Irritable Bowel Syndrome (IBS) is a condition characterised by chronic and relapsing symptoms; lower abdominal pain and discomfort, bloating, wind, distension and altered bowel habit. IBS affects 1 in 7 adults in Australia and worldwide it's estimated to affect from 9-23% of the population.
It is thought that for the vast majority of IBS sufferers, there’s an issue with the “tuning” of the gut brain. The gut brain controls the functionality of the bowels (intestines) & has more nerves than the spinal cord.
Research through Monash University found that a group of short chain carbohydrates (sugars), collectively known as FODMAPs (Fermentable Oligosaccharides, Disaccharides, Monosaccharides and Polyols) , are either poorly or not absorbed during digestion and that as part of this process they draw in excess water and/or produce gas as they are fermented by bacteria, in turn causing distension of the lumen (the “hole down the tube” of the bowel) which is a major stimulus to the gut brain and consequently contribute to the symptoms of IBS.
In order to decrease symptoms, it makes sense to reduce or remove the dietary components (FODMAPs) that cause more liquid to be in the intestines or that produce gas or do both.
A low FODMAP diet has been found to benefit most patients with IBS, with controlled trials resulting in symptom improvement in 76% of cases.
Common examples* of these carbohydrates are:
- Oligosaccharides - onion, garlic, beetroot, artichoke, wheat, rye, legumes
- Disaccharides - lactose (milk, cream, ice cream, yoghurt)
- Monosaccharides - apple, honey, pear, watermelon, mango
- Polyols - apple, apricot, prune, mushroom, cauliflower, celery, sweet corn
The low FODMAP diet has been endorsed by the International Foundation for Functional Gastrointestinal Disorders (IFFGD) as a recognised treatment for IBS and other inflammatory bowel diseases.
The low FODMAP diet has been added to the Therapeutic Guidelines in Australia as a recognised treatment strategy for IBS.
King's College London has embraced the research undertaken by Monash University in Australia, and provides a comprehensive training course for dietitians in how to deliver and implement the low FODMAP diet.
How do FODMAPs Contribute to the Symptoms of IBS?
Researchers found that this group of short chain sugars are poorly absorbed and that as part of the digestion process they draw in excess water and/or produce gas, in turn causing distension of the lumen. FODMAPs aren’t all the same, but they have similar actions as part of the digestion process.
Oligosaccharides - cannot be digested by anyone. To get a carbohydrate into the bloodstream across the lining of the gut, it needs to be a single sugar molecule. Digestive enzymes are responsible for splitting sugars into their single sugar molecules, however no mammals have an enzyme that breaks down oligosaccharides and as a result, none of us can digest and absorb them and so they are passed from the small bowel into the large bowel.
Monosaccharides - Fructose in excess of glucose. Sucrose has equal amounts of fructose and glucose and gets split in the bowel and is absorbed really well because the glucose enables the fructose to be rapidly brought into the blood stream. Where fructose is found in excess of glucose, the rapid absorption doesn’t occur and the mechanisms for absorbing fructose are extremely slow.
Free fructose (monosaccharides) and Polyols are slowly absorbed around the small intestine, some people are better at absorbing them than others, but they are slowly absorbed in everyone. If you have a lot of them, they remain in the lumen for a long time and they drag water in through an osmotic effect and they expand how much water is in the small bowel, which is then passed into the large bowel.
Lactose - lactase is the enzyme in the small bowel that splits lactose into single sugars. If you have good lactase activity, the lactose sugars are well absorbed, however low lactase activity (which occurs in 10-95% of people and is largely dependent on ethnicity along with other factors) will drag water into the bowel and the lactose and excess water will pass into the large bowel.
In the large bowel, these short chain sugars that haven’t been absorbed are rapidly fermented by colonic bacteria, which results in gas production.
The following websites and smartphone App are great resources if you’d like more information about FODMAPs, the low FODMAP diet and IBS management. They contain lots of really useful information as well as recipes and other resources.
The Monash University low FODMAP diet App has the most comprehensive list of foods that have been tested for their FODMAP content. It also has information about the low FODMAP diet, recipes and a shopping list to help organise low FODMAP purchases. The App is available for iPhone and for Android.
“Beating the Bloat: the FODMAP diet & IBS” - a public lecture delivered by Professor Peter Gibson from Central Clinical School at Monash University. It’s well worth a watch. Gibson is an engaging speaker and he’s not afraid to use the F word - by which we mean fart, of course!
Monash University low FODMAP diet Blog:
Patsy Catsos RDN, FODMAP Expert & Author:
Making low FODMAP food yum - Alana uses her personal experience and great research skills to provide practical, research based information about FODMAPs and lots of great recipes to try.