Prevalence of primary adult lactose malabsorption in Poland.

Lactose-absorption capacity was examined in 275 apparently healthy Polish adolescents and adults (214 females and 61 males with an average age of 29.1 years) using a field version of the lactose-tolerance test with breath hydrogen determination. In the total group, 172 lactose absorbers (62.5%) and 103 lactose malabsorbers (37.5%) were identified. Reported milk intolerance and symptoms of lactose intolerance were significantly more frequent in lactose malabsorbers. Subdivision according to the birthplaces of the probands' grandparents did not reveal significant regional differences. The unexpectedly high frequency of lactose malabsorption is further evidence for concentric genetic clines of lactase gene frequencies extending from southern Scandinavia, the area with the lowest observed frequencies of selective adult hypolactasia, to the south and the east.