Lactose Intolerance in Australia

The incidence of lactose intolerance was determined in 100 healthy Australian adults. Six per cent of this group were lactose intolerant, as judged by an abnormal “flat” lactose tolerance test response (maximum rise in blood sugar level of less than 20 mg/100 ml); abdominal pain and diarrhoea after lactose ingestion; jejunal lactase deficiency (less than 15 units per gramme of protein); normal sucrase and maltase activity. Detailed histories of lactose intake were obtained from both adults and children from the University of Melbourne Growth Study Unit. The intake in boys remains relatively constant until adult life and is of the order of 30 gm per day (equivalent to one and a half pints of milk). The lactose Intake in girls declines after the age of 11 years, with increasing numbers consuming less than half a pint of milk per day. Lactose intolerance correlated with prolonged low lactose intake in three subjects. Eleven subjects had false-positive “flat” tolerance curves, but had no symptoms after lactose ingestion and normal jejunal lactase activity.