What is the Gut-Brain Axis?
The gut-brain axis is a complex, bidirectional communication network linking the central nervous system (CNS) with the enteric nervous system (ENS), often referred to as the “second brain”[1]. This sophisticated connection creates constant dialogue between the gut and the brain, influencing digestion, immune function, mood and emotional balance.
This connection operates through several pathways, including:
- The vagus nerve – a major nerve that carries signals directly between the gut and brain
- Neurotransmitters produced in the gut, such as serotonin and dopamine
- Immune and inflammatory signalling
- Gut microbes that interact with both the nervous and immune systems
Due to this close relationship, changes in the gut can influence how we think and feel, while stress and emotional strain can directly affect gut function. This is why many people notice digestive discomfort during stressful periods and why gut and mood are so closely linked. Explore natural support for digestive discomfort in our blog here.
Serotonin and the Gut
Serotonin is an important chemical messenger made from the essential amino acid tryptophan. While it is commonly associated with emotional wellbeing, stability and calm, serotonin is found throughout the body, including the digestive system, blood platelets and the central nervous system[2].
Many people are surprised to learn that around 90% of the body’s serotonin is produced in the gastrointestinal tract (GIT), rather than in the brain[3]. This highlights the close relationship between gut function and mood-related processes.
Within the digestive system, serotonin plays a key role in regulating several important functions, including[4]:
- Digestive motility
- Secretion (how much fluid is produced in your intestines)
- Sensitivity to pain and discomfort
- Appetite and satiety signals
- Communication between gut nerves and the brain
The production of serotonin in the gut is heavily influenced by gut bacteria. A balanced and diverse microbiome supports healthy neurotransmitter signalling, while imbalances may disrupt this process. This is one reason why gut health is increasingly linked to emotional wellbeing and stress resilience.
Gut Dysbiosis and Its Impact on Mood
Gut dysbiosis refers to an imbalance within the gut microbiome, where the composition or activity of gut bacteria becomes disrupted[5]. This can result in a reduction of beneficial bacteria and an overgrowth of less helpful or potentially harmful microbes.
Emerging research suggests that gut dysbiosis and inflammation may be associated with changes in mental wellbeing, including mood and stress-related symptoms[6]. Considering this, disruptions in the gut microbiome may influence mood regulation, stress responses, cognitive function and mental clarity.
This imbalance may interfere with neurotransmitter production, increase inflammatory signalling, and disrupt communication along the gut-brain axis. As a result, gut health and anxiety are increasingly discussed together in both research and daily conversations.
The Role of Inflammation
Gut inflammation and depression are often discussed together due to the role of inflammation in gut-brain signalling.
When the gut lining becomes irritated or more permeable than normal, inflammatory compounds can enter circulation. This low-grade, systemic inflammation may influence brain function and mood regulation.
Factors that may contribute to gut inflammation include:
- Chronic stress
- Low fibre intake
- Poor microbial diversity
- Highly processed diets
Supporting gut barrier integrity and reducing unnecessary inflammation is therefore considered an important part of maintaining overall wellbeing.
Supporting Gut-Brain Health
Supporting the gut brain axis doesn’t require extreme changes. Small, consistent habits can positively influence both digestion and emotional wellbeing.
A balanced approach that considers nutrition, lifestyle and stress levels helps create an environment where gut-brain communication can function more effectively.
Key supportive strategies include:
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Probiotics, prebiotics and postbiotics to help support microbiome diversity and overall gut function. Together, they work to nourish beneficial bacteria and support a healthy gut environment. Learn more in our here.
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Dietary fibre from vegetables, wholegrains and legumes, which helps feed beneficial gut bacteria and supports regular digestion.
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Omega-3 fatty acids, which support nervous system function and help maintain a healthy inflammatory balance within the body. Learn more here.
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Stress management practices such as breathing exercises, mindfulness, yoga or gentle movement. Reducing stress can positively influence gut function, as stress signals are directly communicated along the gut-brain axis.
Maintaining regular meals, staying hydrated and supporting sleep quality also play an important role in gut and mood balance.
Supporting Gut Health with Herbal Remedies
Herbal remedies have traditionally played a role in supporting gut health and overall wellbeing.
Note: Before considering any herbal remedies, we recommend speaking to a registered herbalist first. Book a consultation at Napiers to receive personalised guidance based on your individual health profile.
The Napiers Gut Health Protocol is a thoughtfully curated four-week supplement regime designed to support the digestive system. Combining probiotics, traditional herbal support and essential nutrients such as vitamin D, this bundle supports the gut microbiome, digestive function and gut-immune interaction from multiple angles.
This 4-week protocol combines:
- Napiers Happy Gut
- Napiers Jarropick Herb Blend
- Napiers Vitamin D3 and K2 Spray
Rather than focusing on bacteria alone, the protocol takes a whole-system view of gut health. Probiotics and prebiotics in Napiers Happy Gut help nurture microbiome diversity, while Napiers Jarropick Herb Blend supports digestion, liver function and comfort after meals. The addition of Napiers Vitamin D3 and K2 Spray contributes to immune function and nutrient absorption – both important factors in maintaining gut barrier health and overall wellbeing.
This protocol is ideal for anyone seeking longer-term digestive comfort, improved microbiome diversity and gentle, ongoing digestive support as part of a balanced lifestyle.
By combining herbs, probiotics and minerals, the protocol avoids a one-size-fits-all approach often seen in standalone gut and digestive supplements. A four-week structure allows for gradual, consistent support as part of a wider gut health routine.
Save 20% when you shop this 4-week reset protocol with code PROTOCOL20.*
Shop our personalised 4-Week Reset Protocols here.
*Code PROTOCOL20: Code valid once per customer between 00.01 on 26/12/25 and 23.59 on 31/01/26 (GMT). Offer valid on Brain & Stress Support Protocol, Gut Health Protocol, Hormone Balance Protocol, Strength & Joint Health Protocol, Sleep & Recovery Protocol, Complete 4‑Week Reset, and Detox Protocol. This code cannot be used in conjunction with any other discount. Napiers terms of the site apply.
To explore gut health further, read our blog on why the gut microbiome matters and discover practical, everyday ways to support gut health naturally.
FAQs
What are prebiotics?
Prebiotics are types of dietary fibre that feed beneficial gut bacteria, helping them grow and function effectively.
Can gut health really affect mood?
Research suggests gut and mood are closely linked through the gut-brain axis.
How long does it take to see changes in gut health?
Gut changes vary between individuals, but consistent dietary and lifestyle habits over several weeks are commonly recommended.
Is stress linked to digestive issues?
Yes, stress can affect gut motility, digestion and microbial balance via the gut-brain axis.
References
- Carabotti, M., Scirocco, A., Maselli, M.A. and Severi, C. (2015) 'The gut-brain axis: Interactions between enteric microbiota, central and enteric nervous system', Annals of Gastroenterology, 28(2), pp. 203–209. Available at: NCBI.
- Scaccia, A. (2024) Everything you need to know about serotonin. Healthline. Medically reviewed by Balingit, A. (MD). Updated 3 July. Available at: Healthline.
- Bektaş, A., Erdal, H., Ulusoy, M. and Uzbay, I.T. (2020) Does serotonin in the intestines make you happy? Turkish Journal of Gastroenterology, 31(10), pp. 721–723. Available at: NCBI.
- Case-Lo, C. (2020) IBS and serotonin: the brain–stomach link. Healthline. Medically reviewed by Sethi, S. (MD, MPH). Updated 5 November. Available at: Healthline.
- DeGruttola, A.K., Low, D., Mizoguchi, A. and Mizoguchi, E. (2016) 'Current understanding of dysbiosis in disease in human and animal models', Inflammatory Bowel Diseases, 22(5), pp. 1137–1150. Available at: Oxford Academic.
- Clapp, M., Aurora, N., Herrera, L., Bhatia, M., Wilen, E. and Wakefield, S. (2017) Gut microbiota’s effect on mental health: the gut–brain axis. Clinics and Practice, 7(4), p. 987. Available at: MDPI.
