The frequency distribution of lactose malabsorption among adult populations from the eastern and western Egyptian deserts.

The study consisted of 172 subjects belonging to ethnic groups from Sinai in the Eastern Desert and the New Valley in the Western Desert, with respective mean ages of 36.7 +/- 2.0 and 26.6 +/- 1.0 years. Lactose absorption was assessed by measurement of urinary galactose in pooled 2-hr urine samples following ingestion of an oral lactose dose of 40 g. Mean 2-hr excretion values after ingestion were 32.3 mg galactose in the Sinai and 7.7 mg in the New Valley. In the evaluation of lactose malabsorption, a diagnosis of lactose malabsorption is based upon a cutoff point of 0.075 mg/mg urinary galactose:creatinine ratio. The overall prevalence rate in those populations is 34.3%. The proportion of lactose malabsorbers was 11.1% in Sinai and 51.0% in the New Valley. Highly significant differences (chi 2 = 29.5, P < 0.0001) were found between the two ethnic groups with regard to the frequency distribution of lactose malabsorption. The existence of an east-west gradient of increasing frequencies of lactose malabsorption gene is suggested.