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All You Need To Know About The FODMAP Diet

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Posted: 13/11/2017

Updated: 13/11/2017

FODMAPs are a type of carbohydrate or sugar naturally found present in many foods and beverages. By restricting FODMAPs, it has been found to improve gastrointestinal symptoms including abdominal pain, bloating, and diarrhoea in people with irritable bowel syndrome (IBS) and other functional gastrointestinal disorders (FGID) (1).


Intestinal bowel syndrome (IBS) can be a long-lasting problem that changes how you are going to live your life. Some people with IBS miss work or school more often, and they may feel less able to take part in daily activities – some might even change their work setting like shifting to working at home or stop working at all, while other people will experience feelings of depression and anxiety.


There is no cure for IBS, but the symptoms can in most situations be managed by making changes to your diet and lifestyle – which is best done by the low FODMAP diet. Up to 86% of people with IBS symptoms experience an improvement when following the diet (2).

Note: low FODMAP diets should only be used when first-line advice has been tried and symptoms still remain. You should see a dietitian before following such a restrictive diet.


  • NOT a weight-loss diet

  • NOT about eating lots of fibre

  • Might NOT improve symptoms completely as other things can be a cause of IBS symptoms e.g. stress, too much alcohol and medications

How does it help?

how does it help

FODMAPs are poorly absorbed in the small intestine of the digestive tract and continue on until reaching the large intestine where bacteria have the enzymes to ferment them. This is usually not an issue unless when hydrogen is produced by gut bacteria. Hydrogen can stretch the bowel causing discomfort, abdominal pain, gas (flatulence) and constipation (3).

FODMAP Acronym 


FODMAP stands for "Fermentable, Oligo-, Di-, Mono-saccharides, And Polyols"


Fermentable oligosaccharides

are several sugar units linked together that are broken down (fermented) by bacteria in the large intestine.



Fructans are fructose units attached to each other.

Source: gluten grains (wheat, rye, and barley), onions, garlic, asparagus


These are galactose units attached to each other.

Source: mainly legumes (chickpeas, baked beans, kidney bean, and lentils)


These are double sugar molecules. 

Lactose The ability to make lactase that is responsible for the breakdown of lactose reduces as you age which makes lactose indigestible.

Source: dairy products e.g. milk, soft cheese, ice cream, etc.


These are single sugar molecules. 


The mechanism behind fructose absorption is easily overwhelmed which can trigger adverse gut symptoms.

Source: fruits and junk foods as high fructose corn syrup (HFCS)

Polyols (Sugar alcohols)

These are sugar alcohols that cannot be digested or absorbed.   

Isomalt, lactitol, maltitol, mannitol, sorbitol, and xylitol

Source: fruits (apples, avocados, cherries, etc.), vegetables, low-calorie sweeteners and other confectionaries

Some people only have symptoms triggered by one or two types of FODMAPs, where others might be sensitive to all five.


You should naturally only restrict food if they contribute to your symptoms, and therefore it’s important to seek guidance from a dietitian or doctor, so you can individualise according to the problematic FODMAPs.

Additional Factors


Other Sugars

Some foods have inulin which is non-absorbable.

Source: ground chicory root, asparagus, leeks, garlic, and onions.


Fibre is fermented by bacteria in the colon, which can result in excess gas production, bloating, constipation, etc. 

Too little fibre 

hard/pellet stools, stomach pain, straining

Enough fibre 

soft, firm stools, normal amount of gas

Too much fibre

loose/frequent stools, stomach pain, excess gas, bloating

FODMAP foods

fodmap foods

FODMAPs are often grouped into 3 categories: low, moderate and high.


Moderate FODMAP foods are safe to eat but only at the maximum serving size suggested and high FODMAP foods should be avoided. Some low FODMAP foods can still trigger symptoms in certain individuals and this highlights the importance of working closely with a FODMAP trained dietitian to identify these foods.


Thus, certain nutrient requirements including fibre and calcium can be hard to meet on a restrictive diet and nutritional advice can be provided by a dietitian to ensure you are not missing out on key nutrients!


The list below which shows examples of low and high FODMAP groups is not exhaustive and has been adapted from Monash University


The Monash app developed by the University of Monash is a handy app for those who have IBS. 


Diet Phases

Diet phases

After covering briefly low and high FODMAP groups, an elimination diet is where foods that are suspected to cause symptoms are removed for a period of time so foods that contain little or no FODMAPs are eaten for approximately 2 to 6 weeks or until symptoms are well managed.

Once the symptoms have improved, this reintroduction or challenge phase is where one food item from each FODMAP group is reintroduced one at a time to see the reaction and tolerance to a high FODMAP food which tends to take around 8 to 12 weeks.

After each FODMAP group challenge, a list of foods that are safe for that particular individual and foods that trigger symptoms (plus the amount that triggers the symptoms) can be recorded and this is the maintenance phase.


Additional Questions

additional question

Does everyone react the same to foods on the high FODMAP list?

People can tolerate different levels of FODMAPs, and therefore some foods may be fine for you to consume while others on the diet can’t. After a period of the diet you can work out which high FODMAP foods you are able to tolerate, and you, therefore, can stop avoiding.


Can the low FODMAP diet cure IBS?

Nothing can cure IBS, but the low FODMAP diet is a great way to manage and possibly lower the symptoms of the disease.


How long does it take until I’m symptom-free?

It differs from person to person how long time it takes to make you symptom-free, but it mostly takes 2 to 4 weeks before people see a noticeable improvement. If you don’t see any improvements after 6 weeks you might either have an issue that’s not related to FODMAPs, or you might be overlooking high FODMAP foods or serving sizes in your diet without you noticing.


Dried fruits and fresh fruits

Drying fruits increases the amount of FODMAPs in the fruit as it becomes concentrated and therefore some dried fruits have fructans, while the raw version of the same fruit does not.

Data Sources

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