How to avoid FODMAP stacking

FODMAP stacking is a tough cookie. I'm talking about the saddest, driest, gluten free cookie you ever had! Let's explore FODMAP stacking, who it affects, and how to avoid it without biting off more than you can chew.

When I first began the FODMAP elimination diet, I treated low FODMAP, green light foods like an all-you-can-eat buffet. Needless to say, I noticed little improvement in my symptoms until I learned about FODMAP stacking.

Before you start

If your symptoms are well managed by simply reducing your overall FODMAP intake, then stop reading this post now. The low FODMAP diet can be hard enough without stressing over stacking. Most people find that reducing overall FODMAP intake in line with low FODMAP guidelines and portions is enough to improve their symptoms.

However, if you've been successfully working through the diet for a few weeks but your reactions to FODMAPs seem unclear or changeable then FODMAP stacking may be contributing to your flare-ups.

It's important to work closely with your dietitian to determine if FODMAP stacking is affecting you. Other issues could be at play and your dietitian is trained to spot the patterns you may be missing. [1]

Tip: I created a food, mood and poop journal to help you record what you're eating and how you're feeling. It's a great way to share your low FODMAP journey with your healthcare team and see how far you've come.

What is FODMAP stacking?

FODMAP stacking is when the total amount of FODMAPs you eat stack together to exceed your personal tolerance. This can occur even if you stick to low FODMAP portions. This is because FODMAPs are accumulative, so if you're sensitive to them, the more you eat, the more likely you are to experience symptoms.

Whilst some people are sensitive to even the smallest amount of FODMAPs, most people have a FODMAP tolerance to each different FODMAP type. This differs for everyone but generally refers to the amount of FODMAPs you can tolerate in a meal without triggering unwanted gut symptoms.

The likelihood of FODMAP stacking can be influenced by:

• Quantity = Eating FODMAPS in excess of your threshold. This can be several foods containing FODMAPs of the same type or multiple FODMAPs.
• Combinations = Eating foods containing more than one FODMAP type or combining several foods of different FODMAP types to which you have different tolerances.
• Tolerance = Most of us have different tolerance levels for each FODMAP type. This means we may be able to eat more of one FODMAP versus another. Once we exceed our individual tolerance, symptoms are likely to occur.
• Timing = Eating meals or snacks close together or grazing throughout the day. This allows the foods we've eaten separately to gradually accumulate in the digestive tract and cause symptoms. This is especially true of those suffering from IBS-C.

Tip: Stacking typically happens in a single meal. Depending on the speed of your digestive system, it can occur throughout several meals or snacks when eaten close together.

A quick reminder about different FODMAP types

The letters O, D, M and P in the FODMAP acronym refer to the types of carbohydrates (sugars) that the different FODMAPs belong to. We only attempt to reduce the most widely problematic FODMAPs on a low FODMAP diet.

F = Fermentable

O = Oligosaccharides

D = Disaccharides

M = Monosaccharides

P = Polyols

Oligosaccharides = fructans (FOS) and GOS found in foods such as beans, garlic, onions, peas and wheat.

Disaccharides = lactose found in dairy foods such as cheese, ice cream, milk and yoghurt. Interestingly, lactose is not included in FODMAP stacking as it is digested differently. Unless you also have lactose intolerance in addition to IBS, then stacking low FODMAP servings of lactose is unlikely to be an issue for you.

Monosaccharides = fructose (in excess of glucose) found in many fruits and some vegetables such as asparagus, broccoli heads, mango, raspberry, red bell pepper, strawberry and tomato.

Polyols = mannitol and sorbitol are sugar alcohols found in avocado, celery, cauliflower, mushroom and sweet potato.

Tip: You're not expected to memorise which foods belong to which FODMAP types. Use the low FODMAP tools available (listed below) and free up some brain power for more important things.

The bucket effect

Think of your tolerance to each FODMAP type as a bucket. Most people will have buckets of varying sizes for each FODMAP. This bucket is the maximum amount you can consume of each FODMAP type before experiencing symptoms. Once your bucket (or buckets) are overflowing, you have exceeded your personal FODMAP threshold and may begin to experience symptoms.

The purpose of the low FODMAP diet is to discover the size of each of your buckets and at what point they overflow into symptoms. The idea is to eat the widest range of foods possible, at the amounts you can personally tolerate, without overflowing. Some buckets will overflow quicker than others. This occurs when eating multiple portions of the same FODMAP type in a short period, either within the same meal or sometimes within the same day.

The good news is that each bucket can only overflow by eating the type of FODMAP it contains. So if your GOS bucket is half full and you eat a portion of FOS, they go into two separate buckets. For this reason, you need to eat as wide a variety of foods as possible to stay within your FODMAP threshold and reduce the risk of accidentally overflowing your buckets.

How do I know if I'm stacking FODMAPs?

First and foremost, go with your gut! If your symptoms are controlled to a point that's comfortable and acceptable to you, then FODMAP stacking is not an issue.

However, if you've experienced some relief from the low FODMAP diet but still feel caught out or confused by seemingly random flare-ups, you may be unknowingly stacking your FODMAPs.

If you're anything like me, you'll be sorry to hear that calculating the FODMAPS you eat requires a bit of maths....Groan! The good news is that it doesn't have to be overly complicated once you know how.

To figure out if you're potentially FODMAP stacking your plate, you need to know the following:

• FODMAP type found in the food(s) you're eating or intend to eat.
• Low FODMAP portion size of the food(s) you're eating or intend to eat.
• Amount of each food(s) you're eating or intend to eat.

Once you have this information, you can roughly see how much of each FODMAP type you're eating and make any changes to suit you and your tolerances.

Research has shown that most people can tolerate 0.5 g of total FODMAPs in a single sitting. [2] Unfortunately, without access to a laboratory, there's no way for us to accurately determine how many grams of FODMAPs we're eating.

What we can do, using a variety of tools, is count the number of portions of FODMAP-containing foods we eat in a single sitting. We can then add these together to see if we're unknowingly FODMAP stacking.

FODMAP stacking tools

Here are some of the best tools from the most reputable sources. Using these as part of the low FODMAP diet is essential to help you determine low, moderate and high FODMAP portions. They can also help you understand how these foods may stack together and the swaps you can make to avoid it.

One of the easiest ways to do this is to download the Monash FODMAP or the FODMAP Friendly apps.

As you'll see from the examples below, there are differences between the two apps, the way they list FODMAPs and the amounts considered low FODMAP. FODMAP Everyday has a great article that explains why Monash University and FODMAP Friendly test results differ.

Tip: Which app you use is up to you. Just be aware that whichever you use, this is the starting point of your journey. The most important data is what you discover to be true for you as you work through the diet under the guidance of a FODMAP-trained dietitian.

Monash FODMAP app

In the Monash FODMAP app, foods receive an overall traffic light rating:

• green for low FODMAP foods and portions
• amber for moderate FODMAP foods and portions
• red for high FODMAP foods and portions

The individual listing then breaks down further, showing where the portion sizes change from low to moderate to high FODMAP.

Each listing also notes which FODMAP type(s) a food contains.

Pros

• Extensive database of foods and brands.
• Lists even the smallest amounts of low FODMAP servings. This can help you to diversify your food choices and include more moderate to high FODMAP food in your diet.
• Detailed reintroduction guide.

Cons

• Paid app (one-time fee, no hidden or recurring charges).
• The steep learning curve when you first start using it can be a bit intimidating to beginners.
• Includes branded items within each category of the food lists. This can be frustrating when you want to quickly find general ingredients and have to scroll past numerous branded foods that may or may not be available in your country.

FODMAP Friendly app

In the FODMAP Friendly app, foods are listed as pass or fail. The tested serving sizes are listed along with the maximum serving that's classed as low FODMAP.

Every listing in the app also shows the percentage of each FODMAP type in that particular food. This information can help you to visualise the FODMAPs in your meal and is great for beginners.

Edit November 2024: The FODMAP Friendly app now includes an optional in-app purchase to access their recipe maker feature. This one-of-a-kind resource allows you to create, save and experiment with making your own low FODMAP recipes whilst avoiding the risk of FODMAP stacking. See the FODMAP Friendly recipe maker in action here.

Pros

• Free app, (with a small, no-brainer, in-app purchase for the recipe maker).
• Makes FODMAP stacking easier to understand and avoid.
• Lists the maximum serving size that remains low FODMAP.

Cons

• Database of foods is not as extensive, inclusive or diverse outside of common Australian ingredients.
• Not as easy to see low FODMAP serving sizes of higher FODMAP foods.
• Doesn't highlight newly added, retested or reclassified foods.

See the FODMAP Friendly Recipe Maker in action

https://youtu.be/Kcr0EDyd2cs

Monash stacking cup

This is a simple but effective concept that I'd like to see rolled out in the Monash app. Unfortunately, at the moment, the only way to use this is within the Monash FODMAP cookbook.

The idea is that one full cup contains the maximum amount of FODMAPs most people can tolerate in a single sitting (0.5 grams). Each recipe in the book visually depicts how much of the stacking cup it fills. This allows you to mix and match recipes in the book to create filling meals or plan multiple courses.

Pros

• Easy to understand the concept of FODMAP stacking, making it great for beginners and those with limited time. No maths or calculations required!
• Allows you to confidently combine different recipes from the book to encourage you to eat more diversely.
• If you're an omnivore, there are enough recipes and combinations to see you through the elimination phase of the diet.

Cons

• Cookbook and shipping costs outside of Australia are expensive. Update 2024: The book is now available in digital format without the need for shipping.
• Not optimised for vegan or vegetarian diets/nutritional needs.
• Stacking information is limited to the lab-tested recipes in the cookbook. The stack cup technique doesn't translate to real-world recipes, recipe substitutions and possible combinations.

I use both the Monash and FODMAP Friendly apps, but for simplicity and consistency, throughout this blog, I refer to the data and the way FODMAPs are listed in the Monash app.

Tip: Depending on which of these tools you use, you may find that recipes and resources online have conflicting data. Sometimes, it's because they're just plain wrong or out of date. However, it may also be because they use a different tool from the one you're using. That doesn't necessarily make them wrong, just different. Remember, the most important FODMAP data to you is what you learn from your elimination and reintroduction challenges.

FODMAP stacking examples

Some examples of situations where FODMAP stacking might occur are:

• Christmas, holidays and special occasions. Portion sizes are typically larger than usual, we tend to indulge more and you may be eating several courses in a single sitting.
• Buffets, parties, BBQs and celebrations. Social eating, lots of options and grazing multiple times over the space of a few hours.
• Restaurants or takeaways. You may not be aware of the number or quantity of FODMAPs in the food you're eating. High FODMAP drinks and mixers will contribute to the overall FODMAP load.
• Comfort/mindless eating. Snacks and drinks during a movie, comfort eating during your period or when you're bored. Anytime our focus is elsewhere, and we're not thinking about quantities, combinations or timing.
• Grab n Go. Rushing to fit in meals around a busy schedule, grocery shopping without a list or a meal plan and grabbing whatever is available last minute. Leaving your food and FODMAPs to chance means more room for stacking and symptoms. Shift/night workers are also increasingly more likely to experience irregular eating patterns that can contribute to gut issues. If this applies to you, this nutrition for shift workers blog post may be helpful.

Single FODMAP stacking example

Stacking single FODMAPs can occur when we eat multiple, low FODMAP portions of different foods that contain the same FODMAP type.

For example, you eat a portion of vegetable stir fry containing

• 65 g courgette/zucchini = 1 low FODMAP portion of fructan
• 90 g edamame = 1 low FODMAP portion of fructan
• 75 g green bell pepper = 1 low FODMAP portion of fructan
• 75 g vermicelli wheat noodles = 1 low FODMAP portion of fructan

Although all of these foods have been eaten in low FODMAP servings, they all contain the same FODMAP type, fructans. By keeping portion sizes low FODMAP overall, many people won't have issues with this. However, for some people, all of those low FODMAP servings will stack together to exceed their tolerance for fructans. This is when symptoms can potentially occur.

Stacking in this example is more likely when including ingredients such as courgettes. This is because although they have a low FODMAP serving size, the difference between the low-moderate-high serving sizes is small.

A low FODMAP serving of courgette is 65 grams, but at just 10 grams more, it becomes moderate for fructans. At 20 grams more, it becomes high for fructans. The difference between a low and high FODMAP serving is only 20 grams. This narrow threshold makes it easier to stack courgettes with other fructan-containing foods.

Alternatively, edamame has a generous low FODMAP portion size of 90 grams. They do not become moderate for fructans until 210 grams, more than double their low FODMAP serving. This wide threshold makes them less likely to stack with other fructan-containing foods.

To help reduce the fructan load of the stir fry example above, we could make the following changes

• 75 g bok choy/pak choi = 1 low FODMAP portion of sorbitol
• 90 g edamame = 1 low FODMAP portion of fructan
• 43 g red bell pepper = 1 low FODMAP portion of fructose
• 120 g rice vermicelli noodles = 0 excess FODMAPs listed

As you can see, a few simple changes can dramatically change the FODMAP content of a meal without compromising the recipe or our enjoyment too much.

Tip: Get to know which of your favourite foods have wide FODMAP tolerances, where the difference between a low and high FODMAP portion is generous. Filling up on these foods can help limit the chances of FODMAP stacking.

Multiple FODMAPs stacking example

Stacking multiple FODMAPs can happen when we eat foods containing multiple FODMAPS or several foods containing different FODMAP types. These may combine to take our total overall FODMAP load above our maximum threshold, roughly 0.5 grams for most of us.

You eat a portion of chilli containing:

• 100 g canned plum tomatoes = 1 portion of fructose
• 2 tablespoon tomato puree = 1 portion of fructose
• 45 g butternut squash = 1 portion of GOS + 1 portion of mannitol
• 45 g canned black beans = 1 portion of GOS + 1 portion of fructan
• 75 g green bell pepper = 1 portion of fructan

As you can see in this example, even though we've eaten only low FODMAP portions, we've had 2 full portions of fructose, GOS and fructans in one meal. Depending on our tolerance of each FODMAP type, eating more than one of those in excess may lead to unwanted symptoms.

It's in cases such as these when we're likely to focus the blame on one ingredient, for example, the black beans. You'll tell yourself the last time I ate that chilli, I felt awful, which could result in eliminating black beans from your diet, when they may be fine for you when eaten away from other GOS and fructan foods.

To help spread the FODMAP load across the different FODMAP types, we could make the following changes to our chilli:

• 100 g canned plum tomatoes = 1 portion of fructose
• 1 tablespoon tomato puree = 0.5 portion of fructose
• 75 g sweet potato = 1 portion of mannitol
• 42 g canned chickpeas = 1 portion of GOS
• 75 g green bell pepper = 1 portion of fructan

In our new example, we've included foods of different FODMAP types without making huge changes to the integrity of the recipe.

Tip: In the Monash app, the majority of foods containing more than one FODMAP type are listed as high FODMAP. These foods are not advised to be used during your initial reintroduction tests as the multiple FODMAPs can skew the results.

Stacking across several meals example

Stacking across several meals can occur when we eat FODMAP-containing meals, snacks and drinks in a short space of time.

Let's take a look at a possible busy workday morning.

• 7 am - 62 g gluten free toast (fructans) + 2 tablespoon peanut butter (fructose)
• 9 am - 32 g white grapes (fructose)
• 10.30 am - coffee with ½ cup oat milk (fructans + GOS)
• Noon - chickpea (GOS) and brown rice pasta salad (fructans)

Although we appear to have eaten a variety of foods, we can see how easily some of them might stack together across the space of a few hours. Snacks and drinks can often seem like the most insignificant part of our diet, but can have a dramatic effect on the amount of FODMAPs we eat between meals or in a short space of time.

Let's see if we can make a few shifts to reduce the likelihood of ending up hunched over our desk in pain by mid-afternoon.

• 7 am - 62 g gluten free toast (fructans) + 2 tablespoon peanut butter (fructose)
• 9 am - coffee with ½ cup almond milk (0 excess FODMAPs listed)
• 10.30 am - 32 g white grapes (fructose)
• Noon - chickpea (GOS) and brown rice pasta salad (fructans)

Can you spot the difference? A few minimal swaps to timing and food choices mean we can eat and drink practically the same way but potentially with a very different effect on our digestion.

With a bit of know-how, we can avoid FODMAP stacking without significantly sacrificing our favourite recipes or routines.

Tip: The timing of meals can potentially have a huge impact on how well you tolerate FODMAPs. This is one of the first areas to observe before considering restricting FODMAPs further or calculating FODMAP stacking.

The effects of FODMAP stacking

Thankfully, with a well-planned, diverse low FODMAP diet, we won't all experience the effects of FODMAP stacking. If you think your symptoms may indicate otherwise, it's important to troubleshoot your concerns with your dietitian. Unknowingly stacking FODMAPs in our diet can:

• cause flare-ups and symptoms even if we appear to be restricting FODMAPs
• skew FODMAP results or limit your perceived tolerances
• increase the likelihood of giving up or poorly complying with the diet

If we don't identify that FODMAP stacking is to blame, or we suspect it might be but don't know how to rectify it, then we're at risk of:

• negative, restrictive mindset around food
• unnecessarily eliminating certain foods or food groups
• struggling to reintroduce or increase FODMAPs back into our diet
• nutritional deficiencies that can arise from overly restricting your diet

Overlooking FODMAP stacking can also impact the reintroduction phase of a low FODMAP diet and, more seriously, your long-term diet diversity. When challenging individual FODMAPs, it's essential to ensure that we're not stacking the challenge food with other high FODMAP foods or portions.

Including other FODMAPs in excess can affect how well we perceive our tolerances. Whilst we may be able to introduce some high FODMAP foods in isolation, we may not be ready to combine them with other FODMAP types.

This can potentially cause us to fail our challenges and continue to avoid those FODMAPs unnecessarily. This may lead to permanent restrictions and nutritional inadequacies, especially if we're in the position of having to go it alone without a dietitian to help.

What the experts say

FODMAP stacking can be one of the trickiest aspects of the low FODMAP diet to understand. It's not even referred to in FODMAP research, but is based on clinical observations and lived experiences of those following the FODMAP diet in practice.

The gastroenterology research team at Monash University are responsible for developing the FODMAP diet as we know it today. To minimise the possibility of unnecessary restrictions on what is an already restricted diet, their perspective on FODMAP stacking is to take an individual approach. In their blog post, FODMAP stacking explained they say,

"Everyone’s threshold level of FODMAP tolerance is different. While FODMAP stacking will be relevant to some people who may find they experience IBS symptoms when multiple 'green serves' are eaten in one sitting, for many, the conservative FODMAP cut-offs set by Monash mean they will achieve good symptom control when consuming a varied diet that includes numerous 'green serves' at each sitting." [3]

Kirsten Jackson, aka The IBS Dietitian, offers us an insight into her clinical recommendations in this FODMAP stacking post when asked to put a number on, "How many portions of moderate containing FODMAPs can I have?"

"This is not an exact science. But I advise clients to have no more than 1 safe portion of moderate containing FODMAP foods every 3-4 hours. This period allows enough of a gap to ensure that a huge load of FODMAPs is not reaching your large bowel all at the same time. This is when symptoms occur. This advice usually equates to 1 portion for every one of your 3 main meals a day".

Whilst this seems like a conservative figure, I'm sure this recommendation will be individually tailored to each client. It's also important to note that she specifies moderate containing FODMAPs. These are foods that have moderate to high FODMAP portions depending on serving sizes. With these foods, symptoms are more likely to occur at smaller portion sizes.

Kate Watson, registered dietitian and part of the team behind the FIG (Food is Good) app, emphasises in her post on preventing FODMAP stacking that,

"FODMAP stacking is unlikely to be an issue for most people. As we know, though, everyone with IBS has a unique set of sensitivities, and what causes symptoms for one person may not cause symptoms for another".

She also says that where stacking is an issue, "If choosing foods from the same FODMAP category at one sitting, limit to 1 full serving of one and ½ serving of the other".

Joanna Baker, the registered dietitian behind Everyday Nutrition, offers us her pragmatic final thoughts on the deal with FODMAP stacking,

"When it comes to IBS, it’s important to remember that some daily fluctuations in digestion are normal. We are not looking for zero symptoms. If anything a small amount of bloating is a reflection of a varied and balanced diet. What we do want to avoid are the painful and embarrassing symptoms that impact on quality of life. A good rule of thumb is that we want you to be 70% better about 70% of the time".

This is such an important point to help us keep our expectations realistic. This type of thinking is what helped me to get over some of my fears and begin experimenting with higher FODMAP combinations and portions.

As we can see, there is no one-size-fits-all when it comes to FODMAP stacking. Taking your individual FODMAP journey into account, preferably with the help of someone trained to tailor your experience to your needs, is the best approach.

Avoiding stacking

If your symptoms are controlled to a level that suits you (this is different for everyone), then you don't need to worry about FODMAP stacking. If you feel your symptoms might benefit from a more structured approach, try the following:

1. Space out meals and snacks at least 3 hours apart. This allows the FODMAPs you last ate to be well on their way through your digestive system before you add more.
2. Eat plenty of low FODMAP protein with each meal. This will help to keep you feeling fuller for longer and less likely to reach for a snack soon after eating.
3. Choose from a wide range of dietary fibre, food types and FODMAPs. This diversity will help you spread your FODMAP load for the day.
4. Keep fruit to a single portion or two half portions per sitting (3 hours).
5. Prioritize foods with little to no FODMAPs or wide, low FODMAP thresholds. Things such as rice, millet, polenta, quinoa, potatoes, carrots, parsnips, kabocha squash, leafy greens, yams, ackee, blueberries, kiwis, plantain, and tempeh. This is especially important if you're snacking or grazing regularly throughout the day.
6. If the rest of these tips haven't helped, consider taking a more strategic look at the number and combination of FODMAPs you eat. The general starting point is to aim for a maximum of 1.5 portions of each FODMAP type in a single sitting.

Tip: For most people, FODMAP stacking occurs in the space of a single meal. Those with sluggish digestive systems and chronic IBS-C are more likely to experience it over several meals or days. This is where the help of a dietitian is essential. Establishing your tolerances to each FODMAP type is trickier when they're inadvertently stacked together.

FODMAP stacking guide

I found stacking really confusing when I began my low FODMAP journey. It quickly became a big sticking point and source of anxiety at an already difficult time.

This is why I created a free FODMAP stacking guide to help you navigate FODMAP stacking. If you want to be confident in eating the widest possible variety of food and FODMAPs, this guide is for you.

Final thoughts

FODMAP stacking is not an issue for everyone on the low FODMAP diet. The overall reduction of FODMAPs during the elimination phase should be enough to see improvements in most IBS sufferers.

If you suspect FODMAP stacking might apply to you, your first steps should be to note your food and symptoms and speak to your dietitian.

There are a variety of tools and techniques to help you understand and limit the chances of FODMAP stacking. These require you to take the time to use and apply them but shouldn't dramatically overburden you.

If you feel that avoiding FODMAP stacking is having a negative effect on your eating habits, mindset or meeting your nutritional needs, then please speak to your healthcare team as soon as possible.

Simple swaps = stacking stops. A little know-how and focused attention can make a big difference to your low FODMAP journey.

If you've got a recipe that you're craving but you just can't get your little low FODMAP head around it then tell me about it in the comments below. We'll have it back on the menu in no time.