REVIEW - FAT DIGESTION IN THE NEWBORN - ROLE OF LINGUAL LIPASE AND PRE-DUODENAL DIGESTION

The neonatal period represents one of the most vulnerable periods in human life, particularly with respect to nutrition. During this period of rapid growth and development, there is a high demand for essential nutrients as well as for an adequate energy supply. At birth, with the sudden transfer from the high carbohydrate diet of the fetus to the high fat diet of the newborn, fat becomes the major energy source for the growing infant. In human milk and in most infant formulas, 45-50% of the total calories are present as fat, although the fat content is only 3.5-4.0%. The fat content varies widely in the milk of different species, from 1.9% in the horse to 12 and 17% in the rat or reindeer, respectively; the highest amounts of fat (as much as 50%) are found in the milk of aquatic mammals. More than 90% of milk fat is in the form of triglycerides which contain saturated and unsaturated long-chain fatty acids contain more than 14 carbon atoms). The overall process of fat digestion and absorption is dominated by the fact that dietary lipids, in contrast to other nutrients such as carbohydrates and protein, are nonpolar and, therefore, largely water insoluble. Digestion and absorption of dietary fat represents thus a process of transport of water-insoluble molecules from one water phase, the intestinal lumen, to another water phase, the lymph and plasma. The role of lingual lipase in the fat digestion of the newborn is discussed.