While previous studies have suggested that the microbiota begins to stabilize and evolve toward an adult-like composition two to three years after birth, several bacterial taxa that have been associated with human health are acquired later in childhood and have not reached their adult abundance by five years of age, according to a study published in the journal Cell Host & Microbe.
One factor of particular interest is infants born by cesarean section, a birth mode that results in newborns having less diverse gut bacteria than those delivered naturally. Researchers are especially curious how C-sections may impact children in adult life.
"There has been a lot of focus on the gut microbiome in infancy, which is a very important period of development for both the gut microbiome and other physiological and biological processes," said co-first author Josefine Roswall of Hallands Hospital Halmstad in Sweden. "However, much less is known about the continuing development of the gut microbiome after the first few years."
Researchers analyzed the microbiota from 471 Swedish children followed from birth to 5 years of age, collecting fecal samples at 4 and 12 months and again at 3 and 5 years old. The samples were analyzed using 16S rRNA gene profiling.
The largest changes in microbiota composition occurred between four and twelve months of age.
The authors noted that by following these children through age-specific community types, they observed that children have individual dynamics in the gut microbiota development trajectory.
“We observed age-specific community types at each time point up to 3 years of age, confirming significant development in the gut microbiota during the first years of life. Bacteria associated with a more complex microbiota and common in adults, appeared around the time when the children began to eat solid food,” the authors noted.
Indeed, gut microbiome maturity differs from child to child, with babies delivered via C-section initially having less diverse gut bacteria at four months when compared to infants delivered naturally. However, this normalized over time, with gut bacteria diversity similar in both groups by the age of three. But the authors also observed that 25 genera showed different abundances in five-year-olds born with c-section compared to those born naturally.
Over the five-year period, different microbial genera followed four main colonization trajectories, increasing in abundance and stabilizing at various time points after birth.
One fascinating discovery that the authors pointed out was that in a small number of five-year-old children, their microbiota makeup actually appeared more 'mature' than those of some adults.
A dynamic organ
"Our findings show that the gut microbiota is a dynamic organ, and future studies will have to show whether the early differences can affect the cesarean children later in life," said study leader Fredrik Bäckhed, a professor of molecular medicine at the University of Gothenburg in Sweden.
Bäckhed said the study provides a reference point for the normal establishment and development of the gut microbiota in early childhood.
"Although our data is insufficient to make claims about future metabolic conditions, experimental studies have demonstrated that, if the microbiota is disrupted by antibiotics before weaning, mice develop obesity later in life. Future, larger studies are required to identify potential time windows when the gut microbiota may be particular important for the development of diseases in humans,” said Bäckhed.
Source: Cell Host & Microbe 2021
1931-3128(21)00100-1 , DOI: 10.1016/j.chom.2021.02.021
"Developmental trajectory of the healthy human gut microbiota during the first 5 years of life"
Authors: J. Roswell et al.
Links : https://www.nutraingredients.com/Article/2021/04/06/Children-s-gut-microbiota-mature-along-similar-trajectories-but-at-different-speeds-Study