For the body to function at its best, it needs thriving colonies of bacteria that perform important biological processes. Sometimes they help to support our natural defences, others might help us produce certain nutrients that we need. We have bacterial colonies in many areas, including the skin, our mouth and our airways – but the biggest collection we have is in the gut.

Bacterial cells are extremely small, around 1000 times smaller than the tip of a pencil. Because they can’t be seen with the naked eye, it can be difficult to get a true sense of scale when it comes to bacteria. Your gut microbiome is a great example! 

So, what is the gut microbiome?

When we think about the gut, we often picture a series of organs that digests food and absorbs nutrients. However, it doesn’t work alone, it needs the gut microbiome to help out. The gut microbiome is the complex ecosystem of microscopic living things that exist throughout the gut, but particularly in a small section of the large intestine known as the cecum. Your microbiome includes bacteria, viruses and other microorganisms.

There are up to an astonishing 100 trillion bacterial cells in your gut microbiome. To help demonstrate the sheer numbers, there is an estimated ratio of 1:1-  1:3 ratio of human to bacterial cells[1] in the body, which means that we often hold more bacterial cells than human ones!

In the trillions of bacteria that operate in our gut, there are also many different kinds. It’s thought that the human gut microbiome can hold up to 1000 different species of bacteria and each one has a role to play. Some of these are particularly helpful to us. They help us to digest food, but certain kinds also help us to absorb and produce certain vitamins, nutrients or chemicals that our bodies need, such as short chain fatty acids. Other kinds might help the body fight off certain pathogens or diseases. We call these bacteria the ‘good bacteria’.

There are other kinds that are less useful to us, and other types that take up valuable space that could be better used by good bacteria. These are the kinds we know as ‘bad bacteria’, or benign. This category can also include pathogens, types of bacteria that can cause illness or disease.

Does our microbiome change?

Absolutely, our microbiome isn’t fixed! The combination of bacteria in your gut, and the various levels of each type, can vary from person to person. In fact, your gut microbiome is as unique to you as your fingerprint.

We begin developing our gut microbiome at birth – that’s our first big ‘microbial meal’! In fact, how we’re born can even play a part! Babies born vaginally are understood to begin life with a very different set of gut bacteria to those born by caesarean section, who are believed to hold more bacteria from the skin microbiome. 

Again, as we grow, we see changes emerge in our microbiome composition. We see differences in children who are breast fed, versus those fed with formula. Breast milk contains Human Milk Oligosaccharides (HMO), a prebiotic fibre that encourages the growth of certain good bacteria. Because of this, it’s thought that breastfeeding is a good way to set a strong foundation of gut health in infants.

As babies grow, the bacteria that colonise their gut are fed by the fibre and other nutrients that come from solid food they eat.

Why is the gut microbiome important to health?

The bacteria in our body play a lot of important roles, which means our microbiome has to take centre stage. When looking at how best to improve certain aspects such as gastrointestinal health, immune health or sleep patterns, the health of the gut microbiome can be one of the most effective areas to explore.

Studies show that our gut bacteria are linked to our overall health and wellbeing. For example, individuals with certain digestive disorders such as Irritable Bowel Syndrome (IBS), Diabetes and Crohn’s Disease have been found to have altered – and usually less diverse – bacteria profiles. While the precise mechanisms are yet to be identified by science, this confirms that there is a link to be found, and more to be uncovered!

Not only that, our bacteria can also influence our mood and cognition! This happens via the gut-brain axis, where the gut can send signals to the brain and vice versa. If you’ve ever wondered why your emotions such as stress and anxiety seem to be so closely linked to your gut, that could be why.

Plus, this communication with the brain is why your gut bacteria is thought to influence sleep health, too. If you’re struggling to get a good night’s rest, your gut health could hold the key.

It’s a common misconception that our gut bacteria simply help to break down food – they’re actually responsible for a lot more.

Your good gut bacteria can help to:

  • Break down some nutrients into forms that can be more easily absorbed by the body[2]
  • Release certain chemicals that can reduce inflammation[3]
  • Ferment carbohydrates in the large intestine to create by-product nutrients, such as short-chain fatty acids (SFCAs)[4]
  • Strengthen the intestinal wall, supporting the natural protective barrier against pathogens[5]
  • Develop your immune system, by teaching it which pathogens to attack - and which cells to leave alone[6]
  • Regulate hormones and chemicals that are released from the gut[7]
  • Communicate directly with the immune, endocrine, and nervous systems[8]

Our gut microbiome plays a significant role in general health, particularly as there are certain kinds of bacteria that help our bodies to perform at their best. Ideally, we should aim for higher levels of these ‘good bacteria’ to reap the benefits!

Gut health science is continually progressing and expanding the knowledge of the complex relationship between gut health and wider bodily health. It’s thought that the gut microbiome is a significant part of the puzzle – so why not get to know your bacteria better today?



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Many of us are looking to support ‘gut health’, but what does that mean? Well, inside all of us there is a complex eco-system known as the gut. It’s home to trillions of microorganisms, including many different types of bacteria, that are known collectively as the gut microbiome.


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