FODMAP stacking is a concept that gets talked about a lot in the FODMAP world. And I’ve noticed that it often causes people to feel overwhelmed and worried, afraid of doing something “wrong” when combining different foods.

In this blog, I’ll explain what FODMAP stacking actually is and how you can deal with it.

What does “FODMAP stacking” mean?

FODMAP stacking is the question of whether it is possible to stack FODMAPs or go over your threshold for FODMAPs if you eat several foods in one meal.

This can happen, either with foods from the same FODMAP group or with foods from different FODMAP groups. It is about eating too many FODMAPs in a meal in total.

I want to reassure you right away. In the elimination phase of the FODMAP diet, you generally don’t need to worry about this concept.

You can combine “green servings” of food together in one meal

The Monash University FODMAP app shows you the amounts of foods that are considered low FODMAP. These “green” servings are specifically tested and designed to be safe, even when combined with other green servings in one meal.

Monash University understands that we often combine different foods in a meal. You’ll often combine multiple veggies, a carb source, maybe a sauce… That’s completely normal. And the green portions reflect that. They are set conservatively.

So don’t worry about which FODMAP group a product belongs to, or whether the other foods you’re eating contain the same group. If it’s green, it’s considered safe to mix and match.

This means you can combine a “green serving” of tomato, red bell pepper and zucchini in one meal for example.

Phew, that’s a relief, right?

An important other point to mention is that low FODMAP servings are per meal. Monash University advises to leave 2-3 hours between meals and snacks, to avoid additive effects. After this time, you can enjoy green servings of foods again without worrying about stacking FODMAPs.

Make sure you’ve got the right information

To stick to low FODMAP amounts during the elimination phase, it’s really important to use accurate information.

There’s a lot of outdated or incorrect information floating around online. Even booklets from doctors or dietitians are often not up-to-date. Research is ongoing and Monash keeps testing and re-testing foods. So things change and paper resources get outdated very fast.

So always check when a list was last updated. If it’s older than a few months, chances are it’s no longer accurate.

I strongly recommend downloading the Monash FODMAP app, it’s the official app from the creators of the diet and it’s always up-to-date.

Green, amber and red foods

The Monash app uses a traffic light system:

• Green = low FODMAP → safe to eat during the elimination phase.
• Amber = moderate FODMAPs → Monash University says that quite some people still tolerate these amounts as well, but for the elimination phase, it is advised to focus on green foods temporarily.
• Red = high FODMAP → avoid during elimination.

Just because a food is red doesn’t mean it’s “bad”. It just means it’s a portion that commonly causes issues for people with IBS. That’s why these are best left out during the elimination phase.

Eat as varied as possible

Even during elimination, you want to keep your meals as varied as possible. There are still plenty of foods you can enjoy, you just have to pay attention to the portions. And some foods may need a low FODMAP swap.

Are there foods you can eat freely?

Yes! FODMAPs are carbohydrates, so foods that don’t contain carbs are naturally FODMAP-free and can be eaten freely:

• Meat: chicken, beef, lamb, pork, etc. → As long as it’s not breaded, marinated, or seasoned with high FODMAP ingredients like onion or garlic.
• Fish & shellfish: salmon, tuna, shrimp, mussels, etc. → Same rules apply.
• Eggs: eggs don’t contain carbs, so they are FODMAP-free.
• Fats and oils: olive oil, sunflower oil, butter, margarine, etc. → Just check for high FODMAP additives. Pure fats are safe.

Some foods have large low FODMAP portions

In the Monash app, you’ll also find foods that have very large safe portions, sometimes up to 500g per meal, or with no upper limit found.

Examples include:

• Endive
• Bamboo shoots
• Pickled beets
• Oyster mushrooms
• Olives
• Carrots
• Kiwis
• Jackfruit
• Papaya
• Rhubarb
• Rice
• Potatoes
• Cheeses like brie, camembert, manchego, parmesan, and mozzarella

These are great foods to help fill your plate without worrying about eating too much of it.

Listen to your own body

At the end of the day, it’s your body that knows best. Everyone has their own tolerance levels.

Monash says most people can combine multiple green servings without any issues. Often, amber portions go well too. It’s usually the red amounts, especially things like onions, garlic, and beans that cause trouble.

Don’t make things too complicated for yourself

Start by following the tips I shared above. Focus on the “green servings” for foods in the elimination phase of the FODMAP diet.

Give it about 2 to 6 weeks, and if your symptoms haven’t improved enough, check in with your dietitian. Together, you can see if you need to be more careful with stacking or if something else might be going on.

I hope this has made the idea of FODMAP stacking much clearer and less stressful!
If you still have questions, feel free to drop them in the comments below

Sources from Monash University that I used for this article:

• FODMAP stacking explained
• FODMAP stacking: Can I overeat green foods