Fructose intolerance


Fructose belongs to the Simple sugars and comes naturally in Fruit and honey in front. After Intestinal absorption and Split in the liver, fructose serves the Provision of energy in the human body. Depending on requirements, the energy gained is converted directly or stored as an energy store in the fat metabolism during the production of so-called triglycerides (fats).

The Symptoms the fructose intolerances range from increased urination, about intestinal complaints like diarrhea, up to Symptoms of intoxication in the hereditary form (hereditary form).

The therapy the various fructose intolerances depends on the cause and can in reduced enjoyment of fructose or that total renunciation insist.


It will three different causes of fructose intolerance.

A Malabsorption disorder describes the Inability or insufficient intake the fructose through the intestines. One also speaks of intestinal or alimentary fructose malabsorption. It results from a disturbed function of the transport mechanisms the intestinal wall.
The so-called GLUT-5 transporter is of particular importance. The transport proteins involved are impaired from birth or experience a loss of function in the course of life. This can be done by a Antibiotic therapy, certain Medication with gastrointestinal side effects and Fungal infections triggered become.

The Fructosemia denotes one increased levels of fructose in the blood. This is based on the Failure of a certain enzyme the liver, which breaks down the fructose. The body tries to excrete the fructose through the kidneys.

The hereditary fructose intolerance is based on one genetic enzyme defect. It is a hereditary metabolic disorder. The enzyme Aldolase B usually divides Fructose-1-phosphate into smaller fragments. As a result of the missing enzyme accumulates Fructose-1-phosphate mainly in the kidneys and liver on. The first symptoms appear in infancy.


The symptoms of intestinal fructose intolerance or malabsorption disorder are due to the remaining fructose in the gut traced back. Most of the time, the symptoms come along temporal latency to consumption on. Between intake and symptoms can 24 to 48 hours lie. Under normal circumstances gets the fructose only down to the small intestinewhere it enters the bloodstream. If, on the other hand, it remains in the intestine, it migrates Fructose to the large intestine. Process there bacteria the sugar to hydrogen, carbon dioxide and short-chain fatty acids. carbon dioxide caused Flatulence and painful Stomach cramps.

Read more about the topic here Bloated stomach after eating

The educated Fatty acids however, affect the local Fluid balance on. You condition that increased influx of water in the colon. This serves to balance the osmotic gradient in the intestine, but at the same time leads to liquid, strong smelling stool. In some cases there is one instead of diarrhea Constipation symptoms to observe. Also nausea and Pain frequent symptoms when pressure is applied to the abdomen.

Also occur less often Vomit, a headache, increased fatigue and depressive moods on. Also heartburn with a burning sensation in the area of ​​the sternum is observed.

There remains an intestinal fructose intolerance left untreated for a long time, has this Effects on colon bacteria. Hydrogen-producing bacteria multiply and settle not only in the large intestine, but also in the lower sections of the small intestine. This has the consequence that too Foods without fructose are poorly tolerated and cause discomfort.

The hereditary fructose intolerance already leads symptoms in infancy. As soon as fructose finds its way into the menu, for example in the form of sucrose contained in milk, the metabolic disorder appears. Gets rich Fructose-1-phosphate in the body to step Symptoms of intoxication on. In addition to a Hypoglycemia, a low blood sugar level, and a Hyperacidity (Acidosis), sweats and changed consciousness of those affected can be observed. Keep kicking Nausea, vomiting and diarrhea on. In the course of a Enlargement of the liver with the following connective tissue remodeling (cirrhosis) up to Liver failuredevelop a bleeding disorder and kidney dysfunction.


The diagnosis of intestinal fructose intolerance or malabsorption is primarily made with the help of a breath test. Here is after oral intake of fructose at regular intervals of the exhaled hydrogen determined. The hydrogen fulfills the function of a marker that provides information about the intestinal metabolism of Fructose allows. The sober value increases of hydrogen more than 20 ppm (parts per million) and become at the same time discomfort in the gastrointestinal tract indicated, the likelihood of a present fructose intolerance is high. A week-long nutritional protocol can also substantiate the suspicion.

When referring to the hereditary form of fructose intolerance, become small samples of tissue from the intestine, of the liver and the kidney taken. These are subsequently examined for enzyme deficiency. If the so-called fructose-1-phosphate aldolase is missing, there is a genetic metabolic disorder.

The Fructosemia will in most cases diagnosed by chance. Above all, those affected notice frequent urination. Targeted diagnostic tools do not exist. No treatment measures are necessary for this form of fructose intolerance.

H2 breath test

A best practice for detection The intestinal fructose intolerance or malabsorption is the H2 breath test. If the fructose cannot be absorbed in the small intestine, it reaches the large intestine. Those located there bacteria process it into hydrogen, carbon dioxide and short-chain fatty acids. Of the exhaled hydrogen serves as a diagnostic tool. Of the Increase in value after oral fructose intake Conclusions about the metabolism in the intestine too.

Adults drink one Quarter liter of water, by doing 25 grams of fructose are resolved. children receive a weight-adjusted amount of fructose that one gram of fructose per kilogram of body weight corresponds. Before drinking the sugar solution, the Sober value of exhaled hydrogen is determined. This should ideally be at values ​​around 0 ppm (parts per million) and is highly dependent on oral hygiene. After fructose intake will the Worth every 10 and then every 30 minutes certainly. Overall, the measurements cover a period of around 3 hours.

The test will rated as positive, if next to intestinal complaints (Cramps, diarrhea, Flatulence), a Increase to over 20 ppm measured against the initial value. An early rise in the hydrogen value can indicate bacterial overgrowth in the small intestine.


The therapy intestinal fructose intolerance starts with a significant reduction in fructose intake. You should switch to easily digestible whole foods for a period of two weeks. In this way, the complaints are reduced. In the following four weeks, the nutritional scheme is expanded to include products that are higher in protein and fat. In addition, the personal fructose threshold and determines the tolerance of certain types of fruit. Then a constant, individually tailored diet change recommended.
Fruit should be consumed in small portions and certain types (raisins, prunes and grapes) should be avoided. Foods with a high sorbitol or fructose content should be avoided, while sufficient consumption of vegetables should be ensured.

Just one strict renunciation on fructose can in the case of counteract long-term damage caused by hereditary fructose intolerance. This is especially true for developing a Cirrhosis of the liver.

As a rule, fructosemia does not require treatment.


In the most common form the fructose intolerance, the intestinal malabsorption disorder, can be a Enzyme preparation help. It contains the so-called Xylose isomerasewhose function is based on the conversion of fructose to glucose and vice versa from glucose to fructose. As long as both sugar molecules are not present in equal quantities, the enzyme tries to strive for a balance. Since glucose from the intestine is absorbed into the blood much faster than fructose, this state is not reached. The xylose isomerase continues to convert fructose. The enzyme is from different manufacturers available in capsule form. One capsule each will Twice a day right away before meals taken. Since a change in diet promises greater therapeutic success, should only in exceptional cases to take medication.

The Incorrect colonization of the intestine can with Antibiotics be reduced. However, there is still no scientific evidence of the effectiveness of such a treatment.

What foods can I eat?

Of the Simple sugars Fructose comes in its natural form especially in fruit and honey in front. All foods that partly consist of fruits therefore also contain fructose. Some fruits have a higher sugar content than others. Which includes in particular apples, grapes, pears, pineapples and mangoes. Dried fruits also have a high fructose content.

In addition to these "obvious" occurrences of fructose, it is hidden in many industrial products. Fructose is used here for sweetening pastries and sweets and is mixed with drinks such as soft drinks. In Finished products like dressings, sauces, packet soups and ready-made pizzas, there is often a considerable amount of sugar hidden.

In addition to avoiding or reducing consumption of fructose-containing foods, you should be advised if you are diagnosed with fructose intolerance also avoided sugar substitutes become. Products that for example Sorbitol, maltitol or xylitol contain, have an inhibiting effect on fructose absorption in the intestine. This results in a Intensification of symptoms.

Despite avoiding certain foods, a wide variety of options exist healthy, low-fructose products. In general, the daily fructose requirement is around 2 grams. Food tables help to put together a healthy and at the same time varied diet. They provide information about the fructose content in foods.
Particular attention should be paid to the Consumption of sufficient amounts of vegetables be placed. Zucchini, avocado, green leafy vegetables, mushrooms and potatoes are particularly low in fructose. Onions, legumes and leeks, on the other hand, have a flatulence effect and should not be consumed at the beginning of the diet change. Whole grain products without added fructose can be included in the menu in small quantities. As filling side dishes serve gluten-free grains such as buckwheat, millet, rice, corn and quinoa. Animal products such as eggs, meat and fish contain only very small amounts of fructose. This also applies to various types of nuts, almonds and coconuts. Oil seeds, which include pumpkin seeds, sunflower seeds and flax seeds, are high in fat and low in fructose.

Fiberthat have a digestive effect in healthy people are in intestinal fructose intolerance enjoy with caution. They make the symptoms worse. The consumption of Dairy products should as low as possible being held. If there is already a fructose intolerance, there is one increased risk of impaired lactose intake in the intestine. If fructose is tolerated in small quantities, fruits with a low sugar content can also be consumed. Papaya, tangerines and apricots as well as rhubarb are particularly suitable for this.

The simultaneous consumption of fructose-containing foods and glucose, for example in the form of grape sugar, improves the transport of fructose through the intestinal wall into the blood.

Can fructose intolerance be cured?

The hereditary form who is fructose intolerance not curable and can only through the strict waiver be treated for fructose.

The intestinal form or Malabsorption disorder can correspond to a total or partial inability to absorb fructose. In many cases, symptoms only manifest themselves over the years. Albeit one complete healing is rare is, so can the correct diet change a significant relief of the symptoms cause.
If the nutritional measures are consistently maintained over a longer period of time, in some cases the fructose intake can be increased gradually. It is due to a recovery of the transport mechanisms in the intestinal wall. In this sense, a self-test for tolerance can also be risked again and again as part of consistent nutritional therapy.


The fructose intolerance summarizes three different forms the fructose intolerance together. What they have in common is a disturbed fructose metabolism.

The intestinal or alimentary fructose intolerance is also known as fructose malabsorption disorder and goes with one insufficient intake of fructose. A further distinction is made between the Fructosemia with fructosuria, an accumulation of fructose in the blood, and the hereditary fructose intolerancewhich is due to a hereditary enzyme deficiency.

The Symptoms the fructose intolerances range from increased urination, about intestinal complaints like diarrhea, up to symptoms of poisoning in the hereditary form.

The therapy of the various fructose intolerances after the cause and can insist on the reduced consumption of fructose or the total renunciation of it.