What is the Microbiome?

What is the microbiome?

Each of us has around 100,000 billion viable microbes living in our intestines, comprising over 1,000 different species and more than 5,000 strains. These microbes weigh around 1.5 kg in total and are referred to collectively as the microbiome.

95% of the microbiome is in the large intestine, with only around 50g (weight) of the microbiome residing in the small intestine.

When does it form?

The microbiome is established immediately when we are born. At birth the baby acquires his or her microbial bacteria from the environment it is born into. For babies born vaginally, the first colonisation is from their mother’s vaginal, skin and rectal bacteria. For those born via caesarean section, these bacteria come from skin and the hospital environment.

A few hours following birth, a mucosal layer starts to form on the baby’s GI tract to act as a barrier to prevent pathogens from crossing into the gut. This mucosal layer is where the beneficial bacteria colonise, helping to reinforce the barrier and support immunity.

The development of the baby’s microbiome is then influenced by diet. Breast milk contains the mother’s bacteria and prebiotic oligosaccharides, which are the fibres that feed the bacteria and help them to colonise as part of the baby’s microbiome. If the baby is formula fed, he or she will not receive the ‘mammary microbiota’.

When the baby is weaned onto solid foods, the microbiome can be further supported by including fruits and vegetables for prebiotics and plain yoghurt and some fermented foods for probiotic bacteria.

Can it change?

Whilst the basic structure of our microbiome is established by the time we are around 3 years of age, its total composition will change on a daily basis throughout our lives. Bacteria forms around half of the faecal mass we excrete every day and replenishing this bacteria with friendly species depends upon what we eat and drink on a daily basis.

Before refrigeration was invented, we ate lots of fermented and cultured foods, which gave us an ongoing supply of friendly bacteria and help to maintain balance in the microbiome. Today’s diet lacks these foods and probiotic supplements can help feed this balance.