Associations between Dietary Sugar and Fiber with Infant Gut Microbiome Colonization at 6 Mo of Age

Background: The taxonomic composition of the gut microbiome undergoes rapid development during the first 2-3 y of life. Poor diet during complementary feeding has been associated with alterations in infant growth and compromised bone, immune system, and neurodevelopment, but how it may affect gut microbial composition is unknown. Objectives: This cross-sectional study aimed to examine the associations between early-life nutrition and the developing infant gut microbiota at 6 mo of age. Methods: Latino mother-infant pairs from the Mother's Milk Study (n = 105) were included. Infant gut microbiota and dietary intake were analyzed at 6 mo of age using 16S ribosomal RNA amplicon sequencing and 24-h dietary recalls, respectively. Poisson generalized linear regression analysis was performed to examine associations between dietary nutrients and microbial community abundance while adjusting for infants' mode of delivery, antibiotics, infant feeding type, time of introduction of solid foods, energy intake, and body weight. A P value of <0.05 was used to determine the statistical significance in the study. Results: Infants with higher consumption of total sugar exhibited a lower relative abundance of the genera Bacteroides (beta = -0.01; 95% CI: -0.02, -0.00; P = 0.03) and genus Clostridium belonging to the Lachnospiraceae family (beta = -0.02; 95% CI: -0.03, -0.00; P = 0.01). In addition, a higher intake of free sugar (which excludes sugar from milk, dairy, and whole fruit) was associated with several bacteria at the genus level, including Parabacteroides genus (beta = 0.03; 95% CI: 0.01, 0.05; P = 0.001). Total insoluble fiber intake was associated with favorable bacteria at the genus level such as Faecalibacterium (beta = 0.28; 95% CI: 0.03, 0.52; P = 0.02) and Coprococcus (beta = 0.28; 95% CI: 0.02, 0.52; P = 0.03). Conclusion: These findings demonstrate that early-life dietary intake at 6 mo impacts the developing gut microbiome associated with the presence of both unfavorable gut microbes and dietary fiber-associated commensal microbes.