garlic and onion are high fodmap foods

IBS diet: Should I try a low FODMAP diet?

Avoiding high FODMAP foods is the cornerstone of some of the most common IBS diets. But such restricted eating isn’t for everyone.

Food is one common trigger for digestive conditions such as irritable bowel syndrome (IBS). In many cases, high FODMAP foods are to blame. So, it makes sense to cut them out, right? But whilst there’s growing evidence to show restricting these foods can drastically improve IBS symptoms, it takes serious commitment. A low FODMAP diet is a significant dietary intervention. And unless you have diagnosed IBS and have exhausted all other IBS diet options, it can do more harm than good.

Before you consider a low FODMAP IBS diet

Following a low FODMAP IBS diet is not a decision to take lightly. Only attempt it if:

  • Your IBS is formally diagnosed by your GP
  • You’ve tried other less restrictive diet strategies already (e.g. increasing your fibre intake and probiotics)
  • You’re recommended this diet by a FODMAP trained dietitian. Don’t attempt it alone – you need ongoing professional nutrition advice and support to implement this diet plan effectively

This final point is particularly important. If this is a diet change you would like to initiate, careful implementation is crucial. A FODMAP trained dietitian can assess if it’s appropriate for your IBS symptoms and also ensure what you’re eating continues to be nutritionally sufficient.

What is a low FODMAP diet?

Some (but not all) carbohydrates are poorly absorbed in the small intestine. As a result, they move further through the gut and ferment in the large intestine. In people with IBS, this can trigger symptoms such as bloating, constipation, wind, diarrhoea, stomach pain and flatulence.

The guiding theory of a low FODMAP IBS diet is to replace high FODMAP foods that are poorly digested with low FODMAP foods that easily breakdown in the stomach. This decreases the fermentation of sugars in the large intestine. Consequently, this can reduce bloating, constipation and other IBS symptoms.

However, IBS sufferers aren’t all sensitive to the same high FODMAP foods. To help reduce IBS symptoms, a dietitian may recommend you eliminate high FODMAP foods for a short period.

They are then gradually reintroduced in phases to identify which exact foods you are most sensitive to. It can also show which are better tolerated.

This is not an allergy diet

Eliminating high FODMAP foods isn’t a long-term solution. This is where IBS diets can differ from allergy diets. It’s important to recognise, IBS is not caused by a food allergy. It has nothing to do with your immune system. Whereas diets for food allergies and intolerances often involve permanent exclusion of an allergen, this is not usually required in IBS diets. For example, after the initial elimination period in a FODMAP diet, most IBS sufferers can start to tolerate small to moderate quantities of high FODMAP foods.

What are FODMAPs?

FODMAPS are a collection of carbohydrates that contribute to IBS symptoms. To spell this out:

Fermentable Oligosaccharides Disaccharides Monosaccharides Polyols

High FODMAP foods

  • Garlic
  • Onions
  • Fruits containing high concentrations of fructose
  • Some vegetables, legumes and pulses
  • Polyol sweeteners such as maltitol, mannitol and sorbitol (if it ends in -ol, it’s probably a polyol)
  • Some grains, such as rye, wheat and barley
  • Dairy products

Keeping a food diary

The list above shows how complex and restricted a low FODMAP diet can be. Just to reiterate, a low FODMAP diet isn’t for everyone. But that’s not to say you can’t take inspiration from some of the theory.

For example, keeping a food diary to track the severity of your symptoms against what you’ve consumed. Most of us can’t remember exactly what we eat on a day-to-day basis. This is why it can be helpful to write it down.

This visibility allows you to recognise patterns between your diet and IBS symptoms. With this knowledge you could then reduce or eliminate a food for a short period to see if it has an impact on symptoms. This is a simple but effective way to, see how an individual food may be causing your digestions problems.

How to start a food diary

  • Write down everything you eat daily, the time you ate it, and the severity and time of your IBS symptoms on the same day.
  • If you recognise a pattern where eating a certain food seems to regularly coincide with a rise in your digestion problems, consider eliminating this from your diet for a few weeks.
  • During this elimination period, continue to keep a food diary and track your symptoms.
  • After this period, gradually reintroduce the food and record any changes in your symptoms.
  • Repeat with other foods if necessary.

It’s always recommended that any changes to diet are done in consultation with your GP or a dietitian.

And before you start any IBS diet…

Remember, diet is only one cause of IBS. If lifestyle factors, such as stress, are the trigger of your IBS symptoms, making behavioural changes could be more valuable. In addition, if you suffer with food anxiety of any form, or have other underlying health conditions, it’s particularly important to seek medical guidance before pursuing an IBS diet.

Last updated: 6 July 2020

DietsDigestive HealthDigestive Health NutritionIBS