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Fructose intolerance, or fruit sugar, is one of the food intolerances. There are two forms of fructose intolerance: fructose malabsorption and fructosemia. The latter is particularly dangerous because it can lead to liver and kidney failure and, consequently, even death. What are the causes and symptoms of fructose intolerance? What is the treatment?

Fructose intoleranceis an inappropriate reaction of the body that occurs after consuming products containing fructose - fruit sugar. There are two types of fructose intolerance: hereditary fructose intolerance ( fructosemia ), which affects 1 in 40,000 people, and visceral fructose intolerance ( fructose malabsorption), which affects 3 out of 10 people.

Fructose intolerance - causes

Congenital fructose intolerance , or fructosemia, is a genetically determined disease. It is caused by the deficiency or absence of fructose-1-phosphate aldolase (aldolase B) - an enzyme involved in the metabolism of fructose in the liver - which is the result of a mutation in the gene encoding this enzyme. With the deficiency or absence of aldolase B, no further stages of fructose decomposition can take place. As a consequence, fructose metabolites (specifically fructose-1-phosphate) accumulate in the liver cells to a toxic level and impair its function.

Fructosemia is inherited in an autosomal recessive manner (for a child to become ill, they must receive one copy of the defective gene from each parent).

Fructose intolerance must be distinguished from fructosuria, which is caused by the lack of another fructose-degrading enzyme, fructokinase.

In turn, fructose malabsorption is the result of a deficiency or lack of protein, which is responsible for the transport of fruit sugar through the cell membrane. When the body lacks this protein, fructose cannot be broken down and is fermented by bacteria in the large intestine. As a consequence, acids and gases are formed, which increase the osmotic pressure of the intestinal contents and irritate the mucosa, which results in unpleasant ailments from the digestive system.

50 percent cases of visceral fructose intolerance are diagnosedcomorbidities such as irritable bowel syndrome, lactose intolerance, histamine intolerance, zinc and folic acid deficiency.

Congenital fructose intolerance (fructosemia) - symptoms

In infants who have been breastfed so far (breast milk does not contain fructose), the symptoms of fructosemia appear when the child is weaned and the diet includes products containing fructose (most often fruit and vegetable meals and fruit juices), i.e. around 6 months of age. month of the baby's life.

People suffering from fructosemia are often averse to sweet foods.

On the other hand, in artificially fed infants, symptoms appear immediately after administering mixtures sweetened with sucrose.

Symptoms of fructosemia include:

  • severe hypoglycaemia, i.e. hypoglycaemia (apathy, drowsiness, and even convulsions and fainting), which is the result of carbohydrate metabolism disturbance by fructose-1-phosphate
  • vomiting
  • liver enlargement
  • jaundice
  • hemorrhages
  • symptoms of urinary tract infection (with fructosuria, fructose appears in the urine, which increases the risk of urinary tract infections);
Important

If fructose is not eliminated from the diet at this stage, further episodes of hypoglycemia result, and then liver and kidney failure, which can even lead to death!

Malabsorption of fructose syndrome - symptoms

In the case of visceral fructose intolerance, the symptoms of the digestive system appear shortly after consuming products containing fruit sugar:

  • nausea and vomiting
  • stomach pains
  • diarrhea
  • flatulence
  • excess gas flow
  • anorexic
  • weight and height deficiency
Important

It should be noted that in the case of fructose malabsorption, everyone has their own individual fruit sugar tolerance threshold and in one person the symptoms of intolerance may appear after a small dose of this sugar, and in the other one only after consuming a large amount of it.

Fructose intolerance - diagnosis

If fructosemia is suspected, the activity of the enzyme fructose-1-phosphate aldolase in the liver is determined after transdermal extraction of a fragment of this organ. Another diagnostic method is thefructose loading test- fructose is administered intravenously and then blood levels are measured. You can also perform a genetic test to determine the most common mutations in the gene encoding aldolase B.

Fructose malabsorption is diagnosed onbased on the hydrogen breath test. The fasting patient is given a prescribed dose of fructose and the hydrogen concentration in the exhaled air is then measured. In people with this type of fructose intolerance, the hydrogen concentration in the exhaled air is exceeded. This is because fructose is fermented in the large intestine, producing large amounts of hydrogen which is removed through the respiratory tract.

Important

People struggling with fructose intolerance should inform about this at each admission to the hospital. For some medical procedures, fructose is used, e.g. during anesthesia for surgical procedures, an intravenous infusion of fructose solution is used, which may lead to sudden death of the patient.

Fructose intolerance - treatment

Diet is the only known treatment for fructose intolerance. In the case of fructosemia, it is necessary to completely exclude fruit sugar from the diet, because patients cannot tolerate even small amounts of it. Failure to follow the rules of an elimination diet can be life-threatening. However, with the fructose malabsorption syndrome, you should limit the consumption of fruit sugar - depending on the degree of intolerance.

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Category:

Gastrology