Low FODMAPs diets for treatments of irritable bowel syndrome (IBS)

Irritable bowel syndrome (IBS) is a common gastrointestinal disorder affecting one in five people in the UK. Abdominal pain, cramps, swollen belly, gas, constipation and diarrhoea are some of the main symptoms.

It is a long-term but not life-threatening condition that can interfere with many aspects of daily life.

There is no specific test for IBS, therefore it is diagnosed only after testing for and ruling out all other GI problems. It is not known exactly what causes IBS, and so far there is no cure for it so treatment focuses on controlling symptoms.

IBS has traditionally been managed in many different ways, including dietary intervention, supplements, and medications like anti-cramping and ant-diarrhoea drugs.

The low-FODMAP diet is a fairly new approach to treating IBS and it is proving to be an effective way to manage symptoms.

What are FODMAPs?

FODMAPs stand for "fermentable oligosaccharides, disaccharides, monosaccharides and polyols.

  • Fermentable - they can be broken down by bacteria in the gut, resulting in gas and other symptoms of IBS.
  • Oligosaccharides - carbohydrates including fructans and galacto oligosaccharides (GOS).
  • Disaccharides - double-unit sugars such as fructose.
  • Monosaccharides - single-unit sugars such as lactose.
  • Polyols - sugars that are found in some fruits and vegetables and sweeteners such as sorbitol and mannitol.

These are sugars that are found naturally in many foods and ordinarily, they play a good role in the body.

If you suffer from IBS, you can be sensitive to them and this causes the unpleasant symptoms that characterise the condition.

High FODMAP groups that are avoided or very restricted on a low-FODMAP diet include:

  • Lactose - cow’s milk and dairy products.
  • Fructose - some fruits including apples, peaches, mangoes and pears, and sweeteners such as honey and agave nectar.
  • Fructans - some vegetables including artichoke, broccoli, garlic, onions and beetroot, and grains such as wheat and rye.
  • GOS - some vegetables including broccoli, and chickpeas, lentils, kidney beans and soy products.
  • Polyols - some fruits including apples, apricots, blackberries, cherries, nectarines, pears, peaches, plums and watermelon, vegetables such as cauliflower, and sweeteners such as xylitol, sorbitol and mannitol.

Why are FODMAPs a problem for IBS?

We are lacking the enzymes that digest FODMAPs, which means they are not absorbed in the small intestine and pass through to the large intestine.

Once FODMAPs reach the large intestine, they get fermented by colonic bacteria. In the fermentation process, bacteria increases fluids and produces gas in the large intestine. This results in symptoms such as gas, pain and diarrhoea.

Eating less of these types of carbohydrates should decrease these symptoms..

FODMAP diets

The low-FODMAP diet has been around since 2010 and was devised by researchers at Monash University in Australia.

Low-FODMAP diets cut out foods that contain particular types of carbohydrates, notably sugars and fibres. These can lead to digestive problems such as diarrhoea, constipation, gas, bloating and abdominal pain in people with IBS.

There is some evidence that following a low-FODMAP diet can be beneficial for IBS. In one study, 76% of people following a low-FODMAP diet felt they were seeing improvements with their IBS symptoms compared to 54% who were following “conventional” IBS nutrition advice.

FODMAP diets are often challenging to follow as they involve cutting a lot of foods out of your diet. This can put you at risk of having an unbalanced diet if you get it wrong but working with a dietitian can ensure that a low-FODMAP diet still gives you key nutrients without making IBS symptoms worse.

FODMAP elimination diets

A FODMAP elimination diet involves restricting all of the main FODMAPs for a short time and then introducing them back into your diet one by one. Working with a dietitian can help you to reintroduce foods from particular categories in a way that helps you to see exactly which of them are contributing to your IBS symptoms.

You will probably find that one particular group is the one that is causing you problems and that within that, certain foods are more of an issue than others. It’s not usually the case that you will need to avoid everything from the group.

Once you know what the culprits are, you can swap them for low FODMAP choices.

The views expressed in this article are those of the author. All articles published on Nutritionist Resource are reviewed by our editorial team.

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Bournemouth BH2 & Amersham HP7
Written by Anita Bowes, On-line Registered Dietitian & Nutritionist, MSc, BSc, PGDip
Bournemouth BH2 & Amersham HP7

Anita is a registered dietitian with the Health and Care Professions Council (HCPC), a member of the British Dietetic Association. Anita has in depth experience of varied areas of nutrition gained in her private practice and over 12 years working as a clinical and research and innovations dietitian at the leading UK Hospitals.

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