Stuck on FODMAP Stacking? Here’s what you need to know.

Have you been following the low FODMAP diet to a tee but still seem to be experiencing symptoms? One possible cause of this is FODMAP stacking – a term used to describe the compounding effects (or adding up) of low FODMAP foods that become high FODMAP when consumed together.

This article will run you through what FODMAP stacking is and how it may affect those following the low FODMAP diet, as well as give you some handy tips on how to reduce stacking.

A refresher on FODMAPs

To understand FODMAP stacking, it’s helpful to have a good grasp on the basics first. The FODMAP acronym is a bit of a mouthful – it stands for Fermentable Oligosaccharides Disaccharides Monosaccharides And Polyols. FODMAPs are a group of carbohydrates (sugars) that aren’t absorbed properly in the gut, which can trigger uncomfortable digestive symptoms in people with Irritable Bowel Syndrome (IBS).

Many foods naturally contain FODMAPs (such as wheat, onion, garlic, legumes, dairy products, apples, honey and mushrooms) and they are found in some additives too. Foods vary in the amount of FODMAPs present, and for that reason some foods are considered low FODMAP and some high FODMAP. Some high FODMAP foods, however, are low FODMAP at certain serving sizes and thus may be suitable at those low FODMAP serve sizes on the low FODMAP diet.

What is FODMAP stacking?

FODMAP stacking is a process that occurs when two or more low FODMAP serve sizes of foods from the same FODMAP group are consumed either together (in the same mealor snack) or close together (in quick succession) across the day. This can effectively cause two or more low FODMAP foods to “stack” together in your digestive tract and become high FODMAP, potentially triggering IBS-type symptoms.

If you are following the low FODMAP diet, FODMAP stacking may be an issue that you encounter. During the first phase of the diet, all high FODMAP foods are swapped for low FODMAP foods. In this time, you may think you are consuming lots of low FODMAP foods in low FODMAP suitable serve sizes.  However if you consume multiple low FODMAP serve sizes of foods containing the same FODMAP (e.g. all containing sorbitol), you may go above your threshold for sorbitol tolerance and experience adverse symptoms.

It may be helpful to know that lactose is digested differently to other FODMAP groups. If you are intolerant to lactose, make sure stick to low FODMAP serves sizes. As everyone’s tolerance is different, assess your own tolerance.

What does stacking look like?

To understand how FODMAP stacking works, let’s look at an example. If you want some trail mix for a snack, you may combine ½ cup of banana chips, 3 tablespoons of raisins, ¼ cup of almonds and ¼ cup of walnuts, thinking they are all low FODMAP individually (when using the FODMAP Friendly App). However, these foods all contain fructans and are likely to “stack”(add up) and no longer low FODMAP when consumed together.

How to reduce FODMAP stacking ?

It’s difficult to develop a set of hard and fast rules to avoid FODMAP stacking, as the truth is that everyone’s digestive system and tolerance thresholds for FODMAPs are different. This means that one person may be able to tolerate one group of FODMAPs or an amount of FODMAPs that another person cannot. We recommend seeking the guidance and support of a FODMAP-trained Dietitian, who can help you navigate the low FODMAP diet and determine which foods you can and cannot tolerate.

In general, there are a number of practical ways to reduce FODMAP stacking in your diet. The first is to use the FODMAP Friendly App on Android or Apple (iPhone). Using this App, you can look up individual foods and see which specific FODMAPs are present. Let’s say you wanted to make a snack and were looking at foods to choose from on the App. If you searched for corn thins, you would see that 5 corn thins are suitable to consume and contain predominantly GOS.

If you searched for feta cheese, you would see that 40 grams (about 1 wedge) is low FODMAP, with lactose being the predominant FODMAP.

If you searched tomato, you would find that ½ a cup is suitable for consumption, with regular tomatoes containing predominantly excess fructose.

Combining these three foods would limit stacking, as they contain different FODMAPs and should be well tolerated by people with IBS.

Top Tips to minimise FODMAP Stacking:

1. Spacing out meals and snacks
It can take anywhere from 4-24 hours for food to reach the large intestine, meaning that eating low FODMAP serves of foods containing the same FODMAP group at the same time or close together can result in them reaching the large intestine around the same time. This may potentially trigger gastrointestinal symptoms without you realising. To reduce the risk of this occurring, leave 3-4 hours between meals and snacks where possible.

2. Be aware of serving sizes
Using the App is a great way to get familiar with the low FODMAP serve sizes of different foods. Look at the serve size and the % of the FODMAPs within that food. This is the BEST thing about the FODMAP Friendly App.  It is the BEST tool to help you minimise FODMAP stacking.

3. Include very low FODMAP foods
There are a number of foods that contain no FODMAPs, including plain meat and fish, eggs, pure oils and butter. There are also foods that contain very low amounts of FODMAPs such as rice, carrot, radishes, potato, olives, cucumber, clementine, dragon fruit and kiwi.

4. Aim for variety
The more variety you have in your diet, the smaller the chance is of combining foods with the same FODMAP group and accidentally “stacking”. Including foods from a variety of food groups is a good place to start.

In summary

To summarise, FODMAP stacking may occur when you consume multiple low FODMAP serve sizes of foods containing the same FODMAP group, causing them to ‘add up’ in your digestive system and trigger IBS symptoms. Stacking can be reduced by using the FODMAP Friendly App on Android or Apple (iPhone) when preparing meals and using a variety of strategies, such as spacing meals apart and choosing very low FODMAP foods.

Written by: Amy Lilly (Accredited Practising Dietitian)
Reviewed by: Kiarra Martindale (Accredited Practising Dietitian)