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How The Gut-Brain Axis Can Affect Our Mental Health.

Trillions of microorganisms work together daily to make up the sentient beings that we are, but what happens when things start to go wrong?

“All disease begins in the gut”

- Hippocrates

The human body is a complex super-organism made up of an intricate relationship between human and microbial cells. Each of us has our unique microbiome that lives on and inside our body- known as our microbial fingerprint. Although assembled at birth, our microbiome is constantly evolving. We could even say that it is our ‘second self’.

Currently, we are at the tipping point in our understanding of the microbiome. We know that the microbes we give a home play a critical role in the vital homeostatic mechanisms throughout the body and that diversity is key. However, we still do not understand the complete picture. Nevertheless, present research indicates that any new treatment being developed surrounding the microbiome could change the paradigm of certain illnesses and promote better health and wellness.

“Am I simply a vehicle for the numerous bacteria that inhabit my microbiome? Or are they hosting me?”

- Timothy Morton

The concept of the gut-brain axis is derived from the intestinal microbiota’s influence on our neuro-endocrine-immune pathways. Our microbiota secretes many kinds of neurotransmitters which are active molecules - meaning these secretaries have the ability to regulate nerve signals and can affect neuropsychiatric parameters such as sleep, appetite, mood and cognition. The vagus nerve enables the primary connection between the brain and intestinal tract - controlling the intrinsic neural system made up of 200-600 million neurones.

So, where do things start to go wrong? Well, there are two objectives to consider when analysing the ‘chicken-and-egg gut paradox. Firstly, do our habits influence our gut microbiome, which then goes on to harm our mental health? Or, do our microbes already have a stronghold on our mental health, which, when it starts to decline, influences our habits?

For example, we know that chronic stress disturbs our microbiota. Studies have shown that an increase in cortisol release can play an important role in the changes in our intestinal permeability, which has been known to promote bacterial overgrowth in the liver and spleen. Hence, it seems we are back to the old “leaky-gut argument”.

In addition, about 60% of anxiety and depression patients are described to have intestinal function disturbance, such as irritable bowel syndrome. The link between those with acute mania and the frequency and intensity of their antibiotic prescriptions has been noted. Those with a higher degree of mania severity were shown in the past to have had a history of intense and frequent antibiotic use. The proposed mechanism for this is that the usage of antibiotics could have inflicted a possible change in the microbiota, thus increasing the risk of a mood stage change.

So, it seems that our intestinal microbiota has a bi-directional effect on mood disorders through mechanisms of neurobiochemical, neuroendocrine and neuroimmune systems. This presumption shown in human trials is also being replicated when using murine models.

In one study, the data suggested that mice that had been maternally separated at birth showed a change in the microbiota of their faces, precisely the level of cortisone, in comparison to mice that had not been maternally separated. Furthermore, sterile-raised, microbiota free rats are found to have an increased anxiety-like behaviour, suggesting that an intact, diverse and healthy microbiome can downplay anxiety-like symptoms. It also seems that depression-like symptoms can be transferred from one being to another just by the colonisation of the dysbiotic microbiome - which is what one group demonstrated. Published in The Journal of Psychiatric Research, Kelly et al. showed that by performing faecal microbiota transplantation from a depressed patient and planting it in a microbiota-deficient rat, the recipient would then exhibit behavioural and physiological characteristics of depression. However, utilising faecal transplant methods to cure depression would just be disgusting, right?

Luckily, there seems to be another way out. Studies suggest that ingestion of Lactobacillus strains help to regulate emotional behaviour via the vagus nerve, as the Lactobacillus subspecies can secrete acetylcholine which regulates memory, attention, learning and mood. In addition to L.acidophilus, Bifidobacterium infantis, Bifidobacterium, Candida, Streptococcus have also been clinically proven to have therapeutic effects on our mental wellbeing through the secretion of neurotransmitters such as dopamine. Thus, it seems that administering the correct prebiotics and probiotics infusion, plus maintaining a healthy lifestyle that encourages a diverse and flourishing intestinal flora, holds the key to relieving depression and anxiety-like symptoms.

Interestingly, one method in which we can shape the structure of our gut microbiome and move the needle almost instantaneously is through the use of hyperbaric oxygen chambers. Hyperbaric oxygen, at its simplest, delivers ~100% purified oxygen to the body via the breath at increased atmospheric pressure, thus allowing the blood plasma to absorb up to fifteen times more oxygen. The potential of molecular oxygen as a potential mechanism in treating intestinal disease is showing promising results.

Studies have shown that just after nine days of hyperbaric oxygen, tissue oxygenation within the gut increased by 5-fold, and the microbial community surveyed in the faecal apples also shifted in composition. Furthermore, it has also been suggested that hyperbaric oxygen alters the host mucosal bacterial communities and provides further protection against pathogenesis to potential pathobionts in the gut. The mechanism is primarily based upon the faster healing, enhanced immunity, recruitment of stem cells and prevention of harmful bacteria colonisation due to the increased delivery of oxygen within the intestinal tissues.

“The next generation of microbiome medicines will instead be real drugs that are easy to take and safe” - Roger Pomerantz

The bottom line is that we must pay more respect and homage to these tiny creatures besides us. How many of us are genuinely conscious of the beautiful microscopic world that shapes us every day? Even our perception of the world and the clarity of our thoughts are affected by our microbiome. To put it simply, everything about our health, how we feel both emotionally and physically, hinges on the state of our microbiome. I can conclude that it would be in everyone’s best interest to learn the secret life of our microbiomes.


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Hello there, I'm Jessica Alana.

By trade, I'm a biomedical scientist with a passion for holistic and natural healthcare.

My aim is to bridge the gap between alternative medicine and data-backed science and use this knowledge to help you self-heal and thrive.

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