What Actually Are FODMAPs and who is the Low FODMAP Diet for?

Heard about fructose malabsorption or lactose intolerance?  Seen a FODMAP Friendly food product on the grocery shelves? It’s likely you might know someone who modified their diet for these reasons. Perhaps you even follow or have been advised to follow a Low FODMAP Diet. So what actually are these things called FODMAPs, what foods are they found in and why do some people go on a low FODMAP diet?

A diet low in FODMAPs (a “Low FODMAP Diet”) is a dietary protocol which has been scientifically proven for the management of uncomfortable digestive symptoms of Irritable Bowel Syndrome (IBS).

FODMAPs are certain types of sugars (short-chain carbohydrates) that can trigger uncomfortable digestive symptoms in people with a sensitive gut. They are found in a wide range of food and drinks such as milk, beans, onion, garlic, apples and wheat. FODMAPs are sometimes added to foods during processing as well.

Without getting too scientific, if we flashback to high school science for a moment (if you remember paying attention back then), you may have learnt about the main nutrients that make up food. One of these is carbohydrates (or carbs). Carbohydrates are made up of smaller sugar molecules joined together to make up a chain.

So, FODMAPs are various short carbohydrate chains. They are known to be poorly absorbed in the part of the digestive tract where most nutrients are absorbed (the small intestine) and instead continue to the large intestine (colon). This is where FODMAPs mostly have their effect, triggering symptoms like bloating, excess gas and pain.

The term FODMAPs stands for Fermentable, Oligosaccharides, Disaccharides, Monosaccharides and Polyols which are the scientific names of these different short-chain carbohydrates. Fermentable refers to the fact that these carbohydrates can be fermented by gut bacteria to produce gases. “Saccharide” is a scientific term for sugar and the prefix of the name indicated the length of these sugars, for example, “di” means two, so a disaccharide is made of two sugars.

What foods are the FODMAPs found in?

Oligosaccharides- Fructans and Galactooligosaccharides: Wheat, rye, barley, onion, garlic, legumes and fruit & vegetables.

Disaccharides- Lactose: Cow’s milk, yoghurt, ice-cream, custard, cream and some soft cheeses.

Monosaccharides- Excess Fructose: Certain fruits and vegetables including mango and asparagus, fruit juice, honey and high-fructose corn syrup.

Polyols- Sorbitol, Mannitol, Maltitol, Xylitol: Certain fruit and vegetables (cauliflower, mushrooms, stone fruit) and some low-calorie sweetened products such as sugar-free gums and mints.

What about pre-packaged foods?

Levels of FODMAPs in food vary depending on the portion size and the way the food is processed. Therefore, it can often be tricky to read food labels to work out if a food is low FODMAP. Many food companies are now registering their products for FODMAP friendly accreditation.

If you see the green FODMAP Friendly logo on any food products, then rest assured that product is suitable for consumption whilst following a low FODMAP diet at the packet serve size.

How do FODMAPs trigger IBS symptoms?

FODMAPs have 2 main features that influence how they trigger digestive symptoms:

1.     By attracting water into the intestine. This can create pressure in the gut and can result in loose stools or diarrhoea.

2.     They are rapidly fermented in the large intestine by bacteria that reside the gut (ie. the gut microbiome). The fermentation results in the release of gas which can cause the intestinal wall to stretch and expand. In people with a sensitive gut (ie. people with IBS), the stretching and expansion can trigger digestive symptoms including bloating, cramping, abdominal pain and constipation.

The Phases of the Low FODMAP Diet

The Low FODMAP Diet commonly involves three phases: elimination, reintroduction/challenging FODMAPs and maintenance/individualisation.

Phase 1: Elimination

In the elimination phase, all foods with high FODMAP levels are eliminated from the diet. The purpose of this step is to determine whether removing FODMAPs makes a significant difference in gut symptoms. This step usually lasts 2-4 weeks.

Phase 2: Challenge/ Reintroduction

The challenge phase is then commenced if symptom improvement is seen after the completion of the elimination phase. Challenging FODMAPs is a way of identifying which types of FODMAPs are tolerated and which are problematic. This phase is also essential for understanding the amount of FODMAPs you can tolerate, which is known as your individual “threshold”.

Doing these challenges helps to ensure that only problematic foods are limited long term and prevents the need for an over-restrictive diet which can limit a variety of plant-based foods in the diet. Each FODMAP is challenged with a specific test food one at a time and can take several months to complete all challenges.

Phase 3: Individualisation/personalisation

The individualisation/personalisation phase is the next stage once all the FODMAPs have been “challenged” and individual tolerance of each FODMAP has been identified. This looks like a long-term modified FODMAP diet, where well-tolerated high FODMAP foods are reintroduced and included in the diet and only the problematic high FODMAP foods (identified in the challenge phase) are limited.

The aim is to increase the variety in the diet as much as possible while balancing symptoms. Eating a diverse range of food (especially plant-based foods) is associated with positive long-term gut health and improves the social, cultural and mental factors that play a huge part in food enjoyment.

Generally, most people don’t react to all FODMAPs, but rather have one or two main FODMAP triggers. This means that the long-term personalisation phase of the diet provides much more variety than the initial elimination phase.

‘I think I might benefit from low FODMAP, where do I start?’

Before starting on the diet, it’s firstly important to actually make sure it’s IBS and not another gut-related condition. The symptoms of IBS (bloating, pain, constipation, diarrhoea, flatulence) can present identically to other serious gut conditions, mainly – Inflammatory Bowel Diseases (IBD), coeliac disease and even bowel cancer. That’s not to say the IBS itself isn’t serious, as of course, IBS can be very debilitating and greatly impact one’s quality of life. Although, it is very important to rule out these other conditions which can cause structural damage to the gut and other body parts. If you suffer from uncomfortable gastrointestinal symptoms then seeing a doctor is the first step to take to determine a diagnosis.

If you do have IBS, there may be other more simple strategies to implement before going straight to the low FODMAP diet. For instance, adequate hydration, dietary fibre intake, reduction of gut irritants (such as alcohol and caffeine) and incorporating stress-management strategies into your routine are all useful strategies for managing gut symptoms.

This is where seeing an Accredited Practising Dietitian trained in digestive health comes in to play. An expert dietitian can support you to find the best-individualised management approach. If that happens to be the low FODMAP diet, a dietitian will be able to guide you through the 3 phases while ensuring your diet provides all the nutrients you need and, importantly, that it is flavoursome and enjoyable.

Picture of Rebecca Ponsford

Rebecca Ponsford

Rebecca is an Accredited Practising Dietitian, graduated from Monash University in 2018. She works predominately in the space of gut health and digestive disorders such as Irritable Bowel Syndrome. She has expertise in the practical implementation of the Low FODMAP Diet and also has a strong interest in the link between mental health and gastrointestinal health. Rebecca is passionate about supporting people to achieve their health goals and develop healthy relationships with food where they can eat with ease.

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