Effects of term infant formulas containing high sn-2 palmitate with and without oligofructose on stool composition, stool characteristics, and bifidogenicity

Abstract

Objectives: Levels of stool fatty acid soaps and beneficial bacteria differ between formula-fed and breast-fed infants; addition of specific formula ingredients may reduce these differences. This study evaluated the effects of a term infant formula containing high sn-2 palmitate term infant formula (sn-2) or an identical formula supplemented with oligofructose (OF) at 2 concentrations (sn-2+3 g/L OF, sn-2+5 g/L OF) on stool composition, stool characteristics, and fecal bifidobacteria.

Methods: Healthy, term formula-fed infants 7 to 14 days old (n = 300) were randomized in a double-blind manner to receive standard formula (control), sn-2, sn-2+3 g/L OF, or sn-2+5 g/L OF for 8 weeks. Human milk (HM)-fed infants (n = 75) were studied in parallel. Stool samples were collected from all subjects at week 8 for fatty acid soaps and mineral content, and from a subset at baseline and week 8 for bifidobacteria. Stool characteristics were assessed via 3-day diary.

Results: The sn-2 group had 46% less stool soap palmitate (P < 0.001) and softer stools than control (20% more mushy soft stools, P = 0.026; 50% fewer formed stools, P = 0.003). Addition of OF resulted in even fewer formed stools versus control (65% fewer for sn-2+3 g/L OF, 79% fewer for sn-2+5 g/L OF), with 5 g/L OF more closely resembling that of HM-fed infants. Both sn-2 (P < 0.05) and sn-2 with OF groups (P < 0.01) had significantly higher fecal bifidobacteria concentrations than control at week 8, not differing from HM-fed infants.

Conclusions: High sn-2-palmitate formulas led to reduced stool soaps, softer stools, and increased bifidobacteria, whereas addition of OF further improved stool consistency. Those modifications brought outcomes in formula-fed infants closer to that in HM-fed infants.

Trial registration: ClinicalTrials.gov NCT01861600.

FIGURE 1

Enrollment and discontinuation of study participants. Control = α-lactalbumin–enriched term infant formula with 100% vegetable fat blend; sn-2 = high sn-2 palmitate formula (control formula modified to contain 60% vegetable fat blend and 40% high sn-2 fat blend); sn-2+3 g/L OF = high sn-2 palmitate formula supplemented with OF at 3 g/L; sn-2+5 g/L OF = high sn-2 palmitate formula supplemented with OF at 5 g/L. OF = oligofructose; sn-2 = sn-2 palmitate.

FIGURE 2

Stool soap palmitic acid (C16:0) and total fatty acids at week 8 for all infants according to feeding group. Analysis of variance followed by pairwise comparisons for formula groups, and independent t tests for each of the formula groups versus the HM group. Mean (±standard error) significantly different from control: ^∗∗P < 0.01, ^∗∗∗P < 0.001; significantly different from HM: ^††P < 0.01, ^†††P < 0.001. d-w = dry weight; HM = human milk; OF = oligofructose; sn-2 = high sn-2 palmitate infant formula.

FIGURE 3

Stool consistency at week 8 for all infants according to feeding group. Analysis of variance followed by pairwise comparisons for formula groups, and independent t tests for each of the formula groups versus the HM group. Mean (±standard error) significantly different from control: ^∗P < 0.05, ^∗∗P < 0.01, ^∗∗∗P < 0.001; significantly different from HM: ^†P < 0.05, ^††P < 0.01, ^†††P < 0.001. HM = human milk; OF = oligofructose; sn-2 = high sn-2 palmitate infant formula.

FIGURE 4

Bifidobacteria counts in w-w stool at baseline and week 8 in a subset according to feeding group. Plotted values are unadjusted mean (±standard error). Data were analyzed using analysis of covariance with baseline values and type of delivery (vaginal vs cesarean section) included in the model, followed by pairwise comparisons for formula groups, as well as for each of the formula groups versus the HM group. LS mean log₁₀ counts/g w-w stool (±standard error) significantly different from control: ^∗P < 0.05, ^∗∗P < 0.01, ^∗∗∗P < 0.001; significantly different from HM: ^†††P < 0.001. HM = human milk; LS = least squares; OF = oligofructose; sn-2 = high sn-2 palmitate infant formula; w-w = wet weight.