Intake of live microorganisms and microbial composition in the early stages of life

While diet is known to influence gut microbiota (GM), the role of live microorganisms (LMOs) has not been previously studied in early childhood. The objective of this study was to estimate the intake of LMOs during the first 48 months of life in a cohort of children and to study its potential impact on the GM. To this end, an LMO-content table was created, validated, and used to estimate LMO intake from dietary data obtained using a food frequency questionnaire (FFQ). The fecal microbiota was determined via 16S rRNA gene-based analyses, and SCFAs were quantified by gas chromatography. The intake of LMO increased with age from 6.69 log CFU/day at 0.5 and 3 months to 10.33 CFU/day at 48 months. Human milk was the main source of LMOs during the first 6 months of life, being milk and dairy products the main contributors later on. We observed significant associations between the fecal microbiota and metabolites and the intake of LMO at the different age periods analyzed. For instance, at 0.5 months of age, the intake of LMO was positively associated with the abundance of Bifidobacteriaceae and negatively with Enterococcaceae and propionic acid, at 3 months it was negatively associated with SCFAs and BCFAs, and at 6 months with butyric acid, whereas at 48 months the consumption of LMO was positively associated with Coriobacteriaceae. In conclusion, these findings suggest that LMO intake evolves with age and dietary sources, and is linked to specific changes in the GM in infants.