Do low FODMAP serving sizes matter?

The low FODMAP diet isn’t as easy as a food being categorised as high FODMAP or low FODMAP. Often a food will have low FODMAP, moderate FODMAP and high FODMAP serving sizes. That means even if a food is listed as low FODMAP, that doesn’t always mean you can eat unlimited quantities without triggering symptoms. This article aims to help you understand how low FODMAP serving sizes work, so you can reduce your FODMAP load faster and settle your gut symptoms.

Where do you find information on low FODMAP serving sizes?

The Monash University FODMAP Diet App contains the most up-to-date lists of low and high FODMAP foods, along with recommended serving sizes. This app is also updated every couple of months with new FODMAP information.

Just remember that every person has a different tolerance level to FODMAPs and the serving sizes in the app are conservative, so you might find you can tolerate a little bit more than the recommended serving size. During the FODMAP reintroduction phase, you’ll discover your individual tolerance level for each of the FODMAP groups.

How do you use the traffic light system in the Monash University FODMAP Diet app?

The Monash University FODMAP Diet App organises foods by a traffic light system based on the FODMAP levels for a typical serving size of that food per meal (1). Green is low FODMAP, amber is moderate FODMAP, and red is high FODMAP (1).

When you click on a food in the app, you can find out what FODMAPs are in the food, along with extra serving-size notes (1). You can eat any green-rated serving size for a food during the first phase of the low FODMAP diet (1). That means that if a food has an overall red rating (high FODMAP) but has a smaller green-rated serving size, you can still have the smaller serving size of that food during the first phase of the low FODMAP diet (4).

FODMAP Traffic Light Examples

Here are some examples to help you understand the Monash University traffic light system:

Avocado is rated high FODMAP overall. However, a small 30g (2 tablespoon) serving size is low FODMAP and can be enjoyed in the first phase of the diet (3).

Sweet potatoes are rated low FODMAP overall. However, this vegetable needs good portion control as it can quickly become high FODMAP. The low FODMAP serving size is 75g (1/2 cup) of sweet potato (this is the raw weight) and becomes moderate FODMAP at a 100g (2/3 cup) (3). It is very easy to accidentally eat a high FODMAP serving size of sweet potato once cooked, especially if it’s in a meal like sweet potato fries.

Quick oats are rated moderate FODMAP overall. They are only low FODMAP at a ¼ cup portion (dry measurement before cooking). If you eat a ½ cup portion (dry measurement before cooking), then you will consume moderate levels of FODMAPs (3).

While in the first low FODMAP phase of the diet focus on avoiding high FODMAP serving sizes of foods, limit moderate FODMAP serves, and focus on eating low FODMAP serving sizes of foods (1).

How many different low FODMAP foods can you have in each meal?

The Monash University FODMAP cut-off levels are conservative. This means you can eat multiple low FODMAP foods per meal, just make sure you stick to the recommended serving sizes (4).

What happens if you want to eat more than the recommended serving size for a low FODMAP food?

If you want to eat more than the recommended serving size for a low FODMAP food, check the additional information provided with each food listing in the Monash University FODMAP Diet App. Some low FODMAP foods will become high FODMAP at larger serving sizes, while other foods like carrots, potatoes and rice will remain okay to eat in larger serves (2 4).

Can you eat the same food multiple times in a day?

Providing you stick to the recommended low FODMAP serving size and leave a few hours between each serving, you can eat the same food a couple of times a day.

Do meats and other sources of protein contain FODMAPs?

Chicken, fish, red meat, and eggs are protein-based foods that are FODMAP free (2 3 4). Therefore, if you are feeling especially hungry you can eat a larger serving size of these naturally FODMAP free foods.

What are the serving size guidelines around fruit?

The general guidelines recommend enjoying one serving of low FODMAP fruit per meal (2). You can still enjoy several servings of fruit per day as long as you leave two to three hours between each serving. Check out our article to learn about fruit and the low FODMAP diet. 

Final Thoughts

Understanding low FODMAP serving sizes can help you reduce your gut symptoms faster while on the low FODMAP diet. The Monash University FODMAP Diet App is the best resource for low and high FODMAP food and serving size information to help you on your journey. Just remember you can eat multiple low FODMAP foods for each meal and repeat the same foods throughout the day, providing you leave a few hours between each serving.

References:

1. McNamara, L. Understanding the traffic lights in the Monash FODMAP Diet App. Monash University FODMAP website. October, 2018. Retrieved from https://monashfodmap.com/blog/traffic-light-system/ Retrieved on: 25-02-2023
2. Dwyer, E., McNamara, L. & Varney J. How to avoid FODMAP Stacking. Monash University FODMAP Website. April, 2019. Retrieved from: https://monashfodmap.com/blog/how-avoid-fodmap-stacking/ Retrieve on: 25-02-2023
3. Monash University FODMAP Diet App. Food Guide. The Monash University Low FODMAP Diet App. 2023: Version 3.0.9 (435). Date retrieved: 2023-02-23. Retrieved from :http://www.med.monash.edu/cecs/gastro/fodmap/iphone-app.html. Accessed: 2023-02-23.
4. Monash FODMAP Team. FODMAP Stacking Explained. Monash University FODMAP Website. October, 2022. Retrieved from https://monashfodmap.com/blog/fodmap-stacking-explained/ Retrieved on: 25-02-2023