RESUMO
BACKGROUND: Early life nutrition is crucial for the development of the gut microbiota that, in turn, plays an essential role in the maturation of the immune system and the prevention of infections. OBJECTIVES: The aim of this study was to investigate whether feeding synbiotic infants and follow-on formulas during the first year of life reduces the incidence rate (IR) of infectious diarrhea compared with standard formulas. Secondary endpoints included the IR of other infectious diseases as well as fecal milieu parameters. METHODS: In this double-blind, controlled trial, 460 healthy, 1-mo-old infants were randomly assigned to receive a synbiotic [galacto-oligosaccharides (GOS)/Limosilactobacillus fermentum CECT 5716] (IF, n = 230) or a control formula (CF, n = 230) until 12 mo of age. A reference group of breastfed infants (HM, n = 80) was included. Data on infections were recorded throughout the study period and stool samples were collected at 4 and 12 mo of age. RESULTS: IR of infectious diarrhea during the first year of life was 0.60 (CF), 0.56 (IF), and 0.29 (HM), with no statistically significant difference between groups. The IR of lower respiratory tract infections, 1 of the secondary endpoints, however, was lower in IF than in CF [0.79 compared with 1.01, IR ratio = 0.77 (0.60-1.00)]. Additionally, fecal pH was significantly lower at 4 mo (P < 0.0001), whereas secretory IgA was significantly higher at 12 mo of age (P = 0.015) in IF compared with CF. CONCLUSIONS: Although no difference is observed in the incidence of diarrhea, consumption of a synbiotic formula containing L. fermentum CECT5716 and GOS in infancy may reduce the incidence of lower respiratory tract infections and affect the immune system and fecal milieu. Additional research is warranted to further investigate the potential interaction of the gut-lung axis. This trial was registered at clinicaltrials.gov as NCT02221687.