Development of the Digestive System—Experimental Challenges and Approaches of Infant Lipid Digestion

Abstract

At least during the first 6 months after birth, the nutrition of infants should ideally consist of human milk which provides 40–60 % of energy from lipids. Beyond energy, human milk also delivers lipids with a specific functionality, such as essential fatty acids (FA), phospholipids, and cholesterol. Healthy development, especially of the nervous and digestive systems, depends fundamentally on these. Epidemiological data suggest that human milk provides unique health benefits during early infancy that extend to long-lasting benefits. Preclinical findings show that qualitative changes in dietary lipids, i.e., lipid structure and FA composition, during early life may contribute to the reported long-term effects. Little is known in this respect about the development of digestive function and the digestion and absorption of lipids by the newborn. This review gives a detailed overview of the distinct functionalities that dietary lipids from human milk and infant formula provide and the profound differences in the physiology and biochemistry of lipid digestion between infants and adults. Fundamental mechanisms of infant lipid digestion can, however, almost exclusively be elucidated in vitro. Experimental approaches and their challenges are reviewed in depth.

Scientific Opinion on the essential composition of infant and follow-on formulae

“…Most of the fat in breast milk is triacylglycerol (TAG, > 98 %), but it also contains some cholesterol (around 0.25 g/L) and PLs (around 0.24 g/L), predominantly sphingomyelin, phosphatidylethanolamine and phosphatidylcholine (Abrahamse et al, 2012;Giuffrida et al, 2013).…”

“…In breast milk, PLs that constitute the fat globule membrane have a high content of LCPUFAs compared with the TAG molecules in the core of the milk globules (Abrahamse et al, 2012). The PLs supplied by breast milk are expected to play a role, together with bile PLs, in the emulsification of the fat in the infant gut and thus promote digestion, absorption and transport (Ramirez et al, 2001).…”

“…The PLs supplied by breast milk are expected to play a role, together with bile PLs, in the emulsification of the fat in the infant gut and thus promote digestion, absorption and transport (Ramirez et al, 2001). It has been proposed that, specifically, LCPUFAs may be better utilised if supplied in PLs owing to increased absorption and tissue incorporation (Abrahamse et al, 2012). Furthermore, as constituents of the membranes of all cells in the infant, PLs are involved in a variety of physiological processes, but these are usually not expected to be influenced by dietary intake of PLs (German, 2011;Küllenberg et al, 2012;Oosting et al, 2012;Tanaka et al, 2013).…”

Extending in vitro digestion models to specific human populations: Perspectives, practical tools and bio-relevant information

“…Moreover, prematurity affects strongly the digestive capabilities, with decreased GI functionality in preterm babies compared to full-term newborns (Bruce, 2012;Kelly & Coutts, 2000;Kelly & Newell, 1994;Menard, Monfils, & Tremblay, 1995). In fact, there are various differences between infants and adults mainly in some digestive enzymes and a relatively elevated gastric pH (3.5e6.5), as exhaustively reviewed (Abrahamse et al, 2012;Nguyen, Bhandari, Cichero, & Prakash, 2015b, 2015a. Briefly, infant digestion process neglects oral phase due to liquid meals rapidly transiting through the oral cavity (5e10 s).…”

“…Briefly, infant digestion process neglects oral phase due to liquid meals rapidly transiting through the oral cavity (5e10 s). Small stomach storage capacity, affecting meal frequency, transit and volume, increases quickly during the first month of life from 10 to 20 mL up to 90e150 mL per meal (Abrahamse et al, 2012;. Infant fasting gastric pH is less acidic than of an adult (respectively 4e5 vs. 2 in the fasted state) which may change gastric proteolysis, as optimal activity of pepsin is 1.5e2.2 (Henderson, Hamosh, Armand, Mehta, & Hamosh, 1998;LiChan & Nakai, 1989;Schlamowitz & Peterson, 1959).…”