What Are FODMAPs - and Why Do They Trigger IBS?

What are FODMAPs?   

FODMAPs are a group of sugars (carbohydrates) which are naturally present in many different foods. These include starchy foods like bread and pasta, some fruits and vegetables like onions and apples, and some types of dairy foods.   

The word FODMAP is an acronym for:  

• Fermentable (meaning the sugars can be broken down and used by gut bacteria)
• Oligosaccharides 
• Disaccharides  
• Monosaccharides 
• And 
• Polyols   

Oligosaccharides, disaccharides, monosaccharides and polyols are just scientific names for different types of sugars. The names reflect their sugar composition -for example, a monosaccharide is one sugar, while a disaccharide is two joined together.

How do FODMAPs cause IBS symptoms?  

When we eat carbohydrates, the gut breaks them down into individual sugars. Usually, these sugars get absorbed through the walls of small intestine and into the bloodstream, providing us with energy. 

But unlike other types of carbohydrates, FODMAPs aren’t well absorbed during digestion. This means that they travel though the small intestine to the large intestine.  

 When they arrive in the large intestine, they are broken down by gut bacteria who use them for energy. This is a process known as fermentation. When the FODMAPs are fermented, gases are released. These gases can stretch the walls of the gut, triggering tummy pain, gas and bloating in people with sensitive guts.  FODMAPs can also pull water into the gut during digestion, causing diarrhoea.  

Where did the low FODMAP diet come from?  

The low FODMAP diet was developed by a group of gut health researchers working at Monash University in Melbourne Australia.   

They found that some carbohydrates were not well absorbed in the small intestine. They called these groups of sugars ‘fermentable carbohydrates’ or FODMAPs.    

Their research went on to show that FODMAPs were capable of triggering symptoms like gas, bloating and loose stools in people with IBS.   

They also found that reducing FODMAPs could improve symptoms and help people manage their IBS better.   

Will the low FODMAP diet work for me?  

Research shows that up to 75% of people with IBS feel relief from their symptoms with a low FODMAP diet.  

There’s currently no definitive way of knowing if you'll feel better on a low FODMAP diet without trialling it for 2-6 weeks. There is some new research which suggests that if you also have anxiety, depression or high stress levels, alternative approaches like psychological support or gut directed hynotherapy may be a more effective option.

If you would like to try a low FODMAP diet, it's recommended you do this with the help of a dietitian - you can ask your GP for a referral, or find a FODMAP specialist dietitian in private practice. They can guide you through a trial of a low FODMAP diet. If your symptoms improve during this time, it's likely that FODMAPs are a trigger for you.  

If you don't have any improvement in your symptoms when following a low FODMAP diet, it's unlikely they are a problem for you. If this happens, you can then explore other therapies, like medications, cognitive behavioural therapy or gut directed hynotherapy.