The FODMAP Diet Explained

Apr 15, 2015

If you suffer from IBS or another functional gastro-intestinal disorder, and you’ve looked into ways to improve your condition, you will most likely have come across references to the low-FODMAP diet. Developed by Peter Gibson and Susan Shepherd at Monash University in Melbourne, Australia, it is often recommended to sufferers as a way to reduce their symptoms. But what exactly is it, and how does it help?

FODMAP Defined

FODMAP stands for Fermentable Oligosaccharides, Disaccharides, Monosaccharides And Polyols.

Fermentable: The FODMAPs diet is largely based around poorly-absorbed sugars which are fermented by bacteria in the large bowel.

Oligosaccharides: Individual sugars joined together to make a chain; fructans (fructose sugars chained with glucose at the end) and galacto-oligosaccharides (galactose sugars with fructose and glucose at the end) are the main concerns.

Disaccharides: Two individual sugars joined to make a double sugar. The most important is lactose, which is a glucose sugar joined to a galactose sugar.

Monosaccharides: Individual sugars. The FODMAPs diet is mainly concerned with excess or imbalanced fructose.

Polyols: Also referred to as sugar alcohols, with the most commonly occurring being sorbitol and mannitol.

Thus, the term FODMAP applies to a range of carbohydrates which are commonly found in the Western diet.

Why Reduce FODMAPs?

Many functional gastrointestinal disorders feature distension of the intestinal lumen, causing pain, bloating sensations, abdominal distension and disordered motility. FODMAPs have several characteristics which contribute to or induce distension; they are poorly absorbed and are fermented by intestinal bacteria with hydrogen production. Thus, by reducing the level of FODMAPs in the diet, the therapeutic aim is to reduce the level of intestinal distension and thereby reduce the symptoms and improve the sufferer’s condition.

Foods to Avoid

Fructan sources include wheat, rye, barley, onion, garlic, artichokes, asparagus, leek, broccoli, brussels sprouts, cabbage, fennel and chocolate.

Dietary sources of galactans are generally beans and pulses.

Polyols are naturally found in some fruit; particularly stone fruits. This category includes apples, apricots, avocados, blackberries, cherries, nectarines, peaches, pears, plums, prunes and watermelon. Vegetable sources include cauliflower, mushrooms and mange-tout peas. They are also commonly used as sweeteners.

Fructose is a more complex point; the low-FODMAP diet does not require the exclusion of fructose, but only the avoidance of excess fructose when compared to glucose. Foods that contain more glucose than fructose, or the two sugars in balance, are considered acceptable as part of the low-FODMAP diet.

Lactose is, of course, commonly found in milk, yogurts and some cheeses. It can also be used as a commercial food additive, found in a variety of processed foods, so anyone excluding lactose from their diet should be very careful to check the labels of such items.

Foods to Enjoy

With such a long list of foods to avoid, it is often easier to follow the low-FODMAP diet by knowing which foods are allowed. These include:


Bananas, blueberries, grapefruit, grapes, melon, kiwi, lemons, oranges, mandarins, raspberries and strawberries.


Carrots, celery, aubergine, lettuce, parsnips, sweet potato, tomatoes, peppers and bok choy.


Beef, chicken, canned tuna, eggs, lamb, fish, pork, turkey, nuts and seeds – so long as they are prepared without adding FODMAP foods.


Glucose, butter, hard cheeses, sorbet and rice milk.

The presence of butter and hard cheeses may seem surprising, as they are dairy products which most would assume would be high in lactose; in fact, the process of making butter or cheese (particularly traditionally-made hard cheese) significantly reduces the level of lactose present. Whilst still not suitable for anybody with a specific lactose intolerance, they are appropriate for a low-FODMAP diet.

Is the Low-FODMAP Diet For You?

Following a restrictive diet is difficult to maintain in the long term; it can sometimes be more expensive, and may cause lifestyle issues when you want to eat out. However, it can be an effective self-help measure, and, when combined with a detailed food diary and the careful re-introduction of individual items, it can help you to identify particular trigger foods which you can then completely remove from your diet.

It is important to note, however, that you should be certain of your diagnosis before attempting self-treatment; many of the symptoms of irritable bowel syndrome can also be signs of more serious conditions such as bowel cancer. Our team of experts here at the London Gastroenterology Centre can help you with a diagnosis and advise you on appropriate IBS treatment in London; for more information or to make an appointment, contact us on 020 7183 7965.

We are available to see patients daily for private consultations

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