How is the fodmap content of food determined?

the fodmap restrictions for a watermelon

We therefore have “low”, “moderate” and “high” levels of fodmap for each ingredient, associated with very specific quantities.

But how does one achieve such a level of accuracy? Who comes up with these numbers? How is it measured?

J. Delorme, a dietician expert in fodmaps explains this process in her book:

To determine the level of a fruit or vegetable, it is necessary to collect samples of 500 grams from five supermarkets and five organic shops, and successively grind them, freeze them, dehydrate them with hot water, add specific enzymes and measure each category of FODMAP using a precise high-performance liquid chromatography technique.

[Source 1]

Each ingredient is tested one by one by this method.

graphique présentant les étapes pour analyser la teneur en fodmap des fruits, légumes et céréales
Steps taken to analyse the fodmaps level of fruits, vegetables and cereals (source 2).

For cereals and seeds, the method is a little different from fruits and vegetables, although similar. The method is not exactly the same depending on whether one analyses the fructan level or the GOS level for example, now these are too technical details to be discussed in detail.

However, we can not always generalize when talking about a food, it is sometimes necessary to distinguish certain modes of conservation (canned, in vinegar…), certain parts (green or white part of a leek), certain states (fresh, ripe, dried …) that have impacts on the level of fodmaps.

Meats and fishes

As for meat, fish, shellfish, crustaceans, eggs: we know that they contain no carbohydrates, therefore no fodmaps. It is then useless to test them, there is no restriction regarding fodmaps.

Once the values are established by these analyses

The last step is to determine by a dietician portions that are low, moderate or high in fodmap, which are found in the application for example. (source 3)

How long does it take to analyze a food?

Between 2 and 4 weeks! (source 3)

Yes, it is a long, multi-stage job that requires skilled labour. They still have a lot of ingredients to test and even re-test.

Who conducts these studies?

I am only familiar with Monash University in Australia, but it is possible that other institutions are also working on this subject.

Regional limits

Monash University is the source of reference, and obviously the only institution to conduct these tests, one wonders to what extent their supply of exclusively Australian fruits and vegetables may have an impact on these tests. Do our endives, strawberries, melons or cabbage really have the same levels?

This should not change at all, but when we see that within a few grams an ingredient switches from “weak” to “moderate”, or “moderate” to “strong”, we can ask ourselves the question.

It’s a limitation identified by the Monash researchers themselves:

More comprehensive country‐specific FODMAP composition data are urgently required, with a number of country‐specific factors known to affect FODMAP composition of food and FODMAP intake, including unique food processing techniques, food supply, food habits, and food culture.

[…]

[This is] needed for this diet to be more easily implemented internationally.

[Source 2]

Indeed, non-raw products such as soy sauce, ricotta cheese, honey or beer are all in the Monash database but are very far from being uniform, whether they are commercially available or “home-made”.

Various ricottas sold in french supermarkets have lactose levels with a 50% difference for example. I have established that honeys have very different fructose/glucose ratios, some of which could still be suitable for us (article to come). The variety of beers that can be found in Europe has nothing to do with Australian lager.

When the fodmap diet was introduced in the United States, Monash realized some differences that were sometimes very awkward. Local varieties of cereals showed variations in fodmap levels. Product labelling is often vague, allowing manufacturers to hide onions and garlic behind the terms “flavour enhancer” or “spices”. [source 2]

Limits on quantities tested

An ingredient on the Monash application is often tested in different amounts, which may correspond to normal serving sizes. But sometimes, only one amount is tested and is prohibited.

Chestnut flour, for example, is evaluated as high in fructans at 100 grams, but this is the only quantity tested. This does not mean that in smaller quantities the level is also high, one could easily imagine that it goes down to moderate or even low, especially since chestnuts have no restrictions.

This applies to other ingredients on their list, such as cauliflower (high in mannitol at 75 grams) or Jerusalem artichokes.

You sometimes have to take their work with tweezers. Their methodology is very serious and beyond suspicion, but it would take many more researchers studying every region of the world to achieve a level of finesse that can sometimes be lacking. The Anglo-Saxon world is beginning to be well covered, but not the rest.

Sources

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