Causes and symptoms of FODMAP intolerance

Poorly absorbed short-chain carbohydrates can cause gastrointestinal symptoms in susceptible people. These short-chain carbohydrates are collectively termed FODMAPs (an acronym for fermentable oligosaccharides, disaccharides, monosaccharides and polyols). FODMAPs include fructose, fructans, lactose, polyols and galacto-oligosaccharides; see Common food sources of FODMAPs for common food sources of FODMAPs.

Table 1. Common food sources of FODMAPs
FODMAP	Common food sources
oligosaccharides	fructans: wheat, barley, rye, artichoke, asparagus, beetroot, brussels sprouts, savoy cabbage, chicory, garlic, leek, onion, peas, radicchio, shallots, all legumes (eg baked beans, kidney beans, borlotti beans), pistachios, almonds galacto-oligosaccharides (eg raffinose, stachyose): legumes, chickpeas, lentils
disaccharides	lactose: custard, milk, yoghurt
monosaccharides	fructose: apples, pears, watermelons, mangoes, fruit juice, dried fruit, honey, high-fructose corn syrup. Sometimes added to processed foods as a sweetener
polyols	sorbitol, mannitol, xylitol and other sugar alcohols: apples, pears, stone fruit (eg apricots, peaches, nectarines, plums, cherries, prunes), avocado, mushrooms, snow peas, cauliflower, artificial sweeteners

Poor absorption and digestion of FODMAPS in the small bowel results in increased bacterial fermentation in the large bowel (and subsequent gas production) and increased luminal distension via an osmotic effect. Absorption and digestion of FODMAPs is affected by the amount of enzymes available to digest disaccharides (eg lactase), small intestinal transit time, small intestinal bacterial overgrowth (SIBO), mucosal disease, the amount of carbohydrate ingested and meal composition. Whether symptoms occur depends on factors such as visceral hypersensitivity, altered gut microbiota, abnormal immune responses, anxiety, stress and conditioning.

Many patients with irritable bowel syndrome (IBS) poorly tolerate FODMAPs; a low-FODMAP diet can be an effective therapy for IBS.