Step 1: for everyone (4 weeks)

• Three regular meals; do not skip breakfast Proven
• At least 8 cups of fluid daily, mostly water Proven
• No more than 3 cups of coffee or tea daily; reduce fizzy drinks Proven
• Reduce fatty, spicy and processed food if it worsens symptoms Proven
• Avoid sugar alcohols (sorbitol, mannitol) in gum and "sugar-free" sweets Proven
• No more than 3 portions of fruit daily Proven
• Soluble fibre such as psyllium husk (ispaghula), starting with one teaspoon and increasing slowly with water, helps especially with constipation Proven Coarse wheat bran may worsen bloating.
• 20–30 minutes of physical activity most days improves symptoms and is recommended in guidelines Proven

By symptom type

• Constipation: two green kiwifruit daily worked as well as psyllium and prunes in chronic constipation, with less bloating and fewer side effects Proven Ground flaxseed (one tablespoon daily) is an alternative May help
• Diarrhoea: reduce caffeine, fat and sweeteners; try lactose-free laban or milk if dairy seems to trigger symptoms.
• Constipation, also: about 10 prunes a day, or a spoon of chia seeds or olive oil; your doctor may prescribe magnesium oxide. Vitamin D is checked and replaced if low.
• Diarrhoea, also: oral rehydration solution when diarrhoea is heavy, and banana and rice for a day or two only; laban and kefir are often better tolerated than milk.

Step 2: low FODMAP diet (with a dietitian)

FODMAPs are poorly digested sugars in some foods that cause gas and bloating. This diet improves symptoms in roughly half to two-thirds of patients Proven It has three phases: restriction for 2–6 weeks, structured reintroduction one food group at a time, then a long-term personalised diet. Do not stay on the restriction phase permanently.

Complementary options

• Enteric-coated peppermint oil capsules for pain and cramps.
• Probiotics: benefit is uncertain and guidelines disagree; if you wish to try one, use a single product for up to 12 weeks and stop if there is no benefit.
• Gut-directed hypnotherapy and cognitive behavioural therapy work for persistent symptoms.
• A Mediterranean diet improved symptoms in a small trial and is a less restrictive alternative.
• Curcumin with fennel oil, and anise oil, helped in small trials.
• A gluten-free diet is not routinely recommended; coeliac disease must be tested for first (starting the diet before testing makes the test unreliable) and changes made only on medical advice.