After following the low FODMAP diet elimination phase for 2-6 weeks, it is time to move on to phase 2. Congratulations for making it through phase one! Whilst reintroduction can be exciting, it can also be a source of anxiety and quite a daunting prospect.

If the low FODMAP diet has worked well for you, you may find yourself asking ‘Why should I reintroduce foods that may trigger my symptoms?‘ ^(1,2)

The purpose of reintroduction is to find out which FODMAP subgroups trigger your symptoms and which do not. The reintroduction phase is important to expand the variety of food consumed, reduce unnecessary long-term dietary restrictions, and improve nutritional adequacy. Most people can tolerate several FODMAP groups. This means you will be able to reintroduce foods you love and enjoy. This will make activities such as eating out easier and improve your quality of life.

Furthermore, high FODMAP foods rich in fructans and galacto-oligosaccharides (GOS) act as prebiotics. Prebiotics are non-digestible fibres that promote the growth of good bacteria in the gut conferring a number of benefits; such as boosting gut health, supporting the immune system and lowering the risk of chronic diseases. Hence, maintaining a low FODMAP diet in the long-term can have a negative impact on overall health.

How do I know it is time to start phase 2?

You should start re-challenging foods once you are satisfied with the degree of symptom improvement achieved in phase 1.

What is the FODMAP reintroduction phase? ^{(1, 2, 3)}

The reintroduction phase involves a series of FODMAP challenges to determine your tolerance to the different FODMAP subgroups and identify your triggers. The challenges involve introducing a food rich in one FODMAP subgroup, example milk to challenge lactose or honey to rechallenge fructose. This food should be consumed daily for three days, and the portion size increased over the three days whilst monitoring your symptom response. More information on the portion sizes and examples of foods to rechallenge is provided in more detail later. The reintroduction phase usually takes 6-10 weeks to complete.

The flow chart below outlines the reintroduction protocol.

Tips for success ^{(1, 2, 3)}

1. There are no rules on which FODMAP group to introduce first. However, you may want to start with the food you missed the most.
2. Challenge one FODMAP subgroup at a time following the recommended portion sizes. Please see the tables below.
3. It is important to use a food that contains only one type of FODMAP subgroup e.g. honey only contains excess fructose. This is to ensure you have clear results and know which FODMAP subgroups trigger your symptoms.
4. Challenge the same food on three consecutive days as shown in the flowchart above. However, if you are feeling apprehensive about testing three days in a row you can have washout days in between. Example: Day 1 challenge, Day 2 washout, Day 3 Challenge, Day 4 washout, Day 5 challenge, Day 6-8 washout days
5. Stick to a low FODMAP diet throughout this process. This is important to prevent additive or crossover effects. Example if you successfully reintroduce the subgroup mannitol, you must still avoid mannitol containing foods until you complete all the FODMAP group challenges/reintroductions.
6. Allow a 2-3 day washout after completing each food challenge. This is important to avoid additive and crossover effects when testing the next FODMAP group.
7. Wait until your symptoms are well controlled before proceeding on to the next challenge.
8. If your usual portion is larger than the portion on day 3, titrate up to your portion after day 3 to assess your tolerance to this.
9. If you only develop mild manageable symptoms on any of the days you can still proceed to the next portion size. This is completely up to you. Example if you only experience some wind after day 1 of onion reintroduction you may wish to trial the day 2 portion size to assess how much you could tolerate with minimal symptoms. Testing this out may make eating out and socialising easier.
10. Remember some bloating and wind are a normal part of digestion and would not mean you have failed the challenge.
11. Keep you baseline diet as consistent as possible over the three challenge days. Example avoiding high intakes of caffeine/ alcohol that are higher than normal as these are non-FODMAP IBS triggers which can influence your results.
12. If you feel very anxious about undergoing reintroduction, go for a slower approach. Undertake the challenges over non-consecutive days and start with smaller portions. Be aware that stress/anxiety can trigger IBS symptoms and therefore you may experience symptoms as a result of anxiety as opposed to a reaction to the FODMAPs in food.

Use the reintroduction food and symptom diary below which you can download and print off to help monitor your tolerances.

Guide to FODMAP groups reintroduction ^{(2, 3)}

The portion size of the food tested is increased over a 3 day period. The portion on day is moderate in FODMAPs (amber), day 2 is high in FODMAP (red) and day 3 tends to be very high in FODMAPs.

You only need to challenge one food from each food group except for fructans. Fructans are present in wheat, fruit and vegetables. The quantities present in each vary hence you may tolerate some but not others. Therefore is recommended to test at least two vegetables, two fruit and two grain products that contain fructans.

FODMAP challenges ^{(3, 4)}

Challenge one food from each FODMAP subgroup to test your tolerance. The only exception is fructans ¹. It is advisable to test several fructan containing foods, as fructan content varies a lot between foods therefore you may find you can tolerate some foods but not others!

If you have not done so already download the Monash FODMAP university app to help guide you through reintroduction and monitor your symptoms throughout.

Challenge 1: Fructan -grains

Day 1	Day 2	Day 3
100g cooked wheat pasta 1 slice wheat bread 40g cooked couscous	150g cooked wheat pasta 1/2 slice wheat bread 80g cooked couscous	225g cooked wheat pasta 2 slices wheat bread 155g cooked couscous

Challenge 2: Fructans – vegetables

Day 1	Day 2	Day 3
1g garlic (1/4 clove) 10g onion 55g savoy cabbage 3 brussel sprouts	2g garlic (1/2 clove) 25g onion 75g savoy cabbage 4 brussel sprouts	4g garlic (1 clove) 45g onion 110g savoy cabbage 5 brussel sprouts

Challenge 3: Fructans – fruit

Day 1	Day 2	Day 3
raisins 1 1/2 tablespoon 1 date 60g pomegranate seeds 100g grapefruit (1/2)	2 tablespoon raisins 2 dates 90g pomegranate seeds 210g grapefruit (1)	3 tablespoons raisins 4 dates 120g pomegranate seeds 280g grapefruit (1large)

Challenge 4: GOS

Day 1	Day 2	Day 3
15 almonds OR 85g chickpeas, canned OR 60mls soy bean milk	20 almonds OR 115g chickpeas, canned OR 125ml soy bean milk	30 almonds OR 170g chickpeas, canned OR 250mls soy bean milk

Challenge 5: Lactose

Day 1	Day 2	Day 3
60mls cow’s milk OR 1/2 tub (85g) yoghurt, plain OR 65mls custard	120mls cow’s milk OR 1 tub (170g) yoghurt, plain OR 125mls custard	180mls cow’s milk OR 250g yoghurt, plain OR 170mls custard

Challenge 6: Fructose

Day 1	Day 2	Day 3
1 1/2 tsp honey OR 55g mango OR 140mls orange juice	2 tsp honey OR 105g mango OR 160mls orange juice	1 tbsp honey OR 210g mango OR 200mls orange juice

Challenge 7: Mannitol

Day 1	Day 2	Day 3
10g mushroom OR 2 small cauliflower florets OR 100g sweet potato	40g mushroom OR 4 small cauliflower florets OR 140g sweet potato	80g mushroom OR 8 small cauliflower florets OR 210g sweet potato

Challenge 8: Sorbitol

Day 1	Day 2	Day 3
40g avocado OR 2-3 blackberries OR 5 lychees	80g avocado OR 5 blackberries OR 10 lychees	120g avocado OR 10 blackberries OR 15 lychees

Challenge 9: fructose and sorbitol

Day 1	Day 2	Day 3
45g apple OR 4 cherries OR 45g pear	85g apple OR 8 cherries OR 85g pear	150g apple OR 10 cherries OR 165g pear

Challenge 10: fructan and GOS

Day 1	Day 2	Day 3
10 cashew nuts OR 15 pistachio nuts OR 25g red kidney beans, boiled	20 cashew nuts OR 30 pistachio nuts OR 50g red kidney beans, boiled	30 cashew nuts OR 40 pistachio nuts OR 100g red kidney beans, boiled

FAQs

If I reintroduced a FODMAP subgroup successfully does it mean I can tolerate it in unlimited amounts?

The larger the portion size consumed, the larger the amount of FODMAPs will be consumed therefore you may develop symptoms at larger portion sizes. If the portion tested on day 3 is smaller than your usual portion size, test your tolerance to your usual portion size.

I have challenged each FODMAP subgroup. What do I do next? ^{(2, 3)}

Congratulations for getting this far! Now you should have established your tolerance to each FODMAP subgroup, and you can start bringing foods back into your diet. However, be mindful that whilst you may tolerate these subgroups well individually, you may find that you develop symptoms if you consume these daily or when combined with other FODMAP subgroups.

You may wish to test your tolerance to larger portions, increased frequency, and your tolerance to various combinations of FODMAP subgroups. Example if you tolerate bread and garlic, you may wish to assess your tolerance to garlic bread. There are no set challenges for this or a prescribed way to do this. Simply try combinations of the FODMAP subgroups that you would like to include in your diet. Continue keeping a food and symptom diary to record your symptom response. After this you can continue following your own personalised version of the low FODMAP diet that only restricts your own triggers.  

If I failed a FODMAP subgroup does this mean I cannot eat any foods in this subgroup? ⁽¹⁾

This is not necessarily the case. It is recommended to trial reintroducing a smaller serving when possible and you can also attempt the challenge again, but this time challenge on non-consecutive days i.e. having a washout day in between.

Furthermore, FODMAP tolerance can change over time so if you failed this time, you could try retesting in a 3-6 months’ time to re-assess your tolerance.

References

1. Whelan, K., Martin L., Staudacher, H. and Lomer M., 2018. The low FODMAP diet in the management of irritable bowel syndrome: an evidence-based review of FODMAP restriction, reintroduction and personalisation in clinical practice. J Hum Nutr Diet, 31(2), 239-255.

• Tuck C., and Barrett J., 2016. Re-challenging FODMAPs: the low FODMAP diet phase two. J Gastroenterol Hepatol, 32 (1): 11-15.

• Martin, L, 2015. Re-challenging and Reintroducing FODMAPs: A self-help guide to the entire reintroduction phase of the low FODMAP diet.  Lee Martin e-book.

4. Monash University FODMAP diet app version 3.0.6, 2021. Reintroduction. https://www.monashfodmap.com/ibs-central/i-have-ibs/get-the-app/ [Accessed 3.2.2021]