Diet for IBS: Foods, Triggers and the Low-FODMAP Approach

Quick answer

Start with simple changes; use low-FODMAP under dietitian supervision

First-line IBS dietary advice includes regular meals, adequate fluids, limiting caffeine, alcohol, fatty and spicy foods and fizzy drinks, and managing fibre intake (soluble fibre such as psyllium is better tolerated than wheat bran). If symptoms persist, the low-FODMAP diet, with a temporary restriction, reintroduction and personalisation, improves symptoms in about 50–75% of people, but should be supervised by a dietitian to avoid unnecessary long-term restriction. Probiotics, peppermint oil, gut-directed hypnotherapy and CBT can also help. Alarm symptoms need medical review.

Important. Rectal bleeding, black stools, unexplained weight loss, persistent vomiting, anaemia, difficulty swallowing, new symptoms after age 50, night-time diarrhoea or a family history of bowel cancer or coeliac disease need medical assessment before assuming IBS.

What is IBS?

IBS is a common disorder of gut–brain interaction affecting 5–10% of people. It is diagnosed by symptoms (recurrent abdominal pain linked to bowel movements and changes in stool frequency or form) after excluding other conditions. The causes are multiple: altered gut sensitivity and motility, gut microbiome changes, infections, stress and diet. There are subtypes: with diarrhoea (IBS-D), with constipation (IBS-C) and mixed (IBS-M).

Step 1: general dietary advice

Eat regular meals and take time to eat; do not skip meals or leave long gaps.
Drink enough fluid: at least 8 cups of water or non-caffeinated drinks a day.
Limit tea and coffee to three cups a day, and cut back on alcohol and fizzy drinks.
Reduce fatty, fried and very spicy foods.
Manage fibre: if you have constipation, increase soluble fibre (oats, linseed, psyllium) gradually; reduce insoluble fibre such as wheat bran if it worsens bloating.
Limit sorbitol and other sweeteners (sugar-free gum, “diet” products) which can cause diarrhoea and gas.
Keep a food and symptom diary for a few weeks to spot patterns.
This advice is recommended by the NHS and NICE as first-line.

Common triggers

Large, rich or heavy meals; eating quickly.
Caffeine, alcohol, carbonated drinks.
Fatty, fried and spicy foods.
Wheat, onions, garlic, beans, some fruit and dairy (high-FODMAP foods) in some people.
Artificial sweeteners and sugar alcohols.
Stress, anxiety and poor sleep, which worsen symptoms regardless of food.
Triggers differ from person to person; avoid cutting out many foods without guidance.

The low-FODMAP diet

FODMAPs (fermentable oligosaccharides, disaccharides, monosaccharides and polyols) are short-chain carbohydrates that are poorly absorbed in the small intestine, draw water into the gut and are fermented by bacteria, producing gas and bloating in sensitive people. They include fructans (wheat, onion, garlic), galacto-oligosaccharides (legumes), lactose (milk), excess fructose (apples, honey, mango) and polyols (sorbitol in stone fruit, mushrooms and sweeteners).

The low-FODMAP diet, developed at Monash University, has three phases: 1. Restriction (2–6 weeks) of high-FODMAP foods; 2. Reintroduction of each FODMAP group one at a time to identify triggers and thresholds; 3. Personalisation, where you eat as varied a diet as your tolerance allows. About half to three-quarters of people notice improvement. It is not meant to be followed strictly long term, because it reduces fibre and prebiotic intake and can be nutritionally limiting.

Low and high-FODMAP examples

Lower-FODMAP choices: oats, rice, quinoa, potatoes, carrots, courgette, spinach, tomatoes, cucumber, bananas (firm), oranges, blueberries, strawberries, eggs, meat, fish, tofu, lactose-free milk, hard cheese, sourdough spelt bread.
Higher-FODMAP foods to restrict in phase 1: wheat bread and pasta in large amounts, onion, garlic, cauliflower, mushrooms, beans, lentils, apples, pears, mango, watermelon, honey, milk, soft cheese, sorbitol and mannitol sweeteners.
Portion sizes matter: many foods are tolerated in small amounts. Use a reliable app and work with a dietitian trained in the diet.

Other helpful strategies

Peppermint oil capsules can reduce abdominal pain and bloating in some people.
Probiotics: some strains may help; try one product for four weeks and stop if there is no benefit.
Soluble fibre (psyllium/ispaghula) helps constipation and may help overall IBS symptoms.
Gut-directed hypnotherapy and CBT have good evidence for improving symptoms.
Regular exercise, stress management and good sleep.
Medicines for diarrhoea, constipation or pain, as advised by your doctor.
See also bloated belly (Spanish) and probiotics (Spanish).

Precautions with restrictive diets

Cutting out many foods without guidance can lead to nutritional deficiencies, an unhealthy relationship with food and reduced gut microbiota diversity. The low-FODMAP diet is not advised for children without specialist supervision, people with a history of eating disorders, or those with unexplained weight loss. Gluten-free diets may help some people, but test for coeliac disease first (while still eating gluten).

When to see a doctor

Blood in the stool, black stools, anaemia or unexplained weight loss.
Persistent vomiting, difficulty swallowing or night-time symptoms.
New bowel symptoms after age 50.
Family history of bowel cancer, coeliac disease or inflammatory bowel disease.
Symptoms not improving with first-line measures.
Significant impact on quality of life, mood or sleep.

Three common situations

Bloating and diarrhoea after coffee, fizzy drinks and large meals: adjust meal habits and caffeine first.

Constipation with bloating: gradually add soluble fibre, fluids and exercise.

Persistent symptoms despite first-line advice: consider a supervised low-FODMAP trial with a dietitian.

Key points to remember

IBS responds to diet, but start with simple, general advice, and use the low-FODMAP approach under supervision. Combine diet with stress management and medical care, and report alarm symptoms promptly. Our nutrition and digestive-health team can guide you.

This guide is for general information and does not replace an assessment by your own doctor or dietitian.

Questions about the diet for IBS

These answers are general information and do not replace an examination or individual medical advice.

What is the best diet for IBS?

There is no single best diet; start with regular meals, fluids and limiting triggers, then consider a supervised low-FODMAP diet.

Does the low-FODMAP diet work?

It improves symptoms in about 50–75% of people with IBS, when done in phases with reintroduction.

How long should I follow the low-FODMAP diet?

The restriction phase lasts 2–6 weeks, followed by reintroduction and personalisation; it is not meant to be permanent.

Are probiotics helpful for IBS?

Some strains may help; try one for four weeks and stop if there is no benefit.

Should I avoid gluten?

Not necessarily. Test for coeliac disease first; some people with IBS feel better on less wheat because of fructans.

Can stress affect IBS?

Yes. Stress and anxiety can worsen symptoms, and therapies such as CBT and hypnotherapy can help.

Sources

This guide is for general information and does not replace medical advice. How a problem is diagnosed and treated depends on your examination and medical history. If you think you have an emergency, contact your local emergency services.