Your body utilizes specialized proteins called enzymes to break down sugar received from the diet into forms your organs and tissues can use. Each of the many metabolic enzymes in your body has a specific function. The enzyme aldolase B metabolizes the sugar fructose into usable subunits. Hereditary fructose intolerance is a genetic abnormality that causes impaired aldolase B function that results in fructose from the diet building up in the bloodstream. This leads to an array of digestive and other symptoms, which range from mild to severe.
Abdominal Pain and Vomiting
If you have HFI, ingestion of fructose-containing foods typically causes abdominal pain and vomiting, reports the medical reference website Orphanet. High concentrations of fructose occur naturally in many common fruits, including pears, apples, oranges and peaches. Manufacturers also frequently add fructose to sweeten processed foods such as soft drinks, ready-to-eat cereals and baked goods. Sucrose, or table sugar, contains equal parts of glucose and fructose. Foods that contain sucrose, therefore, can also provoke abdominal pain and vomiting if you have HFI.
Dizziness and Confusion
Fructose ingestion triggers a profound drop in the blood glucose concentration, also known as hypoglycemia, among people with HFI. Your body relies on glucose to generate the energy needed to fuel the brain and other body organs and tissues. Inadequate glucose supply to your brain causes reduced mental function, which commonly manifests as confusion and dizziness. Other symptoms of glucose-deprivation of the brain include irritability, slurred speech, moodiness and drowsiness, reports the National Institute of Diabetes and Digestive and Kidney Diseases.
Weakness and Shakiness
Your muscles utilize glucose to generate the energy needed to maintain an upright posture and move your body. Hypoglycemia associated with HFI causes an energy deficit in your muscles, which manifests as weakness and shakiness.
Aversion to Sweets
If you have HFI, you almost certainly do not like the taste of sweets. This aversion to sweet-tasting foods occurs in virtually all patients with HFI, according to the Johns Hopkins University genetics database, which is called Online Mendelian Inheritance in Man. An aversion to sweets can make it easier to adhere to the strict avoidance of fructose necessary if you are living with HFI.
Malabsorption vs Hereditary Intolerance
Fructose malabsorption is sometimes confused with HFI because both cause digestive upset associated with ingestion of fructose-containing foods. These conditions differ in several important ways, however. Fructose malabsorption is not a genetic disorder and people with the condition do not have an aldolase B deficiency. Although patients with fructose malabsorption do not fully absorb the sugar from the small bowel, the fructose that does enter the bloodstream is metabolized normally. Importantly, patients with fructose malabsorption are not at risk for developing the liver, kidney and brain damage that may occur in patients with uncontrolled HFI. Whereas fructose malabsorption is relatively common, HFI is a rare disorder.
References
- HFI Laboratory at Boston University: Specifics of HFI and Its Diagnosis
- Orphanet: Fructose Intolerance
- "Practical Gastroenterology"; Clinical Ramifications of Malabsorption of Fructose and Other Short-chain Carbohydrates; Jacqueline S. Barrett, B.Sc., M.N.D., Peter R. Gibson, M.D., Ph.D.; August 2007
- University of Iowa Hospitals and Clinics: Dietary Fructose Intolerance
- National Institute of Diabetes and Digestive and Kidney Diseases: Hypoglycemia
- Online Mendelian Inheritance in Man: Fructose Intolerance, Hereditary
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