Which Fibre Is Best for IBS? NICE, Bran, Psyllium and Low FODMAP

For IBS, NICE says to review fibre, usually reducing it, to avoid insoluble fibre such as bran, and to use soluble fibre such as ispaghula powder or oats if more is advised. In a 275-patient GP trial, 10 g of psyllium (ispaghula) a day gave adequate relief to 57% in month one against 35% on placebo; bran's symptom scores did not differ significantly from placebo's.^{1, 2} This page is part of the Wellgard fibre guide.

Evidence at a glance

• Trials: 14 randomised trials of fibre in IBS pooled in 2014, 906 people; 11 trials of prebiotic fibres pooled in 2019, 729 people.
• Largest single trial: 275 adults in general practice, psyllium, bran or placebo for 12 weeks.
• Strongest measured outcome: adequate relief in 57% on psyllium against 35% on placebo in month one.
• Not tested: in the trials cited here, psyllium head to head with oats or linseeds.

Sources checked on 13 October 2026.

Never take psyllium dry: the NHS says at least 150 ml of cold water per sachet, drunk at once, not just before bed.³ Chest pain, vomiting, or difficulty swallowing or breathing after a dose needs urgent help; is psyllium husk safe has more. A GP diagnoses IBS: see one if symptoms last over 4 weeks, and urgently for unexplained weight loss, bleeding from your bottom or a lump in your tummy.⁴

What does NICE say about fibre and IBS?

NICE's IBS guideline tells healthcare professionals to review fibre intake, "adjusting (usually reducing) it while monitoring the effect on symptoms". People with IBS "should be discouraged from eating insoluble fibre (for example, bran)", and if more fibre is advised, "it should be soluble fibre such as ispaghula powder or foods high in soluble fibre", for example oats.¹ Limiting wholemeal bread, bran cereals and brown rice may help, it adds, and oats and up to 1 tablespoon of linseeds a day may ease wind and bloating, as the NHS also advises.^{1, 5}

Why does NICE say to avoid bran with IBS?

Because the trials found no reliable benefit. In the GP trial, 10 g of bran a day beat placebo only in month three, a result that did not hold in the worst-case analysis, and early dropout was highest on bran, mainly because symptoms worsened.² Pooled across 14 trials, bran did not reduce persistent symptoms (relative risk 0.90, not significant), and the authors found no evidence of harm.⁶ The harm signal comes from an uncontrolled UK clinic series: of 100 referrals with IBS who had tried bran, 55% said it made them worse and 10% that it helped.⁷ Soluble vs insoluble fibre explains bran versus a gel.

Does psyllium help IBS?

For many, yes. In the GP trial, 85 people took 10 g a day for 12 weeks: 57% had adequate relief in month one and 59% in month two, against 35% and 41% on placebo, and symptom severity fell 90 points against 49.² Across 14 trials and 906 people the benefit sat in the soluble-fibre trials: seven people needed soluble fibre for one more to stop being symptomatic.⁶ In month one, 43% on psyllium reported no adequate relief, and quality of life did not differ from placebo.² What psyllium husk does covers its other trials.

How do the fibres compare in IBS trials?

Most trials cited here test one fibre against placebo or none; the GP trial tested psyllium and bran side by side.

Which fibre for IBS with constipation, and which with diarrhoea?

For constipation, the NHS says to drink plenty of water and "increase how much soluble fibre you eat": oats, pulses, carrots, peeled potatoes, linseeds.⁵ In 180 adults with constipation-type IBS, 10 g of acacia fibre a day for four weeks raised stool frequency against placebo without changing stool form or quality of life, in a trial part-funded by ingredient companies.¹¹ For diarrhoea, the NHS says to "cut down on high-fibre foods" such as brown bread, brown rice, nuts and seeds, and to avoid the sweetener sorbitol.⁵ Fibre and diarrhoea covers loose stools.

Is psyllium low FODMAP, and how do you keep fibre up on a low-FODMAP diet?

We could not check psyllium's FODMAP rating, so this page gives none; a supervising dietitian can, and can plan your fibre. FODMAPs are fermentable short-chain carbohydrates, and NICE says a low-FODMAP diet should "only be given by a healthcare professional with expertise in dietary management".¹ In a three-week crossover trial with almost all food provided, it roughly halved symptom scores in 30 people with IBS (22.8 against 44.9 on a 100 mm scale); across 13 trials and 944 people it beat standard NICE and dietetic advice for bloating.^{12, 13} In a 104-person trial it lowered bifidobacteria, and a live-culture supplement restored them.¹⁴ The Wellgard probiotics guide covers live cultures.

Does inulin or prebiotic fibre help IBS?

Across 11 trials in 729 people with IBS or similar bowel disorders, prebiotic fibres did not differ from placebo for symptoms or quality of life. Inulin-type fructans increased wind; prebiotics at 6 g a day or less left wind slightly lower than placebo (a borderline result); bifidobacteria rose.¹⁰ Inulin is a fructan, one of the FODMAPs, so a low-FODMAP diet excludes it by design, not because it is a poor fibre. What is inulin has its foods and tolerance data.

How do you add fibre with IBS without a flare?

One change at a time, held for several days, "monitoring the effect on symptoms", as NICE puts it.¹ Wind and bloating from a sudden rise in fibre "should get better after a few days", says the NHS.¹⁵ Drink around 1.5 litres of fluid a day and keep a food diary.⁵ Ask a doctor or pharmacist before taking ispaghula if you have difficulty swallowing, tummy pain with sickness, bowel muscle weakness, or an unusual change in your poo for over 2 weeks.¹⁶ Why fibre makes you bloated explains the wind.

Fibre and diverticular disease: more or less?

More, slowly. The NHS says to raise fibre gradually "and make sure to also drink plenty of water", adding "there are no specific foods you need to avoid".¹⁷ Its symptoms can resemble IBS; worsening tummy pain, a high temperature, or blood or mucus in your poo needs an urgent GP appointment or NHS 111.¹⁷ The constipation guide has more.

What we don't know

• The largest psyllium trial in IBS ran 12 weeks, so longer use was not measured.
• The 55% worse-on-bran figure had no comparison group.
• The linseed trial was an open pilot; 31 of 40 finished.
• The prebiotic analysis found no trial at low risk of bias in every category.

Frequently asked questions

What is the best fibre supplement for IBS?

NICE names a type, not a product: soluble fibre, with ispaghula powder as its example; psyllium has the large GP trial.^{1, 2} Compare supplements by fibre and grams per serving; which fibre supplement is best sets them out.

Is acacia fibre good for IBS or SIBO?

In one trial of 180 adults with constipation-type IBS, 10 g a day raised stool frequency against placebo over four weeks; stool form and quality of life did not change.¹¹ SIBO (small intestinal bacterial overgrowth) is diagnosed and managed by a GP or specialist.

Should I take psyllium every day with IBS?

The GP trial gave it daily for 12 weeks.² When ispaghula is taken to raise fibre intake, the NHS says your doctor "may recommend that you take it for many months".³

Can children with IBS take psyllium?

In a government-funded trial of 84 children, average age 13, six weeks of psyllium cut pain episodes by 8.2 against 4.1 on placebo; pain intensity did not differ.⁸ The NHS says under-6s take ispaghula only on a doctor's prescription.¹⁶

Sources

1. NICE. Irritable bowel syndrome in adults (CG61), recommendations 1.2.1.4, 1.2.1.5, 1.2.1.8. Guideline; last updated 4 April 2017. nice.org.uk
2. Bijkerk CJ et al. BMJ 2009. Randomised trial, 275 adults, 12 weeks; publicly funded, psyllium supplied by a drug company. PubMed 19713235
3. NHS. Ispaghula husk: how and when to take it. Page last reviewed 13 January 2026. nhs.uk
4. NHS. Symptoms of IBS. Page last reviewed 17 March 2025. nhs.uk
5. NHS. Diet, lifestyle and medicines for IBS. Page last reviewed 17 March 2025. nhs.uk
6. Moayyedi P et al. American Journal of Gastroenterology 2014. Pooled analysis of 14 randomised trials, 906 people. PubMed 25070054
7. Francis CY, Whorwell PJ. Lancet 1994. Uncontrolled clinic series, 100 people. PubMed 7912305
8. Shulman RJ et al. Clinical Gastroenterology and Hepatology 2017. Randomised trial, 84 children, 6 weeks; government-funded, psyllium supplied by a manufacturer. PubMed 27080737
9. Cockerell KM et al. Journal of Human Nutrition and Dietetics 2012. Open pilot trial, 40 adults, 4 weeks; funding not checked. PubMed 22690855
10. Wilson B et al. American Journal of Clinical Nutrition 2019. Pooled analysis of 11 randomised trials, 729 people. PubMed 30949662
11. Janssen Duijghuijsen L et al. European Journal of Nutrition 2024 (figure corrected 2025). Randomised trial, 180 adults, 4 weeks; part-funded by ingredient companies, one author at an acacia supplier. PubMed 38653808
12. Halmos EP et al. Gastroenterology 2014. Randomised single-blind crossover trial, 30 adults with IBS and 8 controls, 21 days per diet; government and university funded (PubMed grant record), full text not checked. PubMed 24076059
13. Black CJ et al. Gut 2022. Network analysis of 13 randomised trials, 944 people. PubMed 34376515
14. Staudacher HM et al. Gastroenterology 2017. Randomised trial, 104 adults, 4 weeks. PubMed 28625832
15. NHS. Ispaghula husk: side effects. Page last reviewed 13 January 2026. nhs.uk
16. NHS. Ispaghula husk: who can and cannot take it. Page last reviewed 13 January 2026. nhs.uk
17. NHS. Diverticular disease and diverticulitis. Page last reviewed 7 September 2023 (review overdue). nhs.uk

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