Premium Nahrungsergänzungsmittel | artgerecht

Fructose Intolerance: Causes, Symptoms and Treatment

Fructose intolerance is the inability of the body to properly absorb or metabolize fructose (fruit sugar), leading to digestive symptoms such as bloating, abdominal pain, and diarrhea.

Regular tips about health Regular tips about health

Things worth knowing about "Fructose Intolerance"

Fructose intolerance is the inability of the body to properly absorb or metabolize fructose (fruit sugar), leading to digestive symptoms such as bloating, abdominal pain, and diarrhea.

What is Fructose Intolerance?

Fructose intolerance describes a condition in which the body cannot properly absorb or process fructose (fruit sugar). Fructose occurs naturally in fruits, vegetables, and honey and is widely added to processed foods as a sweetener. There are two fundamentally different forms of this condition: the common intestinal fructose malabsorption and the rare hereditary fructose intolerance (HFI).

Forms of Fructose Intolerance

Intestinal Fructose Malabsorption

This is by far the more common form. The small intestine is unable to fully transport and absorb ingested fructose. The undigested fructose passes into the large intestine, where it is fermented by gut bacteria, producing gases and short-chain fatty acids that trigger typical digestive symptoms. This form is not life-threatening and can be well managed through dietary adjustments.

Hereditary Fructose Intolerance (HFI)

Hereditary fructose intolerance is a rare, congenital metabolic disorder caused by a deficiency of the enzyme aldolase B in the liver. When fructose is consumed, a toxic intermediate (fructose-1-phosphate) accumulates in the liver, kidneys, and small intestine, potentially causing severe organ damage. This form requires strict medical management.

Causes

The underlying causes differ depending on the form:

Fructose malabsorption: Impaired function or overload of the transport protein GLUT-5 in the small intestine, responsible for fructose uptake. It can also develop secondarily due to intestinal diseases such as celiac disease or Crohn's disease.
Hereditary fructose intolerance: A genetically determined defect of the enzyme aldolase B, inherited in an autosomal recessive pattern.

Symptoms

Symptoms vary depending on the form and severity of the condition:

Bloating and flatulence
Abdominal pain and cramping
Diarrhea or loose stools
Nausea
Feeling of fullness
In hereditary fructose intolerance: vomiting, hypoglycemia (low blood sugar), liver damage, and growth disorders in children

Diagnosis

Diagnosis is established through several methods:

H2 breath test: The most common test for fructose malabsorption. After consuming a fructose solution, the amount of hydrogen exhaled is measured. Elevated levels indicate malabsorption.
Genetic testing: Analysis of the ALDOB gene is used to diagnose hereditary fructose intolerance.
Enzyme assay: If HFI is suspected, aldolase B activity can be measured in a liver biopsy.
Elimination diet: Temporary removal of fructose from the diet followed by careful reintroduction to monitor symptoms.

Treatment

Fructose Malabsorption

Treatment is primarily based on a low-fructose diet. Patients learn which foods are high or low in fructose and how to identify their individual tolerance threshold. The ratio of fructose to glucose in foods is also important, as glucose enhances fructose absorption. Guidance from a registered dietitian is strongly recommended.

Hereditary Fructose Intolerance

For HFI, a strictly fructose-free diet is essential for survival. Fructose, sucrose, and sorbitol must be completely avoided. With a consistent diet, patients can lead a largely normal life and liver function can recover significantly.

Suitable and Unsuitable Foods

Well-tolerated Foods

Glucose-rich foods (e.g., dextrose)
Meat, fish, eggs
Potatoes, rice, oats
Lactose-free dairy products
Bananas (in moderation, due to a favorable glucose-to-fructose ratio)

Foods to Avoid

Apples, pears, mangoes, cherries (high in fructose)
Honey and agave syrup
Fruit juices and sweetened beverages
Industrially processed products containing high-fructose corn syrup
Dried fruits

References

Gibson, P.R. et al. - Fructose malabsorption and the bigger picture. Alimentary Pharmacology and Therapeutics, 2007.
Orphanet - Hereditary Fructose Intolerance. www.orpha.net, 2023.
World Gastroenterology Organisation (WGO) - Practice Guideline: Diet and the Gut. www.worldgastroenterology.org, 2018.

Building Blocks for a Healthy Life

As an integrated manufacturer, we develop & produce evidence-based, patented, and non-patented formulations. We work exclusively with plant and natural extracts according to the strictest purity & quality standards.
The combination of science & modern technology with the laws of nature creates solutions consistently tailored to humans – for the highest good: health.

Most read entries

3 Posts in this encyclopedia category