Lipid metabolism in premature infants.

Fats provide 40-50% of the total calories in human milk or infant formula. The milk secreted by mothers of preterm infants differs in fat composition from that of mothers of full-term infants in having higher levels of medium chain fatty acids (C12, C14) throughout the first 3 months of lactation, and higher levels of long chain polyenoic fatty acids during the first 3 months of lactation. These differences in composition benefit the preterm infant by providing higher levels of rapidly absorbed medium chain fatty acids and long chain polyenoic fatty acids needed for brain development. Fat digestion: The low levels of pancreatic lipase and bile salts in the preterm infant are compensated for by lipolysis in the stomach by lingual and gastric lipase and by the intestinal hydrolysis of fat through the action of human milk bile salt-stimulated lipase. Fat digestion is efficient in the preterm infant who absorbs about 80-90% of ingested fat. Lipid clearing from the circulation depends upon the activity of the enzymes lipoprotein lipase, hepatic lipase, and lecithin-cholesterol acyltransferase. The activity of these enzymes is lower or equal to that of term infants, depending upon the degree of prematurity and the nutritional regimen, especially in parenterally fed infants.