Fascinating gut facts
Here are 20 interesting facts about your gut. Some you may know and some you may not.
- Our gut microbiome contains around 100 trillion bacteria and weighs around 2kg
We now know that there are 10 times as many microbial cells (bacteria) in the human gut as there are cells in the whole human body – totalling around 100 trillion microbes. Whilst estimates vary, the gut microbiome includes as many as 5,000 different species of bacteria and weighs approximately 2 kilograms. The gut contains the highest number and species of bacteria, but the human microbiome is also present on our skin, in our mouths and in the vagina
- The gut microbiome is now considered to be a separate organ in the body
Our gut bacteria are now understood to have distinct metabolic (biochemical) and immune functions and are increasingly considered to be an ‘organ’ in their own right, performing specific functions in the same way as our heart, lungs and brain. Overall, the human microbiome is collectively referred to as the ‘second human genome’ as it is both genetically diverse and has specific functions.
- There are two main areas of research into the microbiome – identifying the strains and working out what they do
Currently, the two major areas of investigation into the human microbiota are:
1. identifying and naming the types and strains of bacteria, classifying them by their ‘taxonomic (species/organism) diversity’
2. understanding more about what these strains ‘do’, using an approach known as functional metagenomics to study the function of each bacteria and the impact they may have on human health.
- The gut microbiome is based in our intestines (not our stomach)
Many people assume that gut bacteria live in the stomach as the word ‘gut’ is commonly used to refer to our stomach and most of us don’t even consider our intestines when we think about our body and its function. The gut microbiome is actually all based in our intestines, as the stomach environment is too acidic for the bacteria to survive. The intestines comprise the small intestine (ileum, jejenum and duodenum) and the large intestine (colon) and 95% of our gut bacteria live and function in our large intestine.
- Around 70% of our immune system is in our gut
Our gastrointestinal system plays a central role in our immune system. It is in constant contact with the external environment and helps to protect the body from toxins and pathogens whilst letting food and good bacteria through into the body.
To support this protection function, the gut wall is lined with mucous, which contains around 70% of the body’s immune cells, known as gut-associated lymphoid tissue (GALT). A healthy gut microbiome supports the development of immune cells and the fine-tuning of immune responses.
- Your gut has a brain of its own – known as the enteric nervous system.
The enteric nervous system (ENS) is part of our overall central nervous system (CNS) and controls the function of the gastrointestinal (GI) tract. It comprises thousands of nerves situated in the walls of the oesophagus, stomach, intestines, pancreas and gallbladder. The ENS has been called the second brain as it can operate independently of the CNS and is thought to be involved in many GI disorders. The gut microbiota is thought to have a role in regulating the ENS.
- We are still investigating what comprises a healthy or an unhealthy microbiome
Our understanding of the microbiome is rapidly expanding as a result of advancements in DNA sequencing methods, metagenomics and other scientific methods. Despite this, we still have a lot to learn about what constitutes a healthy microbiome and how this differs from an ‘unhealthy’ microbiome – what we know today is only a small part of its apparent potential in relation to supporting both health and disease.
- There is increasing evidence that development of the microbiome might begin in-utero
The foetal environment was originally thought to be sterile and the microbiome was thought to begin development as the baby was born, influenced by the type of delivery (vaginal vs C-section) and feeding type (breast vs formula). Evidence is increasingly suggesting that babies are born with low numbers of gut microbiota and bacteria have been found in meconium (baby’s first stool) and in the mother’s placenta.
- The baby’s microbiome is influenced by delivery and feeding type and develops over the first few years of life
The composition of the neonatal microbiome is influenced by delivery type (vaginal vs C-section) and feeding type (breast vs formula) and continues to develop until around three years of age when it stabilizes and resembles that of an adult. Other factors that have an impact on the bacterial profile of the microbiome during this time include the diet onto which the child is weaned and the use of antibiotics.
- A normal human microbiome contains both good and bad bacteria strains – the bacterial balance is key
A healthy person’s normal gut microbiota includes strains such as Escherichia coli (E. coli) and Enterococci, which are generally disease-causing, pathogenic species.
A balanced gut bacteria is often considered to have a balance of around 85% beneficial to 15% undesirable, although it is currently unclear if bacteria fall into clear ‘good’ or ‘bad’ categories or if some bacteria have both benefits and drawbacks.
- Our gut bacteria have a number of different functions – from producing energy to manufacturing vitamins
Different species of gut bacteria have different roles. Some gut bacteria are involved in metabolising energy from the food we eat, others help to manufacture neurotransmitters, enzymes and vitamins and some play a role in digestion, immunity and/or metabolic function.
- The composition of our gut microbiome will vary depending on where we live in the world
The gut microbiome of people living in Westernized, industrialized countries is generally less diverse and dominated by different bacterial species than that of people from rural, less developed populations.
Diet plays a role in defining this variety and diversity, but people living in a more natural environment, where they are exposed to soil, animals and other naturally-occurring bacteria generally carry a wider variety of bacteria in their microbiome
Children raised in homes with pets have been shown to have a lower risk of allergic diseases and evidence suggests a link with gut microbiome patterns.
- What we eat seems to be the most powerful influencer on the gut microbiome
As well as eating foods that contain friendly bacteria, such as sauerkraut and kefir, fibre is one of the key nutrients for supporting the growth of the gut bacteria – starch and soluble and insoluble fibre provide food for the bacteria to help them ferment, propagate and colonise the gut. Conversely, the emulsifiers, preservatives and additives in processed foods can potentially damage the gut lining, leading to inflammation in the digestive tract and a condition known as ‘leaky gut’, ultimately leading to digestive and other health issues.
- Stress, obesity and other lifestyle factors have been shown to influence the composition of the microbiome
Obese individuals have been shown to have different gut bacteria to lean people and there are also variations in those with atherosclerosis, diabetes, and metabolic syndrome. Stress has also been shown to change the composition of the microbiota and altered gut bacteria has been shown to contribute to stress and anxiety.
The significance and mechanisms of these differences are not yet understood, but supporting the gut bacteria is thought to be key to helping manage some of these conditions.
- Gut dysbiosis is the name given to an imbalance in the gut bacteria – when the levels of ‘bad’ bacteria increase
An imbalanced microbiome is known as gut dysbiosis – an overgrowth of the more unfriendly types of bacteria that can lead to discomfort and other gastrointestinal symptoms, such as gas and bloating. A balanced microbiome is said to include a ratio of around 85% good:15% bad bacteria – if this ratio changes in favour of the pathogenic types of bacteria, it is thought to lead to gut symptoms.
- The diversity (variation) in our gut bacteria seems to be key to supporting health
Diverse gut microbiota is currently thought to be healthier than one that contains only a few different strains. This variation in bacterial strains is influenced by a diet that contains lots of different plants, vegetables and fruit. Those who have a limited diet are likely to have a limited range of bacterial strains in their microbiota and one recommendation is to aim to eat at least 25 different plant-based foods, vegetables or fruits every week. Ageing is associated with decreasing microbial diversity and this might also be related to changes in diet as we get older.
- Antibiotics affect both bacteria that cause infections and the good bacteria that form our microbiota
Antibiotics are designed to kill bacteria that cause an infection, but they may also affect the healthy bacteria in our microbiome. This can then have a longer-term impact on our gut health as it may lead to reduced microbial diversity, lower protective species and an overgrowth of the pathogenic types of bacteria. For example, an overgrowth of Clostridium difficile bacteria may lead to antibiotic-associated diarrhoea.
- Faecal microbial transplant is the process of transplanting faecal bacteria from a healthy individual into another person
Whilst faecal microbial transplant (FMT) is considered to be a new therapy, it dates back over 1,000 years to Chinese practitioners and was first written about as a therapeutic intervention in 1958. It is the process of taking a faecal sample from a healthy individual and transplanting it into the gastrointestinal tract of a patient. Currently, it is most commonly used in relation to antibiotic-resistant Clostridium difficile diarrhoea. The transplant is most commonly done via colonoscopy, but may also be administered via an enema or nasogastric tube.
- Friendly bacteria supplements are currently the most popular method for supporting the microbiome
The increased interest in the microbiome and its impact on health has led to an explosion in research into the use of friendly bacteria (probiotics) supplements to support a healthy microbiota. Many studies have reported beneficial effects, but not all strains and products have been studied. Before taking a supplement, always ensure that it is a multi-strain product, supported by research and manufactured to current Good Manufacturing Practices, containing clearly-defined strains that survive the stomach acid and have been shown to be completely safe.
- We are all unique – no two microbiomes are the same (even in twins)
The vast amount of research into the composition of the gut bacteria has shown that every individual tested has their own unique microbiome ‘fingerprint’.
Research has shown that some parts of our microbiome are inherited and shaped through genes, but others are influenced by our environment and both identical and non-identical twins only share around 50% of bacterial groups.
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