Hippocrates said 2,500 years ago ’All disease begins in the gut.’ Is this true?
Thanks to recent technological advancements, characterisations of the gut microbiome in particular disease states are studies in great details. A growing body of research suggests that gut microbiome is vital for the health of its host, and plays a crucial role in many aspects of host physiology including metabolism, nutrition, pathogen resistance and immune function. Changes in brain-gut-microbiome communication may be involved in the development of disease and the processes associated with irritable bowel syndrome (IBS), obesity and several psychiatric and neurologic disorders.
The gastrointestinal tract is a long hollow tube starting from the oral cavity, oesophagus, stomach, small intestine, colon, rectum and anal sphincter. Our gut acts as our body’s gatekeeper. The food we ingest get digested, absorbed and eliminated through the gut. Moreover, the gut is one of the main detox organs (apart from the liver, lung, kidneys and skin), therefore it is crucial to have healthy digestive functions and regular bowel movement every day.
One of the most important factor to support your gut health is by supporting the community of microbes that live inside your gut - collectively referred to as ‘microbiome’. The human gut microbiome is recognised as an 'ecosystem' including approximately 500-1000 microbial species, which altogether contain about 100 times more genes than our own human genome. Let’s think of it like a rainforest that is incredibly diverse and complex, with lots of plant and animal species living together.
These microbes benefit the host in numerous ways from digesting food and absorbing nutrients, producing some vitamins (e.g. B vitamins, vitamin K) and other key compounds, particularly butyrate (the primary energy source for your gut cells with anti-inflammatory property and potential benefits on IBS and Crohn's disease). 36% of the small molecules found in the human blood are produced by the gut microbiome. Furthermore, the gut microbiome modulates the host immune system. Did you know more than 70% of our immune system resides in the gut?
When the gut microbiome becomes imbalanced (meaning having less ‘beneficial’ microbes and more ‘harmful’ ones), so called ‘gut dysbiosis’, this would predispose us to develop diseases. A gut with unhealthy microbiome means a toxic body. This is because harmful bacteria produce endotoxins or LPS (lipopolysaccharide), which stimulates the inflammatory immune responses. Chronic inflammation is the underlying cause of many metabolic diseases e.g. type 2 diabetes, cardiovascular disease, obesity and liver disease. Moreover, if the gut lining is not healthy (the condition known as 'increased gut permeability' or ‘leaky gut’), this allows toxins and large molecules such as improperly digested food particles to pass into the bloodstream and stimulate immune reactions, which can manifest into food sensitivities and bloating.
What else can cause alterations in the gut microbiome? Other factors adversely affect the gut microbiome include overuse of antibiotics, medication (e.g. metformin), pesticide and toxin exposure, infections and food poisoning, food preservatives, C-section delivery, ageing and chronic stress.
A gut with unhealthy microbiome means a toxic body.
Good news! The gut microbiome is not static. The diversity of your gut microbiome greatly depends on what you eat as well as how you live (i.e. sleep, exercise, relationship and stress management). Studies have shown diet is a powerful influence. Altered gut microbiome as a result of diet change has been shown to be accompanied by increased risk of obesity. One study found that 23% of adult participants who had a low gut microbiome diversity were more likely to be obese, have insulin resistance and elevated blood lipids and increased levels of inflammation markers in the blood, all of which increase the risk of type 2 diabetes and cardiovascular diseases. Moreover, those who were both obese and had a lower bacterial diversity gained much more weight over the previous nine years. There is also evidence that gut microbiome can influence the host metabolism.
Modification of gut microbiome may be an effective therapy for modulating disease. A study found that certain gut bacterial species i.e. Christensenellaceae are present in higher levels in people with low body mass index (BMI). When these bacteria were given to mice, it protected them against weight gain. Faecal microbiota transplant (FMT) has proven a highly effective therapy to modify the gut microbiome in patients with recurring Clostridium difficile infection (a condition most commonly affecting people who have been treated with antibiotics causing diarrhoea and /or gut inflammation). However, from a safety perspective there is a potential risk of transferring infectious diseases (from the faecal doner) and therefore, this approach is not widely recommended.
There is a safer way to improve your gut microbiome diversity. The easiest, and perhaps the most effective way is to eat varieties of plant-based food rich in soluble fibre, which can feed beneficial gut bacteria. Different plants feed different types of gut bacteria, hence focus on diversity of your diet. Gut bacteria can breakdown fibres into compounds that benefit the host, one of those is butyric acid or butyrate (a short chain fatty acid) that nourishes the intestinal lining.
Probiotics can also shift diversity of the gut microbiome. Most probiotics don’t permanently colonise the gut. However, while being in the gut, they may exert several benefits to the host and may improve / restore the gut microbiota in people with certain diseases. For example, studies showed probiotic intervention with Lactobacillus and Bifidobacteria has proven beneficial for modulating obesity-related microbiota dysbiosis.
A healthy gut microbiome means healthy you. Supporting a healthy gut microbiome is an important cornerstone for our health. The link between gut microbiome and human health is being increasingly recognised and it is now well-established that healthy gut microbiome is a key part of overall health. A diverse gut microbiome may help our body resist the negative impacts of toxic load and lower the risk for developing diseases.
Now that you have learned about gut microbiome. Do you think Hipocrates was right?
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