Summary about Disease
Fructose intolerance refers to several conditions where the body has difficulty processing fructose, a type of sugar found in fruits, honey, some vegetables, and added sweeteners like high-fructose corn syrup. The two main types are:
Hereditary Fructose Intolerance (HFI): A rare, inherited metabolic disorder where the body lacks an enzyme needed to break down fructose. This can lead to a build-up of fructose-1-phosphate, causing damage to the liver, kidneys, and intestines. HFI is a serious condition.
Fructose Malabsorption (Dietary Fructose Intolerance): A more common condition where the small intestine doesn't absorb fructose properly. This can lead to gastrointestinal symptoms. It is generally less severe than HFI.
Symptoms
Symptoms vary depending on the type and severity of fructose intolerance:
Hereditary Fructose Intolerance (HFI):
In infancy (upon introduction of fructose in diet): Vomiting, diarrhea, irritability, poor feeding, jaundice, failure to thrive.
Later in life: Abdominal pain, hypoglycemia (low blood sugar), liver damage, kidney dysfunction, seizures, coma.
Fructose Malabsorption:
Bloating, gas, abdominal pain, diarrhea, nausea.
These symptoms typically occur after consuming foods high in fructose.
Causes
Hereditary Fructose Intolerance (HFI): Caused by a genetic mutation in the ALDOB* gene, which provides instructions for making the enzyme aldolase B. This enzyme is essential for breaking down fructose. HFI is inherited in an autosomal recessive pattern (meaning both parents must carry a copy of the mutated gene for a child to be affected).
Fructose Malabsorption: The exact cause is not always clear, but it involves a deficiency or malfunction in the fructose transporters in the small intestine (specifically, GLUT5). Factors like intestinal inflammation, gut bacteria imbalances, and certain medications may contribute.
Medicine Used
There is no specific medicine to "cure" either type of fructose intolerance. Management focuses on dietary restriction.
Hereditary Fructose Intolerance (HFI): The main treatment is strict avoidance of fructose, sucrose (table sugar, which breaks down into glucose and fructose), and sorbitol.
Fructose Malabsorption: Management involves limiting fructose intake. Some individuals may find relief with enzyme supplements (xylose isomerase) designed to help convert fructose to glucose in the digestive tract, but evidence of efficacy is limited, and this is not a standard treatment.
Is Communicable
No, neither Hereditary Fructose Intolerance nor Fructose Malabsorption is communicable (infectious). HFI is a genetic condition. Fructose malabsorption is a digestive issue, not caused by an infectious agent.
Precautions
Hereditary Fructose Intolerance (HFI):
Strict dietary avoidance of fructose, sucrose, and sorbitol is essential. Read food labels carefully and be aware of hidden sources of these sugars.
Carry identification indicating HFI in case of emergency.
Consult a registered dietitian specializing in metabolic disorders.
Fructose Malabsorption:
Identify and limit trigger foods high in fructose.
Consider a low-FODMAP diet (under the guidance of a registered dietitian) to reduce overall fermentable carbohydrates.
Read food labels to be aware of fructose and high-fructose corn syrup content.
How long does an outbreak last?
Hereditary Fructose Intolerance (HFI): There are no "outbreaks" in the traditional sense. Symptoms are ongoing and will occur whenever fructose, sucrose, or sorbitol are ingested. Proper management prevents symptoms.
Fructose Malabsorption: Symptoms can last for several hours or even a day or two after consuming a high-fructose food. The duration depends on the amount of fructose consumed and the individual's tolerance level. Symptoms resolve when fructose is cleared from the digestive system.
How is it diagnosed?
Hereditary Fructose Intolerance (HFI):
Genetic testing: The most definitive test to identify mutations in the ALDOB gene.
Liver biopsy: Historically used but less common now due to the availability of genetic testing.
Enzyme assay: Measures aldolase B activity in liver tissue.
Fructose Malabsorption:
Hydrogen Breath Test: A common test where the patient consumes a measured amount of fructose, and the hydrogen levels in their breath are measured. High hydrogen levels indicate malabsorption because unabsorbed fructose is fermented by bacteria in the colon, producing hydrogen.
Dietary Elimination and Reintroduction: Symptoms are monitored during a period of fructose avoidance and then upon reintroduction of fructose to identify triggers.
Timeline of Symptoms
Hereditary Fructose Intolerance (HFI):
Infancy: Symptoms typically appear soon after the introduction of fruits, fruit juices, or formula containing sucrose to a baby's diet.
Childhood/Adulthood: Symptoms occur within hours of consuming fructose, sucrose, or sorbitol. Chronic exposure can lead to liver and kidney problems over time.
Fructose Malabsorption:
Symptoms usually develop within 30 minutes to 2 hours after consuming high-fructose foods. The exact timeline can vary depending on individual factors.
Important Considerations
Hereditary Fructose Intolerance (HFI): HFI is a life-threatening condition if left untreated. Early diagnosis and strict adherence to a fructose-free diet are crucial. Untreated HFI can lead to liver failure, kidney failure, and death.
Fructose Malabsorption: While less severe than HFI, fructose malabsorption can significantly impact quality of life due to gastrointestinal discomfort. It is important to work with a healthcare professional and registered dietitian to identify trigger foods and develop a personalized dietary plan. It can coexist with other gastrointestinal conditions, such as Irritable Bowel Syndrome (IBS).
Label Reading: Meticulous label reading is essential for both conditions. Be aware of hidden sources of fructose, sucrose, sorbitol, and high-fructose corn syrup in processed foods, medications, and personal care products.