Evaluating the Relationship between Dietary Intake at the Time Immediately Before and After the Introduction of Solid Foods and the Gut Microbiome in Full-Term Infants: A Longitudinal Study

Abstract

Background: The introduction of solid foods is an important dietary event during infancy and is associated with a time of dramatic shifts in gut microbial composition. The influence of solid food introduction on gut bacterial dynamics remains understudied. Methods: 15 healthy, full-term, vaginally born, and breast-fed infants of the Baby, Food and Mi sub-study of the Baby & Mi Study were investigated. Caregivers were asked to collect daily stool samples and food diaries for 17 days, commencing three days prior to the introduction of solids. Additional stool samples were available up to one year as part of the Baby and Mi study. The exposure of interest, nutritional patterns, was analyzed using food composition output from ESHA’s Food Processor. The number of food items and food groups introduced were used to calculate dietary diversity scores. The outcome of interest, gut bacterial dynamics, was analyzed using RStudio. Results: The mean (SD) age at the introduction of solid foods is 5.5 (0.66) months (n = 15). Over the study period, the proportion of estimated energy intake from solid foods was low (7.5%; SD 6.74%) (n = 14). Alpha diversity increased over time and was highest at 1 year. The gut microbial community influenced by dominant bacterial taxa changed with increasing age. With introduction of solids, individual community composition changed, though to a varying extent. Shannon alpha diversity was directly associated with calories from carbohydrates, particularly daily fiber intake. The infant’s dietary diversity score was directly associated with alpha diversity and was also positively associated with the degree of change occurring in this time period. Conclusion: Fiber intake and the dietary diversity scores had the closest relationships to the gut microbiome’s alpha diversity and community structure in infants at the time of solid food introduction.