How birth and your baby’s environment can influence lifelong gut health

New research shows how birthing methods and natural environments impact infant gut health, highlighting the critical role of time outdoors in shaping healthy gut diversity as babies grow.

Study: The role of early life factors and green living environment in the development of gut microbiota in infancy: Population-based cohort study. Image source: Design_Cells / Shutterstock

In a study recently published in the journal Environment InternationalResearchers in Finland analyzed the influence of early life factors on shaping the community composition of intestinal flora in infancy. High-throughput sequencing along with multiple measures of residential greenness demonstrated the significant role of green environments in determining infant gut diversity, particularly in early infancy.

However, the study found that this connection was limited to alpha diversity, which measures species richness and diversity, rather than the specific microbial community composition. Surprisingly, no such association between residential proximity to green environments and gut flora populations was found in late infancy. Instead, gut microbial communities were more influenced by time spent outdoors. In particular, birth mode and the presence of siblings have been shown to have a much greater impact on infant diversity.

These findings help inform pediatricians and (prospective) parents about early life factors that, although seemingly unrelated, can have profound and potentially lifelong effects on their children’s health.

background

The recent global increase in the prevalence of chronic non-communicable diseases is attributed in part to the influence of environmental factors and behavioral choices on gut microbial health. There is a growing body of evidence linking the benefits of “healthy” dietary habits (e.g. Mediterranean diet) to gut diversity and improvements in community composition.

While improvements in diet and other health behaviors can have a positive impact on current gut health, research suggests that the foundations of lifelong gut health are laid at birth. The initial intestinal flora inoculum, derived primarily from the placental connection of infants to their mothers, may undergo significant environmental variation during early to late infancy, laying the foundation for future intestinal microbial health.

Unfortunately, most conventional intestinal flora studies have been performed on adults. The few gut microbial studies focused on infants suffer from the almost ubiquitous drawback of focusing on a single factor (e.g., mode of birth or presence of pets) rather than the holistic and potentially multifaceted effects of multiple influences operating simultaneously.

About the study

The present study had three main objectives: first, to examine the maturation of the intestinal flora in infancy; second, to identify the environmental influences that alter the microbial community composition in early and late infancy; and third, to examine associations between residential greenness metrics and infant gut microbial health.

Study data come from Steps to Healthy Development of Children (STEPS), a longitudinal cohort of Finnish and Swedish mothers who gave birth to babies between 2008 and 2010 in a specific Finnish hospital (Hospital District of Southwest Finland). A subset of this cohort of 14,946 infants, referred to as the “intensive follow-up group,” was included as participants in the present study. Participants were divided into “early” (0.5–5 months) and “late” (11–17 months) subcohorts.

Data collection included parent/guardian-provided socioeconomic, demographic, and medical records and 1,823 stool samples for sequence-based characterization of infant gut microbiota. Qiagen reagents and protocols were used to extract DNA from stool samples and the Illumina MiSeq v3 platform was used for 16S metagenome sequencing. The resulting measurements were processed (cleaned and assembled), after which the child-specific microbial community composition was determined using the taxonomic database Silva 138.1 prokaryotic SSU.

Additional early life factor data (birth type, gestational age at birth, breastfeeding status, birth weight) were obtained from medical health records and parent-completed follow-up questionnaires. Population Registry Center data for each household was used along with Geographic Information System (GIS) data to measure residential vegetation indices – VCDI (an index of vegetation classes) and NI (an index of human land use).

Study results

The included infant cohort included 892 early and 931 late infants, of which 52% were boys and 46% had older siblings. Over half of the participants’ households were located in non-natural (urban) areas. However, vegetation cover was moderate or high in most cases. Data on mode of birth showed that 11% were delivered by cesarean section and about 10% were given antibiotics shortly after delivery in the maternity hospital.

Analyzes of the variables affecting infant gut community composition revealed that age is an important factor. Comparisons between early and late cohorts revealed that the former was dominated by Actinobacteriota (54%) and was significantly more variable than the latter (Firmicutes). [59 %]), highlighting that age alone was responsible for explaining about 9% of the cohort-wide variation. Previous research in this area has rarely included child-specific age subcohorts and has often considered 0–3 years as a single age category. These results suggest that future research needs to consider age subclasses in child-centered study models.

The analysis showed that birth mode, the presence of siblings and the mother’s age had the strongest influence on microbial accumulations in the gut of infants. While family income, breastfeeding status, perinatal antibiotic exposure, and time outdoors were significantly associated with gut microbiota, their associations were comparatively weaker.

According to the study’s adjusted models, delivery mode (cesarean section/vaginal) accounted for 0.5% of the variation in gut microbiota community composition in early infancy and gradually decreased to 0.3% in late infancy. The presence of siblings became a more important factor in late infancy, explaining 0.7% of the variability compared to 0.5% in early infancy. Overall, siblings in both age groups were associated with an increase in gut microbial diversity.

Surprisingly, although residential greening established a connection between green environments and gut flora, this interaction was mainly limited to early infancy and only included alpha diversity measures, such as species richness. In contrast, outdoor exposure was a more important predictor of microbiota composition in late infancy.

Conclusions

The present study identifies the factors that determine gut microbial diversity in early and late infancy and measures their relative effects. It identifies birth mode, the presence of older siblings and maternal age as the most influential factors and highlights their role in shaping the presence and relative abundance of different bacterial populations. In addition, family income, breastfeeding status, perinatal antibiotic exposure, and time outdoors were found to have weaker influences on gut microbiota.

“Furthermore, our analysis revealed that the associations between green home environment and gut microbiota alpha diversity were more pronounced in early infancy than in late infancy, indicating a critical period of susceptibility to environmental influences on gut microbiota diversity,” they concluded Authors. This highlights the importance of a holistic understanding of early environmental and family influences on children’s health.