The exocrine pancreatic function is adapted to the composition of nutritional substrates. Dietary constituents activate specific neural mechanisms and the release of gut peptides operating on pancreatic enzyme synthesis and secretion. Cholecystokinin (CCK) released by dietary protein and by protease inhibition stimulates protease synthesis in the pancreas and promotes pancreatic growth. The interplay between changes in dietary protein content and increased plasma CCK released by a synthetic protease inhibitor (Foy 305) confirm the essential role of the nutritional support of protein to enable the display of pancreatic adaptation.