Hereditary fructose intolerance

# What is fructose? Fructose (fruit sugar) belongs to the group of carbohydrates and, like glucose, is a simple sugar. It is mainly found in fruit and some vegetables and, together with glucose, forms our household sugar (sucrose). Fructose intolerance is a disorder in the utilization of fructose. A distinction is made between two forms: - Fructose malabsorption: Fructose cannot be adequately absorbed in the small intestine. This leads to flatulence and diarrhea. - Inherited (hereditary) fructose intolerance: This form is extremely rare and is attributed to a congenital enzyme defect that blocks the breakdown of fructose in the liver. The fructose accumulates in the liver and this can lead to kidney and liver damage. Hereditary fructose intolerance is recognized in babies when they are first fed fruit and vegetables. The treatment is strict avoidance of fructose. ## Examples of foods high in fructose: > ## Good to know > > Avoiding fruit and certain vegetables can quickly lead to a vitamin deficiency. We therefore recommend the use of food supplements that ensure the basic requirement of vital substances. People with congenital fructose intolerance can achieve a very good quality of life, provided they stick to a fructose-free diet. Otherwise, symptoms such as hypoglycemia, vomiting, fatigue, neurological disorders or even seizures can occur. Typically, those affected develop an aversion to fruit in early childhood. # What does it mean to be fructose intolerant? Hereditary fructose intolerance is caused by a rare genetic defect. This causes a deficiency of an enzyme that is required for the breakdown of fructose in the body and thus causes a disorder of carbohydrate metabolism. It is estimated that 1 in 20,000 to 60,000 people worldwide suffer from hereditary fructose intolerance. Fructose is a component of most fruits and vegetables, and is also part of sucrose (also known as household sugar or granulated sugar), which is why it cannot be metabolized properly in some cases. Ingesting even a tiny amount of fructose can then lead to low blood sugar levels. Possible signs of inherited fructose intolerance include - vomiting - flatulence - tiredness - heartburn - abdominal cramps If this disease remains undetected, it leads to kidney and liver damage and can have a severe course. # What does genetics have to do with it? The inherited form of fructose intolerance is caused by a genetic defect. A carrier of one of the tested gene variations usually only shows rare or mild symptoms. However, if the partner is also a carrier of a genetic variation, this mutation is passed on to the offspring. It is only in this generation that the symptoms of inherited fructose intolerance are clearly recognizable and should be urgently taken into account. We are investigating a gene for inherited fructose intolerance: The ALDOB gene (aldolase B gene) carries the blueprint for the enzyme aldolase B, which controls the breakdown of fructose, in the cells. - Variant rs1800546 of the ALDOB gene: The C/G genotype is a carrier of an inherited fructose intolerance, but does not have to show any symptoms itself. The G/G genotype is a carrier of an inherited fructose intolerance and does not tolerate fructose itself. Genotype C/C is neither a carrier nor does this type show signs of inherited fructose intolerance. - Variant rs76917243 of the ALDOB gene: The G/T genotype is a carrier of inherited fructose intolerance, but does not necessarily show any symptoms itself. The T/T genotype is a carrier of an inherited fructose intolerance and does not itself tolerate fructose. The G/G genotype is neither a carrier nor does this type show signs of inherited fructose intolerance. - Variant rs78340951 of the ALDOB gene: Genotype C/G is a carrier of inherited fructose intolerance, but does not necessarily show any symptoms itself. Genotype C/C is a carrier of an inherited fructose intolerance and does not tolerate fructose itself. Genotype G/G is neither a carrier nor does this type show signs of inherited fructose intolerance. - Variant rs762198323 of the ALDOB gene: The TTTG/- genotype is a carrier of inherited fructose intolerance, but does not necessarily show any symptoms itself. The -/- genotype is a carrier of an inherited fructose intolerance and does not tolerate fructose itself. The TTTG/TTTG genotype is neither a carrier nor does this type show signs of inherited fructose intolerance.