Your Gut

Your gut is a complex biological machine that enables you to obtain all the nutrients you need from complex foods to grow, repair and fuel your body.

To function correctly, the gut relies on the help of trillions of tiny microorganisms, known as our commensal bacteria. The word ‘bacteria’ often sets off alarm bells in our heads because many of us believe that most bacteria are harmful, disease-causing organisms. We couldn’t live without them! Some bacteria can indeed cause nasty diseases and infections, but what many people do not know is that pathogenic disease-causing bacteria only make up 5% of all bacteria species! So… what does that other 95% do, and how do they help us?

Microbiome and Immune support

Microorganisms and bacteria are all around us, on every surface we touch, covering our skin and in our gut lining. The bacteria that reside on and inside us are essential as they act collectively as a major defence mechanism that protects us against infection. These bacteria act as commensals (types of microbes). This means that when you are healthy, you and the bacteria on/in you have a symbiotic or mutually beneficial relationship. Your body provides the bacteria with an environment to thrive in with good temperature, pH, and plentiful nutrients. In return, the bacteria colonise various areas of the body leaving no space or nutrients for pathogenic bacteria to grow. These commensals are found throughout the body including the skin, eyes, gastrointestinal tract, respiratory tract, and lower genital tract. However, most of our commensal bacteria inhabit the distal portion of our gut. The gastrointestinal tract is where the outside environment meets our internal environment through things we ingest.

Where it all begins

Our microbiome is kickstarted on the day we are born. Even things like how we were delivered as a newborn can have massive effects on how our microbiome develops as a child and in later life. In contrast to natural deliveries, C-section babies receive their first microbiome population from the surgeon and nurses rather than from their mother.

Early life is when your commensal bacteria colonise and multiply significantly. During this time, your gut bacteria must be allowed to flourish; breast milk, foods high in nutrients, and broad exposure to a wide variety of foods are all needed as they feed the bacteria. Support of gut microbiome development in infancy is essential to a healthy gut later in life. The maturation stage occurs around 3-4 years old when the gut microbiome stabilises.

The immune system / microbiome relationship

You might be curious how our immune systems, designed to attack foreign material and microorganisms, allow commensal bacteria to colonize inside us. Since we are born with both immature immune systems needing stimulation for defence initiation and an immature microbiome, the two develop symbiotically. The co-evolution of our immune system alongside our microbiome enables immune tolerance to aid in the development of beneficial commensal bacteria in our gut. Both systems work mutually and are in constant communication, regulating and supporting each other.

Unsurprisingly, 70-80% of mature immune cells are found in the gut, alongside the greatest proportion of commensal bacteria. In healthy individuals, the immune system promotes growth of a diverse gut microbiome and ensures there is no overgrowth of a particular species, while the gut bacteria provide healthy antigenic stimulation, which facilitates immune cell development and tolerance to both commensals and self-antigens (preventing auto-immunity).

Other Roles of Microbiome within Your Body

Digestion

In addition to supporting our immune system, commensal bacteria play various roles in our bodies. Our bodies do not naturally produce all the enzymes required to break down every component of our food. However, gut bacteria possess different enzymes that aid in breaking down and fermenting micronutrients into by-products. For instance, gut bacteria ferment indigestible, soluble fiber into a gel-like substance that facilitates the healthy movement of food through the gut. Commensals also assist in breaking down fats into short-chain fatty acids (SCFAs) like butyrate, acetate, and propionate, which are absorbed by intestinal cells and used as fuel. Additionally, gut bacteria contribute to vitamin and mineral uptake, as well as the synthesis of amino acids, the building blocks of protein.

Weight Management

Maintaining a healthy gut microbiome composition has been demonstrated to support weight management. Individuals with disruptions in their gut bacteria may experience systemic inflammation caused by excess lipopolysaccharides (LPS). This inflammation can lead to disturbances in cell metabolism, resulting in weight gain.

Your microbiome, the collection of bacteria on and within you, is entirely unique, even more so than your fingerprint. It is shaped and altered by your individual experiences, encounters, and both exogenous and endogenous stimuli. Not only do we exhibit different proportions of various bacterial species, but we also each possess a completely distinct set of bacterial species. Even for individuals living in the same or similar environments (e.g., households), consuming similar diets, and engaging in similar activities, no two microbiomes will be identical. Nevertheless, there will be discernible patterns in their microbiomes that reflect the shared aspects of their lifestyles.

Did you know?

No two people have the same microbiome: not even identical twins!

Help metabolise toxins

The liver, a major organ responsible for metabolizing toxins into excretable by-products for elimination from the body, requires enzymes to break down excretory products and toxins. Some enzymes involved in the detoxification process, such as those facilitating the transport of bile acids, hormones, and cholesterol, are produced by our gut microbiome.

Allergies

Going back to the relationship between the immune system and the gut microbiome, we understand that these two systems are intricately linked, growing and developing together from the day of birth. The co-evolution of these systems is crucial for educating our cells and bodies about what is a friend and what is foe. When this immune cell education falters, it can lead to conditions like allergies and autoimmunity. Disturbances in the gut microbiome, which significantly impact immune development, could contribute to the onset of these conditions. With a deeper understanding of our gut bacteria and how to support it, there may be opportunities to enhance conditions such as asthma, hay fever, and eczema.

We are not alone in our bodies

Inside every person are trillions of microorganisms — bacteria, yeasts, viruses, fungi, and other life forms collectively known as the microbiome. Various parts of the body have distinct microbial inhabitants, but those drawing considerable attention in biomedical research are the ones residing in your gut.

The gut microbiome is a massive, diverse ecosystem in your digestive tract. Scientists increasingly treat it as an organ in its own right, and researchers around the globe are investigating what makes a ‘good’ gut microbiome. There are, after all, hundreds of distinct bacterial species in the gut — some pathogenic and some beneficial.

You are what you eat

Our gut microbiome stabilizes at around 3-4 years of age. However, this does not mean it is completely set at that point. Even when healthy, our gut microbiome is constantly influenced by what we eat, what we do, and our environment. The community of gut commensals is flexible and can endure small changes to help your body adapt to changing stimuli. This means that despite the importance of gut microbiome development during infancy, you can support and improve it to a degree throughout your life. So, how can we go about doing this?

Prebiotics and probiotics play crucial roles in supporting a healthy gut microbiome.

Prebiotics

One thing that many people are often not aware of is that the gut microbiome is a living mass of microorganisms that need nutrients to survive. While incorporating a variety of probiotic foods and/or supplementation into your diet is beneficial, these bacteria won’t thrive in your gut without a balanced diet. For your gut bacteria to flourish, it’s essential to provide them with the necessary nutrients. Prebiotics act as the fertilizer for these commensals, and they can be obtained from both natural food sources and additional supplementation.

The primary feature of prebiotic foods is that they are high in indigestible fibre. This fibre passes through to the large intestine, where bacterial colonies utilize it as fuel. Natural prebiotic foods include onions, leeks, raw garlic, raw asparagus, and unripe bananas. Gut commensals also thrive on ‘resistant starch,’ which they can ferment into short-chain fatty acids. Resistant starch foods include sourdough bread, cooked and cooled legumes/white potatoes, oats, and unripe bananas. Similar to probiotics, prebiotics can be supplemented, but it’s important to ensure that this is always in addition to natural sources and not a replacement.

Probiotics

Foods that contain lots of good bacteria include live yoghurts, kefir, kombucha, unpasteurized cheeses, and sauerkraut. Incorporating these foods into your diet will help maintain good gut health and allow your gut microbiome to thrive. Each of these foods contains different bacterial species, emphasizing the importance of variety. If you have been on a course of antibiotics, or for additional support, you can take probiotic supplements to boost your gut commensal communities. However, reliance on supplements alone is not recommended. Natural food-based probiotics are crucial and should always be prioritized as the first port of call.

With both pre and probiotic foods, if you do not already have these in your diet, make sure you slowly increase your intake to let your gut acclimatise. Sudden intake of these foods can cause your gut bacteria to become overly excitable, leading to excess gas production from the fermentation frenzy.

Disturbances to the Gut Microbiome

Antibiotics and gastrointestinal upsets

If you get an infection caused by pathogenic bacteria, you may be given a course of antibiotics as treatment. Antibiotics cannot differentiate between good and pathogenic bacteria, so a course of antibiotics can cause depletion of your good gut bacteria and other ‘friendly’ bacteria colonies in your body. Additionally, illness and gastrointestinal infections or inflammatory conditions such as gastroenteritis (commonly caused by the consumption of contaminated food or liquid) can wreak havoc on your gut microbiome.

This is why it is imperative to ensure you are getting enough probiotic and prebiotic intake once you have finished a course of antibiotics or during and after a gastrointestinal upset, to build up your ‘friendly’ gut bacterial colonies again and support their growth.