Fructose intolerance: symptoms and treatment
About 30 percent of the population in western countries are affected by fructose intolerance. Consuming fructose leads to unpleasant symptoms such as flatulence, abdominal pain or diarrhea. Find out here how fructose intolerance is recognized and what you can do about it.
What is fructose intolerance?
Fructose intolerance is not actually an allergy, but an intolerance to fructose. This can appear in two different forms:
- Hereditary fructose intolerance: Fructose intolerance is present at birth in about one in 20,000 babies. This is a metabolic disorder caused by an enzyme defect. As a result, fructose can be absorbed from food, but not completely broken down. Due to the increasing fructose content in the blood, glucose is displaced from it. However, this type of sugar is urgently needed to supply the cells with energy. Failure to thrive and development can result. The first symptoms usually appear during or after the transition to complementary food. If a hereditary fructose intolerance is diagnosed, a strict diet with very small amounts of fructose is usually necessary for life.
- Intestinal fructose intolerance: Much more common than congenital fructose intolerance is that which first develops in adolescence or adulthood. About 30 percent of the western population is affected by such an “acquired” fructose intolerance. Therefore, this article will deal with this form below.
Intestinal fructose intolerance is not a metabolic disorder but a resorption disorder. This means that the fructose ingested through food cannot be absorbed into the bloodstream via the mucous membrane of the small intestine. It therefore reaches the large intestine, where it is broken down by intestinal bacteria. The gases that form as a result cause the typical symptoms in about a third of those affected.
How does fructose intolerance develop?
A defect in the transport proteins, which are supposed to transport fructose from the small intestine into the bloodstream, is primarily responsible for the development of fructose intolerance. These either do not work at all or work too slowly, so that the fructose cannot be sufficiently removed from the intestine.
However, since two-thirds of lactose-intolerant people do not show any symptoms, this suggests that, in addition to the faulty absorption, another factor also contributes to the development of the symptoms. For example, an incorrect composition of the intestinal flora comes into question, which could have been caused by treatment with antibiotics or a fungal infection.
Chronic stress of all kinds, such as years of unfavorable nutrition or persistent stressful situations, can also promote the development of fructose intolerance.
What are the symptoms of fructose intolerance?
Fructose intolerance can cause a range of symptoms and conditions. Some of these usually appear shortly after eating fructose-containing foods in the form of various digestive problems:
- stomach pain
- cramps
- bloated belly
- gas
- Diarrhea
- nausea
If fructose intolerance is not treated at all or not treated early, secondary symptoms can also develop in the long term:
- headache
- persistent fatigue
- irritability
- dizziness
- difficulty concentrating
- Nutrient deficiencies (especially zinc and folic acid)
- hair loss
- susceptibility to infection
- depressions
Damage to the intestinal mucosa can also lead to the development of other intolerances over the long term, for example to lactose or histamine.
Which foods trigger fructose intolerance?
The simple sugar fructose found primarily in honey and fruit and products made with or from fruit:
- apples
- pears
- mangoes,
- Grapes
- dried fruit
- fruit juices
- yogurts
- jams
Tip: Low-fructose fruit alternatives include bananas, apricots or berries.
Household sugar also consists of half glucose and half fructose, which is why sugared products in general can lead to symptoms of fructose intolerance. This applies in particular to sweets of all kinds or ready-made products. As a rule, however, symptoms only occur if fructose intolerance has existed for a long time. If the intolerance is only mild, table sugar is usually well tolerated.
Pure fructose is often used as a sweetener in light or diabetic products. Since the proportion of such artificially produced sweeteners in industrial products has increased significantly in recent decades, cases of fructose intolerance have also increased sharply.
How is fructose intolerance diagnosed?
Since the symptoms are very diverse and non-specific, it is often difficult to reliably diagnose fructose intolerance. The symptoms are often wrongly attributed to irritable bowel syndrome. The fact that it is not uncommon for several intolerances to coexist makes a clear diagnosis more difficult.
Through a detailed anamnesis interview , the doctor treating you may be able to establish connections between the eating habits and the symptoms that occur. A food diary is also helpful , which is kept for about two weeks and also makes it easier to distinguish a possible fructose intolerance from other intolerances.
A reliable test to diagnose fructose intolerance is a breath test , which measures the hydrogen content of the breath. Because the gases produced during the decomposition of fructose in the large intestine are not only released in the form of flatulence. Some of the gases also get into the bloodstream, from there into the lungs and can then be detected in the breath.
To carry out the test, the patient is given a fructose solution to drink on an empty stomach. The doctor then measures the hydrogen level in the breath at half-hour intervals over a period of two hours. These values are then compared to the value measured before the fructose solution was taken.
Another way to identify fructose intolerance is to measure the tryptophan concentration in the blood . Tryptophan is an important nutrient that combines with fructose and therefore cannot be properly absorbed in fructose intolerance. If the values are very low, this also indicates a fructose intolerance.
How is fructose intolerance treated?
Acquired fructose intolerance can often be cured or at least improved so that the intake of small amounts of fructose is possible again. The following applies: the earlier the fructose intolerance is recognized and the therapy is initiated, the more promising the result is.
Fructose intolerance is treated by changing your diet. A nutritionist helps to create an individual nutrition plan that is adapted to the respective tolerance limits. In general, it is very different for those affected to what extent fructose is tolerated.
Therapy usually begins with a two to four week phase in which fructose is largely avoided. A food diary is also kept during this time. After this first phase, foods containing fructose are gradually added back to the diet. In this way you can find out what level of fructose is tolerated, or which foods cause problems and which do not. The task of the nutritionist is then to create a plan on this basis that ensures that all important nutrients are covered with the permitted foods.
Good to know:It is worthwhile to test again and again as the process progresses, whether previously critical foods are perhaps tolerable again. If the intestinal flora has time to recover and regenerate, this is not unlikely.
The following diet tips may also be useful:
- In the case of an existing fructose intolerance, as few sugar substitutes as possible should be used, as they impede the absorption of fructose into the blood. This not only applies to light and diabetic products, but also to sugar-free chewing gum or sweets.
- If foods with a high fructose content are consumed, it is advisable to add some dextrose, as this facilitates fructose absorption in the intestine.
- If possible, fruit should not be eaten on its own, but should be eaten with a meal, for example as a dessert. A combination with dairy products is also an option. Because fat and protein slow down the absorption of fructose, which makes it easier for the transport protein in the intestine to do its job.