Page 21

WGO Handbook on Diet and the Gut_2016_Final

World Digestive Health Day WDHD – May 29, 2016 CARBOHYDRATE INTOLERANCE (LACTOSE, SUCROSE AND FRUCTOSE): IDENTIFICATION AND TREATMENT, continued lactase is associated with the point polymorphism C/T 13910. This consists of a substitution in a sequence of DNA that regulates the lactase gene. While genotype CC correlates with hypolactasia, TT genotype correlates with lactase persistence.4 PATHOPHYSIOLOGY AND CLINICAL SYMPTOMS The lactase enzyme is located in the brush border (microvilli) of the small intestinal epithelial cells. The enzyme splits and hydrolyzes dietary lactose into glucose and galactose for transport across the cell membrane. The absence or deficiency of lactase leads to failure of hydrolysis of lactose, hence unabsorbed lactose remains in the intestinal lumen and fluid drives osmotically into the intestinal lumen.5,6 In addition to increasing the volume and fluidity of the gastrointestinal contents, unabsorbed lactose enter colon. The fermentation of lactose by colonic microflora produces lactic acid and hydrogen. In the presence of methanogenic bacteria, hydrogen and carbon dioxide combine together to form methane in the colon. The excessive production of hydrogen and methane in the intestine leads to bloating, distention of the abdomen, excessive flatulence, nausea, and abdominal pain (non-specific in nature). The excessive unabsorbed lactose with osmotically driven water, in excess of colonic absorption, can lead to diarrhea in some patients. In patients with common adult-type hypolactasia, the amount of ingested lactose required to produce symptoms varies from 12 to 18 g, or 8 to 12 ounces of milk. Ingestion of small to moderate amounts of lactose usually produces bloating, cramps, and flatulence, but not diarrhea. Ingestion of larger amounts of lactose, a faster gastric emptying time, and faster intestinal transit time all contribute to more severe symptoms. Several factors determine the symptoms onset of symptoms of lactose intolerance, such as lactose content in the diet, gut transit time, fermentation capacity of gut, and (possibly) neuropsychological factors. DIAGNOSIS The diagnosis of lactose intolerance should be suspected in patients who have symptoms of bloating and chronic diarrhea. A relationship of symptoms occurring with the intake of milk and milk products and relief in symptoms with avoidance further strengthens the diagnostic possibility of lactose intolerance. The diagnosis of lactose intolerance can be confirmed by lactose hydrogen breath test, lactose tolerance test, and genetic study. Lactose hydrogen breath test is most commonly used test for the diagnosis and the test has a sensitivity of 88% and specificity of 85%. The test is performed and the results are interpreted as depicted in Figure 1.2 LACTOSE TOLERANCE TEST Patient consumes 50g of lactose dissolved in water. Samples of capillary blood are obtained to test the plasma glucose concentration at −5, 0, 15, 30, 45, and 60 minutes. A maximal plasma glucose increase of 1.4 mmol/L( 25.2 mg/dl) or higher indicates lactose intolerance.7 The sensitivity and specificity of lactose tolerance test is high (both >90%). -12 hr -5min 0 2 hr Fasting from solids and liquids Collect breath sample for baseline H2 levels No antibiotics and prebiotics in previous 2 weeks No prokinetics and laxatives in previous 1 week Low fiber meal in previous 24 hours Collect breath samples at 20 min interval for 2 hours and record symptoms Record H2 and CH4 levels 20% patients are non H2 producers. So, CH4 levels should be measured. Start breath test Lactose: 1gm/kg body weight (20% water, max 50 gm) Positive result: • Increase in breath hydrogen levels of > 20ppm or in methane levels of > 10ppm • Two-fold increase in hydrogen above baseline in three consecutive samples Figure 1. World Digestive Health Day WDHD May 29, 2016 WGO Handbook on DIET AND THE GUT 21


WGO Handbook on Diet and the Gut_2016_Final
To see the actual publication please follow the link above