Solid food source is a previously under-investigated driver of infant microbiome variability, with effects contingent on milk feeding, as human milk may buffer against dietary choices whereas formula-fed infants show heightened sensitivity to complementary food source.
Key Findings
Results
Solid food source explained a very small proportion of gut microbiota variability in the overall cohort.
Solid food source explained only 0.53% of gut microbiota variability.
No significant differences in gut microbiome diversity and composition were observed in the overall cohort (q > 0.25).
Beta-diversity was evaluated using PERMANOVA based on OTU-level Bray-Curtis dissimilarities.
Total sample size was 368 infants.
Results
At 6 months, the majority of infants were mixed-fed, followed by homemade-fed and commercially-fed.
Mixed-fed infants: n = 154 (41.8%).
Homemade-fed infants: n = 143 (38.9%).
Commercially-fed infants: n = 71 (19.3%).
Solid food source was assessed at 6 months within the Canadian Healthy Infant Longitudinal Development (CHILD) cohort.
Results
Formula-fed infants given homemade or mixed foods at 6 months showed higher abundances of specific bacterial taxa compared with commercially-fed formula-fed infants.
Higher abundances of Firmicutes, Turicibacteraceae, and Turicibacter were observed in formula-fed infants receiving homemade or mixed foods compared with those receiving commercial foods (all q < 0.25).
Mixed feeding within the formula-fed group was further linked to higher Eubacteriaceae and Lachnospiraceae (all q < 0.25).
Differences were most pronounced in formula-fed infants.
Taxa-level associations were examined using MaAsLin2 with centered log-ratio normalization, adjusting for relevant perinatal and dietary covariates.
Results
At 1 year, formula-fed infants who received homemade foods had both higher microbial diversity and lower Shannon diversity compared with those receiving commercial foods.
Higher microbial diversity (p = 0.028) was observed in formula-fed infants who received homemade foods.
Lower Shannon diversity (p = 0.041) was observed in the same group compared with commercially-fed formula-fed infants.
These opposing findings suggest shifts in both community richness and evenness.
Stool samples at 1 year were profiled using 16S rRNA sequencing.
Results
No significant differences in gut microbiome diversity and composition were observed among infants receiving human milk or those fully weaned.
No significant differences were found in the human milk or fully weaned groups (q > 0.25).
Effect modification by milk feeding type (human milk, formula, combination, or weaned) at 6 months and 1 year was examined.
Benjamini-Hochberg correction was applied (p < 0.05; q < 0.25).
The authors interpret this as human milk potentially buffering against dietary choices.
Discussion
Human milk may buffer the infant gut microbiome against the effects of complementary food source, while formula-fed infants show heightened sensitivity to solid food source.
No significant microbiome differences by solid food source were observed in human milk-fed infants.
Significant taxa-level and diversity differences by solid food source were observed specifically in formula-fed infants.
The authors suggest this finding informs precision nutrition in early life.
This is described as the first examination of how solid food source (homemade, commercial, or mixed) relates to infant gut microbiome diversity and composition.