Hypolactasia in a fixed cohort of young Finnish adults. A follow-up study

Selective late-onset hypolactasia (lactose malabsorption) was examined in a fixed cohort of Finnish adolescents, now aged 17 to 25 years. This was the third examination of the same subjects. In the first examination 10 years ago the prevalence of hypolactasia was 6.2%. In the second examination 5 years ago three more cases of hypolactasia were diagnosed, and the prevalence was 9.3%. In this examination the prevalence was 10.3% (10/97); 2 newly manifested hypolactasia cases were diagnosed. If those subjects were included who were not examined this time but whose hypolactasia was diagnosed previously or who were at least 20 years old at the second examination, the prevalence of hypolactasia was 12.7% (13/102). In the 17- to 20-year-olds the prevalence was 15.4%, and in the 21- to 25-year-olds it was 11.1%. The results were in agreement with our previous conclusions that hypolactasia manifests itself in the Finnish population mostly between 10 and 20 years of age and that the prevalence in adults is 17%. Eight of the 13 subjects with hypolactasia had weekly abdominal symptoms; all except one of them had symptoms after the lactose tolerance test. Nine subjects had realized milk intolerance; six of them had symptoms from one glass of milk or less. Symptoms varied considerably from person to person, the commonest symptom being meteorism. The reason was probably the variation in the remaining small-intestinal lactase activity and in the functional stability of the colon.