Is the low FODMAP diet a way of treating fructose intolerance through diet? This approach is widespread in the English-speaking world, but does it make sense? To answer this question, we need to take a closer look at the topic of FODMAP.
What are FODMAPs?
FODMAP is understood to mean f fermentable O ligo- and D isaccharides, M onosaccharides and a nd) P olyols. Fermentable means that these are substances that bacteria in the intestine can process into gases, among other things, and thus cause flatulence. Oligosaccharides are carbohydrates such as fructans and galactans. These are found, for example, in wheat, onions and garlic. The term disaccharide refers to lactose, while monosaccharide refers to fructose. However, fructose is a special case, because the FODMAP diet is not about total fructose, but about excess fructose. For example, pineapple contains 5.1g fructose and 4.7g glucose and is considered poorly tolerated by fructose intolerant people. One portion (200g) would contain almost 10g of fructose. However, it is permitted in the FODMAP diet due to the low fructose surplus of 0.4g. Polyols are the sugar alcohols sorbitol, mannitol, xylitol and maltitol.1) All these carbohydrates must be fermentable, i.e. metabolizable by the bacteria in the intestine. Polyols such as erythritol are therefore not included because they are not fermentable in this sense.
In 2005, Sue Sheperd and Peter Gibson from Monash University in Melbourne, Australia, published a paper in which they linked Crohn’s disease to these FODMAPs2). It soon became clear that a low FODMAP diet could provide relief for irritable bowel syndrome patients in particular. This has also been proven in studies.
What is irritable bowel syndrome?
In order to answer the question of whether a low FODMAP diet is recommended for fructose intolerance patients, we need to clarify what irritable bowel syndrome actually is. Irritable bowel syndrome patients often experience severe pain when the bowel is stretched, in addition to other symptoms. This happens when they eat flatulent food and the air in their stomach expands. However, irritable bowel syndrome is the very last diagnosis to be made. All other illnesses and intolerances are excluded beforehand. This means that you first do H2 breath tests for lactose or fructose intolerance. Only if these are negative or an appropriate diet does not bring any relief and all other possibilities have been ruled out is a diagnosis of irritable bowel syndrome made. This diagnosis is usually the last stage of a marathon of examinations.
FODMAP – the business
In the English-speaking world, it often happens that people try to make a business out of scientific findings. You can see this very well with the FODMAPs. The “Low FODMAP Diet” is trademarked by Monash University, there is a very expensive app, certified foods, books, training courses and much more. Business is booming. Just enter “FODMAP” in the Amazon search…
Low FODMAP yes or no?
We summarize: FODMAPs are certain sugars and sugar alcohols. These include, for example, lactose, fructose and sorbitol. If you follow the low FODMAP diet, you leave all this out or only eat it in small quantities. Fructose is about the excess fructose, not the total fructose. This already shows that the low FODMAP diet does not make sense for fructose intolerance. On the one hand, you leave out many foods that you would tolerate very well. For example, you have to avoid many dairy products and wheat products, which would be perfectly suitable. On the other hand, you can eat certain foods that you should actually avoid. We have seen the pineapple as an example. But there are other examples such as kiwis, oranges and grapes. The list would be much longer.
Incidentally, this fact is also known to the Monash researchers and they always explicitly point this out in their publications: The FODMAP diet is intended for irritable bowel syndrome patients, not for people with fructose intolerance3).
And yet this dietary trend is also spilling over into Europe for fructose intolerance. On the one hand, thanks to the good advertising machinery, which does not communicate these explanations so precisely, and on the other, because in these countries there are often no proper diagnostic pathways. People with bowel problems are immediately put on the irritable bowel diet, even if they do not have irritable bowel syndrome. An H2 breath test does not take place. FODMAP has become so well established as a buzzword that it is immediately recommended without thinking about whether this strict diet makes sense at all.
We can therefore clearly say that a FODMAP diet is not useful for fructose intolerance, as it is far too restrictive and also allows incompatible foods.
1) 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
2) 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