Writing in the journal Frontiers in Nutrition, researchers from the United States explored the effect of maternal probiotic supplementation on infant neurodevelopment, investigating various factors considered crucial to the function of the microbiome-gut-brain axis (MGBA).
"Overall, we argue that this study adds to the growing literature regarding maternal probiotic use to optimize infant outcomes," they wrote. "These preliminary data are important in that they have provided additional hypotheses that can be used to design future studies aiming to develop early probiotic supplementation strategies to optimize infant neurodevelopmental outcomes."
Infant gut microbiome
The infant gut microbiome is influenced by factors like maternal microbiomes, birth mode and diet. Research increasingly focuses on promoting healthy microbiomes during infancy to improve long-term health outcomes, especially in infants at risk for microbiome disruption.
Probiotics have been linked to improved pregnancy outcomes and metabolic health in pregnant women, while in infants, they are associated with better gut health, immunity and reduced risks of certain diseases.
Some animal studies have shown that the gut microbiome can influence brain function through the MGBA, especially during early development, however, findings have excluded human research.
Study details
The pilot observational study reported findings from a subset of exclusively breastfeeding mother-infant pairs recruited as part of the Mothers and Infants Linked for Healthy Growth (MILk) study, a multi-site study conducted in Oklahoma and Minnesota. The mothers included in the study had delivered full-term and most vaginally (83%).
About half of the women experienced optimal or excess gestational weight gain, and maternal antibiotic use was reported at various time points (23% prenatal and 48% postnatal). Only a small percentage of infants received probiotics (2% to 4%).
Clinical data were collected from medical records and questionnaires at one and six months, with maternal and infant antibiotic exposure, probiotic use and diet quality recorded. Probiotic exposure was categorized into groups based on timing (prenatal, postnatal or both). Breast milk and fecal samples were collected at one and six months.
Inflammatory markers like C-reactive protein (CRP) and interleukin-6 (IL-6) were quantified in breast milk, and DNA from breast milk and infant feces was isolated for microbiome sequencing.
Results showed that mothers who took probiotics had significantly lower levels of CRP and IL-6 in their breast milk at one month postpartum, particularly if they took probiotics prenatally.
Infants whose mothers took probiotics (especially prenatally) had significant differences in their fecal microbiome composition, with higher levels of Lactobacillus and Bifidobacteria at one month. This pattern persisted at six months for infants with recent postnatal maternal probiotic exposure.
Additionally, at six months, infants whose mothers had recent postnatal probiotic exposure showed differences in brain activity, indicating potential improvements in memory function. This group reportedly also had lower breast milk IL-6 levels and distinct fecal microbiome profiles.
The study also highlighted the presence of Lactobacillus and Bifidobacteria in the infant gut, which are linked to improved health outcomes like reduced inflammation, better gut health and enhanced cognitive function.
In particular, six-month-old infants exposed to probiotics showed greater memory skills, suggesting that probiotics may influence brain circuits related to memory and learning.
However, the study found that there was no significant difference in breast milk microbiome composition based on probiotic intervention.
As limitations, the researchers noted the study's observational design, inconsistent probiotic exposure and a relatively small sample size and emphasized the need for controlled clinical trials to confirm these findings.
Does breast milk bacteria colonize an infant’s gut?
During the recent Yakut Symposium held in Amsterdam, Professor Christine Edwards presented evidence to suggest research is lacking on whether the breast milk bacteria can colonize an infant's gut, referencing a recent systematic review that cast doubt on this.
Out of 88 full texts, only 15 studies met the criteria for proper methodologies, such as sample handling and bacterial analysis, and evaluated the transfer of bacteria from breast milk to the infant's gut.
Some studies reported bacterial transfer from the infant to breast milk, but overall, there was little strong evidence supporting the idea that breastmilk microbiota significantly impacts infant gut colonization.
Different factors influence breast milk microbiota, however, there remains limited evidence on whether this microbiota leads to gut colonization in infants, and some studies even suggest reverse bacterial transfer from the infant's mouth to the breast.
“Bacteria in breast milk might not necessarily establish long-term colonies in infants, and moreover, research shows that skin and oral microbiota might play a larger role,” she said.
Professor Edwards explained that proving bacterial transfer is challenging due to methodological limitations, such as the lack of strain-specific tracking from breast milk to infant feces.
She concluded that further research with standardized methods and detailed strain-level analysis is required to understand these interactions fully.
Journal: Frontiers in Nutrition
“Maternal oral probiotic use is associated with decreased breastmilk inflammatory markers, infant fecal microbiome variation, and altered recognition memory responses in infants—a pilot observational study.”
doi: 10.3389/fnut.2024.1456111
Authors: Gonia, S. et al.