What is FODMAP?

FODMAP does sound a bit rude but it’s actually one of the hottest dietary trends and one that has legs.

A diet low in FODMAP carbohydrate is an effective dietary treatment for almost 80% of IBS suffers and relieves gut symptoms such as bloating, wind, abdominal pain and altered bowel habits. The low FODMAP diet was originally developed at Monash University, in Australia and has recently been adapted for the UK at King’s College London. It is currently used at Guy’s and St Thomas’ NHS Trust in London; so its ‘kosher’ and not a fad diet.

FODMAP is an acronym that stands for: Fermentable, Oligo-polysaccharides, Di-saccharides, Mono-saccharides and Phenols, all of which are types of small carbohydrate molecules.

The science bit

All carbohydrates consist of simple sugars (saccharides) like glucose and fructose that are joined together into long chains. A single sugar molecule is known as a Mono-saccharide; two sugars joined together are di-saccharides; 3 – 6 sugars joined together Oligo – polysaccharides and longer chains of more than 6 sugars are polysaccharides (either starch or fibre). Phenols are a special type of carbohydrate, sugar alcohols.

The digestion of carbohydrates takes place in the small intestine (gut) and involves enzymes that break down the bonds between the sugars in the chains to yield small sugar molecules that are absorbed into the blood stream. However, some types of small carbohydrate molecules (FODMAPs) are difficult for our body to digest so they pass, undigested, from the small intestine into the large intestine (colon). The colon is colonised by a huge, dense population of bacteria that ferment the FODMAP carbohydrates. The fermentation breaks down the carbohydrate molecules into short chain fatty acids (acetate, propionate and butyrate). A side effect of the bacterial fermentation is that water is pulled into the colon and gases (carbon dioxide, hydrogen and/ or methane) are produced. It is this that can cause bloating and discomfort. The idea is that by following a diet low in FODMAP containing foods, IBS sufferers can reduce and even eliminate their symptoms.

The FODMAP diet

So what are the FOMAP containing foods that should be avoided? FODMAPs are widespread the diet and include:

  • Mono-saccharides: fructose (when in excess of glucose), found in honey, fruit and fruit juices

  • Di-saccharides: lactose (milk sugar)

  • Oligo-saccharides: fructans, found in wheat, rye and some vegetables and galacto-oligosaccharides (GOS), found in pulses and legumes

  • Polyols: sorbitol and mannitol, found in some fruits and vegetables

There are 3 progressive stages to the low FODMAP diet, but this is a difficult, complex, time-consuming and restrictive process.

The first stage is Restriction: in this stage FODMAP intake is reduced by avoiding foods that are high in FODMAPs for 4 to 8 weeks, as this period is considered long enough to identify if symptoms will respond to a low FODMAP diet.

The second stage is Reintroduction: if symptoms have improved by following FODMAP restriction, high FODMAP foods are slowly reintroduced on an individual basis. This allows the identification of which FODMAPs cause a problem and how much of the food triggers symptoms.

The last stage is Personalisation: the long term aim of a low FODMAP diet is to personalise the diet so that only those foods that trigger symptoms are avoided and the person returns to as normal a diet as possible.

A word of warning

Elimination diets can be dangerous, particularly if followed for a prolonged period as it is very important to have a varied and well-balanced diet to meet nutritional requirements. The FOODMAP diet is designed to be individualised, taking into consideration usual dietary intake and symptom profile. The diet can be difficult to follow without specialist advice because it is not quite as simple as following a list of ‘foods to eat’ and ‘foods not to eat’; for example high FODMAP ingredients are often hidden in packaged foods.

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