The Gut Microbiome 101
If it’s culture you’re looking for, then look no further than your gut. Your microbiome is an ecological community, much like a jungle, where trillions of microbes live and work together to make you the superhuman you are. Look after your gut microbiota and it’ll look after you. Get ready to step into this micro world and discover the good bacteria powering you to reach ultimate health goals.
You Are Not Alone
That’s right, on a smaller scale, the human body is an ecosystem, too. You are not the only inhabitant in your body. The truth is, there are more bacterial than human cells in you [1].
The human body is host to trillions of microorganisms, not just bacteria but fungi, viruses, and archaea. By forming a strong bond over centuries of evolution, these microscopic organisms and humans have created adaptive and complex ecosystems which ultimately contribute positively to human health [2].
Bacteria are everywhere. Wherever there is interaction with the outside world, you’ll be sure to find bacteria. They live on the skin, in the mouth, nose, throat, vagina, even between your toes! But by far the most inhabited bacterial settlement is the gut.
So, ditch the idea that all bacteria are bad and discover the wonderful and fascinating bacterial habitat inside you. Let’s take a journey into the microbial universe inside your gut. .
But I’ve heard bacteria are bad for my life?
Wrong. It’s true that some strains are responsible for illness and infection, food borne diseases are a major example, but bacteria are useful, too. They will do anything to keep you well and happy, just like your best friend!
Bacteria are found in every habitat on Earth - in soil, rocks, the sea, snow, even on and in living organisms. They are single-celled powerhouses responsible for many important jobs. There are types of bacteria that decompose dead organic matter contributing to the structure of the soil, they provide nutrients to plants and keep ecosystems thriving. Others are well-renowned in the medical world, are used in industrial applications and even in food production, think fermented foods - cheese, wine, bread, and pickled veggies. Without bacteria we wouldn’t have these culinary delights. That’s one of our favourite microscopic magics!
To put their usefulness into perspective, there are trillions of bacterial species but less than 1% are pathogenic (illness causing) to humans [3]. Many are mutually beneficial (symbiotic), some are harmless (commensal) but in terms of human health and survival, bacteria are saviours.
The Gut 101 - Have you got the guts to find out more?
Before we immerse ourselves into the complex and mutually beneficial relationship between the gut and bacteria, let’s discuss what the gut really is.
What is the gut?
The gut describes your digestive tract – the spaghetti junction of your body. It’s where food enters and travels through, along the way the nutrients are absorbed, and the waste continues its journey outwards and onwards. More specifically, though in terms of the gut microbiome, the gut describes the large intestine also known as the bowel or the colon.
Function
The large intestine has 3 major functions:
Absorbs water and electrolytes to keep your body hydrated.
Chemical digestion via microbes including fermentation and the production and absorption of some vitamins. This keeps your physical and mental health in top notch condition.
Forms stools and excretes them from the body, so you don’t feel bloated and uncomfortable.
Structure
The gut is an impressive structure. If it was unravelled, your colon would be almost 5 feet long [4] that’s almost as long as the height of the average woman! It’s divided into sections and each has roles within the digestive process:
Leaky Gut – The Colon’s Dripping Tap
There’s a lot of attention focussing on the term “leaky gut” especially on social media platforms and various blogs, but what exactly is it? To explain what leaky gut is, we need to home in on the micro-structures of the gut. And it’s clever stuff.
The gut is lined with millions of epithelial cells (surface layer) and together these act like security gates, deciding what is and what isn’t allowed to enter the bloodstream. In some people, however, this security system can weaken, perhaps because of a poor diet, causing the gut microbiota to become imbalanced. In these cases, holes appear in the gut lining, allowing undigested food particles, toxins, and pathogenic bacteria to enter the body. Once they’ve evaded the security gates, this triggers inflammation, not only in the gut but elsewhere, and can have some uncomfortable consequences like bloating, cramps, headaches, and tiredness. No thank you, we hear you cry! Microbiome diversity is key. Stay tuned to find out how you can influence your intestinal microbiota.
The Gut Microbiome – A 5* hotel for microorganisms
Now you know what bacteria are and what the gut is, how do these combine to produce one of the finest (in our opinion), and most complex ecosystems?
Influencers: not just for social media
Your microbiome is unique to you.
The gut microbiota has been influenced by internal and external factors from the moment you were born. As you grow and develop so does the gut microbiome, ultimately defining who you are. The way you entered the world, whether you were fed breast milk, and the lifestyle choices you make as you get older are all aspects which can alter the microbiome composition for better or for worse [9].
It’s like a jungle in there…
The human gut microbiome is all about the little microbes that live in your intestine and their genes, and trust us, there’s loads of them. Together, these organisms live in harmony with one another and with you. You can think of your gut like a 5-star microbe hotel – you provide them with a home and nutrients, and, in return, they benefit you. Bacteria with Benefits *wink*.
Without microbes your body is unable to break down dietary fibre. Studies show specialist bacteria ferment (break down) these otherwise indigestible food components and transform them into useful metabolites like short chain fatty acids (SCFAs) and vitamins [6].
Butyrate is an important example of an SCFA produced by gut microbes because it is the main fuel source for colonocytes (the cells in the colon) and it strengthens the gut barrier. It’s also a powerful antioxidant which protects the gut from free radicals, oxidative stress, and inflammation which is implicated in many diseases, like ulcerative colitis and Crohn’s disease (inflammatory bowel disease) as well as cancer [7].
Healthy bacteria such as Bifidobacteria produce vitamins like B and K which have many roles in the body including energy production, carbohydrate metabolism, and blood clotting [8].
Microbes are also integral to the strength of the epithelial wall, making it difficult for pathogenic bacteria to penetrate inside and make you ill. Some also help to secrete mucus and work with the tight junctions (think of these like the hotel concierge) to regulate what should and shouldn’t be allowed to enter the body, like the gut bacterium Akkermansia muciniphila. The acidic environment that is most associated with the gut is also maintained by gut bacteria, making it difficult for alkaline loving bacteria to set up camp in your gut.
Gut microbiome: you definitely want to care
Your gut is the gateway to another civilisation within the human body. It is a microbial community standing guard to keep you protected from outside pathogens as well as regulating many of the body’s internal functions. The gut microbiome is so revered in the scientific world that it is quickly becoming known as the body’s last organ.
Macro functions of the gut microbiome
The gut microbiome function is not only geared towards the health of the digestive tract but further afield, too. The good gut bacteria are largely responsible for boosting your immunity and protecting you from disease. Gut microbes regulate many of the key metabolic functions in the body including blood glucose levels. Research suggests that type 2 diabetes can be improved through targeted use of probiotics and prebiotics [10].
Circulating levels of good cholesterol known as high-density lipoprotein (HDL) and triglycerides are also influenced by gut microbes [11]. Lactobacilli, a probiotic bacterium, has also been shown to have cholesterol lowering properties. Keeping the balance in the gut is vital as unhealthy gut species can contribute to the risk of developing heart disease by producing an artery blocking chemical called trimethylamine N-oxide (TMAO) [12]. There are even some microbes that protect against obesity, keeping body weight in check.
Your skin also benefits from a healthy gut microbiome. Small changes can affect the appearance of your skin. Modulating the gut microbiome with probiotics, prebiotics and synbiotics has helped to prevent and treat some inflammatory skin diseases, like acne and psoriasis [13].
And there’s one aspect of the gut we must mention. It’s so integral to you we could dedicate a whole page to it, and that’s the gut-brain axis. Essentially, it’s like a tin can telephone, like the ones you made as a kid. The brain is one tin can, the gut is the other and the vagus nerve, the control centre for most of your bodily functions including digestion and heart rate so it’s super vital, is the string that connects the two. Via the vagus nerve, the brain and gut can talk to each other, but they can do this wirelessly too, through neurotransmitters. These are chemical messengers, a bit like text messages, they are made by nerve cells to transmit a message to another part of the body i.e., from the gut to the brain. What does really mean? Simply, it’s believed that some of the bacteria in your gut can produce specific compounds that can affect your brain function.
How?
Because these compounds can cross into the brain. Interestingly, imbalanced gut flora is found in many diseases even those not linked to digestion like anxiety, depression, autism, and Parkinson’s. Who knew gut health could be so central to your wellbeing?
Wait, there’s more. Taking care of your gut microbiota =
Better digestion
More useful metabolites for your body to use
Stronger immune system
Better mood = smiley you 😊
Lower risk of diseases like Alzheimer’s and Parkinson’s.
Striking a balance
Happy, healthy gut means happy, healthy you. An imbalance in the abundance of your gut flora and low microbiome diversity is called dysbiosis, and is associated with many chronic diseases, like diabetes, obesity, inflammatory bowel disease, inflammatory bowel syndrome, cancer and more [14]. And no one wants that!
If your gut is out of sync, you might experience symptoms such as diarrhoea, constipation, excessive gas and cramping or discomfort. And that’s not good for anyone. Find out more about how to improve gut microbiome by reading our Food, Prebiotics and The Microbiome Section [link].
References
[1] Gilbert, J., Blaser, M, J., Caporaso, J, G., Jannsson, J., Lynch, S, V and Knight, R. Current understanding of the human microbiome. Nat Med 24. https://doi.org/10.1038/nm.4517 (2018)
[2] Lloyd-Price, J., Abu-Ali, G and Huttenhower, C. The healthy human microbiome. Genome Medicine 8. https://doi.org/10.1186/s13073-016-0307-y (2016)
[3] Microbiology Society. Microbes and Disease. https://microbiologysociety.org/why-microbiology-matters/what-is-microbiology/microbes-and-the-human-body/microbes-and-disease.html (2021)
[4] Azzouz L, L, Sharma S. Physiology, Large Intestine. Available from: https://www.ncbi.nlm.nih.gov/books/NBK507857/ (2017)
[5] Nigm, Y et al. Gastrointestinal tract 5: the anatomy and functions of the large intestine. Nursing Times 115. https://www.nursingtimes.net/clinical-archive/gastroenterology/gastrointestinal-tract-5-anatomy-functions-large-intestine-23-09-2019/#:~:text=Anatomy%20of%20the%20large%20intestine,is%20completely%20devoid%20of%20villi. (2019)
[6] Valdes, A, M., Walter, J., Segal, E and Spector, T. Role of the gut microbiota in nutrition and health. BMJ 361. https://doi.org/10.1136/bmj.k2179 (2018)
[7] Liu, H., Wang, J., He, T., Becker, S., Zhang, G., Li, D and Ma, X. Butyrate: A double edged sword for health? ASN 9. https://doi.org/10.1093/advances/nmx009. (2018)
[8] Kho, Z, Y and Lal, S, K. The Human Gut Microbiome – A Potential Controller of Wellness and Disease. Front. Microbiol https://doi.org/10.3389/fmicb.2018.01835 (2018)
[9] Wen, L and Duffy, A. Factors influencing the gut microbiota, inflammation, and type 2 diabetes. J Nutr. 147. https://doi.org/10.3945/jn.116.240754 (2017)
[10] Gérard, C and Vidal H. Impact of gut microbiota on host glycaemic control. Front Endocrinol (Lausanne) 10. https://doi.org/10.3389/fendo.2019.00029 (2019)
[11] Fu, J et al. The gut microbiome contributes to a substantial proportion of the variation in blood lipids. Circ Res 117. doi: 10.1161/CIRCRESAHA.115.306807 (2015)
[12] Zhu, W., Wang, Z., Wilson Tang, W, H and Hazen, S, L. Gut microbe-generated trimethylamine N-oxide from dietary choline is prothrombotic in subjects. Circulation 25. doi: 10.1161/CIRCULATIONAHA.116.025338 (2017)
[13] Salem, I., Ramser, A., Isham, N and Ghannoum, M, A. The gut microbiome as a major regulator of the gut skin axis. Front Microbiol 9. https://doi.org/10.3389/fmicb.2018.01459 (2018)
[14] Belizário, J, E and Faintuch, J. Microbiome and gut dysbiosis. Exp Suppl 109. doi: 10.1007/978-3-319-74932-7_13 (2018)
