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The Gut: Our Second Brain

Updated: Apr 6, 2021

A brief overview of how our gut microbiome affects our behaviour.

How Our Gut Affects Mood

The gut microbiota is the collective term for the trillions of microorganisms that live in our gut. Our microbiome begins to diversify from the moment we are born, and research suggests a diverse microbiome is a marker for good health and can have a significant impact on our mood. (Mawe & Hoffman, 2013)

Factors such as stress, prolonged antibiotic use and processed high sugar foods such as bread, sweets, fizzy drinks and pastries can deplete the level of good bacteria and affect the diversity of our microbiome. These factors may even be a driver to the development of gut issues such as irritable bowel syndrome (IBS) and Irritable bowel disease (IBD).

An unhappy gut can often lead to inflammation which can alter our neurotransmitters, affecting the way we feel and behave. Neurotransmitters act as chemical messengers which send signals to the brain, but they can become altered when there are issues going on within the body such as inflammation from an unhappy gut. This can affect the signalling of vital hormones such as serotonin.


Serotonin is our happy hormone. It makes us feel good and gives us the motivation to do the things we enjoy. 90% of Serotonin is produced in the gut and is made from the essential amino acid – Tryptophan. (Cote et al. 2003) It is essential because the body does not make tryptophan, we can only obtain it from our diet. Foods containing tryptophan include: chicken, bananas, nuts and seeds, oats and dark chocolate.

“Serotonin, the happy hormone is produced in the gut and is made from the essential amino acid – Tryptophan. (Cote et al. 2003) It is essential because the body does not make tryptophan, we can only obtain it from our diet.”

Both animal and plant based protein including chickpeas, lentils, black beans and quinoa are good for maintaining a healthy gut.

Probiotic rich foods are also vital as these will help feed the good bacteria and allow them to multiply. These include fermented foods such as yoghurt, miso, kimchi, and sauerkraut. If you find that you struggle to digest these foods and experience symptoms such as bloating, brain fog and abdominal pain, you may have an overgrowth of bacteria or an infection which needs addressing. A GP should be able to rule out anything serious or you can see a nutritionist who can help address the cause.


Stress is a very natural response and is needed for survival. Thousands of years ago, people would be faced with huge dangers such as needing to run away from a lion. To give them the best chance of survival, their body would naturally tap into the ‘flight or fight’ response; their senses would become heightened, and their body would become full of adrenaline so they have the energy to run as fast as they could. Once the threat was over, their body would restore, and they would go back into a ‘rest and digest’ state. The issue we have today Is we are unable to switch off from that stress. You may be working long hours, spending too long on phones and technology or having trouble sleeping.

Prolonged stress can impact our digestive system which can lead to inflammation and greatly affect the way we feel and behave.

It is therefore vital to take time out for yourself. This could involve exercise, yoga, meditation, reading or taking up a new hobby where your brain is fully focussed on the present moment. Often, stress can be a result of trauma from an experience we haven’t fully dealt with. To be able to move on or accept the past, you need to address the cause which is where counselling or CBT can be extremely powerful.

Written By Krista Swann for more about nutritional therapy visit


Cote, F. Thevenot, E. Fligny, C. et al. (2003) ‘Disruption of the nonneuronal tph1 gene demonstrates the importance of peripheral serotonin in cardiac function’, Proc Natl Acad Sci USA 100 (23) PP 13525 -13530 PMC [Online]. Available at: (Accessed: 6th May 2020).

Mawe, G & Hoffman, J (2013) Serotonin signaling in the Gastrointestinal tract: functions, dysfunctions, and therapeutic targets’, Nat Rev Gastroenterol Hepatol. 10 (8) pp 473-486. PMC [Online]. Available at: (Accessed: 06th May 2020).

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