What is already known
The colonization and early development of the gut microbiota can influence an infant’s health later in life. Most studies have focused on understanding the impact of individual factors such as breastfeeding and mode of delivery on infant gut microbiota composition, but only few analyses compared the effects of different exposures on the microbiota after birth.
What this research adds
Researchers studied the effect of 109 variables on the gut microbiota of 985 Finnish infants. Factors such as maternal health had little effect on the overall composition of the infant gut microbiota, but delivery mode and exposure to antibiotics during delivery were important early in an infant’s life. Other factors such as the presence of siblings in the same household and feeding practices explained a significant proportion of the differences in microbiota composition.
Conclusions
Analyzing how different exposures affect the infant gut microbiota could help researchers identify confounding factors and potential microbiota modulators.
The colonization and early development of the gut microbiota can influence an infant’s health later in life. Now, researchers have revealed some of the key factors that affect the composition of the infant gut microbiota.
The findings, published in The Lancet, suggest that analyzing how different exposures affect the infant gut microbiota could help researchers identify confounding factors and potential microbiota modulators.
“Our results will guide future research in exploring the potential confounders or stratification in the analysis, and to better understand possible external determinants such as early life nutrition at different stages of the gut microbiota development,” the researchers say.
So far, most studies have focused on understanding the impact of individual factors such as breastfeeding and mode of delivery on infant gut microbiota composition. But only few analyses compared the effects of different exposures on the microbiota after birth.
For 43 months, Roosa Jokela at the University of Helsinki and her colleagues studied the effect of more than 100 variables on the gut microbiota of 985 Finnish infants.
Microbial differences
The infants were part of the HELMi cohort, which included 1,055 families living in the metropolitan region of Finland from 2016 to 2018. The researchers collected 8 stool samples at 3, 6 and 12 weeks of life, and at 6, 9, 12, 18, and 24 months. Parents answered questionaries about their infants’ health and lifestyle. The team also gathered information about mode of delivery, antibiotics use during birth and maternal infections during pregnancy.
In addition to the infants’ stool, the researchers analyzed parental samples from 830 families. They then assessed how 109 variables — including lifestyle, diet and health — influenced the composition of the infants’ microbiotas.
Factors such as maternal health had little effect on the overall composition of the infant gut microbiota, but delivery mode and exposure to antibiotics during delivery were important early in an infant’s life. For example, in infants delivered through C-section the abundance of Bacteroides and Parabacteroides was reduced, whereas the levels of Salmonella were increased compared with vaginally delivered infants.
Explaining variance
Other factors such as the presence of siblings in the same household and feeding practices explained a significant proportion of the differences in microbiota composition, the researchers found.
Bacteria such as Parabacteroides, Actinomyces and Salmonella were reduced early in infants who had no siblings, whereas the levels of Lactobacillus, Sutterella and Bifidobacterium were higher in these children compared with those who had one or more siblings.
Infants who weren’t breastfed had lower levels of Lactobacillus and higher levels of Akkermansia, Blautia and Clostridium bacteria at 3 weeks and from 6 to 18 months, the team found.
“In total, up to 19% of the biological microbiota variation in the infant gut could be explained,” the researchers say. “Our results highlight the need to interpret variance partitioning results in the context of each cohort’s characteristics and microbiota processing.”
