The basics of gut health

Infants establish their gut microbiota at birth and through the first three years of life. Babies are almost completely sterile at birth, but immediately thereafter bacteria start to colonise their mouth, their skin, their gastrointestinal tract and every other part of their body. 

The first and most important factor affecting a baby’s microbiota is how they are born. Babies born vaginally acquire bacteria directly from their mothers as they pass through the birth canal. Whereas babies born via caesarean section primarily pick up bacteria from their mothers’ skin and the hospital environment, and they tend to have less beneficial bacteria overall in the first important days and weeks of life. 

After birth, breastfeeding, bottle-feeding with expressed breastmilk, and/or formula-feeding are the second major factor affecting the baby’s microbiota. Breastfed babies have an abundance of bifidobacteria which consume oligosaccharides - special sugars that are found in breast milk and that can only be digested with the help of bifidobacteria. Other beneficial bacteria such as lactobacilli are passed on from mother to baby during breastfeeding. 

The amount and diversity of bacteria continue to increase until the age of three. After the age of three, the child’s microbiota is more stable and largely resembles the composition of an adult’s.

But how exactly?

You may have heard that 80% of your immune system is located in your gut. In fact, your gut, or gastrointestinal tract actually starts in your mouth and extends all the way through your oesophagus, to your stomach and small and large intestines. It is nine metres long and thanks to its 800-900 folds, it would cover half a tennis court if you laid it out flat. This makes your gut by far the largest contact surface your body has with the outside world and explains the importance your gut has for your immune system. 

The gut microbiome fulfils the dual roles of gatekeeper and personal trainer of the immune system, contributing to the mucus barrier that keeps pathogens out and teaches the immune system’s T-cells to recognise and destroy harmful entities. A balanced microbiota with enough good bacteria is important for a well-functioning immune system. The good bacteria educate the immune system and prepare it to fend off unwelcome invaders like bad bacteria and toxins.