Infant Formula with 50% or More of Palmitic Acid Bound to the sn-2 Position of Triacylglycerols Eliminate the Association between Formula-Feeding and the Increase of Fecal Palmitic Acid Levels in Newborns: An Exploratory Study

Abstract

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.

Keywords: breast milk; infant formula; sn-2 palmitate.

Figure 1

Flowchart of participants. Abbreviations: sn, stereospecific numbering; PA, palmitic acid.

Figure 2

Association of feeding volume of high and low sn-2 PA milk in the multiple regression model showing the anthropometric data. (A) Association between feeding volume of high/low sn-2 PA milk and the infants’ weight; (B) Association between feeding volume of high/low sn-2 PA milk and the infants’ length; (C) Association between feeding volume of high/low sn-2 PA milk and the infants’ head circumference. All analysis models were adjusted by gestational week at birth, sex of the infant, age in days at the 1-month clinical visit, and caesarian section. The unit of feeding volume is expressed as daily feeding volume by body weight (mL/day/bw kg). β represents the partial regression coefficient. ■ represents the partial regression coefficient for each factor, and the bar indicates the 95% confidence interval of β. Abbreviations: sn, stereospecific numbering; PA, palmitic acid.

Figure 3

Results of total and soaped PA levels in stool and fecal pH analysis. The Steel–Dwass test was performed to compare each fecal indicator level in each sub-group. (A) Total PA level in stool; (B) Soaped PA level in stool; (C) Fecal pH. The statistical results with p < 0.1 are shown on the graph. Abbreviations: sn, stereospecific numbering; PA, palmitic acid.

Figure 4

Association between feeding volume of high and low sn-2 PA milk in the multiple regression model showing total and soaped PA levels in stool, and fecal pH. (A) Correlation between feeding volume of high or low sn-2 PA milk and total PA level in stool. The analytical model is adjusted by fecal pH; (B) association between feeding volume of high or low sn-2 PA milk and soaped PA level in stool. The analytical model is adjusted by fecal pH; (C) association between feeding volume of high or low sn-2 PA milk and fecal pH. No confounder was adjusted in this analytical model. The unit for feeding indicates the daily volume of milk per body weight (mL/day/kg). β indicates the partial regression coefficient. ■ indicates the partial regression coefficient of each factor, and the bar indicates the 95% confidence interval of β. ** p < 0.01, *** p < 0.001. Abbreviations: sn, stereospecific numbering; PA, palmitic acid.