FODMAP

FODMAPs are short chain carbohydrates (oligosaccharides), disaccharides, monosaccharides and related alcohols that are poorly absorbed in the small intestine. These include short chain (oligo-) saccharide polymers of fructose (fructans) and galactose (galactans), disaccharides (lactose), monosaccharides (fructose), and sugar alcohols (polyols) such as sorbitol, mannitol, xylitol and maltitol.

The term FODMAP is an acronym, deriving from "Fermentable, Oligo-, Di-, Mono-saccharides And Polyols". The restriction of these FODMAPs from the diet has been found to have a beneficial effect for sufferers of irritable bowel syndrome and other functional gastrointestinal disorders (FGID). The low FODMAP diet was developed at Monash University in Melbourne by Peter Gibson and Susan Shepherd.

Pathophysiology of FGID
The basis of many FGIDs is distension of the intestinal lumen. Such luminal distension may induce pain, a sensation of bloating, abdominal distension and motility disorders. Therapeutic approaches seek to reduce factors that lead to distension, particularly of the distal small and proximal large intestine. Food substances that can induce distension will be those that are poorly absorbed in the proximal small intestine, osmotically active, and fermented by intestinal bacteria with hydrogen (as opposed to methane) production. The small molecule FODMAPs exhibit these characteristics.

FODMAP absorption
Poor absorption of most FODMAP carbohydrates is common to everyone. Any FODMAPs that are not absorbed in the small intestine pass into the large intestine, where bacteria ferment them. The resultant production of gas potentially results in bloating and flatulence. Most individuals do not suffer significant symptoms but some may suffer the symptoms of IBS. Restriction of FODMAP intake in the latter group has been found to result in improvement of symptoms.

Fructose malabsorption and lactose intolerance may produce IBS symptoms through the same mechanism but, unlike with other FODMAPs, poor absorption is found only in a minority of people. Many who benefit from a low FODMAP diet need not restrict fructose or lactose. It is possible to identify these two conditions with hydrogen and methane breath testing and thus eliminate the necessity for dietary compliance if possible.

FODMAP sources in the diet
The significance of sources of FODMAPs varies through differences in dietary groups such as geography, ethnicity and other factors.

Sources of fructans
Sources of fructans include wheat, rye, onion, garlic, Jerusalem and globe artichoke, asparagus, beetroot, chicory, dandelion leaves, leek, radicchio, the white part of spring onion, broccoli, brussels sprouts, cabbage, fennel, chocolate and prebiotics such as fructooligosaccharides (FOS), oligofructose and inulin.

Sources of galactans
Pulses and beans are the main dietary sources.

Sources of polyols
Polyols are found naturally in some fruit (particularly stone fruits), including apples, apricots, avocados, blackberries, cherries, lychees, nectarines, peaches, pears, plums, prunes, watermelon and some vegetables, including cauliflower, mushrooms and mange-tout peas. They are also used as artificial sweeteners and include isomalt, maltitol, mannitol, sorbitol and xylitol.

Sources of fructose
See: Foods with high fructose content

Sources of lactose
See: Avoiding lactose-containing products