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Fiber for irritable bowel syndrome

Goal: What trials of soluble fiber used for overall irritable bowel symptoms, and why fiber can also add 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

10 g of psyllium a day in a trial of 275 people.[1] The European Medicines Agency (EMA) gives 7 to 20 g of psyllium husk a day as an extra treatment in constipation-type irritable bowel syndrome.[2]

Form

Psyllium (ispaghula) husk. NICE says any added fiber should be soluble, such as ispaghula or oats.[1][3]

When to take

With at least 30 ml of liquid per 1 g, during the day and not right before bed.[2]

How long

12 weeks in that trial, and 4 to 12 weeks in most trials of older treatments.[1][4]

What studies found

A 2014 review of 14 trials with 906 people found that soluble fiber improved overall symptoms, with about 7 people treated for one to benefit. Bran had no clear effect.[5] In a trial of 275 people, 57% of those on psyllium had adequate relief in the first month, against 35% on placebo.[1] These trials measured overall symptoms, not bloating alone.[5][1] Inulin-type fructans made gas worse in a review of 11 trials.[6]

Ask a doctor first

More fiber can add gas and bloating, and NICE says fiber intake in irritable bowel syndrome is usually reduced, not raised.[7][3] Psyllium can delay the absorption of medicines and can block the throat or gut if taken with too little liquid.[2]

People who take a daily medicine, and people with weight loss, blood in the stool or bloating that does not go away, should ask a doctor first.[2][8][9]

References

  1. Soluble or insoluble fibre in irritable bowel syndrome in primary care? Randomised placebo controlled trial. Bijkerk CJ, de Wit NJ, Muris JW, Whorwell PJ, Knottnerus JA, Hoes AW BMJ, 2009. PMID 19713235
  2. Community herbal monograph on Plantago ovata Forssk., seminis tegumentum. European Medicines Agency, HMPC, 2013. www.ema.europa.eu
  3. Irritable bowel syndrome in adults: diagnosis and management (CG61), Recommendations. National Institute for Health and Care Excellence. www.nice.org.uk
  4. Efficacy of soluble fibre, antispasmodic drugs, and gut-brain neuromodulators in irritable bowel syndrome: a systematic review and network meta-analysis. Black CJ, Yuan Y, Selinger CP, Camilleri M, Quigley EMM, Moayyedi P, et al. Lancet Gastroenterol Hepatol, 2020. PMID 31859183
  5. The effect of fiber supplementation on irritable bowel syndrome: a systematic review and meta-analysis. Moayyedi P, Quigley EM, Lacy BE, Lembo AJ, Saito YA, Schiller LR, et al. Am J Gastroenterol, 2014. PMID 25070054
  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. Effects of the DASH Diet and Sodium Intake on Bloating: Results From the DASH-Sodium Trial. Peng AW, Juraschek SP, Appel LJ, Miller ER 3rd, Mueller NT Am J Gastroenterol, 2019. PMID 31206400
  8. Psyllium: MedlinePlus Drug Information. MedlinePlus, US National Library of Medicine, 2024. medlineplus.gov
  9. Bloating. NHS, 2026. www.nhs.uk