Distribution of human adult lactase phenotypes in the population of Austria.

A total of 528 unrelated, apparently healthy, adult and adolescent Austrians (270 females, 258 males, mean age 22.1 years) were examined for lactose absorption capacity employing a noninvasive field test based on breath hydrogen (H2) determination. Subjects exhibiting a change of breath hydrogen concentration of less than 15 volumes per million (vpm) after a load of 50 g lactose (n = 422) were classified as lactose absorbers, 106 probands (20.1%) showing increases of breath hydrogen concentration between 16 and 111 vpm were diagnosed as lactose malabsorbers. The distribution of the lactase phenotypes was independent of age and sex. Intolerance symptoms after lactose administration were significantly more frequent in lactose malabsorbers. Grouping of probands according to the birth-places of their grandparents revealed significant differences in the distribution of the lactase phenotypes in East and West Austria (East 25%, West 15% lactose malabsorbers). These differences are discussed in the light of the population history of these regions.