American Journal of Clinical Nutrition, Vol 26, 1224-1228, Copyright © 1973 by The American Society for Clinical Nutrition, Inc.

Lactose feeding in lactose-intolerant monkeys

¹ From the Department of Nutrition, Harvard School of Public Health, the Department of Medicine, Children's Hospital Medical Center, and the Department of Pediatrics, Harvard Medical School, Boston, Massachusetts 02118

By the criteria used for human screening, adult cebus monkeys were "tolerant" to an oral load of lactose (1 g/kg body weight), whereas adult squirrel, rhesus, and galago monkeys were mostly "intolerant." To assess the effects of lactose feeding on the lactose tolerance test and on intestinal enzyme levels, 7 of 12 "lactose-intolerant" adult galago monkeys which had been fed a semi-purified diet without lactose for 7 weeks were fed a similar diet with 20% lactose on a dry weight basis. At the end of a 4-month period, the 7 experimental and 5 control monkeys were tested again for lactose intolerance by oral lactose loads. They were then sacrificed for measurements of lactase, sucrase, palatinase, maltase, and galactosidase in their duodenums and in equal thirds of the rest of their small intestines. There was significant improvement in the utilization of the oral lactose loads in the lactose-fed monkeys compared with the controls. Except for the duodenal segment, intestinal lactase activity, expressed either on a wet weight or protein basis, was significantly higher in the lactose-fed animals. There were no important differences among the other enzymes although duodenal maltase and palatinase were higher in the control than in the lactose-fed animals. Thus, under the conditions of this study, an increased tolerance to lactose in galago monkeys was induced by lactose feeding and was associated with higher lactase activity in the small bowel distal to the duodenum.