Intestinal lactase deficiency and milk drinking capacity in the adult.

The milk drinking capacity of 200 adults was determined experimentally and the results correlated with their milk drinking habits and intestinal lactase activity as judged by a lactose tolerance test. Of the group 65.5% were found to have deficient lactase activity and 5.3% experienced severe gastrointestinal symptoms with 250 ml of milk; 28.2% with 500 ml; 26.0% with 750 ml; 15.3% with 1000 ml and 25.2% tolerated the latter amount without difficulty. Of the normal individuals, 92.7% tolerated 1000 ml without symptoms. Intestinal lactase activity seemed to be important in determining the extremes of milk ingestion: four or more glasses per day or no milk ingestion, but had little effect in the intermediate pattern of milk consumption. It is concluded that intestinal lactase deficiency has clinical relevance and should be considered when nutritional supplementation with milk is contemplated.