Primary lactose intolerance in Zulu adults.

The incidence of lactose intolerance in a sample of 47 Zulu patients from a general medical ward and 14 healthy members of the Zulu population in Durban was investigated. Eighty-nine percent of patients and 93% of control subjects were diagnosed as having lactose intolerance because of failure to increase blood glucose more than 1,1 mmol/l during the 2 hours following 50 g lactose ingestion. Ninety-two per cent of the female and 64% of the male patients complained of symptoms of lactose intolerance, and 61% of the female and 75% of the male patients passed stools with a pH of less than 6. Glucose tolerance (50 g) was normal in 87% of patients and 92% of controls; 2 patients had a diabetic response while 5 patients and 1 control had 'flat' glucose and lactose responses, suggesting delayed absorption. Analysis of nutritional status showed that male patients were significantly more malnourished than female patients, and patients more so than controls. The results indicate that lactose intolerance is a normal observation in the Zulu and that it is primary in origin since there was no association between intolerance, sickness or malnutrition. Practical implications that arise from the study are that milk-based diets should be avoided in refeeding malnourished Zulu patients and that lactose may find a useful place in the treatment of constipation and liver failure in such patients.