Intestinal microbiota: if the first years of life are essential, nothing is played at 5 years old

The intestinal microbiota is shaped throughout life. An unbalanced diet can disrupt it and promote the onset of diseases such as type 1 diabetes. However, it is during childhood that it forms and special care must be taken since eating foods that are too fatty sweet can alter it for life. In a new study, Swedish researchers have argued that the gut microbiota largely reaches an adult-like composition by the age of five, but some bacteria that are associated with overall good health are not acquired and reach their abundance. only later in childhood. These results were presented on March 31 in the journal Cell Host & Microbe.

The development of the microbiota still poorly understood

“We hope to highlight that the gut microbiota continues to develop during childhoodsummarized Redrik Bäckhed, lead author of the study, and researcher at the Swedish University of Gothenburg. Our results underscore the possibility that the microbiota is particularly sensitive to perturbations during this early onset, which may have profound effects on health later in life..” Newborn babies acquire bacteria by transmission from the mother and the environment during childbirth. The microbiota is then formed during early childhood. Previous studies have suggested that it begins to stabilize and evolve into an adult-like composition two to three years after birth.

The way in which the microbiota is constituted during childhood remains poorly understood, in particular the way in which the different bacteria are incorporated. “Much emphasis has been placed on the gut microbiome during infancy, which is a very important developmental period for both the gut microbiome and other physiological and biological processes. However, much less is known about the continued development of the gut microbiome after the early years.”, continues Josefine Roswall, o-first author of the article.

The biggest changes between 4 and 12 months

To fill this knowledge gap, the researchers analyzed the microbiota of 471 Swedish children followed from birth to five years. They profiled the microbes present in fecal samples collected at four months, one year, three years and five years. They also compared the children’s microbiota to that of their mothers and to an adult Swedish population.

They observed that the greatest changes in the composition of the microbiota occurred between the ages of four and twelve months. Bacteria common in adults appeared around the time children started eating solid foods. The researchers’ analysis led them to discover that microbial genera follow four main colonization trajectories, increasing in abundance and stabilizing at various times after birth. They were surprised to find that the microbiota of a small number of five-year-olds was mature for their age, while some adults had a less mature microbiota than expected for their age. “We find that many genera of bacteria that dominate the adult gut microbiota are established at three yearssays Lisa Olsson, co-author of the article. However, we identify several less abundant bacterial and archaeological genera that continue to increase until the age of five..” Children whose weight gain was lower than expected between 12 months and 5 years have a more immature gut microbiota at 12 months. Like malnourished children, these children showed reduced abundance of Faecalibacterium, a bacterium that has been linked to metabolic health.

The mode of birth influences the development of the microbiota

The results allowed the researchers to confirm that birth patterns impact the gut microbiota early in life. Caesarean section is associated with lower microbial diversity at four months but this normalized at three years as the gut microbiota continued to mature. In addition, 25 bacterial genera showed different abundances in five-year-old children born with caesarean section compared to those born vaginally.