Influence of Physical Treatments of Human Milk on the Kinetics of Gastric Lipolysis in Preterm Newborns

The optimization of newborns nutrition is a challenge especially for preterm newborns for whom nutrition plays a crucial part in cerebral and global development. Human milk is considered as the best food for newborns. Several short and long-term beneficial health effects were attributed to breastfeeding and have induced the increase of human milk in preterm newborns nutrition. Whereas the chemical composition of infant formula has been optimized to mimic human milk, there is still a major difference between the structure of human milk and commercial infant formulas. It is well known in adult nutrition that the structure of emulsions influences their susceptibility to hydrolysis, such results have been obtained either on in vitro or in vivo studies. Human milk is a natural emulsion (oil in water). Lipids droplets are dispersed under the form of entities called milk fat globules (average diameter 4 µm, span 0.1-20 μm). The globules are stabilized by a trilayered membrane composed mainly of polar lipids (phospholipids, sphingolipids and gangliosides), of proteins, neutral lipids and other minor compounds. The physical treatments apply to human milk or more generally to bovine milk to pasteurize or stabilize the milk modify the structure of the natural emulsion. Heat treatment for instance induces whey proteins denaturation and the adsorption of protein aggregates on the surface of the milk fat globules. Heat treatment also leads to the denaturation of bile salt stimulated lipase. These effects limit intragastric lipolysis in preterm newborns. Conversely, reduction of milk globules size, by homogenisation of milk, increases the specific surface available for lipase adsorption and limits the lost of fat during enteral administration of milk. Such treatment could thus enhance gastric lipolysis and improve fat absorption of preterm newborns. The objective of this trial is to evaluate the effects of physical treatments (pasteurization and homogenisation by ultrasonicat