Infant Gut Microbiome: A Longitudinal Analysis of Relationships With Feeding Practices, and Behavioural Development in Early Life

Abstract

Background: Previous research has established that there is an association between the composition and diversity of the gut microbiota (GM) and human behaviour. Current literature also highlights the links between dietary intake and behaviour. However, to date there is a paucity of literature investigating the complex relationship between all three aspects across early development. Aims: This thesis aimed to i) investigate changes in diversity and composition of the GM during GM maturation, ii) examine how this is related to temperament and behavioural development throughout early childhood, and iii) explore how this relationship can be influenced by diet. Methods: A systematic review was conducted investigating the influence of GM upon temperament during early childhood. Secondly, 324 participants recruited to the microbiota sub-cohort of the Barwon Infant Study (BIS), which focused on the role of specific environmental factors in early life development, provided faecal samples analysed using 16S rRNA illumine MiSeq to extract Amplicon Sequence Variant (ASV), and dietary information at 1-, 6-, and 12-months, and child behaviour was measured at 4-years. Results: It was established that temperament during early childhood and behaviour measured at 4-years is significantly associated with GM composition and diversity. Furthermore, diet characterised by exclusivity of breastfeeding at 1-month of age, and by solid foods introduced at 6- and 12-months, was a significant moderator of the relationship between GM and behaviour measured at 4-years. Discussion: This thesis has established a relationship between GM, temperament, and behaviour during early childhood. Furthermore, diet is established as a significant modifying factor of the relationship between GM and behaviour. Future research would benefit from using whole genome sequencing to investigate functional and taxonomic composition, addressing the issue of sample sizes, and improved study design by using concurrent GM, diet, and behavioural measures.