Hereditary fructose intolerance

Fructose is a monosaccharide found in many foods. It can be found as such in fruits and many vegetables, or associated with other monosaccharides such as glucose. For example, fructose combined with glucose forms the disaccharide sucrose, commonly known as white sugar. Fructose can also be produced in our body from the breakdown of sorbitol, which is a widely used sweetener, so the latter is also another source of fructose.

Hereditary fructose intolerance (HFI) is a disease in which the enzyme aldolase B, which degrades fructose in the liver, intestine and kidneys, does not function properly. When this enzyme does not perform its function properly, fructose-1-phosphate accumulates in the cells that should metabolize it, and its accumulation is toxic.

Approximately 1 in 20,000 people of European descent have IHF, and about 1% are carriers of the disease.

The onset of symptoms depends on the ingestion of fructose, sucrose and sorbitol, so they usually appear at the time fruits, vegetables and foods with added sugar are introduced into the diet of infants with the intolerance.

Acute symptoms appear immediately after administration of large amounts of fructose and include nausea, vomiting, sweating, lethargy, and acute hepatic and renal impairment, with or without hypoglycemia.

After chronic ingestion of small amounts of fructose, feeding difficulties, occasional but recurrent vomiting, hepatic and renal disturbances, and growth retardation may occur.

Acute symptom management should be performed in the hospital, using intravenous glucose administration, supportive treatment of hepatic and/or renal failure and treatment of metabolic acidosis, if present.

To prevent the occurrence of long-term complications, dietary restriction of fructose, sucrose, sucralose and sorbitol is used. Special caution is advised with the use of pediatric and infant foods containing sugars and oligosaccharides as well as medications containing fructose/sucrose. Infants with HFI may manifest adverse reactions immediately after administration of oral vaccines containing sucrose.

Since reduced fruit and vegetable intake is a dietary requirement, "sugar-free" multivitamins are used to prevent micronutrient deficiencies, particularly water-soluble vitamins. Dietary monitoring by a specialist and medical control of liver function, renal function and growth should be carried out.