What is the low FODMAP diet?

The low FODMAP diet is a strict elimination and reintroduction diet. It's been shown in clinical trials to improve the symptoms of IBS in up to 80% of sufferers sensitive to FODMAPs.

Not everyone who suffers from IBS will be sensitive to FODMAPs. The diet aims to test your sensitivity to the FODMAPs in the food you eat through a process of elimination. Following a 2-6 week elimination you'll begin to learn which FODMAPs, and in what quantities, you can reintroduce back into your diet. [1]

The low FODMAP diet has 3 phases. 

1. The Elimination Phase

2. The Reintroduction Phase

3. The Personalised Phase

Each phase builds on the next, requiring a degree of commitment, compliance, experimentation, and self-learning on your behalf. The diet functions as a whole and its effectiveness has only been tested when it's delivered under the supervision of a trained dietitian.

Elimination phase

The elimination phase is where you'll discover if you are in fact sensitive to FODMAPs. You'll see whether or not reducing them improves your symptoms to a tolerable level.

This phase of the diet is not intended to be long term. It should only be followed for as long as it takes (up to a maximum of 6 weeks) to experience a level of symptom relief acceptable to you.

If during this time you see no significant improvement in your symptoms then it likely means that FODMAPs are not contributing to your IBS. If this is the case there are no clinical or health reasons to continue to eliminate high FODMAP foods. At this point, you should discuss alternative treatments with your doctor and dietitian.

Reintroduction phase

The reintroduction, or challenge phase as it's also known, progresses directly on from the elimination phase.

This is where you'll reintroduce the high FODMAP foods you've been avoiding. This reintroduction takes the form of "challenges". For each challenge, you introduce foods back into your diet, one at a time. This is done in increasing quantities whilst you monitor your reactions.

The challenges are usually done over a period of 3-6 days with a 3 day rest period between each challenge. Other than the food you are challenging at any one time you should continue to eat a low FODMAP diet.

This phase needs to be well controlled to reduce the likelihood of flare-ups. Reintroduction can last anywhere from 8-12 weeks. This depends on how often and at what quantities you react to the foods you are reintroducing.

Personalised phase

Armed with everything you've learned about your FODMAP tolerances in the first two phases of the diet you then move into the personalised phase.

As the name suggests this phase is very much self-directed based on your findings so far. You'll continue to challenge and monitor your individual tolerances to get a clearer picture of what it takes to keep on top of your IBS.

Here you'll lay the foundation for your long term eating habits. The goal is to attempt to return to the most inclusive diet possible for you whilst maintaining symptom control.

Ready to tackle the low FODMAP basics? Check out the other posts in this series.

Leave your questions about the low FODMAP diet in the comments below.