Late-onset hypolactasia in Hong Kong school children.

Three hundred and twenty Chinese school children aged between 6 and 19 years from six schools in Hong Kong were tested for their lactose digestion status. After an overnight fast, the children were challenged with cow's milk, 5 ml/kg bodyweight (i.e. lactose approximately 0.25 g/kg). Malabsorption was assessed by measuring hydrogen concentration from end-expiratory breath samples taken in duplicate before and at 90 and 180 minutes after the challenge. On average, 10% of the children showed an increase in breath hydrogen excretion within 3 h after the challenge, indicating malabsorption of lactose. None of the children complained of gastro-intestinal symptoms or showed any clinical sign of intolerance to the milk. The number of malabsorbers increased significantly (p less than 0.001) with age, starting at about 3% at the age of 8 and reaching about 27% at the age of 18 years. The sharpest rise occurred between 14 and 15 years. It is concluded that, despite the high prevalence of hypolactasia, Hong Kong Chinese children can consume normal amounts of milk without developing any untoward clinical symptom or sign.