The binding ratio of palmitic acid (PA) at the sn-2 position of triacylglycerols in infant formulas is lower than that in breast milk, resulting in higher levels of fecal PA. Even if the ratio is increased to 40–50%, fecal PA levels in formula-fed infants remain higher than those in breast–fed infants. In Japan, infant formulas with 50% or more of PA bound to sn-2 (high sn-2 PA milk) are commercially available; however, their effects on PA excretion have not been investigated. Therefore, this observational study aimed to preliminarily evaluate whether the feeding volume of high sn-2 PA milk is significantly associated with fecal total/soaped PA levels in newborns. Infant formulas were classified as high (≥50% of PA bound to sn-2) or low sn-2 (<50%) PA milk. Associations between feeding volume of high or low sn-2 PA milk and fecal PA levels were evaluated using multiple regression analysis models. The results showed that the feeding volume of low sn-2 PA milk was positively associated with fecal total/soaped PA levels, while there was no significant association between those of high sn-2 PA milk and fecal total/soaped PA levels. Our preliminary study suggests that high sn-2 PA milk may reduce increased fecal PA levels in formula-fed newborns.

Background/Objectives: Soaped palmitic acid (PA) has been reported to be excreted in stool after feeding infant formulas containing low sn-2 palmitate levels, which corresponds to high sn-1 or -3 palmitate levels. While an in vitro study showed that soaped PA inhibits the Bifidobacteria growth, few clinical studies have evaluated effects of soaped PA on intestinal environments of infants. In this study, we aimed to evaluate associations between increased fecal soaped PA levels and inhibition of growth of the intestinal microbiome using clinical data, and to evaluate changes in the intestinal environment with formula-feeding. Methods: This study was conducted as a secondary analysis to our observational study of Japanese 1-month-old infants (n = 172). Infant formulas were classified into high sn-2 formula (≥ 50%) and low sn-2 formula (< 50%) according to the sn-2 binding ratio of PA. Multiple regression analyses and path analysis were performed as statistical analyses. Results: In the multiple regression analysis, the occupancy of Bifidobacteria was negatively correlated with the fecal soaped PA levels (β = −0.15, 95% confidence interval = −0.28– − 0.02). A path analysis suggested that low sn-2 formula feeding led to increased fecal soaped PA levels, decreased Bifidobacteria occupancy, and finally increased fecal pH. Conclusions: Our clinical data showed significant associations between higher fecal soaped PA levels and lower Bifidobacteria occupancy in the newborn gut, which agreed well with the report of the in vitro study. Our study also suggests that feeding infant formula with low sn-2 palmitate causes changes in the intestinal environment through an increase in fecal soaped palmitic acids.

Background: Sn‐2 palmitate is a unique lipid found in breast milk that enhances the absorption of palmitic acid (PA) and prevents the soaping of PA in the gut. Feeding formulas with high sn‐2 palmitate levels influences infant growth and neurodevelopment; however, few studies have evaluated the long‐term effects on these outcomes. In this study, we evaluated the association between feeding formula and exposure to different levels of sn‐2 palmitate in infancy and growth or neurodevelopment in infants after 6 months. Methods: This study was conducted as a follow‐up of 1‐month‐old infants included in a previous study. Infant formulas commercially available in Japan were classified as either high sn‐2 formula (PA sn‐2 ratio ≥ 50%) or low sn‐2 formula (< 50%). The associations between the feeding volume of high/low sn‐2 formula at 1 and 6 months of age and anthropometric z ‐scores or neurodevelopment (Ages & Stages Questionnaires, third edition; ASQ‐3) scores at 9 and 18 months were evaluated. Results: Multiple regression analysis of anthropometric z‐scores showed no significant association with feeding with either the low or high sn‐2 formulas. Multiple regression analysis of the ASQ‐3 scores showed that the communication score at 18 months was negatively associated with feeding with the low sn‐2 formula at 1 month, with no association observed for the high sn‐2 formula. Conclusions: Compared with the formula with low sn‐2 palmitate, feeding formulas with high sn‐2 palmitate at 1 month had a lower association with reduced neurodevelopment at 18 months.