Digestion
What the NHS, NICE, the British Dietetic Association and Guts UK say about probiotics, fibre supplements, peppermint oil and other supplements for digestion.
For people diagnosed with irritable bowel syndrome (IBS), the NHS suggests trying probiotics for a month and asking a pharmacist about medicines such as peppermint oil, and NICE says any extra fibre should be soluble, such as ispaghula. NICE also tells health professionals to discourage aloe vera for IBS. For healthy people, the British Dietetic Association says a probiotic supplement is unlikely to make a difference. Evidence on ginger and apple cider vinegar is limited or lacking.
NHS: Government guidelines say adults should eat 30g of fibre a day as part of a healthy, balanced diet. Most adults eat about 20g.
Each line below is a short summary of what the named source says, with a link to read it in full. None of it is medical advice.
Advised
Probiotics
Live bacteria and yeasts added to some yoghurts and fermented milk drinks, or sold as capsules, tablets and powders.
- NHS: With diagnosed IBS, try probiotics for a month.
- British Dietetic Association: If you are healthy, a probiotic supplement is unlikely to make a difference.
Also covered by NICE (Irritable bowel syndrome in adults: diagnosis and management (CG61), recommendations; Irritable bowel syndrome: Scenario: Management of irritable bowel syndrome), British Dietetic Association, Guts UK and NHS.
Psyllium (ispaghula) husk
The seed husks of the Plantago ovata plant: a soluble fibre sold as powder and capsules, and in laxative medicines.
- NICE: If more fibre is advised for IBS, it should be soluble, such as ispaghula.
- NICE: For constipation, if lifestyle changes fail, a fibre laxative such as ispaghula comes first.
Also covered by NICE and Guts UK.
What psyllium (ispaghula) husk is, and the forms it comes in
Peppermint oil
Oil from the leaves of the peppermint plant; capsules for IBS are sold as licensed medicines.
- NHS: For IBS bloating and cramps, ask a pharmacist about medicines such as peppermint oil.
- NICE: For ongoing IBS pain or spasm, a GP may prescribe it, to take when needed.
Also covered by Guts UK.
Limited evidence
Inulin and FOS (prebiotics)
Plant fibres, often from chicory root, sold as powders and capsules and added to some foods; also called prebiotics.
- British Dietetic Association: Less studied than probiotics, and more research is needed.
Also covered by Guts UK.
No good evidence
Apple cider vinegar
Apple juice fermented twice, first into alcohol and then into acetic acid; sold as a liquid, capsules and gummies.
- Cleveland Clinic: No real science backs the claims made about it for heartburn.
- Cleveland Clinic: Most studies of it are small, and further research is needed.
Advised against
Things to check
- NHS: See a GP if you are regularly constipated or bloated, have blood in your poo, or have lost weight without trying.
- British Dietetic Association: Increase fibre gradually to avoid bloating and gas, and drink plenty of fluid as you do.
- NICE: Drink enough fluid with fibre laxatives such as ispaghula; they are not prescribed for constipation caused by opioid painkillers.
- NHS: If you have a health condition or a weakened immune system, talk to a doctor before taking probiotics.
- NHS: Probiotics are classed as food, not medicine, so it is not always certain a product holds the bacteria stated.
- Guts UK: Peppermint oil capsules can make reflux worse in people who have it.
- NCCIH: Aloe leaf extracts taken by mouth have been linked to cases of acute hepatitis.
- Cleveland Clinic: Undiluted apple cider vinegar can erode tooth enamel and burn the oesophagus.
If you take medication, are pregnant, or have a health condition, check with a pharmacist or GP first.
Sources
- Diet, lifestyle and medicines for IBS (irritable bowel syndrome)Diet changes, probiotics and pharmacy medicines for people diagnosed with IBS, and when to see a GP.
- ConstipationCauses of constipation in adults, diet and lifestyle changes, laxatives from a pharmacist, and when to see a GP.
- How to get more fibre into your dietHow much fibre adults and children need, and the foods to get more of it from.
- ProbioticsWhat probiotics are, the evidence on them, how they are regulated, and who should check first.
- Irritable bowel syndrome in adults: diagnosis and management (CG61), recommendationsThe national guideline on IBS, including advice on fibre, probiotics and aloe vera.
- Irritable bowel syndrome: Scenario: Management of irritable bowel syndromeNICE's summary for GPs on diet, fibre, probiotics and medicines for IBS.
- Constipation: Scenario: Constipation in adultsNICE's summary for GPs on diet, fibre and laxatives for constipation in adults.
- Probiotics and gut healthWhat probiotics and prebiotics are, where the evidence stands, and who might try them.
- Irritable bowel syndrome (IBS) and dietDiet changes for IBS by symptom, and how to try a probiotic.
- FibreTypes of fibre, how much to eat, the best food sources, and increasing it gradually.
- Prebiotics & ProbioticsWhat prebiotics and probiotics are, the evidence on them, and when a supplement may be considered.
- Irritable Bowel Syndrome (IBS)IBS symptoms and diagnosis, diet changes, probiotics, medicines and talking therapies.
- Ginger: Usefulness and SafetyWhat studies show about ginger, including for nausea, and its side effects.
- Feeling sick (nausea)Causes of feeling sick, things to try at home, including ginger, and when to see a GP.
- What Apple Cider Vinegar Can (and Can't) Do for YouA dietitian on the claims made for apple cider vinegar, its side effects and its use.
- Aloe Vera: Usefulness and SafetyWhat studies show about aloe taken by mouth or used on the skin, and its safety.
Sources checked 28 September 2026. Prices checked 20 October 2026, ranked purely by price per dose. Which sources these pages use.