Fructose intolerance is a condition where the liver is unable to digest fructose, leading to hypoglycemia, liver dysfunction and possibly death. It most commonly appears when infants began eating foods that contain fructose. This should be distinguished from fructose malabsorption, which causes gas and bloating and is not life-threatening. If you are concerned that your infant has fructose intolerance, consult a physician immediately. Prompt treatment may be live-saving.
Fructose
Fructose is a simple carbohydrate found naturally in fruits and honey and added to many manufactured foods to make them sweeter. Fructose is combined with glucose to form sucrose, or regular table sugar, and the alcohol-based sweetener sorbitol also contains fructose. While glucose can be metabolized almost anywhere in the body, only the liver can metabolize fructose.
Enzyme Deficiency
When fructose is ingested, it travels to the liver, where it is broken down by an enzyme called aldolase B. Normally fructose is digested and used for energy, but babies with a defect or deficiency of aldolase B are unable to process fructose. This leads to an accumulation of toxic byproducts that interfere with energy production in the liver. Affected babies are unable to use stored sugar or produce new sugar from fats, leading to dangerously low blood sugar levels.
Symptoms
Infants with hereditary fructose intolerance are healthy until they start eating foods that contain fructose. There is no fructose in breast milk. Symptoms develop if a baby drinks formula that contains fructose, or when she begins eating fruits or sweetened cereals. The initial symptoms of fructose intolerance are vomiting and extreme fatigue. Jaundice, or yellow skin, may develop and low blood sugar may trigger seizures. Liver and kidney failure develop if an affected infant continues to ingest fructose, and that may lead to death.
Diagnosis
Hereditary fructose intolerance is usually diagnosed by a blood test to look for a gene mutation that causes deficiency of aldolase B. If there is a high suspicion that an infant has fructose intolerance but the blood test is negative, a liver biopsy may be required to evaluate the function of the aldolase B enzyme.
Treatment
Treatment of fructose intolerance is dietary. This means avoiding ingestion of fructose, sucrose and sorbitol. These sugars are found widely in fruits, manufactured foods and even in medicines. If your child has fructose intolerance, fruit, some vegetables, powdered sugar, honey, soda, flavored drinks and anything containing high fructose corn syrup all must be avoided. It is best to seek the advice of a dietitian to ensure that you are eliminating all potentially dangerous foods from your infant's diet.
References
- “Best Practice and Research: Clinical Gastroenterology”; Inborn Errors of Carbohydrate Metabolism; Ertan Mayatepek, MD et al.; Oct 2010
- Harvard Health Publications; Is Fructose Bad for You?; P.J. Skerrett; April 2011
- "Nelson Textbook of Pediatrics, 18th Edition"; 81.3 Defects in Fructose Metabolism; Priya S. Kishnani and Yuan-Tsong Chen; July 2007
- Southern Fleurieu Health Service; Fructose in Foods: Information on Fructose Intolerance; Sonya Stanley and Mel Reid; June 2007
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