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CLINICAL GASTROENTEROLOGY AND HEPATOLOGY 2010;8:581–586

ORIGINAL ARTICLES—ALIMENTARY TRACT
Subjective Perception of Lactose Intolerance Does Not Always Indicate Lactose Malabsorption
FRANCESC CASELLAS, ANNA APARICI, MAITE CASAUS, PURIFICACIÓN RODRÍGUEZ, and JUAN R. MALAGELADA
Digestive System Research Unit, Hospital Universitari Vall d’Hebron, Barcelona, Spain

BACKGROUND & AIMS:Symptomatic lactose intolerance is common; however, abdominal symptoms that patients experience after ingestion of lactose-containing foods can have causes beyond lactose malabsorption. We aimed to determine whether symptoms that patients usually attribute to lactose intolerance are comparable to symptoms provoked by a controlled lactose challenge and whether these symptoms are related to lactoseabsorption capacity. METHODS: We performed an observational, prospective, transverse study of 353 patients referred for a lactose hydrogen breath test (HBT). Patients completed a validated questionnaire about symptoms associated with consumption of dairy products at home (home symptoms). After a 50-g lactose breath test, they completed the same questionnaire again (lactose challenge symptoms). Patientswere assigned to groups of absorbers or malabsorbers according to HBT results and tolerants or intolerants according to the results of the questionnaire. RESULTS: The total symptom score was significantly higher for home symptoms than for the lactose challenge (16 vs 8, P .01). Symptoms perceived at home were reported to be more intense than those that followed the lactose challenge for lactoseabsorbers compared with malabsorbers (16 vs 4, P .01) and lactose tolerants compared with intolerants (12 vs 2, P .05). Overperception of lactose intolerance at home was similar in men and women. CONCLUSIONS: Daily life symptoms that patients associate with lactose intolerance are often unrelated to lactose malabsorption. Even among true lactose malabsorbers, symptom recall tends to be amplified by thepatient. Thus, conventional anamnesis is a highly unreliable tool to establish symptomatic lactose malabsorption. Keywords: Lactose Intolerance; Lactose Malabsorption; Hydrogen Breath Test; Lactase Activity. dult lactase deficiency and lactose malabsorption are common, but their relation to chronic abdominal symptoms is often unclear. In proven lactose malabsorbers, lactose challenge producesstereotyped symptoms that include abdominal distention, flatulence, abdominal cramping, and diarrhea, independently of whether lactose malabsorption is due to congenital, primary, or secondary lactase deficiency.1 Symptoms of lactose intolerance are, at least in part, related to the amount of unabsorbed lactose but not necessarily to the magnitude of intestinal lactase activity. In this respect, it hasbeen previously observed that symptoms of lactose malabsorption are not directly correlated with intestinal lactase activity2,3 or with the

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magnitude of hydrogen production after a lactose load.4 – 6 The discrepancy between lactose intolerance symptoms and lactase activity might be due to a number of factors that can influence the symptomatic perception of lactose intolerance, such aslactose load, amount of lactose unabsorbed, type of administration (milk is different than lactose with water), consumption of lactose during a meal, gastric emptying, small bowel transit, colonic water absorption capacity, effect of colonic bacterial fermentation, or visceral sensitivity.7–9 Lactase-deficient persons tend to avoid dairy products because of the symptoms produced by incomplete digestionof lactose, even though proven lactase-deficient individuals might tolerate up to 7–12 g of lactose daily without noticeable effects.4,10 More commonly, individuals associate ingestion of lactose-containing products with their abdominal symptoms, but without objective evidence of insufficient lactase activity. In this respect, self-reported milk intolerance in patients with irritable bowel syndrome...