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Gut – Brain Axis: A Psycho-Neuro-Immune Approach

By Jacqui Fernandez


This approach focuses on the bi-directional communication pathway that exists between the gastrointestinal tract and the central nervous system (CNS). This axis involves a complex interplay between the enteric nervous system (ENS), which controls gastrointestinal behaviour and is referred to as the body’s “second brain” and the central nervous system.


The gut-brain axis and the immune system are closely linked, and all three systems play a critical role in maintaining overall health. The gut-brain axis plays a critical role in regulating immune function. The gut and the brain communicate through a complex network of nerves, hormones, and immune cells, which can influence immune function in both the gut and other parts of the body. (O’Mahony et al 2015; Schellekens et al 2015) The gut is home to trillions of microorganisms, collectively known as the gut microbiota, which play an important role in regulating immune function. (Honda et al 2016; Belkaid et al 2014).


A study published in the journal Nature Communications (Keaton et al, 2019) found that gut microbiota can play a crucial role in immune function and affect brain function and behaviour by producing metabolites including neurotransmitter levels (eg GABA) and other brain functions, potentially contributing to conditions such as depression, and anxiety.

Modulating the gut microbiota: Strong evidence suggests that gut microbiota has an important role in bidirectional interactions between the gut and the nervous system. It interacts with the CNS by regulating brain chemistry and influencing neuro-endocrine systems associated with stress response, anxiety and other functions. Many of these effects appear to be strain-specific (Carabotti et al 2015).


Stress, for example, can activate the hypothalamic-pituitary-adrenal (HPA) axis, which releases cortisol and other stress hormones. These hormones can affect the gut by increasing permeability and releasing pro- inflammatory cytokines altering the gut microbiota. In turn, changes in the gut can affect the brain by altering neurotransmitter production and regulation, leading to changes in mood and behaviour. A study published in the Journal of Neuroimmunology (Zhang et al 2014) found that exposure to chronic stress can lead to alterations in immune function including increased levels of inflammatory cytokines in the gut and other parts of the body. This inflammation can, in turn, affect immune, and brain function and behaviour, potentially contributing to conditions such as depression and anxiety.


A study published in the journal Clinical & Experimental Immunology in 2017 found that the gut-brain axis plays a critical role in regulating inflammation in the body. The study suggested that targeting the gut-brain axis could be an effective way to reduce inflammation and improve overall health. Systemic inflammation The umbrella review by Moncrieff (et al 2022) suggests systemic inflammation may be linked to neurological conditions. One proposed mechanism for this link is that the inflammatory molecules produced in the body can cross the blood-brain barrier and trigger neuroinflammation.


Treatment must be designed based on the individual needs of the patient. By targeting multiple systems at once, these treatments have the potential to be more effective and holistic than traditional treatments that focus on a single system or symptom.


This approach emphasizes the connection between the mind and the body and aims to improve overall health and well-being in addition to reducing symptoms.

Mindset: Mindset can impact the gut-brain axis and immune system. Optimism and a positive outlook have been associated with better health outcomes.

Address underlying causes: A comprehensive approach that addresses underlying causes such as environmental factors, lifestyle, diet and psychological factors.

Target symptoms: Target and treat symptoms such as inflammation, pain, gut dysbiosis, and implement effective lifestyle and psychological strategies.

PSYCHOTHERAPY Aims to help improve mental health and well-being. There are many different types of psychotherapy, the most common types of psychotherapy include:

  • Cognitive-Behavioural Therapy (CBT): This focuses on identifying and changing negative thought patterns and behaviours that contribute to mental health problems.
  • Psychodynamic therapy: This type of therapy focuses on exploring unconscious thoughts and emotions that may be contributing to mental health problems.
  • Mindfulness-based therapy: This type of therapy involves practising mindfulness techniques to help individuals become more aware of their thoughts and emotions and develop skills to manage them more effectively.

Detox: Detoxification eliminates harmful toxins from the body. This can help improve digestive function and reduce symptoms such as bloating, constipation, and diarrhea. Detoxing can help reduce inflammation and support overall health.

Microbiota: Probiotics can help restore the balance of gut bacteria, while prebiotics is a type of fibre that feed the beneficial gut bacteria. Consider fermented foods, such as yogurt, kimchi, and sauerkraut, which contain live cultures of beneficial bacteria.

Supplements: Supplements that can help repair and support a healthy gut such as pre and pro-biotics, Digestive enzymes, Glutamine, Zinc, and Omega 3 fatty acids to reduce inflammation and gut function.

Herbal Medicine: Herbs with adaptogenic, anti-inflammatory, immune and digestive health have been shown to be beneficial.

Diet: A diet rich in whole, nutrient-dense foods such as fruits, vegetables, whole grains, nuts and lean proteins can support the gut microbiome and reduce inflammation, which can positively impact the gut-brain axis.

Hydration: Research suggests that adequate hydration can have positive effects on the gut-brain axis by decreasing inflammation, and oxidative stress and can have a positive impact on cognitive and overall health and wellbeing.

Lifestyle: Stress management techniques such as mindfulness, meditation, deep breathing, exercise or yoga in your daily routine, have been shown to promote a healthy gut microbiome and reduce inflammation, which can positively impact the gut-brain axis.

* Please consult with a healthcare professional before taking herbs or supplements, especially if you have a history of liver or kidney disease, or are taking medication.

More about the author

Jacqui Fernandez - Blur
Jacqui Fernandez

Jacqui Fernandez,  Naturopath, Nutritionist, and Psychotherapist (Master of Psychotherapy & Couns, B.HSc (Nat), Dip Nat, Dip Nutr)

Jacqui is a qualified Naturopath, Nutritionist, and Psychotherapist. She has over 20 years of clinical practice, 10 of which were within a medical model working with GPs, specialists and other allied healthcare professionals. Combining education and experience  Jacqui offers a holistic patient-centred integrated model of health care using traditional knowledge backed by scientific evidence.