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forms of fructose intolerance
In the intestine of a healthy person there are proteins that transport nutrients from the inside of the intestine into the blood. One of these transport proteins transports grape sugar (glucose) as well as fruit sugar (fructose) into the body. However, this protein can only transport a certain amount of fructose, which means that each person can only tolerate a certain amount of fructose. Fructose intolerance comes in two forms:
- Intestinal fructose intolerance (fructose malabsorption) is a widespread food intolerance in which the transport of fructose into the blood does not function properly, which is why the body can only process a small amount of fructose. The fructose remains in the digestive tract. Because the fructose is not needed in the small intestine, it reaches the large intestine, where it is converted by intestinal bacteria. This process is called fermentation. This produces gases such as methane, carbon and hydrogen. These in turn can cause uncomfortable flatulence .
- Hereditary fructose intolerance is very rare and is a hereditary congenital metabolic disorder that is very difficult and incurable. Deficiency of the enzyme “aldose B” is known to be the cause of the disease. Insufficient Aldose B enzyme causes fructose-1-phosphate to be stored in the body’s internal organs, which prevents the formation of glucose from fructose. However, glucose is an essential sugar. If there is insufficient conversion in the body, hypoglycaemia occurs.
Symptoms of fruit sugar intolerance
The most common symptoms of fructose intolerance (fructose malabsorption) are diarrhea and flatulence. These symptoms are triggered by the fructose itself, as it enters the large intestine and is broken down by bacteria. The gases produced in this way throw the digestion out of sync. It can also cause nausea, acid reflux , bloating and abdominal pain. How severe and in what form the symptoms occur depends on the person affected. The symptoms manifest themselves differently in each body.
In the case of hereditary fructose intolerance, even small amounts of fruit and vegetables are life-threatening for affected newborns and can cause a small child to fall into a coma. Consequently, you have to reckon with kidney and liver damage. In most cases, newborns and children react to even the smallest amounts of food containing fruit or vegetables with vomiting and tremors, i.e. with symptoms of hypoglycaemia. The disease is often not recognized until then by the doctor. Other symptoms include blood in the stool, profuse sweating and muscle cramps.
Diagnosis and treatment of fructose intolerance
The most commonly used diagnostic route is the hydrogen breath test (H2 breath test). Here, the affected person drinks a defined amount of a fructose preparation on an empty stomach. Then, at certain intervals, he blows into a device that measures the H2 content (hydrogen) in the breathing air. If the fructose is not metabolized properly, as is the case with an intolerance, the bacteria in the intestinal flora produce hydrogen, among other things. This enters the blood and is exhaled through the lungs. The amount of hydrogen exhaled provides information about whether a fructose intolerance is present or not.
If you are diagnosed with fructose intolerance, you should consult a nutritionist who will draw up a suitable nutrition plan with you. The expert explains how you should eat low-fructose foods in the short and long term. With a normal fructose intolerance, it is not necessary to live completely fructose-free , as important nutrients are missing in the body. The situation is different in the case of hereditary fructose intolerance, in which it is crucial to avoid fructose altogether.
