The millions and millions of bacteria that have made themselves comfortable on, around, and inside of us greatly outnumber our own human cells. One could say that it’s a bacterial world and we merely live in it. In recent years, there has been an active spotlight on these trillions of little bugs that live in and on us. Some scientists have even gone on to proclaim this collection of bacteria, viruses, protozoa, and fungi, also called the microbiome – as the forgotten organ of our bodies! Hippocrates may have known something more than us when he said “All disease begins in the gut”.
Physically, the gut microbiome consists of large colonies of bacteria lining our intestines and can weigh up to 2 kilograms. Our microbiome is even heavier than the brain and arguably plays a vital role in digestion and overall health and wellness.
While we have managed to identify what certain strains or groups do, a large number of discoveries are still on the horizon. The gut microbiome and our bodies share a symbiotic and mutualistic relationship with one another: we are reliant on and mutually benefit each other. For example, the indigestible carbohydrates we eat, like resistant starches and fibre, are digested by our gut microbiome and not by the gut itself. This breakdown of carbohydrates then releases short-chain fatty acids, which are an energy source for cells in the gut. We are now learning that gut bacteria, previously seen as ‘commensal’ (i.e. benefitting from living in us, without harming us), are also vital for the maintenance of the inner mucosal layer, gut barrier integrity, and the prevention of inflammation – all important for proper functioning of the gastro-intestinal tract.
Some of these bacteria communicate directly with our brain and form an important pillar of health – called the brain-gut axis. They produce neurotransmitters, chemicals that are essential for communication between brain cells. These neurotransmitters produced in the gut are transported to the brain or the nervous system and have an effect on our digestive system and brain health. Some bacteria in the microbiome are known to regulate sleep cycles and guard our immune system too!
The strength of the microbiome is determined by its diversity – the more diverse the bacterial groups, the better! When someone has an imbalance in the proportions of bacterial levels in their guts, they are said to have dysbiosis. Dysbiosis is shown to have implications on the permeability of the gut barrier, the gateway in our gut that allows nutrients to be absorbed and subsequently alterations to brain health. The increased ease of absorption of amino acids, fatty acids or even toxins could trigger inflammations and imbalances, gut and beyond.
Given the advancement of modern medicine and the ability for us to personalise medicine, it will come as no surprise that the contents of our guts will dictate what medicines we take. We already have a good understanding of how major bacterial groups affect brain health, liver health and even heart health. With the inclusion of AI tools, some of this data can very quickly give us great insights on health and even an action plan on what you should and shouldn’t eat! To borrow from Hippocrates, with one little change – all wisdom begins in the gut.
Galland L. (2014). The gut microbiome and the brain. Journal of medicinal food, 17(12), 1261–1272. https://doi.org/10.1089/jmf.2014.7000
About the author
Dr Saishreyas Sundarajoo is Head of Clinical Affairs at AMILI.