The D-xylose absorption test in different ethnic groups.

Fifty-nine hospital in-patients in England, Saudi Arabia and Zambia had 5-h urinary xylose measured after a 25 g oral load; in 47 of them blood xylose concentration at 90 min. was measured. All of them came from an urban environment and none had significant organic disease. Exactly similar methods were used in each country; the investigator was the same in all of them. Mean xylose excretion was very similar in the English, Asians and Africans. The high incidence of abnormal xylose absorption tests in indigenous populations in tropical countries is due to environmental factors; it does not have a genetic basis.