomised, Double-blind, Placebo-controlled, Cross-over, Re-challenge Trial. Cox SR, Prince AC, Myers CE, Irving PM, Lindsay JO, Lomer MC, et al. J Crohns Colitis, 2017. PMID 28525543
  10. British Dietetic Association Guidelines for the Dietary Management of Chronic Constipation in Adults. Dimidi E, van der Schoot A, Barrett K, Farmer AD, Lomer MC, Scott SM, et al. J Hum Nutr Diet, 2025. PMID 41081513
  11. Prebiotic Galacto-Oligosaccharides Impact Stool Frequency and Fecal Microbiota in Self-Reported Constipated Adults: A Randomized Clinical Trial. Schoemaker MH, Hageman JHJ, Ten Haaf D, Hartog A, Scholtens PAMJ, Boekhorst J, et al. Nutrients, 2022. PMID 35057489
  12. Efficacy and safety of galacto-oligosaccharide in the treatment of functional constipation: randomized clinical trial. Lee JH, Kim GB, Han K, Jung EJ, Suh HJ, Jo K Food Funct, 2024. PMID 38787732
  13. Network meta-analysis of probiotics, prebiotics, and synbiotics for the treatment of chronic constipation in adults. Deng X, Liang C, Zhou L, Shang X, Hui X, Hou L, et al. Eur J Nutr, 2024. PMID 38693449
  14. The Effects of Prebiotics and Substances with Prebiotic Properties on Metabolic and Inflammatory Biomarkers in Individuals with Type 2 Diabetes Mellitus: A Systematic Review. Colantonio AG, Werner SL, Brown M J Acad Nutr Diet, 2020. PMID 30827823
  15. Effects of inulin-type fructans, galacto-oligosaccharides and related synbiotics on inflammatory markers in adult patients with overweight or obesity: A systematic review. Fernandes R, do Rosario VA, Mocellin MC, Kuntz MGF, Trindade EBSM Clin Nutr, 2017. PMID 27771020
  16. A combination of prebiotic short- and long-chain inulin-type fructans enhances calcium absorption and bone mineralization in young adolescents. Abrams SA, Griffin IJ, Hawthorne KM, Liang L, Gunn SK, Darlington G, et al. Am J Clin Nutr, 2005. PMID 16087995
  17. Consumption of Galacto-Oligosaccharides Increases Iron Absorption from Ferrous Fumarate: A Stable Iron Isotope Study in Iron-Depleted Young Women. Jeroense FMD, Michel L, Zeder C, Herter-Aeberli I, Zimmermann MB J Nutr, 2019. PMID 31004135
  18. The Prebiotic Potential of Inulin-Type Fructans: A Systematic Review. Hughes RL, Alvarado DA, Swanson KS, Holscher HD Adv Nutr, 2022. PMID 34555168
  19. Rapidly fermentable prebiotic substrates: Benefits, FODMAP effects and host tolerance. Ibrahim F Clin Nutr ESPEN, 2026. PMID 42762890

More about prebiotics

What are prebiotics?Do prebiotics change your gut bacteria?How long do prebiotics take to work?Which foods contain prebiotics?What are prebiotics used for?Is a synbiotic better than a prebiotic alone?

For education; not medical advice. Talk to a doctor before you start, stop or change a supplement.