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What Is FODMAP Stacking?

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What Is FODMAP Stacking?

Simply put, if you are not paying attention to the AMOUNTS of foods that you eat and the COMBINATION of foods that you eat, then you risk FODMAP stacking.

Backround is fruits and vegetables on a table with a title What Is FODMAP Stacking atop of them.

Defined by Monash researchers, “FODMAP stacking is a term referring to how FODMAPs can ‘add up’ in our gut”. In other words, you might ingest a small amount of FODMAPs and not experience any IBS symptoms, but if you eat more of the exact same food(s), and therefore ingest a greater amount of FODMAPs, you might very well develop IBS symptoms.

Portions & Food Combinations Count!

When following the low FODMAP diet we are consuming amounts of foods in their various FODMAP levels, which initially, and broadly, can be determined by using the Monash University Low FODMAP Diet Smartphone App or the FODMAP Friendly App. These two resources will show you what serving sizes of a particular food will be low FODMAP according to lab testing.

Researchers at Monash University and FODMAP Friendly are the originators of the diet and these are the primary resources used by dietitians, doctors and other researchers. Currently, these are the ONLY two entities that are lab testing foods for FODMAPs. Other apps present incorrect and/or incomplete information. Please stick with these apps – and do download them immediately if you have not already.

Monash University presents the traffic light system (Green for Low FODMAP; Yellow for Moderate; Red for High FODMAP) and much of the time will call out which individual FODMAP is involved. FODMAP Friendly has a system which always lists each type of FODMAP, as well as percentages of those FODMAPs, which can be used to assess stacking on a more micro level.

Ultimately the amount that is low FODMAP for YOU will be determined during a structured Challenge Phase, but the apps, which provide lab-tested results for individual foods, are the place to start.

This article on What Is FODMAP Stacking? will explain what you need to know about stacking and why it is important.

Learn About The Different FODMAPS

First, it is important to understand that there are several types of different FODMAPS, which we explain in our article, What Are FODMAPs?

Brush up on Oligosaccharides, Disaccharides, Monosaccharides and Polyols before continuing.

FODMAP Stacking Explained

There are different ways of assessing stacking.

Stacking The Same FODMAP

One way is to look at stacking one kind of FODMAP, let’s say excess fructose (the monosaccharide, or “M” in FODMAP). It is easy to understand how eating too much of the same FODMAP might tip the scales. It is also easy to look up what FODMAPs foods contain in the Monash University and FODMAP Friendly apps.

In the FODMAP Friendly app in particular, they show percentages, which is very helpful. As an example, let’s say you want a snack. Look up blueberries in the FODMAP Friendly app. The entry tells us that at a 1 cup (150 g) serving that the Excess Fructose is at 60%. A total of 100% would be your maximum amount of fructose to keep the serving size low FODMAP. So, from this entry alone you can see that twice the amount would bring the fructose total to 120%. That would be a high FODMAP serving size. 

But let’s stick with the 1 cup (150 g) serving of blueberries for a moment. Now look at Dried Banana chips. At a ½ cup (40 g) serving, the Excess Fructose is only 20%. This means you could eat both the amount of blueberries and the banana chips, and the Excess Fructose would only total 80%, and the combination would be a great low FODMAP snack!

Stacking Multiple FODMAPs

In late 2022 Monash University made a push for us to look at stacking as eating one or more FODMAP in excess of .5 g per meal. The science backing this up has been around for years, meaning that tests have shown that if one eats less than .5 g total of FODMAPs (excluding lactose) at a meal, it is unlikely that you will trigger IBS symptoms.

However, most lay people have not read the scientific papers, and most importantly, while Monash researchers have written many of those papers, and have raw data available to themselves, they have not shared with the public a way for us to add up foods to determine the .5 g in an exacting way.

This makes things difficult. Our recommendations, which are based upon Monash’s, are as follows:

  • There is no need to worry about stacking if your symptoms are controlled.
  • If you have been basing your stacking approach on avoiding large amounts of the same FODMAP, and that has worked for you, don’t change a thing.
  • If you have breakthrough symptoms and have been having difficulty understanding why, then taking a closer look at stacking would be prudent:
    • Make sure to space out meals by about 3 hours.
    • Focus on “no FODMAP” foods, those with “trace” amounts of FODMAPs, and foods that have generous Green Light Low FODMAP serving sizes according to the Monash app. This will keep your overall level of FODMAPs lowered.
    • Note that Monash designed their system so that you can eat multiple foods at the Green Light Low FODMAP level at once, and remain low FODMAP.
    • According to Monash, the collective reduction of all FODMAPs has a greater, positive affect than focusing on reducing one FODMAP.

According to Monash, the collective reduction of all FODMAPs has a greater, positive affect than focusing on reducing one FODMAP.

Lactose Is Considered Separately

The .5 g of total FODMAPs per meal excludes lactose. Luckily, the easiest FODMAP to determine is the disaccharide lactose (the “D” in FODMAP). Clinical tests have shown that if a serving size of a food has less than 1 g of lactose, that it is low FODMAP. Lactose is a sugar. It is easy to find Sugar listed on nutritional panels. See this cheese label below:

Jarlsberg cheese label

You can see in the image above that the Total Sugars are less than 1 g; this means the serving size of that food is low FODMAP and appropriate even for the Elimination Phase.

Timing is Important

Stacking becomes an issue when too many FODMAPs are consumed at the same meal, or within the same time frame, which is usually considered to be about 3 hours. This is why spacing out your meals is important. Also, note that the amounts of foods listed in the Monash and FODMAP Friendly apps are per meal.

tiny white clock

Meals are assumed to be about 3 hours apart.

In theory, you could eat a low FODMAP amount of 10 almonds (24 g) at breakfast, and eat them again later in the day and experience no ill effects. Practically speaking, your experience might vary. The lab tested and reported amounts of foods are a place for you to begin your exploration of your unique relationship to FODMAPs.

If you cannot tolerate a published low FODMAP serving size, it does mean that anything is wrong. This is just your body’s unique, personal reaction. This article will be of interest: What Is A Low FODMAP Serving Size? We are fond of saying, you are not a lab!

Some dietitians also point out that since it can take quite a while for FODMAP symptoms to occur, that stacking could potentially occur within a 24 hour period. You can review a video Webinar lead by the team at Diet vs. Disease for more info.

Please also see our article on Timing of Digestive Symptoms: What It Means.

Individual Tolerance is What Counts Most Of All!

Whether an IBS symptom is triggered is a highly individual issue. Here is where your unique digestive system comes into play.

One person might be able to actually eat 20 almonds (24 g) – DOUBLE the recommended amount – at one time and experience no symptoms.

Another person might only be able to tolerate HALF of the recommended low FODMAP amount and discover that 5 nuts (6 g) is what sits well with them.

And yet another person might learn that 10 almonds (24 g) is fine, but not twice in one day, or even two days in a row.

a graphic of measuring cups and spoons with the text What is a Low FODMAP serving size
You may want to read: What Is A Low FODMAP Serving Size?

The low FODMAP diet is very nuanced and complex and this is why we always recommend that you undertake the diet along with a registered dietitian to guide you.

The Challenge Phase in particular is best approached with help. We do suggest that you work with a Registered Dietitian (RD) for best results.

You might want to review our articles, Have IBS? Top Reasons To Work With A Dietitian, and also The Role Of The Dietitian vs. The Role Of The Gastroenterologist.

The Takeaway

The low FODMAP diet has many components. There are lab tested prepared foods. There are published amounts of individual FODMAPs in foods. There are meals and recipes that you make in your own kitchens and eat out at restaurants that incorporate multiple foods and stack FODMAPs.

But the most important thing is how you react to FODMAPs yourself and learn to create what we call your own FODMAP Roadmap, that will keep triggers at bay. The best way to accomplish this is to move through the Elimination and Challenge Phases of the diet in a very structured way.

Ultimately it doesn’t matter what any lab testing says; remember, you are not a lab. We will close with a quote from Monash researchers: “It is very difficult to develop specific ‘rules’ about FODMAP stacking as every person with IBS has a varying level of tolerance to different types of FODMAPs.”

“It is very difficult to develop specific ‘rules’ about FODMAP stacking as every person with IBS has a varying level of tolerance to different types of FODMAPs.”

Monash Researchers

Our goal is to provide you with the information that you need to be able to go forth and THRIVE on the low FODMAP diet!

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