If general advice about diet is insufficient, it may be appropriate to consider an exclusion diet avoiding trigger foods. Referral to a dietician may be appropriate for guidance. A common recommendation is a low FODMAP (fermentable oligosaccharides, disaccharides, monosaccharides, and polyols) diet^.1,2

Fermentable foods are only partially digested in the small intestine meaning they are available in the large intestine. Fermentation there involves the carbohydrates being used by bacteria for energy, with the release of compounds such as short chain fatty acids, ethanol, and gases, with resultant bloating, flatulence and abdominal pain.^18,19

Oligosaccharides include fructans (eg in wheat, onion, garlic and the prebiotic inulin) and galacto-oligosaccahrides (found in pulses and legumes, cashews and pistachio nuts). The main dietary disaccharide is lactose, while fructose, a monosaccharide, can be poorly absorbed if consumed in large quantities.¹⁸

In essence, a low MODFAP diet avoids foods which cannot be digested easily, such as some fruits and vegetables, milk and wheat products. A FODMAP diet should be tried for 2-6 weeks and then excluded foods can be reintroduced individually until a trigger food is identified. Food reintroduction should be one food at a time over three days, increasing serving size each day while monitoring symptoms.^1,3,20