How are FODMAPs measured and tested?

The way that FODMAPs in food are tested is a labour-intensive and complicated process. Each individual food needs to be sourced from up to 10 different manufacturers, shops or grocers. It then takes up to 4 weeks to test and classify each one. This can only be done by specialists and requires precise laboratory equipment and scientific controls.

We rely solely on researchers and dietitians, specialising in the field of FODMAPs, to perform this rigorous, controlled testing. They then present their findings to us in the form of lists, booklets and apps.

Why do the FODMAPs in food change?

Due to continued research and improved testing methods, Fodmap results can and do change over time as more is learned. Foods are periodically retested based on when they were last tested. They may also be retested if dietitians and patients are frequently reporting significant issues with a particular food or serving size previously thought to be low FODMAP. These changes can go either way with low FODMAP portions dramatically increasing or decreasing depending on the updated findings.

To make things even more complicated the FODMAP content of the same food can vary with;

country of origin
soil and growing conditions
weather fluctuations and environmental factors
variety and species
which part of the food is tested
processing techniques
storage
ripeness
cooking techniques

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This is why there may appear to be discrepancies between the FODMAP listings of foods in the Monash FODMAP app compared to those in the FODMAP Friendly or Food Maestro apps. This doesn't mean that one institute is right or the other wrong. It simply demonstrates how food tested at different times, in different countries at different times of the year can yield different results.

What FODMAP values can change?

Several factors can change when it comes to testing and retesting the FODMAP values of foods.

New foods and brands are tested and added to databases.
A food or portion size previously thought to be FODMAP free or low FODMAP can be reclassified as high FODMAP. This may result in a slight - significant decrease in recommended portion size.
A food or portion size previously thought to be high FODMAP can be reclassified as low FODMAP. This may result in a slight - significant increase in recommended portion size.
The type of FODMAP a food contains may change from one type to another.
A food with no excess FODMAPs listed previously may have the FODMAP type it contains listed for clarification.

Some examples of these changes in the Monash app include the 2021 changes to strawberries and grapes. Both were previously thought to be FODMAP free and could be eaten according to appetite. After retesting they are now classified as being moderate and high (respectively) in fructose with drastically reduced recommended portions.

Another example is the increase in a low FODMAP portion of leek leaves. These can now be eaten in generous 100g portions with no excess FODMAP type listed. They were previously listed as moderate in FODMAPs at a 75g serving and contained mannitol.

What happens when FODMAPs change?

When FODMAPs are retested the new findings will be updated in the FODMAP app specific to the institute doing the retesting. These changes are often also highlighted on social media. This is why it's worthwhile regularly checking in with your preferred app to see what's recently been added or retested.

This may mean that the values between different apps may differ and discrepancies may occur. For this reason and to avoid confusion I recommend choosing and sticking with one app, particularly during the elimination phase of the diet.

Often blog posts, cookbooks, recipes and food lists containing the retested foods may not be updated to reflect the new findings. This is why it's important to cross-reference recipes you want to try and resources you find online with the most up to date version of your low FODMAP app.

How does this translate to my plate?

If you're already eating food that's been reclassified as high FODMAP without issue then there's no need to remove or restrict it from your diet. If however, you're experiencing unexplained flare-ups or mixed results then it may be worth following the updated guidelines to see if it may help.

This can also work both ways. If you've been avoiding a particular food which has now been reclassified as lower in FODMAPs it's worth experimenting with how this food affects you. It's important to be continually looking to expand your food choices and portion sizes to avoid a restrictive diet and mindset.

How FODMAP testing affects our food choices

FODMAP testing allows us to compare the FODMAPs of individual foods, such as a piece of fruit or a vegetable to the FODMAP food guides available. It also establishes the type and amount of FODMAPs in a particular serving size. It can show us which brands are specifically creating foods certified as suitable for a low FODMAP diet.

Thanks to FODMAP testing, creating a low FODMAP, whole-food meal at home from scratch can be fairly straightforward. However, it's much less apparent for us to work out the FODMAP content of the many foods and brands that are untested.

The packaging and labelling of ready meals or menu items at a restaurant can be baffling. Looking up the individual ingredients can only tell us so much. Often the only definitive way to know if pesky FODMAPs are lurking (usually in the additives and flavourings) is to contact the company directly.

These limitations, differences and discrepancies are some of the most frustrating aspects of the low FODMAP diet. All of these factors can influence what and where we choose to eat. Through working with a dietitian we can ensure that our diet and mindset are only as restricted as they need to be in order to manage the symptoms of IBS.

How to minimise the impact of FODMAP fluctuations

My top 4 tips to reduce the frustration of FODMAP fluctuations are:

Ensure your elimination phase is only as long and as restrictive as it needs to be to experience symptom relief. Once you've completed the elimination phase any changes to FODMAP values will have little real-world impact on your food choices.
Acknowledge your body does not work like a laboratory. Your IBS doesn't function like anyone else's and we all have unique needs, tolerances and triggers. These cannot be defined by a simple, generic list of high and low FODMAP foods, however accurate or up-to-date they may be.
Stick with one FODMAP app or set of guidelines that work for you. This avoids unnecessary stress, conflicts and confusion. Become familiar with your chosen app and regularly check for updates.
Be aware when speaking to others, researching recipes or asking questions that other people may be working from different guidelines than yours. This doesn't mean they are automatically wrong. They may simply be working with different information or be unaware of recent updates. Keep an open mind and double-check with your dietitian or chosen app to decide what's best for you and what modifications you may need to make.

Wherever possible, particularly during the elimination phase, the diet can be made simpler by aiming to;

cook from scratch where possible
reduce reliance on ready meals from untested brands
stick to simple recipes, whole foods and ingredients
use FODMAP-certified brands where possible
avoid additives and ingredients you can't pronounce or identify as food
get familiar with using herbs and spices to add flavour
base meals around a wide variety of FODMAP free and low FODMAP foods
experiment with prepping and cooking techniques
log your findings and symptoms and explore the patterns that emerge
eat out infrequently

As you progress through the diet it's up to you to continue experimenting with the foods you want to eat that may not yet be FODMAP tested. Just because a food hasn't been tested doesn't mean it's not suitable to include in your diet. Likewise, just because a food has tested as low FODMAP does not mean it won't cause digestive issues for you.

FODMAP food guides are a mere starting point for your own experiments with your digestion. Working with a dietitian to spot and minimise your individual triggers will be far more beneficial to you in the long run than any generic FODMAP food list.

Ready to tackle the low FODMAP basics? Check out the other posts in this series.

How do you manage the pesky FODMAPs in your diet? Share your tips in the comments below.