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.

Trial registration CTRI/2010/091/001111 (Clinical Trials Registry - India; www.ctri.nic.in)

APJ and NPH employees of Nestle. SG was employed by Nestle at the time of study conduct.

www.ctri.nic.in CTRI/2010/091/001111

The study was funded by Societe des Produits Nestle S.A. (previously Nestec Ltd). Co-authors employed by the funding body were involved in designing the study, data analysis and interpretation, and writing the manuscript.

I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.

Yes

The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

(CTRI/2010/091/001111 [Clinical Trials Registry - India; www.ctri.nic.in]). The study protocol and informed consent form were reviewed and approved by an Independent Ethics Committee at each center (Chaitanya Hospital, Dolphin Hospital, Institute of Child Health Ethics Committee, KEM Hospital Research Center, Rajarajeswari Hospital). Written informed consent was obtained from the infants parents or legal guardian prior to enrollment.

I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals.

Yes

I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance).

Yes

I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable.

Yes

All gut microbiota data produced in the present study are available upon reasonable request to the authors.