What Is A Low FODMAP Serving Size?

The low FODMAP diet is entirely dependent on serving sizes. You might hear people say that a food is “high FODMAP”, or “low FODMAP”, but these designations are based on serving sizes – and depending on the serving size, the same food can be “high”, and “low”. For instance, ripe bananas are low FODMAP at a 35 g serving size, but are high FODMAP in larger serving sizes. This article will help explain more, so that you can make wise serving size choices.

Editor’s Note: The terms “serving size” and “portion size” are often used interchangeably by the average person, outside of the realm of the diet. Within strict dietary guidelines they have distinct definitions. A “serving size” is what is recommended (by whom, we will discuss later in this article).

A “portion size” is what you might choose to eat, which may or may not be the same as the recommended “serving size”.

This article is focused on our FODMAP world and I have chosen to use the term “serving size” fairly liberally as it is what most of us use in conversation and I am most interested in helping you get the information you need in the most accessible way possible.

So, What IS A Low FODMAP Serving Size?

It depends on YOU! The “right” “serving size” is the one that does not trigger symptoms for YOU. “Serving sizes” are highly individual.

So, how can we discuss what a “serving size” is of blueberries, or almonds, or spinach?

And why have I put “serving size” in quotes? Because the best serving size for YOU might be different from the best serving size for me and the FODMAPer down the street might have yet a different serving size that works for them.

“Serving Sizes” Vary AND Can Be Fairly Arbitrary

In this section I am going to discuss two types of serving sizes: 1) serving sizes found on FDA Nutrition Facts Labels and 2) serving sizes found on the Monash University Low FODMAP Diet Smartphone App.

FDA Nutrition Facts Labels

You can read more about the FDA Nutrition Facts Label in our article called, How to Read a FDA Nutrition Facts Label.

The FDA & RACCs (Reference Amounts Customarily Consumed)

In brief, when you see “serving size” on the prominent black and white nutrition label on a U.S. product, such as 2 tablespoons barbecue sauce, this amount, which is called a RACC (Reference Amounts Customarily Consumed), has been determined by SELF REPORTED consumption data. In other words, those surveyed reported what they say that they eat.

These amounts on the FDA Nutrition Facts label are:

•  NOT a recommended amount for consumption
• NOT a nutritionally proper amount

Most people assume they are one or the other.

RACCs Are Indiscriminate

In my opinion RACCs are indiscriminate and in phone conversations with FDA representatives they have agreed that they are fairly arbitrary. This is because self-reporting is notoriously inaccurate.

(As an aside, I queried the FDA about how RACCs were collected. I stated that someone telling you how much they eat, a government official observing amounts eaten, or a multiple-choice survey would all likely result in different answers. Their response was to file a Freedom of Information Act, which we did, and resulted in a circular response that this information was disclosed in available documents. It is not.)

Your Typical Is Not Necessarily My Typical

I have taught cooking for over 30 years and know first hand that the average person does not know what typical amounts of food look like. When someone says they have eaten 1-ounce of cheese or had 1 “cup” of coffee my experience is that they wildly under-report amounts, sometimes even by half.

I do not actually believe it is because people want to be seen as eating less than they do, although that happens of course, rather I think it is because they actually believe that they have only eaten 1-ounce of cheese, or had a “cup” of coffee.

Did you think of a cup of coffee as 6 oz, 8 oz or 12 oz?

A true “cup” of coffee would be 8-ounces. In coffee and culinary lingo, a cup of coffee is 6-ounces. (Did you know that your 2 tablespoons of coffee grounds are meant to be prepared with a “6-ounce” cup of water?)

The most common size coffee ordered by the American public in 2018 was 12-ounces. Can you see some of the issues we are dealing with here?

At any rate, self-reporting amounts of ingested food by the average American really doesn’t mean anything from a FODMAP perspective.

What the RACCs do is allow the FDA with a put to stake in the ground. This way they can create their nutritional profile for their labels for all of us to read, contrast and compare.

Various Weights & Serving Sizes for the Same Items

• According to the FDA the “serving size” of blueberries is 140 g.
• Driscoll’s, a berry company, says a “serving size” of blueberries is 1 cup, which they say weighs 148 g.

And then there are serving sizes in the FODMAP world.

• According to Monash University, a serving size of blueberries is 1 cup, and their calculations state that weighs 125 g

Serving Sizes on the Monash University & FODMAP Friendly Apps

When developing the low FODMAP diet, Monash researchers had to collect extensive composition data and also determine what they call “cutoff values”. In their own words, “cutoff values were derived by considering the FODMAP levels in typical serving sizes of foods that commonly trigger symptoms in individuals with irritable bowel syndrome, as well as foods that were generally well tolerated”.

What this means to you is that the serving sizes represented on the app do have a basis in statistics, which may or may not relate to the way YOU interact with that food.

Use this data as a starting point and a guide, especially when embarking on the Elimination Phase.

Let’s look at an entry for Almonds:

According to Monash University, a “serving size” of almonds is 20 nuts, which they say weighs 24 g. This “serving size” is RED LIGHT and considered to be HIGH FODMAP (see image below, which is a snapshot of their smartphone entry for almonds as of May 2024).

This is why, it is not surprising, that many people think that “almonds are high FODMAP”.

Don’t Always Stop At Red Lights

BUT, as always, we encourage everyone to use the Monash University Low FODMAP Diet Smartphone App AND to always click through the RED LIGHT foods to read the entire entry.

Then you will be able to see that Monash says a Low FODMAP GREEN LIGHT portion of almonds is 10 nuts at 12 g.

Does this mean you should not eat almonds? NO! There actually is a lab-tested low FODMAP/Green Light amount.

What this means is that 12 g of almonds will most likely be tolerated by most individuals and not trigger IBS (irritable bowel syndrome) symptoms (if your issue is FODMAP related). 

Can you see how the term “serving” size” is not the end-all?

Australian Healthy Eating Guidelines

Also, please note that Monash University has also told us that while they are principally reporting on FODMAP levels in the app, they are also using Australian healthy eating guidelines, which can often make things confusing. For instance, the entry for sugar says that a low FODMAP serving size is 50 g or ¼ cup. In fact you could eat much more sugar than this and not create a FODMAP overload, except that Australian healthy eating guidelines suggest this serving.

Foods Can Be Both High FODMAP & Low FODMAP

Yes, foods can be high FODMAP and low FODMAP – and it all comes down to serving size!

Let’s look at broccoli as another example. We bet that you have seen broccoli on low FODMAP food lists AND high FODMAP food lists. This is because lab test results tell us that broccoli heads (florets) are Red Light High FODMAP in servings of 270 g, yet Green Light Low FODMAP at 75 g, which a-is a very generous serving.

Neither list or mention is “wrong”, yet neither is “right” – without at least a discussion about serving sizes and how it relates to the person consuming the broccoli. The high FODMAP “serving size” is what will most LIKELY trigger symptoms in someone with IBS.

Please read our article, High FODMAP Foods With Low FODMAP Serving Sizes.

But it is not etched in stone. Read on.

Why Are Serving Sizes Important?

Why are serving sizes important? Serving sizes are important because they provide a place for us to BEGIN to look at our relationship with FODMAPs, which will be unique for each and every one of us. (Like that stake in the ground for the FDA, it is a place to start). 

FODMAPs can trigger IBS symptoms, so the low FODMAP diet is built around knowing what foods are high FODMAP and which are low FODMAP – but that’s just the beginning.

During the Elimination Phase you will be removing high FODMAP foods from your diet. This is to calm your system and to create a cleaner baseline for your Challenge Phase.

We start by looking at what foods in which specific amounts have been determined to be high FODMAP in the lab. Foods in these amounts will be removed from the diet during the Elimination Phase.

 But remember, you are not a lab!

The Importance Of The Challenge Phase

The Challenge Phase is often the most, well, challenging phase for FODMAPers. This is because during this phase the idea is to introduce foods slowly and methodically, each individual FODMAP at a time (and even multiple foods within the same FODMAP group separately from one another), in varying amounts, assess your digestive reactions – good and bad – and keep accurate records.

This is complex and nuanced and best approached with the help of a registered dietitian.

If you burp or fart 20 minutes after testing a FODMAP, does that mean you failed the test?

What if you get diarrhea the next day?

These are the kinds of questions that a FODMAP trained RD can answer. And, by the way, we have an International’s RD Directory for you. And an article on symptom timing, that you might be interest in.

The Takeaway on “Serving Sizes”

Remember those almonds? Monash tells us that 20 almonds will most likely trigger symptoms and that 10 almonds will most likely not trigger symptoms in those with IBS.

And of course, always remember that high FODMAP foods are not “unsafe”. Read more in FODMAPs Are Not “Unsafe” to learn more.

During your Challenge Phase you might learn that you can eat 25 almonds! Or maybe only 5.

And then that amount, my fellow IBS friends, will be YOUR true serving size. This is the serving size that counts for YOU.