Double blind study of milk lactose intolerance in a group of rural and urban children

240 rural and 101 urban children were studied in a double blind fashion to determine their clinical response to three types of milk. Each participant received in three different days, 250 ml of lactose free milk, regular milk, and lactose enriched milk. In the urban girls a control period in which no milk was given was included. In both study groups, lactose free milk was highly significantly better tolerated than the others. However, the frequency of subjects asymptomatic after its ingestion was much lower, particularly in the rural group, to that found previously in a group of adults of high socioeconomic status. It is thought that in the rural children, part of this phenomenon can be explained by intercurrent gastrointestinal infections. There also appears to be a 'background' of gastrointestinal symptoms present in the children, which wrongly classifies them as symptomatic to milk ingestion. It is concluded that probably no less than 15% of children have gastrointestinal complaints after the ingestion of 250 ml of regular milk and that lactose hydrolyzed milk is highly significantly better tolerated than the others.