The effects of chemical composition and microstructure on lipid digestion in human milk and infant formulas.

Infant formula (IF) is an important substitute for infants when human milk (HM) is unavailable, however the formula fed infants were often observed "insufficient use of fat" and showed different metabolic phenotype, which may impact the growth and brain development. Considering the milk fat digestion rate may impact the fat absorption and metabolism and further influence the metabolic phenotype, it is valuable to study the fat digestive behaviors between IF and HM. In the current study, we investigated the in vitro digestion properties of fats in HM, with comparison of 4 formulas (IF1, 2, 3, 4) including IFs enriched in OPO lipids (IF1 and IF3) and IFs with common mixed plant oils (IF2 and IF4). Results showed that the extent of eventual lipid hydrolysis of HM (98.9+/-2.70%) was higher than that of IF1 and IF3 (90.4+/-3.39% and 91.1+/-1.67%, respectively) (p<0.05) and, IF2 and IF4 (81.9+/-1.64% and 79.9+/-1.05% respectively) (p<0.01). The native fat globules and protein aggregation were observed at the end of HM gastric digestion, and the aggregates became smaller and then resolved from 60 to 120 min in intestinal digestion, while a large number of aggregates were observed in IF may slow the lipid digestion. The absorption differences between HM and IFs in lipid conducted by the digestive behavior were needed further study to elucidate the nutritional relevance to infant development and growth.