Lifestyle | Health & Wellness

When Low FODMAP Lab Test Results Differ

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Hopefully by now you know that we highly recommend that everyone following the low FODMAP diet have both the Monash University smartphone app and the FODMAP Friendly smartphone app. This is because these are the two entities doing the original research and lab testing; they are the primary resources for the diet. 

But what do you do when their lab tests results for the same food – such as avocados, beets, strawberries, red bell peppers and many others – differ? Or, just as confusing, what if one the institutions, like Monash, re-tests a food and the results are different from prior tests?

Two Main Reasons Why Lab Test Results Differ

There are two main reasons why lab tests for FODMAP content differ:

  1. Monash University and FODMAP Friendly use slightly different FODMAP thresholds.
  2. FODMAP content is variable in food. Every lab test is expected to have different results.

This article will take you through it step-by-step.

When Monash University And FODMAP Friendly Low FODMAP Lab Test Results Differ Feature Image.

FODMAP Thresholds

One of the very first things to understand is that Monash University and FODMAP Friendly base their cut-offs for FODMAPs on slightly different values, in certain instances. This means that the serving size recommendations in their apps are values that have been determined to be amounts that will not trigger IBS symptoms in most people. Take a look below (you can read more in the individual articles on Monash and FODMAP Friendly):

The different thresholds partly explain why the app entries for the same foods in each app differ.

Oligosaccharide Threshold Comparisons

You can see below that Monash University divides Oligosaccharides into two group, while FODMAP Friendly does not.

Oligos FODMAP Thresholds Compared

Polyol Threshold Comparisons

For Polyols as a group, and for the individual polyols – sorbitol and mannitol – all numbers are very similar, but they doing differ between Monash and FODMAP Friendly.

Polyols FODMAP Thresholds Compared

Excess Fructose Threshold Comparisons

Monash University divides the way it looks at fructose. The first entry applies to foods where fructose is greater than glucose, but other FODMAPs might also be present in that food, therefore the amount is lower.

Fructose FODMAP Thresholds Compared

Lactose Threshold Comparisons

The thresholds for lactose are the most dissimilar.

Lactose FODMAP Thresholds Compared

FODMAP Content in Foods is Variable

We have written an entire post for you, FODMAP Content In Food Is Variable; please read it now.

Here is a snapshot:

  • There can be thousands of varieties of any given fruit or vegetable, and we typically do not know what variety is tested.
  • Microclimates (temperature, soil, air, water) of farms vary hugely and can affect FODMAP content.
  • Differences in agricultural methods, such as fertilizer use, ripeness upon harvesting, storage conditions and more can influence nutrients in crops.
  • Research has demonstrated that plants can change their chemical structure when exposed to stressors in their environment. 
  • Cold storage, pests, disease, and environmental changes, for instance, can lead to the development of fructans where they did not exist before.
  • Increases in fructose content are also known to occur in these environments.

Foods Included In Our List of Conflicting Low FODMAP Lab Test Results

This graph below not an exhaustive list. We have focused on very popular food fruits and vegetables that people following the low FODMAP diet want to know about, and in some cases that we know have had different lab results between the two testing bodies (Monash University and FODMAP Friendly). We have also included outliers that were just so extreme, we thought they deserved a mention – check out blackberries!

The reason why we have focused on fruits and vegetables is because they are the ones most likely to vary quite a bit in FODMAP content due to country of origin, ripeness, harvesting, handling and storage procedures, etc. 

Comparison Chart of Conflicting Low FODMAP Serving Sizes

Here are some of the low FODMAP amounts reported by Monash University and FODMAP Friendly. The “Max Serve Size” (right column) that is still low FODMAP is a new feature from the FODMAP Friendly app (we love it). If a cell is empty, it is because there is no data available for a low FODMAP serving size. 

Where we have data available from multiple testing times, we have included them in order. So, if it says, “No FODMAPs/Now 50 g”, it means initial lab tests showed “no FODMAPs”; subsequent tests showed 50 g to be the low FODMAP serving size. Both tests are accurate (again, read those articles linked above).

Note that the Monash University and FODMAP Friendly vertical columns show recommended serving size, which is not necessarily the maximum that you can eat and remain low FODMAP. Please review our article, What Is A Low FODMAP Serving Size?

Now, let’s look at some ingredients.

IngredientMonash University FODMAP Friendly FODMAP Friendly Max Low FODMAP Serve Size
Avocadowas 30 g/now 60 g80 gwas 1000 g/now 80 g
Apricot16 g53 g
Beet root25 g75 g150 g
Black Grapes100 g1000 g
Blackberry4 g150 g375 g
Blueberrywas 40 g/now 125 g150 g250 g
Broccoli (heads)75 g
Broccoli (stalks)45 g
Broccoli (whole)75 g750 g
Brussels SproutsWas 38 g/Now 50 g75 g250 g
Butternut Squash45 g75 g188 g
Canned Peaches66 g
Canned Pumpkin75 g120 g150 g
Cherry Tomatoes75 g75 g750 g
Common Ripe Banana35 g88 g
Common Tomato (beefsteak)65 g75 g84 g
CucumberNo FODMAPs 64 g1000 g
Dried Dates8 g30 g60 g
Dried Figs40 g58 g
Dried Pineapple31 g
Edamame90 g168 g259 g
Fresh Figs5 g64 g214 g
Grapefruit (image shows pink)80 g150 g250 g
Green Beans75 g75 g125 g
Green Bell Pepper75 g75 g750 g
Leek Bulb14 g46 g
Leek Leaves100 g37 g83 g
Mango40 g54 g
Nectarine (white)150 g215 g
Nectarine (yellow)18 g93 g
Onion (brown/yellow)26 g
Pearwas 5 g/now 4 g0 g
Raspberries60 g45 g82 g
Red Bell PepperNo FODMAPs/Now 43 g75 g750 g
Red GrapesNo FODMAPs/Now 28 g150 gwas 750 g/now 900 g
Red Onion28 g
Roma Tomato75 g75 g108 g
Scallion Bulb19 g
Scallion GreensNo FODMAPs16 g161 g
StrawberryNo FODMAPs/Now 65 gwas 50 g/now 45 gwas 51 g/now 45 g
Watermelon (seedless)15 g50 g
Peach (white)18 g83 g
Peach (yellow)30 g100 g
Yellow Bell Pepper24 g
Yellow Summer Squash100 g101 g
Zucchini (courgette)65 g75 g375 g

The Main Gist

The over-arching concept that you have to understand is that both Monash University and FODMAP Friendly conduct valid and trustworthy lab tests. You can read much more in our articles, Monash University Lab Testing Explained and FODMAP Friendly Lab Testing ExplainedThey might report different results occasionally, but that does not mean one test was right and one was wrong. Or that one is “more” correct! Even when it is the same institution testing foods and then re-testing foods and getting different results. Both results are valid.

Both Monash University and FODMAP Friendly conduct valid and trustworthy lab tests.

As the above linked articles explain, it simply means that for the items tested at that time, those are the results that the lab tests revealed and – especially when it comes to fresh fruits and vegetables – the produce you eat will then again be different from what they tested.

It is literally impossible for the food that you buy today, next week, or next month to be the same as what was lab tested. This is why the app entries are guides.

You Are Not A Lab

Always look at lab tests as lines in the sand from which to begin your exploration of FODMAPs; use the lab information to help guide what your unique relationship is to FODMAPs, which might be very different from what the labs report. You might be able to eat more, or less. As we are fond of saying, you are not a lab.

It is literally impossible for the food that you buy today, next week, or next month to be the same as what was lab tested. This is why the app entries are guides.

Frequently Asked Questions

Which Lab Test Should You Use As Reference?

Which lab test you use as your starter marker is up to you. They are all accurate. We know some Facebook groups and some RDs only use Monash and caution folks away from FODMAP Friendly. I have never heard one convincing argument as to why. If you read the articles linked above, you can certainly draw your own conclusions.
To those who say it makes things more confusing, here is my take: your patients, or you yourself, will find conflicting information online and elsewhere. If you do not know the sources of the differences of opinion, or how they came to those conclusions, you truly cannot make a judgement or a decision. 
Once you do know that all the labs used are reputable, that lab results will vary regardless due to variety of produce, ripeness, handling, storage and country of origin, then you begin to understand that all these results are just what were detected in a snapshot in time.

Which Testing Entity Is More Conservative?

You might be asking yourself, of Monash University and FODMAP Friendly, which is more conservative? Or, perhaps you want to know who is more lenient with their serving size recommendations?
Each of the testing bodies have examples of reporting more stringent recommendations, more generous ones, and they are sometimes in agreement. There is no black and white answer.

FODMAP Lab Testing Articles At A Glance

Here are all of our other articles that pertain to lab testing for FODMAPs. We suggest that you read them all:

The Takeaway

Both Monash University and FODMAP Friendly lab test foods for FODMAP content and provide reliable results – even when they report different findings from test to test (of the same food) and from one another as lab testing bodies. It is to be expected that FODMAP content in foods, especially fruits and vegetables, will vary.

You can use any of the lab tested findings, new or older, from either Monash University or FODMAP Friendly as a baseline from which to begin to explore your relationship with FODMAPs, which will be unique. 

You can use any of the lab tested findings, new or older, from either Monash University or FODMAP Friendly as a baseline from which to begin to explore your relationship with FODMAPs, which will be unique. 

Also, what you do or do not tolerate today will most likely be different a few months or a year from now. Your digestive tract is not static, and neither are your FODMAP reactions. This is why it is important to re-introduce foods periodically if you have breakthrough IBS symptoms or are wondering if you can tolerate something now that you couldn’t before.

Please make sure to read our articles on Monash University Lab Testing Explained, and also FODMAP Friendly Lab Testing Explained.

Rely on primary resources like Monash University and FODMAP Friendly to help guide your three phases of the low FODMAP diet.

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