The practical significance of lactose intolerance in children.

Lactose intolerance is observed in black and Mexican-American children by age 3 years, and it probably occurs in other non-northern European ethnic groups at a similar age. However, intolerance to the consumption of 250 ml of milk apparently is rarely seen in preadolescents. Current research on the response of adolescents to hydrolyzed lactose milk suggests that the symptoms observed in lactose-intolerant subjects after milk ingestion may be unrelated to lactose or may be mild enough to be of little practical significance. The effects of undigested lactose on nutrient absorption has received little attention, but preliminary data suggest that this is not a problem, except perhaps when overall intakes are marginally adequate.