[Lactose malabsorption in children and adolescents: diagnosis through breath hydrogen test using cow milk].

OBJECTIVE To determine the prevalence of lactose malabsorption and its association with skin color and age in children and teenagers attending public schools in Porto Alegre, Brazil. METHODS A cross-sectional study was performed with 225 subjects between 8 and 18 years attending two public schools in Porto Alegre, Brazil. Patients were randomly selected. Subjects were classified according to skin color (white and non-white) and age group (8 to 12 and 13 to 18 years). Lactose malabsorption was diagnosed using the breath hydrogen test after ingestion of 250 ml of whole cow milk. The test lasted for 3 hours, with collections after fasting and 60, 120, and 180 minutes after milk ingestion. Malabsorption was determined in the presence of increase of > or =20 ppm in hydrogen concentration regarding the basal levels. RESULTS Two-hundred and twenty-five students were studied, with a mean age +/- standard deviation of 12.2 +/- 2.0 years. The subjects consisted of 134 females (59.6%); 154 white (68.4%); and 71 nonwhite. Lactose malabsorption was observed in 19/225 cases (8.4%). It was diagnosed in 8/154 white patients (5.2%) and in 11/71 non-white patients (15.5%) (p=0.02). Regarding the age group, we found 15/143 cases of malabsorption in students between 8 and 12 years (10.5%), and 4/82 cases in students between 13 and 18 years (4.9%) (p=0.227). CONCLUSIONS The prevalence of lactose malabsorption in students attending public schools in Porto Alegre is significant, especially if we consider that the physiological doses (250 ml of milk) were used for diagnosis. The malabsorption rate was higher among non-white children, which confirms the influence of race on primary adult type hypolactasia. No association was observed between lactose malabsorption and age group.