Lactose absorption and malabsorption in healthy Italian children: do the quantity of malabsorbed sugar and the small bowel transit time play roles in symptom production?

Using breath hydrogen analysis after an oral lactose load (2 g/kg; maximum 50 g), we investigated the prevalence of lactose malabsorption in 61 healthy Italian children aged 6-13 years. We also examined the relationship between symptoms and small bowel transit time and the degree of sugar malabsorption. Three of 61 subjects produced no H2 after both lactose and lactulose load and thus were eliminated at the outset. Lactose malabsorption was defined as excretion of greater than 20 ppm H2. Lactose intolerance was classified as mild (colicky pain, flatulence, abdominal distension, borborygmi) or severe (diarrhea). The frequency of lactose malabsorption in the children aged 6-8 years (group I) was 25%; in the children aged 8-11 years (group II), it was 35%, and in the children aged 11-13 years (group III) 56%. The differences in frequency between the first and the third groups were significant (p = 0.05). Three of 20 (15%) in group I, two of 20 (10%) in group II, and three of 18 (17%) in group III were classified not only as lactose malabsorbing, but also as lactose intolerant, with symptoms during and after the test. We found no difference in the small bowel transit times or in the quantities of malabsorbed lactose in symptomatic and asymptomatic malabsorbing subjects. Other factors that may play a role in symptom production are discussed.