Using this test, 80 healthy Japanese infants and children (aged between one month and 15 years) and 18 adults were examined for lactose malabsorption after a dose of 1 g/kg lactose. All infants and children under 2-years old absorbed lactose completely. The incidence of lactose malabsorption was 30 % in 3-year, 36 % in 4-year, 58 % in 5-year, and 86 % in 6-year-old children, 85 % in schoolchildren, and 89 % in adults. Thus the incidence of lactase deficiency gradually increases with age from 3 years, and about 90 % of all normal Japanese adults are lactase-deficient.At birth, humans have abundant lactase activity in the small intestine but, in most ethnic groups, there is a pronounced decrease in lactase activity during early childhood (Huang and Gayless, 1967;Johnson et al., 1977). The definitive diagnosis of lactase deficiency requires the collection of biopsy specimens from the small intestine and demonstration of decreased lactase activity therein. Attempts have therefore been made to develop indirect methods for detecting lactase deficiency. Tolerance tests, although commonly used for this purpose, are influenced by many factors-such as, the rate of gastric emptying and intermediary glucose metabolism. In addition, these tests need a large amount of lactose and therefore give no information on the ability of the intestine to absorb

The mean plasma levels of 25-hydroxyvitamin D (25-OH-D) were measured before and after the administration of 2000 units of daily oral vitamin D2 for a period of 2 weeks in 9 normal infants and children, 7 infants with neonatal hepatitis and persistent neonatal hepatitis, and 4 infants with congenital biliary atresia. The mean plasma level of 25-OH-D increased significantly from 19.5 +/- 3.7 (S.E.) ng/ml to 34.0 +/- 6.8 (S.E.) ng/ml after administration of vitamin D2 in controls (p less than 0.05). The mean plasma level of 25-OH-D also increased from 8.0 +/- 2.1 (S.E.) ng/ml to 22.1 +/- 2.6 (S.E.) ng/ml after vitamin D treatment in hepatitis group (p less than 0.05). In patients with congenital biliary atresia, vitamin D treatment did not affect eh plasma levels of 25-OH-D.

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