Sphingomyelin (SM) is a nutritionally important polar lipid in human milk (HM), crucial for infant neurodevelopment.Its digestion is uniquely mediated by alkaline sphingomyelinase (Alk-SMase) primarily in the distal intestine, leaving its initial fate in the upper gastrointestinal tract less defined.This study employed an in vitro digestion model simulating gastric and proximal intestinal conditions, supplemented with sphingomyelinase, to compare the digestibility of SM and glycerophospholipids between human milk and 3 commercial infant formulas (IFs).Lipidomic analysis via UPSFC-Q-TOF-MS and compositional analysis by 31 P-NMR were used.The results demonstrated that SM was remarkably stable during upper gastrointestinal digestion, with hydrolysis limited to ~4% in HM and up to ~16% in IF-1.In contrast, glycerophospholipids, especially phosphatidylcholine (PC), showed extensive hydrolysis (>88%).Confocal laser scanning microscopy (CLSM) suggested the native milk fat globule membrane (MFGM) structure in HM contributed to the stability of its polar lipids compared with the more accessible phospholipid structures in IFs.These findings highlight differences in polar lipid digestibility in the upper gut and emphasize the potential role of MFGM-mimetic structures in infant formula design to modulate early lipid digestion.
Liu et al. (Fri,) studied this question.