Letzte Aktualisierung am 9. September 2024 von Dr. Michael Zechmann-Khreis

The treatment of fructose intolerance should always be supported by a state-certified and recognized nutritionist . Treatment and a life with a needs-based and tasty diet is possible.

The three-phase program

elimination diet

In the first two weeks of treatment for fructose intolerance, fructose, sugar and sugar alcohols should be avoided as much as possible to allow the intestines to recover. It is also important to avoid flatulent foods such as pulses, cabbage and too much fiber in the first few weeks. After around two weeks (maximum four weeks, although the recommendation is two weeks), these foods can then be slowly reintroduced into the diet. It is important to drink 2-3 liters of fluids per day (water, no carbonated drinks, no alcohol).

It is wrong to assume that people with fructose intolerance should no longer consume any fructose at all. After the elimination diet, you should start with small amounts of fructose – both free and bound – and slowly increase the amount. Completely avoiding fructose or consuming too little fructose can worsen fructose intolerance.

The elimination diet chapter is very complex and you should definitely seek advice from a certified nutritionist. We have also written a book about the elimination diet for fructose intolerance, which explains this period in great detail and contains many recipes.

As soon as you feel better (which will be soon) and there are no more symptoms, you can end the elimination diet and continue the treatment of fructose intolerance with the test phase.

Basic points of the elimination diet

• Always start the elimination diet in consultation with your team of doctors and/or dieticians
• Do you have time to focus on your diet in the coming weeks? The elimination diet should be taken during a stress-free period.
• Lent is a good time to do this, as you don’t have to expect any social pressure because you are fasting.
• Concentrate on eating, i.e. don’t read the newspaper or watch TV at the same time.
• Keep a food and symptom diary
• Deficiency symptoms: Deficiency symptoms can occur with untreated fructose intolerance due to the intestine-damaging diet. Your doctor should therefore carry out blood work before the elimination diet to detect any deficiencies. However, you don’t need to worry about developing deficiencies during the elimination diet. After the elimination diet, however, you should make sure you eat a balanced diet.
• Watch out for additional intolerances or allergies.
• Watch out for other illnesses that could make your fast dangerous. This applies, for example, to liver diseases or eating disorders.
• You should not start an elimination diet while taking antibiotics.
• Don’t let others influence you. We live in a culture where everyone believes they are an expert – especially when it comes to nutrition.

Eating and drinking during the elimination diet

• Use our fructose table or the “Ask Ingrid!” app
• Counting grams” is not useful, as fructose tables only ever give guide values or the experiences of others.
• Start the first few days without any vegetables, fruit or sugar.
• It is best to drink only tap water and herbal teas (e.g. aniseed-fennel-caraway).
• Caffeine and cigarettes: If you only want to drink your coffee or tea with sugar, replace it with stevia products (check the list of ingredients) or dextrose. Other sweeteners are not recommended, as many people also have a poor tolerance to them. After the elimination diet, you can test sweeteners individually and include them in your diet again if necessary. It is even better to remove coffee from your diet completely. Caffeine puts the body in a state of stress, which often affects the stomach. You should therefore generally avoid caffeine during the elimination diet. Cigarettes should also be avoided, as nicotine causes the intestines to become agitated. Black tea is often – but not always – tolerated. If you can’t do without caffeine, you should give it a try. The tannins in black tea are good for the stomach. Green tea or mate tea are also usually well tolerated.
• Always cook fresh food yourself.
• Do not eat ready-made products.
• Eat small portions, but rather several times a day.
• Flatulence and bowel sounds are normal. What we tend to forget, especially those of us with intolerances, is that our digestive system is loud and smelly. Gases and unpleasant odors are produced during digestion. Our intestines sometimes gurgle, bubble, pinch and our digestive system lets the resulting gases escape through the only two possible openings, the mouth and the anus. That is quite normal. Our chair is also sometimes firm, sometimes softer. Not every twinge and gurgle, every soft stool and every burping is a symptom or indication of too much consumption of fructose, lactose, sorbitol or other substances.
• Don’t make any exceptions! You can cope well with the elimination diet without chocolate or sweet sins.

The test phase

Depending on your mood, you can start by consuming small amounts of fructose. You should pay close attention to your body’s reactions – and continue to keep a food and symptom diary. Now you can eat household sugar and long-chain sugars such as inulin or oligofructose in small quantities again. The test phase usually lasts a few weeks to months and varies greatly from person to person.

The bottom line is: find out what you can tolerate and don’t let others influence you! Everyone reacts differently to different amounts of fructose and everyone reacts differently to the same amounts from day to day, because the composition of the food, exercise or stress also play a role. However, this does not mean that every body reaction is due to fructose. Don’t make the mistake of immediately interpreting every twinge and tweak as a symptom. It is completely normal for the bowels to make noises and for you to have bowel movements from time to time.

This test phase should also be accompanied by a qualified nutritionist, especially to prevent deficiency symptoms and unbalanced eating. In particular, the supply of vitamins and minerals such as vitamin A, vitamin C, folic acid, potassium, magnesium and zinc can be at risk in people with fructose intolerance, as they consume little fruit and vegetables. Well-tolerated types of fruit should therefore be eaten regularly. It can also be useful to take vitamins via dietary supplements (prescribed by your doctor).

A few more helpful everyday tips:

• Fructose is less well tolerated on an empty stomach than on a full stomach.
• Many sufferers tolerate fructose better in the afternoon than in the morning.
• High-fat meals slow down the intestinal passage, allowing more fructose to be absorbed.
• Exercise reduces intestinal transit, which is why you tolerate less fructose before exercise than after exercise.
• “Light” Products often contain incompatible sweeteners. Light sodas in particular sometimes contain fructose instead of sucrose as a sweetener. Always read the list of ingredients.
• Instead of honey or sugar, you can use rice syrup, erythritol, stevia or dextrose (including rice syrup). No other syrups should be used! Sugar is usually tolerated in small quantities, as it consists of equal parts fructose and glucose. Not all sugar alcohols are intolerable! Xylitol and erythritol in particular are considered to be well tolerated. Of course, this is not a license for excessive consumption.

The permanent diet

If you know your limits and your digestion a little better, you should move on to permanent diet or long-term diet. This is the last phase of therapy. The aim here is to ensure a near-normal diet which, above all, meets the patient’s needs and requirements. Today, general nutritional guidelines are no longer recommended, but an individually tailored diet. The advantage of individual nutritional therapy is that it can be tailored to the needs and possible other stresses. However, this type of nutritional therapy should always be developed with a professional and not on your own or through advice on internet forums.

In the permanent diet, it has been shown that an annual fructose fast, i.e. an elimination diet of 1-2 weeks, increases the body’s ability to tolerate fructose. This recommendation for the treatment of fructose intolerance comes from the observations and feedback of many sufferers here on the nmi portal and is therefore not included in the official recommendations of professional associations.

Treatment of fructose intolerance: Acute measures

If you forget to follow a diet or simply go overboard, you will be plagued by the usual symptoms of fructose intolerance. A few tricks can help here: you can place hot water bottles on your lower abdomen. This treatment relaxes the stomach. You can also drink yarrow, fennel, caraway tea and other decongestant teas. Heartburn can be counteracted with suitable medication or teas. Nausea can also be treated with ginger tea, which is low in fructose, or appropriate medication. Please always discuss these measures with your doctor. He or she will work with you to find the right medication.

Of course, it is important not to go overboard in the first place or to avoid the symptoms from the outset. If you get diarrhea, it is advisable to use soft toilet paper and to lubricate the anus with a skin cream or wound healing ointment after a bowel movement.

The glucose trick

The absorption of fructose is significantly improved by the simultaneous intake of glucose. As glucose facilitates the absorption of fructose in the small intestine, the intake of glucose can improve the tolerance of fructose-containing foods.

What is particularly important here is that glucose is absorbed very quickly, whereas fructose remains in the intestine for a relatively long time. This means that if you consume 1g of fructose and 1g of glucose, you will have an excess of fructose after a short time, as the glucose has been absorbed more quickly. It is therefore advisable to consume more glucose than fructose.

Caution: This trick should only be used rarely – and after the elimination phase – as excessive consumption of glucose has negative effects on insulin levels and other nutritional factors.

Enzyme for ingestion

Help is now also available in tablet form for intestinal fructose intolerance: the enzyme xylose isomerase (often also called glucose isomerase). This enzyme converts fructose into glucose in the small intestine, but also glucose into fructose. In principle, the “glucose trick without glucose” is used here, as the fructose eaten is converted to glucose and then absorbed. The enzyme has the property of always wanting to create a balance between fructose and glucose. This means that if equal amounts of both sugars are present, it no longer converts fructose. However, as glucose is absorbed very quickly, there is no equilibrium in the intestine and almost all the fructose can be metabolized. In theory, however, this also means that an additional intake of glucose would suppress the effect. But the glucose is absorbed so quickly that even then there is an imbalance. This means that if you take this enzyme, you don’t need any more glucose.

Recommended intake and products

Important: The enzyme is deactivated above approx. 60°C, which means that you should not open the capsules and stir them into hot food or leave them in a hot car while on vacation. It is best to take the capsules whole with plenty of water directly before a meal rich in fructose. Please always refer to the package leaflet of the respective product.

Why take an enzyme as therapy for a transport protein problem?

Fructose is transported through the small intestinal mucosa by the transport proteins GLUT-5, among others. If these transporters are missing or do not function properly, the fructose reaches other parts of the intestine, is digested by the bacteria living there and the typical symptoms occur. The orally ingested xylose isomerase intervenes beforehand and converts the fructose into glucose in the small intestine, which can then firstly also be absorbed via other transport mechanisms (GLUT-2, SGLT-1) and secondly sets the “glucose trick” in motion.

Do these remedies also help with sorbitol intolerance?

No, as described above, fructose is converted into glucose and vice versa. However, sorbitol is not metabolized. Therefore, these products do not help if you have a sorbitol intolerance. In the case of pure fructose intolerance, sorbitol can also lead to problems, as it impairs fructose absorption. This means that the little bit of fructose that someone with fructose intolerance could absorb is not absorbed. However, if no fructose is present because it has been converted by xylose isomerase, sorbitol – in small quantities – does not cause any problems, even if you are fructose intolerant. This is because there is no fructose involved and small amounts of sorbitol, without having fructose in the intestine at the same time, are not a problem with fructose intolerance.

Sources:

1) Rainer Klinke, Hans-Christian Pape, Stefan Silbernagl (eds.): Lehrbuch der Physiologie, 5th edition. Thieme, Stuttgart 2005
2) Zechmann-Khreis, M., Nahrungsmittel-Intoleranzen: Elimination diet, healthy eating & well-being: Understanding and living with lactose, fructose, histamine. Nutrition guide with over 100 recipes and a nutrition plan , MZK verlag, 2020
3) Denisova, V., & Rubin, D. (2022). Lactose and fructose intolerance. Tagliche Praxis, 65(4), 581-595.
4) Benardout, M., Le Gresley, A., ElShaer, A. & Wren, S. P. Fructose malabsorption: causes, diagnosis and treatment. Br. J. Nutr. 127, 481-489 (2022).
5) Tuck, C. J., Ross, L. A., Gibson, P. R., Barrett, J. S. & Muir, J. G. Adding glucose to food and solutions to enhance fructose absorption is not effective in preventing fructose-induced functional gastrointestinal symptoms: randomized controlled trials in patients with fructose malabsorption. J. Hum. Nutr. Diet. 30, 73-82 (2017).