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The introduction of solid foods is an important dietary event during infancy that causes profound shifts in the gut microbial composition towards a more adult-like state. Infant gut bacterial dynamics, especially in relation to nutritional intake remain understudied. Over 2 weeks surrounding the time of solid food introduction, the day-to-day dynamics in the gut microbiomes of 24 healthy, full-term infants from the Baby, Food & Mi and LucKi-Gut cohort studies were investigated in relation to their dietary intake. Microbial richness (observed species) and diversity (Shannon index) increased over time and were positively associated with dietary diversity. Microbial community structure (Bray–Curtis dissimilarity) was determined predominantly by individual and age (days). The extent of change in community structure in the introductory period was negatively associated with daily dietary diversity. High daily dietary diversity stabilized the gut microbiome. Bifidobacterial taxa were positively associated, while taxa of the genus Veillonella, that may be the same species, were negatively associated with dietary diversity in both cohorts. This study furthers our understanding of the impact of solid food introduction on gut microbiome development in early life. Dietary diversity seems to have the greatest impact on the gut microbiome as solids are introduced.

ABSTRACT Initial colonisation of the infant gut is robustly influenced by regular ingestion of human milk, a substance that contains microbes, microbial metabolites, immune proteins and oligosaccharides. Numerous factors have been identified as potential determinants of the human milk and infant gut microbiota, including maternal diet; however, there is limited data on the influence of maternal diet during lactation on either of these. Here, we review the processes thought to contribute to human milk and infant gut bacterial colonisation and provide a basis for considering the role of maternal dietary patterns during lactation in shaping infant gut microbial composition and function. Although only one observational study has directly investigated the influence of maternal diet during lactation on the infant gut microbiome, data from animal studies suggests that modulation of the maternal gut microbiota, via diet or probiotics, may influence the mammary or milk microbiota. Additionally, evidence from human studies suggests that the maternal diet during pregnancy may affect the gut microbiota of the breastfed infant. Together, there is a plausible hypothesis that maternal diet during lactation may influence the infant gut microbiota. If substantiated in further studies, this may present a potential window of opportunity for modulating the infant gut microbiome in early life. Maternal diet during the lactation period likely has direct and indirect impacts on the infant gut microbiome, via modulations to the milk microbiota and other milk components.

Background The infant intestinal microbiome plays an important role in metabolism and immune development with impacts on lifelong health. The linkage between the taxonomic composition of the microbiome and its metabolic phenotype is undefined and complicated by redundancies in the taxon-function relationship within microbial communities. To inform a more mechanistic understanding of the relationship between the microbiome and health, we performed an integrative statistical and machine learning-based analysis of microbe taxonomic structure and metabolic function in order to characterize the taxa-function relationship in early life. Results Stool samples collected from infants enrolled in the New Hampshire Birth Cohort Study (NHBCS) at approximately 6-weeks ( n  = 158) and 12-months ( n  = 282) of age were profiled using targeted and untargeted nuclear magnetic resonance (NMR) spectroscopy as well as DNA sequencing of the V4-V5 hypervariable region from the bacterial 16S rRNA gene. There was significant inter-omic concordance based on Procrustes analysis (6 weeks: p  = 0.056; 12 months: p  = 0.001), however this association was no longer significant when accounting for phylogenetic relationships using generalized UniFrac distance metric (6 weeks: p  = 0.376; 12 months: p  = 0.069). Sparse canonical correlation analysis showed significant correlation, as well as identifying sets of microbe/metabolites driving microbiome-metabolome relatedness. Performance of machine learning models varied across different metabolites, with support vector machines (radial basis function kernel) being the consistently top ranked model. However, predictive R 2 values demonstrated poor predictive performance across all models assessed (avg: − 5.06% -- 6 weeks; − 3.7% -- 12 months). Conversely, the Spearman correlation metric was higher (avg: 0.344–6 weeks; 0.265–12 months). This demonstrated that taxonomic relative abundance was not predictive of metabolite concentrations. Conclusions Our results suggest a degree of overall association between taxonomic profiles and metabolite concentrations. However, lack of predictive capacity for stool metabolic signatures reflects, in part, the possible role of functional redundancy in defining the taxa-function relationship in early life as well as the bidirectional nature of the microbiome-metabolome association. Our results provide evidence in favor of a multi-omic approach for microbiome studies, especially those focused on health outcomes.

This study provides the first comprehensive analysis of gut microbiome development in Icelandic children, covering the time from before the introduction of solid foods to 5 years of age. Although the overall developmental patterns of the gut microbiome in Icelandic children were similar to what has been seen in other studies, interesting differences were observed, such as a higher abundance of Blautia at an earlier age compared to other study populations. Higher alpha diversity in archaeal-positive samples, both in mothers and in children at the ages of 2 and 5, compared with archaeal-negative samples seen in the present study, is worth further investigation. Additionally, the study suggests a potential role of maternal and perinatal factors, particularly GDM, which was not evident until the age of 5 years, emphasizing the necessity of long-term studies.

While it is widely recognized that nutrition during pregnancy and lactation can affect the microbiome of breast milk as well as the formation of the infant gut microbiome, we are only just beginning to understand the extent to which maternal diet impacts these microbiomes. Given the importance of the microbiome for infant health, we conducted a comprehensive review of the published literature to explore the current scope of knowledge regarding associations between maternal diet and the breast milk and infant gut microbiomes. Papers included in this review assessed either diet during lactation or pregnancy, and the milk and/or infant gut microbiome. Sources included cohort studies, randomized clinical trials, one case-control study, and one crossover study. From an initial review of 808 abstracts, we identified 19 reports for a full analysis. Only two studies assessed the effects of maternal diet on both milk and infant microbiomes. Although the reviewed literature supports the importance of a varied, nutrient-dense maternal diet in the formation of the infant’s gut microbiome, several studies found factors other than maternal diet to have a greater impact on the infant microbiome.

This study is aimed at exploring the relationship between maternal weight categories, including pre-pregnancy body mass index (P-BMI) and gestational weight gain (GWG), and the composition of the infant gut microbiome in the early days of life. We recruited 71 mother-infant pairs from Kangwon National University Hospital and Bundang CHA Hospital, collecting meconium samples from the infants within the first 5 days postpartum. Using 16S ribosomal RNA gene sequencing (V3-V4 region), this study assessed microbial diversity and the relative abundance of specific bacterial taxa in these initial stool samples. Participants were categorized into groups based on maternal P-BMI and GWG, enabling a comprehensive comparison of the microbiota composition in the infants' meconium across different maternal weight metrics. Our analysis identified significant variations in the infant gut microbiome correlated with maternal weight categories. Key findings include a differential abundance of genera such as Sphingobacteriaceae, Bacillaceae, Cytophagaceae, and Alteromonadaceae across maternal P-BMI groups, whereas Moraxellaceae and Rhodospirillaceae varied across GWG groups. In the P-BMI category, infants born to overweight mothers demonstrated a higher abundance of Pseudopedobacter, and a lower abundance of Citrobacter and Lachnospira, while infants in the underweight group showed a higher abundance of Lachnospira and Weissella. In the normal weight group, Citrobacter and Pseudopedobacter were more abundant. Within the GWG category, infants in the inadequate group showed a higher abundance of Klebsiella, whereas the normal group showed a higher abundance of Holdemania. The composition of the infant gut microbiome in the early postnatal period is significantly influenced by maternal weight categories. Understanding the role of maternal weight in shaping early microbial colonization may provide insights into developing strategies to optimize infant health outcomes through targeted interventions before and during pregnancy.

Over the past decade, extensive research has revealed strong links between the gut microbiome and the brain, at least in adults or those with neuropsychiatric disorders. This study explores how these associations emerge in early development using a longitudinal sample of 194 infants with repeated microbiome metabolism and electroencephalography (EEG) measures during the critical early period of visual cortex neuroplasticity. We examined microbial genes encoding enzymes for neuroactive compounds (e.g., GABA, glutamate, tryptophan, and short-chain fatty acids) and their association with the visual-evoked potential (VEP). Genes from 4-month stool samples strongly correlated with VEP features between 9 and 14 months, suggesting that early microbial metabolism influences later visual neurodevelopment. These prospective associations were more numerous than the concurrent ones. Our findings suggest that early gut microbiome metabolic potential plays a crucial role in shaping neural plasticity and visual neurodevelopment.

Inter-subject variability in human milk microbiome is well known; however, its origins and possible relationship to the mother’s diet are still debated. We investigated associations between maternal nutrition, milk fatty acids composition and microbiomes in mother–infant dyads. Breast milk and infant fecal samples were collected across three time points (one week, one month and three months postpartum) from 22 mother–infant pairs. Food frequency questionnaires for the months of pregnancy and three months postpartum were collected. Milk fatty acids were analyzed by GC–MS and the microbiome in breast milk and infant feces was determined by 16S rRNA sequencing. Statistical interactions were computed using Spearman’s method and corrected for multiple comparisons. We found significant negative correlation between Streptococcus relative abundance in maternal milk and intake of unsaturated fatty acids and folic acid at one month postpartum. At three months postpartum, vitamin B-12 consumption was significantly associated with a single operational taxonomic unit belonging to Streptococcus. Comparison between milk microbiome and lipid composition showed, one-month postpartum, significant negative correlation between Streptococcus relative abundance and the abundance of oleic acid. Additional correlations were detected between Staphylococcus hominis and two medium-chain saturated fatty acids. Our results reinforce the hypothesis that maternal nutrition may affect milk microbiome.

Background The infant gut is rapidly colonized by microorganisms soon after birth, and the composition of the microbiota is dynamic in the first year of life. Although a stable microbiome may not be established until 1 to 3 years after birth, the infant gut microbiota appears to be an important predictor of health outcomes in later life. Methods We obtained stool at one year of age from 173 white Caucasian and 182 South Asian infants from two Canadian birth cohorts to gain insight into how maternal and early infancy exposures influence the development of the gut microbiota. We investigated whether the infant gut microbiota differed by ethnicity (referring to groups of people who have certain racial, cultural, religious, or other traits in common) and by breastfeeding status, while accounting for variations in maternal and infant exposures (such as maternal antibiotic use, gestational diabetes, vegetarianism, infant milk diet, time of introduction of solid food, infant birth weight, and weight gain in the first year). Results We demonstrate that ethnicity and infant feeding practices independently influence the infant gut microbiome at 1 year, and that ethnic differences can be mapped to alpha diversity as well as a higher abundance of lactic acid bacteria in South Asians and a higher abundance of genera within the order Clostridiales in white Caucasians. Conclusions The infant gut microbiome is influenced by ethnicity and breastfeeding in the first year of life. Ethnic differences in the gut microbiome may reflect maternal/infant dietary differences and whether these differences are associated with future cardiometabolic outcomes can only be determined after prospective follow-up.

This study found that supplementing exclusively breastfed infants with a probiotic, Bifidobacterium infantis EVC001, between 2 and 4 months of age can successfully restore beneficial bacteria in their gut, even after the newborn period. Although previous research showed this effect in newborns, this is the first study to demonstrate that older infants, whose gut microbiomes are typically more stable, can still benefit. The probiotic was effective at all tested doses, with higher levels of B. infantis and overall Bifidobacteriaceae in infants' stool during and even 1 month after supplementation. This study demonstrates that B. infantis can take hold in the gut and potentially improve gut health in older breastfed babies, offering a promising approach to support infant health in settings where beneficial gut bacteria are often missing. This study was registered at clinicaltrials.gov as NCT03476447 .