7 min readConcept sheetOften a 5-mark answer; FODMAP comes as a 2-mark question

Irritable bowel syndrome (IBS)

IBS is a functional bowel disorder: recurring belly pain with changed bowel habit but no visible damage. Diet care uses regular meals and, if needed, a low-FODMAP diet.

DefinitionRecurrent abdominal pain linked to a change in bowel habit, with no structural disease

TypesIBS-C (constipation), IBS-D (diarrhoea), IBS-M (mixed), IBS-U (unclassified)

Rome IV criteriaPain on at least 1 day a week for 3 months, with 2 of: linked to passing stool, change in frequency, change in form

FODMAPFermentable Oligo-, Di-, Monosaccharides And Polyols

At a glance

DefinitionA functional disorder of the gut-brain axis: the bowel looks normal but works and feels abnormally

CausesAltered gut movement, an over-sensitive gut, stress and anxiety, after a gut infection, changed gut bacteria, poorly absorbed sugars (FODMAPs); more common in women

SymptomsCramping pain eased by passing stool, bloating, gas, diarrhoea or constipation or both, mucus in stool, feeling of incomplete emptying

Red flags (not IBS)Blood in stool, weight loss, fever, anaemia, onset after 50 years, symptoms waking the patient at night; refer to a doctor

Dietary principles

Point	Recommendation	Why
Meal pattern	Regular meals; do not skip or eat late; eat slowly	Irregular eating upsets gut movement
Fibre	Soluble fibre (isabgol, oats) for IBS-C; limit wheat bran	Bran often worsens bloating and pain
Fluid	8 glasses of water a day	Softens stools; replaces losses in IBS-D
Fat and spice	Limit fried, fatty and very spicy foods	They trigger cramps and loose stools in many
Caffeine, alcohol, fizzy drinks	Limit to small amounts	They speed the bowel and add gas
Low-FODMAP diet (second line)	Under a dietitian: cut high-FODMAP foods for 2-6 weeks, then reintroduce one group at a time, then personalise	Poorly absorbed sugars ferment in the colon, making gas and drawing in water

FODMAP groups with Indian foods

Group	High-FODMAP foods (limit in elimination phase)	Lower-FODMAP swaps
Oligosaccharides (fructans, GOS)	Wheat in large amounts, onion, garlic, rajma, chana, cashew	Rice, ragi, oats, small portions of soaked and rinsed moong or masoor dal, chives or spring onion greens
Disaccharide (lactose)	Milk, ice cream, milk sweets	Lactose-free milk, small amounts of curd, paneer
Monosaccharide (excess fructose)	Honey, mango, apple	Firm banana, papaya, orange, grapes
Polyols	Apple, pear, mushroom, cauliflower, sugar-free gum (sorbitol, mannitol)	Carrot, cucumber, tomato, brinjal, spinach, potato

Sample one-day menu (IBS with bloating)

Meal	Menu
Early morning	Warm water; weak tea with lactose-free milk
Breakfast	Ragi dosa or oats upma with carrot, tomato chutney (no onion or garlic)
Mid-morning	Papaya (1 cup)
Lunch	Rice, small bowl of moong dal, brinjal-potato curry, cucumber raita with a little curd
Evening	Roasted peanuts (small handful); orange
Dinner	Rice or ragi roti, egg or fish curry made with tomato and ginger, spinach poriyal
Bedtime	1 teaspoon isabgol in water (for IBS-C)

At the bedside

In the clinic, ask the patient to keep a food and symptom diary for two weeks. A strict low-FODMAP diet is only a short test diet; foods must be brought back so the diet does not become poor in fibre and calcium.

Exam angle

2 marks: “Expand FODMAP.” Fermentable Oligosaccharides, Disaccharides, Monosaccharides And Polyols: short-chain carbohydrates that ferment in the colon and trigger IBS symptoms.

5 marks: “Write a note on irritable bowel syndrome.” Definition as a functional disorder, types, causes, symptoms, red flags and diet principles including the low-FODMAP approach.

10 marks: “Discuss the causes, symptoms and dietary management of irritable bowel syndrome.” Define with Rome IV, four types, causes, symptoms, diet principles table, FODMAP groups with Indian foods, sample menu.

Remember it

IBS: the bowel looks fine but behaves badly. FODMAP elimination in 3 steps: cut out, bring back, personalise.