World Digestive Health Day WDHD – May 29, 2016 CARBOHYDRATE INTOLERANCE (LACTOSE, SUCROSE AND FRUCTOSE): IDENTIFICATION AND TREATMENT, continued DIAGNOSIS In clinically suspected patients, diagnosis is made on small intestinal biopsy, which was gold standard for years. Criteria applied to make the diagnosis include normal small bowel morphology in the presence of absent or markedly reduced sucrase activity, isomaltase activity varying from 0 to full activity, reduced maltase activity, and normal lactase activity, or in the setting of reduced lactase, a sucrase:lactase ratio of <1.0. Molecular genetics helps in making early diagnosis and avoids invasive, repetitive procedures. At least 80% of patients have one of four common mutations, namely p.Val577Gly, p.Gly1073Asp, and p.Phe1745Cys in the sucrase domain and p.Arg1124X in the isomaltase domain.12 It has replaced the need for small intestinal biopsy for diagnosis. TREATMENT The sucrase-isomaltase intolerance is treated mainly by the dietary restriction. (See Table 3) Oral supplementation of sucrosidase (derived from Saccharomyces cerevisiae) can also be used, if available. FRUCTOSE INTOLERANCE Fructose is a monosaccharide, which is naturally present in fruits and vegetables.13 Fructose, because of its sweet taste, is used extensively in food industry as a sweetener such as in juices, candies, and beverages. Fructose is also a constituent of disaccharides sucrose along with glucose. HEREDITARY FRUCTOSURIA Hereditary fructosuria is a rare clinical disease, which occurs due to a deficiency of this aldolase B enzyme. The deficiency of enzyme leads to incomplete metabolism of fructose, which leads to accumulation of fructose-1-phosphate in the liver, kidney, and intestine. Patients may have symptoms in the form of hypoglycemia, abdominal pain, vomiting, and diarrhea. 14 FRUCTOSE INTOLERANCE Fructose is generally absorbed passively along with glucose via GLUT-2 transporter present on the basolateral membrane of enterocytes. Fructose is also absorbed by GLUT-5 is non glucose dependent transporter located in the brush border of the small intestine. Defects in these transporters can lead to fructose malabsorption. Transportation of ingested glucose Table 3: Food items, which are restricted and allowed in patients having sucrose-isomaltose intolerance Foods to avoid Food items which are allowed Apple, apricot, banana, cantaloupe, grapefruit, melon, mango, orange, peach, pineapple, and tangerine Carrot and potato Beans, chickpeas, green peas, lentils, peas, and soy Yogurt sweetened with sucrose, sweetened condensed milk, and sweetened cream Sugar (sucrose), ice cream, all desserts made with sugar, marmalade, candies, jellies, chocolate, and licorice Commercial cookies and cakes with added sugar, sweetened drinks Wheat, rice, corn, einkorn, oats, kamut, spelt, rye, bread, pasta, flour, and cereals with no added sugar Avocado, berries, cherries, fig, grapes, kiwi, lemon, lime, olives, papaya, pear, pomegranate, prunes, and strawberries All vegetables Milk, dairy product, butter, cream, cheeses, and yogurt sweetened with dextrose or fructose All meat, fish, and eggs All fats Fructose, honey, cocoa, unsweetened juice, homemade low-sucrose cookies, and cakes through SGLT-1 activates GLUT-2 which in turn gets inserted on the apical membrane. Therefore, ingestion of glucose enhances absorption of fructose as well. Glucose also increases paracellular absorption of fructose. These mechanisms explain the possible fructose malabsorption after eating foods whose fructose component is in excess of glucose. Fructose intolerance can also occur because of diffuse mucosal diseases of intestine such as celiac disease. Clinical features are similar to symptoms caused by other carbohydrates intolerances such as lactose intolerance, as described above. The diagnosis of fructose malabsorption can be made by hydrogen breath test after ingestion of fructose 0.5 gm/kg (maximum 25 gm) dissolved in water. The diagnosis is confirmed by an increase of >20 ppm in hydrogen or >10 ppm in methane levels over the baseline twice in succession and abdominal discomfort after the consumption of the test dose. Fructosehydrogen test has both sensitivity and specificity of over 80%. World Digestive Health Day WDHD May 29, 2016 WGO Handbook on DIET AND THE GUT 23
WGO Handbook on Diet and the Gut_2016_Final
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