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Fructose intolerance is a condition where the body has difficult digesting and using fructose and fructose-containing foods. It is treated by complete elimination of fructose and sucrose from the diet.
There are two types of fructose intolerances. The first, hereditary fructose intolerance (HFI), also known as fructosemia or fructose aldolase B-deficiency, is a rare genetic disease of the metabolism of fructose due to the absence of the enzyme that breaks it down (aldolase B). As a result, fructose accumulates in the liver, kidney, and small intestine and the body is unable to convert its energy storage material (glycogen) into glucose. If untreated, the blood sugar level falls (hypogly-cemia) and there is formation of harmful substances that damage the liver. HFI is difficult to diagnose so its incidence rate is not known, but it is believed to be quite rare (between 1 in 12,000 to 1 in 58,000). Since it is inherited, it lasts for life.
Sugars and sweeteners
This list of sugars and sweeteners for fruitose intolerant individuals was prepared by the HFI Laboratory at Boston University .
(Illustration by GGS Information Services/Thomson Gale.)
seems to be caused by the lack of special cells (epithelial cells) on the surface of the intestine that are not available to help digestion. As a result, the body is not able to absorb fructose efficiently.
Although having different causes, both HFI and DFI are treated by dietary adjustments. Complete elimination of fructose and sucrose from the diet is the only effective treatment for HFI. As for DFI, treatment also involves a fructose-free diet, with the treating physician allowing some concessions in mild cases. Some patients may find a threshold level where they can eat some fructose without getting symptoms. Close dietary monitoring is important for good outcome and should include at least semiannual visits to a biochemical geneticist (for HFI) and monthly meetings with a nutritionist.
A strict fructose-free diet involves exclusion of any beverage or food containing fructose, sucrose, or sorbitol. Fructose is a monosaccharide, or simple sugar, that has the same chemical formula as glucose, the main source of energy for the body, but a different molecular structure. It is found in all fruits, in some vegetables and in honey. Fructose and other sugars are carbohydrates, which are important sources of energy for the body. The main types of sugars found in beverages and foods are:.
The symptoms of both types of fructose intolerance are gastrointestinal distress, flatulence, bloating, diarrhea, fatigue, vomiting, low iron and other nutrient deficiency. For dietary fructose intolerance, there is clinical evidence also associating it with mood disturbances and depression. The function of a fructose-free diet is to eliminate dietary sugar intake so as to alleviate these symptoms.
Absolute elimination of fructose and glucose from the diet produces good outcomes in most people with fructose intolerance. For the rapidly diagnosed and treated infant, the outcome for a normal state of health is excellent. In the absence of substantial liver damage, life expectancy is normal.
Eating out is one of the most challenging parts of maintaining a fructose-free diet. This is because restaurant employees have little time to check food contents from the labels of the ingredients used by the kitchen to prepare menus. Some guidelines in dealing with restaurant staff include:.
With the increasing popularity of processed foods, sugar is often an ingredient about which the consumer is not aware, and not only in restaurants. For example, high fructose corn syrup (HFCS) is present and unsuspected in numerous products including soft drinks, fruit drinks, sports drinks, baked goods, candies, jams, yogurts, condiments, canned and packaged foods, and other prepared and sweetened foods. Also, potatoes, when prepared a certain way, may provide a significant amount of fructose. For this reason, the advice of a highly trained nutritionist is required in the treatment of fructose intolerance.
After ingesting fructose, infants and children may become sufficiently ill to require hospitalization. If untreated, fructose intolerance leads to hypoglycemia and acidosis that may act together to cause organ shock and coma. Ongoing liver damage may result in cirrhosis and eventual liver failure. Death may result from any or all of the above. Hereditary fructose intolerance may be relatively mild or a very severe disease. In the severe form, even eliminating fructose and sucrose from the diet may not prevent progressive liver disease.
Clinical intolerance to fructose was initially described in 1956. Some 4-5 years later, the defect in aldolase B enzyme in the liver was demonstrated, and hereditary fructose intolerance (HFI) became clinically recognized. The rapid early progress in the understanding of this disorder may be due to the fairly clear symptoms associated with ingestion of fructose, which are difficult to miss. In many young infants, the age of onset of symptoms leads to the diagnosis. Genetic counseling may be of value to prospective parents with a family history of fructose intolerance. Medical experts agree that definitive treatment simply consists of eliminating fructose from the diet. By doing so early in the course, the affected child’s health is usually fully restored within days.
Recent research performed at the University of Innsbruck in Austria shows that fructose and sorbi-tol-reduced diet in subjects with fructose malabsorp-tion does not only reduce gastrointestinal symptoms but also improves mood and early signs of depression. Improvement of the signs of depression was also more pronounced in females than in males.
Medical researchers unanimously agree that symptoms can improve in dietary fructose intolerance patients willing to adhere to a low fructose diet.
Smith, J. Living With Dietary Fructose Intolerance: A Guide to Managing your Life With this New Diagnosis Charleston, SC: BookSurge Publishing, 2006.
Gazzola, A. Living with Food Intolerance London, UK: Sheldon Press, 2006.
Saville, A., Haynes, A. Food Intolerance Bible New York, NY: ThorsonsElement (Harpercollins), 2005.
Minocha, A. Handbook of Digestive Diseases Thorofare, NJ: Slack Incorporated, 2004.
Emsley, J., Fell, P. Was It Something You Ate?: Food Intolerance: What Causes It and How to Avoid It. Oxford, UK: Oxford University Press, 2002.
Frieri, M, Kettelhut, B. (eds). Food Hypersensitivity and Adverse Reactions Boca Raton, FL: S. CRC Press, 1999.
Cornblath, M., Schwartz, R. Disorders of Carbohydrate Metabolism in Infancy. Cambridge, MA: Blackwell Scientific Publications, 1991.
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), National Institutes of Health. 31 Center Drive, MSC 2560, Bethesda, MD 20892-2560. 1-800-891-5389. <digestive.niddk.nih.gov/ddiseases/pubs/facts/index.htm>.
American Gastroenterological Association. 930 Del Ray Avenue, Bethesda, MD 20814. (301)654-2055. <www.gastro.org>.
International Foundation for Functional Gastrointestinal Disorders Inc. P.O. Box 170864, Milwaukee, WI 53217-8076. 1-888-964-2001. <www.iffgd.org>.
United States Food and Drug Administration (FDA). 5600 Fishers Lane, Rockville, MD 20857-0001. 1-888-INFO-FDA (1-888-463-6332). <www.fda.gov>.
Genetic and Rare Diseases (GARD) Information Center, PO Box 8126, Gaithersburg, MD 20898-8126. 1-301-519-3194.<http://rarediseases.info.nih.gov/html/resources/info_cntr.html>
Monique Laberge, Ph.D.