Comparative tolerance of adolescents of differing ethic backgrounds to lactose-containing and lactose-free dairy drinks. I. Initial experience with a double-blind procedure.

A lactose-free (LF) chocolate dairy drink and one containing 4.5% lactose (LC) were administered randomly in 240- and 480-ml volumes on 4 consecutive mornings under double-blind conditions to 110 healthy teenagers (14 to 19 years old) of differing ethnic backgrounds. Capillary blood glucose analysis after 50 g of oral lactose identified 67 of them as lactose malabsorbers. Neither absorbers nor malabsorbers reported significantly different gastrointestinal symptoms after 240 ml of LC compared with the same amount of LF. However, 17 absorbers and 21 malabsorbers reported symptoms inconsistent with intolerance due to lactose. These subjects had symptoms after LF only, after both LF and LC, or after 240 ml but not 480 ml of LC. After 480 ml of LC, 26 malabsorbers had symptoms, compared to 15 after 480 ml of LF. The prevalence of symptoms after 480 ml of LC, but not after 480 ml of LF, was 7% for absorbers, and 24% for malabsorbers. The results indicate that most of the individuals who reported gastrointestinal symptoms after ingestion of the two beverages did so for reasons other than their lactose content.