The human gut microbiota is a complex community of microorganisms Infant diet influences the composition and diversity of the gut microbiota, which may impact neurodevelopmental outcomes. Herein, the mediating role of the infant gut microbiota in the associations between infant diet and infant neurodevelopment and an analysis of the influence of breastfeeding patterns on infant gut microbiota are presented. Participants in the Michigan Archive for Research on Child Health (MARCH), a cohort study in Michigan, provided infant fecal samples at 3 months of age and neurodevelopment information using the Ages and Stages Questionnaire at 9 months of age. 16S rRNA sequencing data was processed through mothur. Microbiota and statistical analyses were conducted using R. In Chapter 2, associations between gut microbiota and neurodevelopmental outcomes are described. Gut microbiota richness (Chao 1) was negatively associated with gross motor scores. However, gut microbial diversity (Shannon index) was positively associated with problem-solving scores. Beta diversity (Bray-Curtis) was associated with fine motor and communication scores. Thus, the gut microbiota was associated with cognitive development. Chapter 3 examined the potential mediating role of early-life gut microbiota in the associations between infant diet and neurodevelopmental outcomes. The gut microbiota was impacted by diet. Breastfeeding and vitamin D supplementation was positively associated with fine motor scores. Infant gut microbial composition, measured by the Bray-Curtis dissimilarity index, mediated the association between infant feeding and fine motor scores. These results suggest the importance of promoting optimal gut health through nutrition to support healthy cognitive development. In Chapter 4 relationships between breastfeeding patterns (breastfed, bottle-fed, and mix- fed), the proportions of breastmilk intake and infant gut microbiota among exclusively breastmilk-fed infants at 3 months of age are described. Infants fed at the breast had a lower abundance of Bifidobacterium but a higher abundance of Enterobacteriaceae compared to bottle- and mixed-fed infants. These microbiotas were then compared to those of infants fed some formula. Though bottle-fed infants were 100% breastmilk fed, they had similar microbiota composition as infants fed with >50% and <50% breastmilk. Thus, breastfeeding patterns influence the gut microbiota of infants. In summary, this work describes relationships among infant diet, breastfeeding patterns, gut microbiota, and neurodevelopment. The work underscores the importance of promoting optimal gut health through infant feeding practices and nutritional interventions, such as vitamin D supplementation, to support neurodevelopment. Notably, this work advances prior work by using infant dietary intake data collected in the week, as well as in the 24 hours, immediately prior to stool collection. Overall, these results contribute to our understanding of the role of gut microbiota in infant development and may inform the development of interventions aimed at promoting healthy gut microbiota and neurodevelopmental outcomes in early life.
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