Safety and tolerance of infant formulas containing probiotics: a multicenter, randomized, controlled trial in healthy term infants

Several studies have documented the safety and tolerance of probiotics in infants, however, most studies are conducted with supplement. This randomized, double-blind, multicenter trial evaluated growth of healthy term infants fed infant formula supplemented with Limosilactobacillus reuteri DSM17938 ( L. reuteri ; n=92) or Bifidobacterium lactis CNCM I-3446 (B. lactis ; n=92 ) or the same formula without probiotics (n=95). Mixed feeding with breast milk was allowed in each group. Exclusively breastfed infants (n=100) were included for reference. Non-inferiority in weight gain (margin −3 g/day) from enrollment to age 6 months was the primary outcome. Length, BMI, head circumference, and WHO z -scores from birth to 12 months were assessed, as was digestive tolerance, and, in a subset of infants, urinary D-lactate parameters and stool microbiota composition. Of 279 infants randomized, 256 completed the study. The mean difference in weight gain between each probiotic group and the standard group at age 6 months was −0.378 g/day (97.5% confidence interval [CI], −1.541, 0.776; P <0.001) for L. reuteri and −1.724 g/day (97.5% CI, −2.845, −0.603; P =0.005) for B. lactis , indicating non-inferior growth. Anthropometric z -scores were not significantly different between any of the formulas, over the entire study, except for a slightly lower weight-for-age z -score in the B. lactis vs. standard group at 8 months ( P =0.034). No differences in adverse events or urinary D-lactate levels were observed. Significantly higher fecal Lactobacilli counts were observed with L. reuteri supplementation (7.0 log10[CFU/g]; n=24) compared with standard formula (6.2 log10[CFU/g]; n=21). Parent-reported digestive tolerance symptoms were similar among the formula groups and comparable to the breastfed group. Weight gain from enrollment to age 6 months in Indian infants fed formula containing probiotics L. reuteri DSM17938 or B. lactis CNCM I-3446 was non-inferior versus infants fed the same formula without probiotics. Both probiotic formulas were safe and well-tolerated.