A Stepwise Diet for Irritable Bowel Syndrome

IBS results from several overlapping factors: a gut that is more sensitive to stretching and gas, changes in how fast food moves through the bowel, the gut–brain connection (stress, anxiety and poor sleep make symptoms worse), changes in gut bacteria, and in some people a past gut infection. Food can trigger symptoms in several ways. Some carbohydrates are poorly absorbed in the small intestine and are fermented by gut bacteria, producing gas and drawing water into the bowel (these are grouped as FODMAPs). Fatty meals, caffeine, large meals and artificial sweeteners such as sorbitol also stimulate the gut. Food does not cause IBS itself; it acts as a trigger.

IBS affects roughly 4 in 100 people worldwide by the stricter Rome IV criteria and about 1 in 10 by older definitions. It is more common in women and often starts between the late teens and the forties. Studies from Saudi Arabia report similar or higher rates, especially among young adults and students.

Many traditional dishes are naturally rich in FODMAPs: wheat-based bread, samboosa pastry, harees and jareesh (wheat), kabsa and other dishes built on onion and garlic, foul medames, hummus and lentil dishes (legumes), laban and milk (lactose), honey and dates. You do not need to give them up; during a supervised low-FODMAP trial, a dietitian will help you swap or reduce them and then reintroduce them in turn. Rice, chicken, fish, eggs, potatoes, cucumber and tomato salads, hard cheese and lactose-free laban are usually well tolerated. Arabic coffee, tea and energy drinks contain caffeine, which can speed up the bowel, so count cups. Hospitality can be a trigger: take a small first plate. During Ramadan, a long fast followed by a large, fatty iftar often worsens pain, bloating and diarrhoea. Break your fast with water and dates, wait, then eat a moderate meal; drink enough fluid between iftar and suhoor; keep some soluble fibre (oats, fruit, cooked vegetables) in your diet to avoid constipation; and avoid starting a strict low-FODMAP restriction phase in Ramadan unless your dietitian agrees. Illness-related relaxation of fasting is a matter for you and your doctor.

IBS is diagnosed from your symptoms by the Rome IV criteria after warning signs have been excluded. Typical first tests are a blood count, inflammation markers and a blood test for coeliac disease, with a stool calprotectin test if you have diarrhoea, to look for inflammatory bowel disease. A colonoscopy is done if there are warning signs or the symptoms are new in older age. Please have coeliac disease excluded before you try a gluten-free diet, because stopping gluten first can make the test unreliable. A food and symptom diary kept for 2 to 4 weeks shows your patterns, and referral to a dietitian is advised before a low-FODMAP trial.

Good habits are Step 1 for everyone and continue through every other step.

• Eat regular meals at a relaxed pace, sit down, chew well, and do not skip meals.

• Be physically active most days; walking, swimming or cycling can ease symptoms.

• Look after sleep and stress. Breathing exercises, relaxation and, for persistent symptoms, gut-directed hypnotherapy or cognitive behavioural therapy have good evidence.

• Keep a food and symptom diary for 2 to 4 weeks, and bring it to your doctor or dietitian.

• Do not make big changes to everything at once; change one thing at a time for a couple of weeks so you can tell what helps.

Work through the steps in order and stop when your symptoms are well controlled. Review with your doctor after each step. Step 1 is the same for everybody; the later steps are personal.

• Step 0, before any diet: have the diagnosis confirmed, red flags checked and coeliac disease tested for. Do not start a gluten-free or very restrictive diet first.

• Step 1, healthy eating advice for 4 weeks: regular meals; about 1.5 to 2 litres of fluid a day, mostly water; no more than 3 cups a day of tea, coffee or other caffeinated drinks; little alcohol and few fizzy drinks; less fatty, fried, spicy and heavily processed food if they trigger you; no more than about 3 portions of fresh fruit a day (a portion is about 80 g); avoid sorbitol and other “-ol” sweeteners in sugar-free gum, sweets and “diabetic” products. This simple step helps many people.

• Step 2, targeted changes by your main symptom. For bloating or constipation: oats, a tablespoon of linseed a day, and soluble fibre such as ispaghula (psyllium) started low and increased slowly with plenty of water. Avoid wheat bran. For diarrhoea: reduce insoluble fibre (bran, wholegrain and nuts and seeds in large amounts) and caffeine. If you suspect lactose, try a short lactose-free trial. A single probiotic product may be tried for up to 12 weeks, and stopped if there is no benefit.

• Step 3, a time-limited low-FODMAP diet with a dietitian, only if steps 1 and 2 are not enough. FODMAPs are fermentable carbohydrates: fructans (wheat, onion, garlic), galacto-oligosaccharides (beans, lentils, chickpeas), lactose (milk, soft cheese), excess fructose (honey, some fruits) and polyols (sorbitol and mannitol in some fruits and sweeteners). It has three phases: (1) restriction for about 2 to 6 weeks; (2) systematic reintroduction of one group at a time to find your own triggers and amounts; (3) a personalised long-term diet that is as varied as possible. If there is no clear improvement after the restriction phase, stop and return to normal eating.

• Do not stay on the restriction phase long term. It can reduce fibre, calcium and gut bacteria diversity. It is not suitable for people with a history of an eating disorder, and for children it should only be done under specialist supervision.

• Gluten: only a minority of people with IBS improve on a gluten-free diet once coeliac disease is excluded, and often it is the fructans in wheat that matter. Do not cut gluten out for long without advice.

• Step 4, if symptoms continue: ask your doctor about gut-directed psychological therapy and medicines (see below), and review the diagnosis. Do not keep adding food restrictions.

• Examples that are often lower in FODMAPs: plain rice, potatoes, oats, eggs, chicken, fish, meat, lactose-free dairy or hard cheese, carrots, cucumber, tomatoes, spinach, strawberries, oranges, kiwi and firm bananas. Examples that are often high: wheat bread and pastry, onion and garlic in large amounts, beans, lentils and chickpeas, milk, apples, pears, mango, watermelon, honey and large portions of dates. Portion size matters, so use a dietitian’s list.

Evidence in brief: moderate for soluble fibre and for basic healthy-eating advice; low certainty but consistent benefit for a supervised low-FODMAP diet in the short term; weak for gluten-free diets and for probiotics (strain-specific). The best diet is the least restrictive one that works for you.

Medicines are described in our IBS article. In brief, your doctor may suggest:

• Antispasmodics or enteric-coated peppermint oil for cramps and bloating.

• For constipation: ispaghula or an osmotic laxative; for diarrhoea: loperamide in the short term.

• Low-dose antidepressants of the tricyclic or SSRI type, used as gut–brain modulators rather than for depression, and prescription medicines for IBS-C or IBS-D if the above do not help.

There is no procedure that treats IBS. Tests are used to rule out other conditions:

• Colonoscopy if there are warning signs, a family history, or symptoms start later in life.

• Hydrogen breath tests for lactose or other sugars may be done in selected people.

• Faecal microbiota transplantation is not recommended for IBS outside research studies.

The British Society of Gastroenterology IBS guideline (2021) and NICE guidance recommend simple dietary advice first (regular meals, adequate fluids, limiting caffeine, alcohol, fizzy drinks, fatty and processed food, fresh fruit to about three portions a day, and sorbitol sweeteners), soluble fibre such as ispaghula (psyllium) rather than insoluble fibre such as wheat bran, and, if symptoms persist, a low-FODMAP diet supervised by a dietitian. The ACG IBS guideline (2021) also suggests soluble fibre and a limited trial of a low-FODMAP diet (conditional recommendation, very low certainty evidence). Randomised trials and meta-analyses show that a low-FODMAP diet improves symptoms in roughly half or more of people, more than control diets, but the studies are short, blinding is difficult and the certainty of evidence is low; in a head-to-head trial it performed similarly to standard NICE-style advice (Böhn and colleagues, 2015). Long-term restriction can reduce fibre, calcium and gut bifidobacteria, so reintroduction is an essential part of the diet. Blinded trials suggest that fructans, rather than gluten, are often the reason wheat bothers people with IBS, and a gluten-free diet is not routinely recommended. Evidence on probiotics is strain-specific and of low certainty: the BSG says a 12-week trial of one product is reasonable, whereas the ACG suggests against probiotics as a class for overall IBS symptoms.

IBS is usually long-lasting with symptoms that come and go, but it is not dangerous. Most people can reduce their symptoms enough to live normally by combining diet changes, stress and sleep care, physical activity and, when needed, medicine or gut-directed psychological therapy. The aim of diet is the most varied diet that keeps symptoms under control, not the most restrictive.

• Have I had the right tests to be sure this is IBS and not coeliac disease or inflammatory bowel disease?

• Which step of the diet should I start with, and for how long?

• Can I be referred to a dietitian trained in the low-FODMAP diet?

• Which fibre supplement or medicine is suitable for my type of IBS?

• How should I manage my symptoms and meals during Ramadan?

This guide comes from the Saudi Gastroenterology Association (SGA) patient library, prepared by the Approved for publication by SGA; individual clinician review is ongoing. Last reviewed: 2026-04-24. It is for education and does not replace your doctor's advice.