Fructose intolerance

Fructose intolerance is a recessively hereditary disease. A certain enzyme is missing in the liver, which means that fructose is not broken down sufficiently. The symptoms often start in childhood. A test can be done to see if there is fructose intolerance. This is a hydrogen breath test. Treatment consists of a special diet. If patients do not comply, symptoms will return, such as vomiting.

What is fructose?

Fructose is fruit sugar. Fructose should not be confused with glucose, which is grape sugar. Fructose is mainly found in sweet fruits and in cane sugar and beet sugar. In the latter two, fructose is linked to glucose. Honey contains the most fructose: more than 40 percent. Because fructose is sweeter than glucose, it is often used as a sweetener in the food industry.

Fructose intolerance

Fructose intolerance is sometimes also called fructose poisoning. A certain enzyme is missing in the liver that is necessary for the breakdown of fructose. When fructose is not broken down sufficiently, poisoning occurs in the body, resulting in a number of complaints.
The enzyme that is missing is aldolase B, also known as fructose bisphosphate. This enzyme is located on a gene on chromosome 9. A defect in the gene results in fructose intolerance. The disease is recessively hereditary. This means that the disease is not dominantly hereditary and is not always expressed. So you can be a carrier without having the disease yourself. Both the mother and father must be carriers to pass the disease on to the child. If only one of the parents is a carrier, the child can also become a carrier but will not express the disease itself. The disease is just as common in boys as in girls.


Because fructose cannot be broken down, it ferments in the intestines. This often results in severe abdominal pain. In addition, there may also be diarrhea. The complaints often start in childhood. Many patients have had problems with their intestines for years and are diagnosed with spastic intestines or another condition. It is often difficult for doctors to diagnose fructose intolerance. Typically, after eating fructose, the liver is enlarged and the patient vomits. Foods containing fructose are unconsciously avoided. Fatigue and chills may also occur. Sometimes pain is felt around the kidneys. In children we notice that they have an aversion to fruit and a preference for foods containing dextrose. These children also prefer to drink milk and avoid syrup or other sweet drinks.


Children have sometimes had stomach aches for years and do not want to eat foods containing fructose. This is often seen as posturing or trying out. However, the doctor may ultimately decide to do a test. It is often checked whether the child has a lactose intolerance. If this is not the case, fructose intolerance can be checked. This is done by means of a breath test. This is a simple test in which the exhaled air is checked for the concentration of hydrogen. Fructose that has not been broken down ends up in the large intestine in high concentrations. There it is converted into hydrogen, among other things. After the evening meal (1 day in advance) no food is allowed and the teeth are not allowed to be brushed in the morning. You are also not allowed to drink anything from the night before. Fructose is ingested and after half an hour to an hour, a device is blown into. This measures the amount of fructose in the hydrogen. The test can be repeated at different times. The test sometimes works slightly differently in every hospital. A high concentration of fructose results in fructose intolerance.


There are no medications that cure fructose intolerance. A diet that limits fructose will be prescribed, also called a fructose-restricted diet. Fructose is not only found in fruits and to a lesser extent in vegetables, but is also widely used as a sweetener in sweets, cookies and pastries. Sucrose should also be kept out of the diet. Some sweeteners contain some fructose in addition to glucose. It is often difficult to find a good diet. The main thing is to read a lot of packaging and, if necessary, call in an expert in this field. If the patient adheres to this diet, there is little chance that the complaints will return. If you make a mistake, the complaints will arise again almost immediately. The complaints can persist for several hours to several days after eating fructose.

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