FODMAP Stacking: When Small Portions Add Up in One Meal

Salad bowl seen from above with avocado, chickpeas, sweet potato, red cabbage, tomatoes and peppers

Updated October 2026

Are you eating only green portions and still getting symptoms? FODMAP stacking may be one reason. It means that the FODMAPs from several foods in one meal add up. This guide explains how it relates to the traffic lights used by Monash University, which combinations Monash says stay low FODMAP, and how to avoid stacking in everyday life.

Key points

FODMAP stacking means that the FODMAPs from several foods eaten in one meal are added together. Portions that are green on their own can then add up to a moderate or high amount of FODMAPs.
Monash University says it is the total across all FODMAP groups that counts, even if each food contains a different one. Lactose only counts if you do not tolerate it well.
The amounts in the Monash app apply per meal, and the thresholds are set conservatively. Most people with irritable bowel syndrome (IBS) can eat several green portions together without problems.
If symptoms persist despite green portions, it can help to vary your foods, keep to one green portion of fruit per meal and leave two to three hours between meals and snacks.
Monash does not offer a stacking calculator. For its own recipes, however, it uses the Stack Cup, a symbol that shows the amount of FODMAPs per meal.

What is FODMAP stacking?

The term describes FODMAPs piling up, or stacking, within a single meal. A green portion contains few FODMAPs, but not necessarily none at all. If you eat several of these portions together, the small amounts add up. A meal made up entirely of green portions can therefore contain a moderate or high amount of FODMAPs overall.

In the gut, the result is the same as after any high FODMAP meal: the FODMAPs draw in water and are fermented by bacteria in the large intestine. A sensitive gut reacts with bloating, pain or diarrhoea. Our article What are FODMAPs? explains exactly how this works.

Monash University, which developed the FODMAP diet, bases the concept on studies in which several FODMAPs combined caused stronger symptoms than a single one, with symptoms increasing as the amount went up.

Same group or different groups? According to Monash, what counts in a meal is the total amount of fructose, fructans, GOS and polyols, no matter which group they come from. So stacking also affects meals in which each food contains a different FODMAP group. Lactose is a special case. It only counts if your gut produces too little lactase and you therefore do not tolerate milk sugar well.

Traffic lights and portion sizes: what green means

In its laboratory, Monash University measures how many FODMAPs a food contains and compares the result with thresholds. These show how much most people with IBS can tolerate without symptoms. This is the basis for the traffic lights in the Monash FODMAP app:

Greenlow FODMAP

The portion is below the threshold for every FODMAP group. In phase 1, you mainly choose green portions.

Ambermoderate

The portion contains a moderate amount of FODMAPs. In phase 1, you limit portions like this.

Redhigh FODMAP

The portion contains a lot of FODMAPs. In phase 1, you leave it out.

The large traffic light rates a typical portion, such as 75 g of vegetables, a medium-sized piece of fruit or 250 ml of milk. Smaller traffic lights below it show the amount at which the rating changes. All amounts are per meal, not per day.

One point matters most for stacking: Monash deliberately set the thresholds conservatively so that several green portions fit into one meal. This means you do not need to count FODMAPs like calories. Foods that are only green in small amounts and quickly turn amber or red in larger ones are trickier. If several of them come together in one meal, stacking becomes more likely.

Foods with no upper limit: Some foods stay green even in large amounts. For carrots, for example, the app says they stay low FODMAP up to 500 g. Meat, chicken, fish and eggs naturally contain no FODMAPs, as long as nothing else is added. Foods like these contribute little or nothing to stacking.

Examples from the Monash data

These examples come from Monash University blog posts. For each FODMAP group, you can see which portion is green and which FODMAP comes into play in larger amounts.

Fructans1 slice of wholemeal wheat bread, 40 g of raspberry jam and 75 g of red cabbage are each green. In larger amounts, all three contain fructans.

GOS30 g of tahini (sesame paste) is green. Larger amounts contain GOS.

Fructose3 cherry tomatoes (45 g) are green. Larger amounts contain fructose.

Sorbitol75 g of aubergine is green. Larger amounts contain sorbitol.

Mannitol75 g of sweet potato is green. Larger amounts contain mannitol.

LactoseAn espresso topped up to 250 ml with cow’s milk is red because of the lactose. But this only counts if you do not tolerate milk sugar well.

Based on Monash University posts from 2013 to 2025. Monash retests foods regularly, because their FODMAP content can change over time. The app shows the current amounts.

Everyday combinations

Low FODMAP according to Monash

1 slice of wholemeal bread with 40 g of raspberry jam for breakfast, even though both contain fructans in larger amounts
2 rice cakes with 30 g of tahini and 3 cherry tomatoes as a snack, even though in larger amounts these contain fructans, GOS and fructose
Sweet potato, red cabbage and aubergine as a side dish, each in a green portion. Monash says the vast majority of people with IBS tolerate this.

More likely to add up

A fruit salad or smoothie made from several fruits, each in a full portion. Many fruits contain several FODMAP groups at once.
A large bowl of soup made only from sweet potato. Monash says it stays low FODMAP if you bulk it out with carrots, potatoes and parsnips.
Several foods with an upper limit in one meal, each at the largest green amount
Snacks every one to two hours. FODMAPs can then stack up over several small meals.

How to avoid FODMAP stacking in everyday life

As long as you are doing well on the FODMAP diet, you do not need to worry about stacking. If symptoms persist despite green portions, these tips can help. Most of them come from Monash University’s recommendations.

Stick to green portions. Keep to the green amounts in the Monash app. Our FODMAP list gives you a first overview. When you are starting out, kitchen scales help you quickly get a feel for portion sizes.

Vary rather than double up. Choose three different vegetables in green portions rather than a double portion of one that is only green in small amounts. Monash considers three or more types of vegetable at dinner to be fine.

Fill up on foods with no upper limit. Rice, potatoes, carrots, meat, fish and eggs contain few or no FODMAPs, even in larger amounts. In the app, you can recognise these foods by a note showing the amount up to which they stay low FODMAP.

Spread fruit across the day. Many fruits contain several FODMAP groups. Monash therefore advises no more than one green portion of fruit per meal. For a fruit salad, use only half a portion of each fruit. Smoothies can easily end up containing too much fruit.

Count your drinks. What you drink with your food is part of the meal. A cup of camomile, fennel or oolong tea is high FODMAP, and so is strongly brewed chai. If you do not tolerate lactose well, the same goes for milky coffee. Water, black coffee, green tea and peppermint tea are low FODMAP.

Check ready-made products. Onion and garlic powder, inulin, honey, fructose syrup and sugar alcohols such as sorbitol (E420) turn up in many ready-made products, from stock to cereal bars. Monash points out that salad dressings and aioli can contain garlic too. For certified products, the certification applies to one serving as defined by the manufacturer.

Leave two to three hours between meals. Stacking refers to one meal at a time. If you leave two to three hours between meals and snacks, your food has already moved on, and the FODMAPs from your next meal do not add to those from the last one. If you get hungry in between, Monash suggests a boiled egg, tinned tuna, a small handful of walnuts or plain popcorn, for example.

Keep a diary. Write down what you eat, when and how much, and how you feel afterwards. Note your stress levels and sleep too, because not every symptom comes from food. That way, you can find out whether stacking plays a role for you at all.

Onions and garlic are among the biggest sources of fructans and are found in many ready-made products. If you do your own seasoning, you know exactly what goes into your food. Garlic-infused oil brings the flavour without the fructans, because they do not dissolve in oil. According to the manufacturer, Massel vegetable stock contains no onion or garlic, and it is certified low FODMAP by Monash University.

Fody Garlic-Infused Olive Oil low FODMAP

Fody Garlic-Infused Olive Oil
garlic flavour without fructans

Massel Vegetable Stock Powder low FODMAP

Massel Vegetable Stock Powder
no onion or garlic

Stacking in the three phases of the FODMAP diet

How much attention stacking deserves depends on the phase you are in. Our article What are FODMAPs? explains the basics of the three phases.

1Elimination

2 to 6 weeks

You choose green portions and can combine several of them. Only once most of your symptoms have improved but some remain is it worth taking a closer look at stacking.

2Reintroduction

usually 8 to 12 weeks

You test one FODMAP group after another. You eat everything else in green portions, so that you can clearly link any symptoms to the test.

3Personalisation

long term

You know which groups you tolerate. In the Monash app, you can hide them with a filter, and the traffic lights then adjust to you. You mainly watch out for stacking with your own triggers.

Timings based on the current information sheet from Monash University (2026).

For phase 2, our reintroduction test plan gives you test foods and amounts for each group. After that, it is often enough to eat a trigger food in a small portion or not to combine it with other FODMAP sources.

Is there a FODMAP stacking calculator?

Not from Monash University. The Monash FODMAP app does not show FODMAP amounts in grams, only the traffic lights. Monash’s reasoning is that the thresholds are conservative enough that you do not need to count FODMAPs like calories.

For its own recipes, however, Monash has developed a tool called the Stack Cup. The cup symbol appears in the ‘Monash University Low FODMAP’ cookbook and next to recipes on the Monash website.

How the Stack Cup works

Full cupIt stands for about 0.5 g of FODMAPs. According to Monash, this is how much most people with IBS tolerate in one meal.

Four ringsEach ring stands for about 0.125 g of FODMAPs. The recipe shows how many rings one serving fills.

CombiningFor each meal, you combine recipes up to a total of four rings, for example a dal with three rings and a potato curry with one ring.

BreakAfter two to three hours, the cup counts as empty again.

A full cup is an upper limit, not a target. Monash says these values are also on the cautious side, and most people can tolerate a little more. However, the Stack Cup only works with Monash recipes. There are no ring values for individual foods.

Online calculators: Other providers have developed stacking calculators. Because the Monash app does not show values in grams, these rely on their own estimates. Instead, Monash recommends green portions, breaks between meals and, if symptoms persist, a food diary.

Frequently asked questions about FODMAP stacking

What does FODMAP stacking mean?

Stacking means that the FODMAPs from several foods in one meal add up. Each portion is low FODMAP on its own, but together the amount can become moderate or high. In sensitive people, this can trigger symptoms even though they only eat green portions.

Do different FODMAP groups add up?

Yes. According to Monash, what counts in a meal is the total amount of fructose, fructans, GOS and polyols, no matter which group they come from. Lactose only counts if you do not tolerate milk sugar well.

How many green portions can I eat per meal?

There is no fixed number. Monash set the thresholds so that several green portions fit into one meal, for example three types of vegetable at dinner. With fruit, it is best to stick to one green portion per meal.

Does stacking count per meal or per day?

Per meal. All amounts in the Monash app apply per meal, not per day. There is no fixed rule for how long to wait between meals, because everyone’s gut works at a different pace. Monash suggests two to three hours between meals and snacks.

Can I add up FODMAPs myself?

Not reliably. The app shows the amount up to which a food is green, but not how many FODMAPs it contains. Calculations based on fractions of a green portion are therefore only rough estimates. For Monash recipes, there is the Stack Cup, explained in the section on the stacking calculator.

Do I need to think about stacking if I am feeling well?

No. Monash says there is no need to worry about it as long as your symptoms are well controlled. Stacking only becomes relevant if the FODMAP diet has improved most of your symptoms but some remain.

What if I accidentally eat too much?

Do not panic. Monash says one larger portion will not undo all your progress. Wait a little longer before your next meal and make sure it is low FODMAP. The next day, carry on as normal.

Why do I still have symptoms despite eating green portions?

Stacking is one possible cause, but not the only one. Stress, anxiety, very fatty food or a lot of coffee can also irritate the gut. A diary can help you find your triggers.

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