Fibre and the Low FODMAP Diet

The low FODMAP diet is often used in the dietary management of irritable bowel syndrome (IBS). Whilst the diet can be an incredibly effective short term strategy for IBS if implemented correctly, it is also not uncommon for people to struggle consuming adequate fibre whilst following the elimination phase of the diet. Inadequate dietary fibre can make symptoms like constipation, abdominal pain and bloating worse and can negatively affect the gut microbiome.

The Low FODMAP Diet

FODMAP is an acronym for Fermentable Oligosaccharides, Disaccharides, Monosaccharides and Polyols. Essentially these are all short chain sugars or carbohydrates which are found in many foods naturally but also can be added to foods during processing. These carbohydrates as the name suggests are fermented by the bacteria in our large bowel and they are a substrate for our gut microbes. Below is a table of some of the common high FODMAP foods (you will notice most of them are incredibly healthy foods).

The low FODMAP diet is a diet used under dietetic guidance for the management of IBS by initially restricting these fermentable sugars or carbohydrates to restrict the amount of substrate available for fermentation by the bacteria. The problem is that the fermentation of these sugars and carbohydrates is actually a beneficial process and helps us to develop a thriving gut microbiome. This is why it is essential that firstly we consume adequate fibre during the FODMAP elimination process but also why we need to re-introduce high FODMAP foods within a matter of weeks after excluding them.

Types of Fibre

There are two predominate types of fibre, soluble fibre and insoluble fibre. Insoluble fibre does not absorb water, is not digested by the enzymes in the upper gastrointesitinal tract but instead makes its way to the large bowel where it provides bulk for our stools. Insoluble fibre like wheat bran, the skins of fruits and vegetables and seeds assist us by increasing transit time through the colon. Soluble fibre on the other hand absorbs water and can form a gel like consistency. Soluble fibres such as psyllium husks, oats, lentils and flaxmeal are great for improving the consistency and bulk. 

Fibre and FODMAPs

Consuming adequate fibre on a low FODMAP diet doesn’t have to be challenging, you just need to know what foods to eat. In IBS we often recommend focusing on those foods which are high in soluble fibre over, rather than over doing the insoluble fibre to reduce wind and gas. Foods like oat bran, flax meal, chia seeds and psylium husk are all fantastic Low FODMAP sources of soluble fibre. 

High Fibre, Low FODMAP Foods:

Low FODMAP Fibre Illustration
Low FODMAP Fibre
  • Kiwifruit 
  • Flaxseeds / Flaxmeal
  • Oatmeal / Oatbran
  • Gluten free seed/grain bread
  • Brazil/Walnuts 
  • Brown rice 
  • Quinoa
  • Chia seeds
  • Potato with skin 
  • Green beans
  • Raspberries 

A note on Fluid

When increasing your fibre intake, it is important to ensure adequate fluid intake and even increase fluid intake along with the increase in fibre. Fluids will help to keep the fibre moving along the digestive tract smoothy and result in a much more comfortable movement. Aim for a minimum of 2L per day, more in hot whether or if you are a heavy sweater. 

 

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