Although breastfeeding and early dietary practices may exert lasting effects on adolescent gut microbiota composition, these associations appear modest and did not remain significant after multiple testing correction.
Non-breastfed children exhibited higher relative abundance of Ruminococcus at age 12 compared to exclusively breastfed children.
Children who had mixed breastfeeding at three months showed a higher probability of Alloprevotella detection at age 12 compared to exclusively breastfed children.
Early introduction of liquids before 6 months was associated with lower Ruminococcus abundance at age 12.
Early introduction of semi-solid foods was associated with lower odds of Alloprevotella presence at age 12.
No significant differences in microbial alpha or beta diversity were observed between exclusive breastfed, mixed feeding, and non-breastfed groups at three months when assessed at age 12.
The study found that associations between breastfeeding patterns and specific bacterial taxa at adolescence did not survive multiple testing correction.
This research investigated whether how babies are fed in their first months of life — whether through breastfeeding, formula, or a mix of both — has any lasting effect on the community of bacteria living in the gut (the gut microbiota) when those children reach adolescence. The study followed 362 children from birth to age 12 in a Brazilian birth cohort, comparing gut bacteria in early adolescence based on recorded feeding practices at three months of age and the timing of introducing other foods and liquids. The study found that overall measures of gut bacterial diversity (how many different types of bacteria are present and how evenly distributed they are) did not significantly differ between groups based on how they were fed as infants. However, there were some suggested associations at the level of specific bacterial types: children who were not breastfed had somewhat higher levels of a bacterium called Ruminococcus, while those who were mixed-fed had higher odds of having a bacterium called Alloprevotella detected. Additionally, introducing liquids early (before 6 months) was linked to lower Ruminococcus levels, and early introduction of semi-solid foods was linked to lower odds of having Alloprevotella. Importantly, the associations related to breastfeeding status did not hold up after statistical corrections for multiple comparisons, meaning they could be chance findings. This research suggests that while early feeding practices may leave some traces on gut bacterial communities more than a decade later, these effects appear to be modest and specific to certain bacterial groups rather than broadly affecting the diversity of the gut microbiome. The practical takeaway is that the gut microbiota in adolescence is shaped by many factors, and the long-term influence of infant feeding, while potentially real, may be relatively small. The authors call for larger studies using more comprehensive biological measurement approaches to better understand whether and how these early-life dietary exposures have meaningful health implications.
Alves E, Carpena M, Bierhals I, Matijasevich A, Barros A, Santos I, et al.. (2026). Breastfeeding, early-life feeding practices and adolescent gut microbiota: Long-term associations in a birth cohort.. Clinical nutrition ESPEN. https://doi.org/10.1016/j.clnesp.2026.103101