LAUSR

Objectives Clinical recommendations for optimal timing of introduction to solid foods vary, but earlier introduction has been associated with childhood overweight and obesity (OWOB). The gut microbiota and short chain fatty acids (SCFAs) they produce are postulated to modify this relationship. Our objective was to determine if introduction to solid foods at or before 3 months is associated with differential abundance of gut microbiota, SCFAs, and OWOB at 3 and 12 months of age. Methods Stool was collected from a subset of infants in the prospective Nurture birth cohort at 3 months (n = 68 infants) and 12 months (n = 50) of age. We conducted paired-end sequencing of the 16S rRNA V4 region using an Illumina MiSeq and quantified SCFAs using gas chromatography. We defined early introduction of solids as ≤3 months of age. We calculated weight-for-length z scores (WFL-z) using the WHO's age- and sex-specific standards. OWOB was defined as a weight-for-length z score > 1 SD. We assessed differential abundance of taxa using beta-binomial regression, considering a two-sided FDR corrected p-value < 0.05 significant. We fit logistic and linear regression models to assess OWOB, WFL-z, and SCFA abundance. We adjusted for breastfeeding and delivery method. Results Mother-infant dyads in the early solids group (n = 20) had similar baseline characteristics to those in the late solids (n = 47). After adjustment, there were 8 differentially abundant microbial amplicon sequence variants (ASVs) by timing of introduction to solids at 3 months and 10 ASVs at 12 months (Figure). Infants introduced to early solids had non-significant WFL-z at 12 months of age (B = 0.27, 95% CI: -0.38, 0.91) and odds for OWOB (OR = 1.4, 95% CI: -0.94, 1.7). Infants introduced to solids early had significantly higher concentrations of (log + 1) butyrate (B = 0.74, 95% CI: 0.39, 1.09, P < 0.001) at 12 months vs. those introduced later, but not at 3 months. No other SCFAs were significantly different by timing of solids. Conclusions Our findings are consistent with the hypothesis that early infant introduction to solid foods is associated with OWOB, along with altered gut microbiota composition and butyrate production. Further research is needed to determine if the changes in the microbiota modify or mediate the associations of early solids with child obesity. Funding Sources This study was supported, in part, by a grant from the National Institutes of Health. Supporting Tables Images and/or Graphs