The Gut Microbiota Differ in Exclusively Breastfed and Formula-Fed United States Infants and are Associated with Growth Status

Abstract

BackgroundEvidence regarding the effects of infant feeding type (exclusive breastfeeding compared with exclusive formula feeding) on the gut microbiota and how it impacts infant growth status is limited. ObjectivesThe primary objective was to compare gut microbiota by feeding type and characterize the associations between gut microbiota and infant growth status. MethodsStool samples from healthy, full-term infants (4–5 mo-old) who were either exclusively breastfed (BF) or exclusively formula-fed (FF) in Denver, CO, United States were collected, and fecal 16S ribosomal ribonucleic acid gene-based profiling was conducted. Length and weight were measured at the time of stool collection. Length-for-age z-score, weight-for-age z-scores (WAZ), and weight-for-length z-scores were calculated based on the World Health Organization standards. Associations between gut microbial taxa and anthropometric z-scores were assessed by Spearman’s rank correlation test. ResultsA total of 115 infants (BF n = 54; FF n = 61) were included in this study. Feeding type (BF compared with FF) was the most significant tested variable on gut microbiota composition (P < 1 × 10-⁶), followed by mode of delivery and race. Significant differences were observed in α-diversity, β-diversity, and relative abundances of individual taxa between BF and FF. BF infants had lower α-diversity than FF infants. Abundances of Bifidobacterium and Lactobacillus were greater in the breastfeeding group. FF infants had a higher relative abundance of unclassified Ruminococcaceae (P < 0.001), which was associated with a higher WAZ (P < 0.001) and length-for-age z-score (P < 0.01). Lactobacillus was inversely associated with WAZ (P < 0.05). ConclusionsFeeding type is the main driver of gut microbiota differences in young infants. The gut microbiota differences based on feeding type (exclusive breast- or formula feeding) were associated with observed differences in growth status.This trial was registered at clinicaltrials.gov as NCT02142647, NCT01693406, and NCT04137445.