Protocols › Prebiotics

Prebiotics for constipation

Goal: What studies used to raise stool frequency. Newer guidance is less positive, and inulin can increase gas.

Each protocol describes what studies used, for one goal or for one group of people. It is not advice for you: talk to a doctor before you start a supplement.

Updated 4 Nov 2026
Dose

12 g a day: the amount in the EFSA opinion on stool frequency.[1]

Form

Native chicory inulin, a mix of sugars, inulin-type fructans and inulin extracted from chicory.[1] GOS and polydextrose changed neither stool frequency nor stool form in a 2025 British guideline.[2]

How long

In a 2022 review of fiber supplements, stool frequency improved only after 4 weeks or more.[3]

What studies found

6 studies with 86 people found that at least 12 g a day raised stool frequency.[1] A 2014 review of 5 trials with 252 people also found better stool frequency and form, but no less pain or bloating.[4] A newer 2025 guideline found that inulin-type fructans softened stools a little and did not change frequency, with low certainty.[2] In a 2022 review of fiber supplements, psyllium and pectin had the significant effects.[3]

Ask a doctor first

Inulin-type fructans at 12 g and 15 g a day made flatulence worse in people with constipation.[2] Stool frequency counts as a benefit only when it does not lead to diarrhea.[1]

People with irritable bowel syndrome or inflammatory bowel disease should ask a doctor or pharmacist first.[5][6]

References

  1. 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
  2. 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
  3. The Effect of Fiber Supplementation on Chronic Constipation in Adults: An Updated Systematic Review and Meta-Analysis of Randomized Controlled Trials. van der Schoot A, Drysdale C, Whelan K, Dimidi E Am J Clin Nutr, 2022. PMID 35816465
  4. Effectiveness of inulin intake on indicators of chronic constipation; a meta-analysis of controlled randomized clinical trials. Collado Yurrita L, San Mauro Martín I, Ciudad-Cabañas MJ, Calle-Purón ME, Hernández Cabria M Nutr Hosp, 2014. PMID 25208775
  5. Colon Hypersensitivity to Distension, Rather Than Excessive Gas Production, Produces Carbohydrate-Related Symptoms in Individuals With Irritable Bowel Syndrome. Major G, Pritchard S, Murray K, Alappadan JP, Hoad CL, Marciani L, et al. Gastroenterology, 2017. PMID 27746233
  6. 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