A proposed mechanism of normal intestinal lactase decline in the postweaned mammal

Intestinal lactase declines to low levels in the postweaned mammal as an adaptation to normal termination of lactose ingestion. Although a well known phenomenon and presumably the basis of milk intolerance among most human adults, the mechanism of this decline has remained obscure. Evidence is presented to support a proposal that temporally related cytokinetic changes, which effect a generally corresponding reduction in enterocyte life-span, serve as the causal basis of lactase decline in the postweaned mammal.