Statistical analysis
A sample size of 100 subjects per group was based on a similar study comparing formulae on stool characteristics [Data normality of continuous variables was assessed with the Shapiro-Wilcoxon test. Since all the variables analyzed showed a nonparametric distribution, outliers were identified using 1.5xIQR. For comparison among IF groups of IGSQ scores, pH, dry matter content, and calprotectin levels, a Kruskal–Wallis test was used with Dunn’s post-hoc test to determine significant differences between groups, and Bonferroni adjusted p-values were used to correct for multiple comparisons. For IGSQ scores the Quade test was used as a nonparametric alternative to adjust for covariates. All analyses were performed unadjusted, and adjusted for sex (male/female), type of birth (C-section/natural), and age.Intention to Treat (ITT) population entailed all included subjects. For the Per Protocol (PP) dataset all randomized subjects without protocol violations or deviations (e.g. out-of-window visit, prohibited medication use, or formula incompliance), and that had complete primary outcome data available were included. Due to the real-life setting of this study and the absence of large differences between ITT and PP populations, only ITT analyses are presented, with differences to PP indicated where applicable. Missing data were not imputed. Statistical analyses were performed in SPSS, SAS, and R, with p-values < 0.05 being considered statistically significant.