The term fructose intolerance (also known as fructose malabsorption) refers to an intolerance to fructose. Fructose intolerance occurs in almost 30 percent of Central Europeans, which makes it one of the most common food intolerances. In comparison, "only" 15 percent of Europeans suffer from lactose intolerance (lactose intolerance).

Fructose intolerance is a congenital gene mutation that makes it impossible for the body to break down fructose due to a deficiency of a certain liver enzyme. Patients who suffer from fructose intolerance already develop gastrointestinal disorders as babies or toddlers when consuming fructose, as well as life-threatening low blood sugar levels (hypoglycemia) and liver dysfunction.

What is fructose?

Fructose stands for fruit sugar. Fructose not only has the same chemical formula as glucose ("dextrose"). Fructose belongs to the group of carbohydrates and, just like glucose (glucose), is one of the so-called monosaccharides. Monosaccharides consist of many individual sugar molecules. Because fructose can be produced industrially at very low cost since the 1970s, it is often added to foods and often declared as a "natural fruit sweetener".

Why can some people not tolerate fructose?

People with fructose intolerance cannot digest fruit sugar properly. The metabolic disorder can be congenital or acquired. However, this does not mean that those affected have to do without fruit altogether. Small amounts are usually tolerated. This is different with the rare hereditary fructose intolerance, where a very strict fructose intolerance diet must be followed.


Fructose is normally well absorbed, i.e. it is well absorbed into the bloodstream through the intestinal wall. Special transporters in the intestinal mucosa make this possible. In case of fructose malabsorption (intestinal fructose intolerance), the transport of fructose in the intestine is disturbed.

Less than 25 g fructose per hour can be absorbed by the body. The fructose is therefore not or only incompletely absorbed.

It therefore reaches deeper sections of the intestine where it is broken down by bacteria into short-chain fatty acids, hydrogen and carbon dioxide. This causes discomfort that can vary depending on the amount absorbed.


Hereditary fructose intolerance must be distinguished from intestinal fructose intolerance. This is a very rare, congenital form of fructose intolerance, which is caused by a lack of an enzyme. The sufferers have to completely renounce fructose in their diet throughout their life. In contrast, many sufferers with intestinal fructose intolerance can tolerate small amounts of fructose - depending on the severity of the condition.

Intestinal fructose intolerance (fructose malabsorption) is a widespread food intolerance in which the transport of fructose into the blood does not function properly, so the body can only process a small amount of fructose. As a result, 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 process produces gases such as methane, carbon and hydrogen. These in turn can cause unpleasant flatulence.

Hereditary fructose intolerance is very rare and is a hereditary congenital metabolic disorder that is very severe and not curable. The cause of the disease is known to be a deficiency of the enzyme "Aldose B". Due to the insufficient enzyme Aldose B, fructose-1-phosphate is stored in the inner organs of the body, which prevents the build-up of glucose from fructose. However, glucose is an essential sugar. Thus, insufficient conversion in the body results in hypoglycemia. Those who suffer from this condition have to do without fructose in their diet completely throughout their life.


Symptoms occur after the intake of foods containing fructose or sorbitol. Sorbitol (also known as sorbitol or E 420) is a sugar substitute that can be converted to fructose in the liver. Since sucrose (household sugar) is made up of fructose and glucose molecules, the consumption of sucrose also causes complaints.

As a result of the fructose breakdown in the large intestine, those affected may experience symptoms such as flatulence, cramps, diarrhea, nausea and abdominal noises.

It is also possible that changes in the intestinal flora may occur in the long term, which can have a negative effect on the production of folic acid there, among other things.

In the long term, fatigue, depression and irritability may also occur, as the absorption of certain nutrients is restricted.

Diet for fructose intolerance

Many of those who suffer from intestinal fructose intolerance can tolerate small amounts of fructose, depending on the severity of the condition. Those affected by hereditary fructose intolerance must completely avoid fruit sugar in their diet for the rest of their lives.

If you are not sure which products are low in fructose, simply scan the barcode with your TIOLI App and find out if other people with histamine intolerance can tolerate this product.

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