Why a low FODMAP diet is not a solution for fructose malabsorption

Written by Michael

What are FODMAPs?

FODMAPs are fermentable oligo- and disaccharides, monosaccharides and polyols. Fermentable means that they are substances that can be processed by bacteria in the intestine. The bacteria produce gases and other nasty stuff and thus cause flatulence and pain. Oligosaccharides are carbohydrates such as fructans and galactans found in wheat or onions and garlic. Disaccharides refers to lactose, not sucrose. By monosaccharides is meant fructose. However, fructose is special, because the FODMAP diet is not about the total amount of fructose but about excess fructose. An example: The pineapple has 5.1g of fructose and 4.7g of glucose⁽¹⁾ and is considered to be poorly tolerated in fructose malabsorption. One serving (200g) would contain almost 10g of fructose. Due to the low fructose excess of 0.4g, however, it is allowed in the FODMAP diet.
Finally polyols are the sugar alcohols sorbitol, mannitol, xylitol and maltitol.⁽²⁾ But all of these carbohydrates must be fermentable, so they can be metabolized by the bacteria in the gut. Polyols such as erythritol are therefore not among them because they are not fermentable in this sense.

In 2005 Sue Shepherd and Peter Gibson from Monash-University in Melbourne, Australia, published a scientific paper in which they brought Crohn's disease with these FODMAPs in connection⁽³⁾. It soon became clear that with a low FODMAP diet, especially irritable bowel syndrome (IBS) could be improved. This has been proven in many studies and is common practice nowadays.

What is irritable bowel syndrome (IBS)?

So to clarify the question of whether a low FODMAP diet is recommended for fructose intolerance patients, we need to clarify what an irritable bowel syndrome is. Irritable bowel syndrome patients experience, among other things, a strong pain when the intestine is stretched. Therefore, they are in great pain when eating flatulent food. However, the diagnosis IBS is made as the very last diagnosis. All other diseases and intolerances must be excluded before. So you first have to make an H2 breath test for lactose or fructose intolerance. Only if these tests are negative or a corresponding diet brings no relief and only if all other options are excluded, the diagnosis IBS can be made. This diagnosis is the very last step in a very long diagnostic journey.

FODMAP - the business

Other than in Europe, in English-speaking countries, especially the U.S. and Australia, it is common to try to create a business out of your own scientific work. You can see this very well with the FODMAPs. The "Low FODMAP Diet^TM" is a trademark of the Monash University. There is an quite expensive app, certified food, books, training courses and so on. Business is booming. Just put “FODMAP” in the amazon search box.

Low FODMAP for FM: yes or no?

To summarize: FODMAPs are certain carbohydrates. These include, for example, lactose, fructose and sorbitol. Anyone who does the low FODMAP diet doesn’t eat those carbs or only eats them in small quantities. Fructose is about the excess fructose, not about the total amount fructose. So a first answere is: the low FODMAP diet does not make sense for people with fructose malabsorption. On the one hand, you leave out many foods that you would very well tolerate. For example, you wouldn’t eat many dairy products and wheat products, which would be very well tolerable cause they have nothing to do with fructose malabsorption. On the other hand, one may eat certain foods that one should avoid, like the pineapple. But there are other examples like the kiwi, orange, or the grapes. The list would be much longer.

Incidentally, this fact is also known to the Monash researchers and they point out correctly in their publications: The low FODMAP diet is intended for IBS patients, not for people with fructose malabsorption⁽⁴⁾. Thanks to the good advertising machinery, which does not communicate these explanations very well, and because in some countries often no proper diagnostic procedures take place, people with bowel problems are immediately put on the irritable bowel syndrome diet, even if they have no irritable bowel. An H2 breath test is never done, a proper intolerance diagnostic has never taken place. FODMAP has become so well-established as a catchphrase that it is immediately recommended without worrying whether this strict diet makes sense at all.

So we can clearly say: A low FODMAP diet does not make sense for fructose malabsorption. Monash researchers do a very good job and they do great science, but they do it for IBS, not for fructose malabsorption. There are other groups and researchers, especially in German speaking Europe, who specialized on food intolerances. They have better lists and articles about fructose malabsorption and should therefore be the ultimate source of information for people with fructose malabsorption.

1) Zechmann MW, "nmidb"; Society for Public Health; https://www.nmidb.de
2) Gibson PR, Shepherd SJ. "Evidence-based dietary management of functional gastrointestinal symptoms: The FODMAP approach"; Journal of Gastroenterology and Hepatology, 2010; https://doi.org/10.1111/j.1440-1746.2009.06149.x
3) Gibson PR, Shepherd SJ. "Personal view: food for thought-western lifestyle and susceptibility to Crohn's disease." The FODMAP hypothesis ". Aliment. Pharmacol . Ther . 2005; 21: 1399-409. https://doi.org/10.1111/j.1365-2036.2005.02506.x
4) https://www.monashfodmap.com/about-fodmap-and-ibs/ (accessed 4.7.2018)