A Comparative Analysis of Lipid Digestion in Human Milk and Infant Formulas Based on Simulated In Vitro Infant Gastrointestinal Digestion

To investigate the lipid digestive behaviors of human and infant formulas and analyze the differences between them, we investigated the fat globule particle size distribution, lipolysis rate, and fatty acid release of infant formulas with different fat sources and human milk using an in vitro infant digestion model. The results suggested that the particle size in infant formula increased rapidly during gastric digestion and decreased significantly after intestinal digestion, whereas the particle size in human milk increased slowly during gastric digestion but increased rapidly during intestinal digestion (p < 0.05). Despite having a larger droplet size, human milk demonstrated a very high lipolysis rate due to the presence of MFGM. In terms of the distribution of fatty acids in digestion products, the proportion of saturated fatty acids (SFAs), monounsaturated fatty acids (MUFAs), and polyunsaturated fatty acids (PUFAs) in vegetable oil-based infant formulas was close to that of human milk. The amount of SFAs in milk fat-based infant formulas was significantly higher than that in human milk, and the content of MUFAs in all infant formulas was significantly lower than that in human milk (p < 0.05). After digestion, the most abundant fatty acid released by human milk was C18:2n6c, while the fatty acids released by infant formulas were SFAs, such as C14:0, C16:0, and C18:0.