What exactly is fructose intolerance or fructose malabsorption?

Fructose (fruit sugar) is not only found in fruits, as one might guess from the name. Fructose is also found in vegetables, lemonades, alcohol, baked goods and confectionery, ready meals and sauces, and in many types of sugar.

In the case of fructose intolerance, the fructose is not completely absorbed in the small intestine and it ends up in the large intestine. This creates an excess of short-chain fatty acids and gases, which cause flatulence, diarrhea, stomach pain, etc.

The fructose transporter (Glut-5) usually has a malfunction, it does not transport the fructose from the small intestine into the cells as desired. This is how the fructose reaches the large intestine where it is fermented by intestinal bacteria and leads to digestive problems. Sorbitol can block the absorption of fructose and make the symptoms worse. Accordingly, sorbitol should also be avoided if possible if you have a fructose intolerance.


What are the symptoms?

 There are many different symptoms. Most of them come from the gastrointestinal tract. Abdominal pain, bloating, diarrhea and abdominal cramps are very often a constant accompaniment. But constipation, heartburn, bowel pain, nausea, and gas can be just as good. There are also people who develop a rash, dizziness, headache and general ill feeling.🤢



How can you find out? Are there any tests?

 First, if you have a possible fructose intolerance, you should have a test done by a doctor who is familiar with it. A "hydrogen breath test" (H2 breath test) is carried out to determine whether there is any fructose intolerance. A solution containing 25 g of fructose in 250 ml of water is consumed under medical supervision. The concentration of hydrogen in the breathing air is then measured at short intervals. Unfortunately, a breath test is not always meaningful. Therefore, it is also important to write a nutrition and symptoms book beforehand. Preferably over a couple of weeks.

 Unfortunately, there are many doctors who still test incorrectly.

 A breath test with 25 g of fructose is correct, no more! 🙄



Is it Hereditary?

Fructose malabsorption is not hereditary. But there is hereditary fructose intolerance and this is inherited due to various genetic changes. It is innate and can appear in infancy. With hereditary fructose intolerance, no fructose is tolerated at all, in contrast to fructose intolerance, where some fructose is tolerated.

It is estimated that 247 million people in Europe are affected by fructose intolerance.

From 25 g of fructose, 1/3 of people have problems with fructose.

5% of people do not tolerate fructose at all

35% of people can tolerate up to 25 g of fructose

 60% of people can tolerate any amount of fructose, although there may be complaints if there is too much fructose. (About 25g a day)



Can it be cured?

There is no cure for a fructose intolerance. But you can improve the symptoms, or eat so that the symptoms almost disappear (with patience), if you really pay attention to your diet and only eat "permitted" foods.

There is medication that can make an improvement possible in the short term. 

They contain the enzyme xylose isomers. This enzyme converts the fructose in the small intestine into glucose, but also glucose into fructose. The enzyme is deactivated from a heat of 60 degrees Celsius.

The simultaneous intake of glucose also helps the absorption of fructose in the small intestine. But glucose is absorbed faster than fructose. Accordingly, you have to consume more glucose than fructose. 

Watch out!! Larger amounts of glucose can give you digestive problems as well


I am overwhelmed. Where can I find help and support?

Try to find a good nutritionist who is familiar with fructose intolerance. Unfortunately, there are many who are not familiar with food intolerance and unfortunately, they give wrong advice and information.

(You can book a coaching with me😎)

There are also many starting points in social media and the internet. Exchange groups, information pages, recipes and basic knowledge. Unfortunately, there are black sheep here too.

Do not let yourself be disorientated or confused.

Everyone has their own tolerance limit, which you just have to find out slowly, step by step.

The basic rule is to try and not to despair if you eat something “wrong”. 



What other problems may there be?

Social contacts could become less because you no longer dare to go out because of your complaints. Or because you don't know what you can / should eat and drink when you go to a restaurant or when are invited somewhere. Constant abdominal pain, gas and diarrhea are not a comfortable companion when you are around people. This can lead to depression, listlessness, and lower self-esteem.

Vitamin and mineral deficiencies can also occur due to diarrhea. Here you lose very valuable nutrients. It has been proven that people with a fructose intolerance should consume additional zinc and folic acid.

But here you have to pay attention to the ingredients again, not that hidden sugar is to be found.

It is best to do a blood check at the doctors to see which vitamins and minerals your body needs.




Help fructose intolerance, what now ???

... grace phase, test phase, patience!

After the diagnosis you are first lost. Lots of information, lots of questions, no plan…

First of all, it is important to take a grace period. That means avoiding all fructose-containing foods for 2 to 4 weeks so that your intestines can come to rest. But you should also do without so-called "bloating vegetables" such as cabbage.

During this time, symptoms may increase at first, but there will be an improvement, be patient.

After the grace phase comes the test phase. Re-insert food with a little fructose into your diet bit by bit. On the first day, just test one new food, wait 3 days and watch your body. Fructose can stay in the body for up to 72 hours!

The best thing to do is to write it down in a food diary so that you can look back later on what you tried, in what quantity and how it worked. After the 3 days, try the same food again in the same amount. Observe and write down. It may be that you can tolerate one food one day but not the next time. It depends on your "form on the day". Stress, fatigue, problems, excitement, menstruation, and medication can all affect how well fructose is tolerated in your body. Then increase the amount of food step by step.

It is a slow, long road to take baby steps around the feeling of being able to eat somewhat “normally”. But patience is very important, do not give up, even if you have eaten “wrong” or have a bad day, do not despair. Then just eat low-fructose foods for a day or two. 




Beware of fructose traps !!

There are many "fructose traps".

These are foods that you can buy in supermarkets and do not suspect that fructose is in them.

When shopping, it is best to ALWAYS read the ingredients on the package. It's not about how much sugar is on the package, it's really all about the ingredients. Many foods naturally contain sugar, such as wheat in pasta. Average nutritional value for 100 g of pasta is 3.5 g of sugar, but it has nothing to do with fructose, which is safe to eat (if you can tolerate wheat)

Packaged cold cuts / sausages: You have to be careful here mostly with the spices. Onions and garlic, no matter how little, can cause discomfort. Ingredients like paprika, chili, ginger could cause slight discomfort. Most types of sausage are nowadays "sweetened" with dextrose (why you have to sweeten a sausage is still a mystery to me!) which is tolerable by fructose mal absorption, check anyway!

Bread: Yes, most types of bread contain fructose. A good example is a “healthy” multigrain bread from a discounter. It contains caramel syrup and invert sugar syrup, both of which are totally incompatible with fructose intolerance. This bread also contains malt extract and yeast, both individually tolerated. It is best to bake bread yourself, because you know 100% what it contains, or from a baker you trust (just ask for the list of ingredients)

Vegetable broth: The vegetable broth may contain sugar, caramel sugar, garlic and onion powder. All of these ingredients can cause discomfort. Yeast extract, tomato powder and leek could also appear as ingredients in the vegetable broth. These ingredients are individually compatible. Sometimes it comes down to the price of vegetable broth. Those that are a little more expensive are usually more tolerable

Spice mixture: You really have to be careful here. Even if it always seems to be “a little”, it can still have an impact. I found onion grated, tomato flakes, paprika grated, garlic grated and even raw cane sugar in a spice mix. All incompatible. Leek flakes, chives, chili powder and fennel powder could potentially cause problems

Ready-made sauces and dressings: it's really bad here! Ketchup has an average of 29 g of sugar per 100 g. I know it's not always about the sugar content, but when sugar comes second in the ingredients, it does count! The concentrated tomato juice is also full of fructose. Many ready-made sauces and dishes have sugar as an ingredient and many spices (it has to be tasty too). But there are also ready-made sauces that are compatible. Just read the ingredients.

Caution!! "Sugar-free" "Without added sugar"

Many foods are labeled "sugar-free" or "no added sugar". Yeah, you think, I can eat them if they don't contain sugar. This is not correct!!

There may not be “real” sugar in such foods, but sweeteners such as maltitol syrup, maltitol, isomaltose or inulin. These sweeteners can cause damage to our digestive tract because we cannot digest them. And lead to diarrhea when we consume larger quantities. But there are some products with erythritol or stevia that can be tolerated, but not for everyone. Again, tried and found out what you can tolerate.


How much fructose can be tolerated?

Good question, next question…

You can't just say that, everyone can tolerate a different amount. In the case of fructose intolerance, it is under 5g of fructose per day. But there are people who can take more, but also less. In the case of hereditary fructose intolerance, you are not allowed to consume any fructose at all, you have to follow a very strict diet. 



And now??


I can support you as a nutritionist or give you baking ideas.

You can book a coaching by me, receive recipes, ideas and tips….

Just write me a mail with your questions or quiries



But I am not a doctor. All information is without guarantee.


Best regards

Joanne 🤗🤗🤗