Persistence of high intestinal lactase activity (lactose tolerance) in Afghanistan.

Two hundred and seventy apparently healthy adult subjects from Afghanistan, mainly from the central and eastern parts of the country, were subjected to a lactose tolerance test. The change of blood glucose from the fasting concentration at 20 min after the administration of lactose showed a bimodal distribution. Forty-seven subjects had a rise of blood glucose concentration of more than 1.1 mmol/l and were classified as persistence of high intestinal lactase activity (PHILA), a term which lays emphasis on the fact that high lactase activity in the adult is an unusual state whose prevalence in some populations requires explanation. In the Afghan sample there were no significant differences of the frequency of PHILA in different ethnic groups.