The gut-brain axis: How your microbiome affects mood, digestion, and stress

Have you ever felt your stomach flip before a big presentation, or noticed how a nourishing meal leaves you calmer? These aren’t random quirks - they’re signs of a powerful two-way system called the gut-brain axis. In this post, we’ll explore what that connection means, why it matters for your mood and digestion, and how you can support it in daily life.

Table of contents

1. What is the gut-brain axis?

2. Why your gut microbiome matters for mental health

3. How stress disrupts the gut-brain connection

4. Signs your gut-brain axis might be off balance

5. Everyday ways to nurture gut and brain health

What is the gut-brain axis?

Your gut and brain are in constant conversation through the gut-brain axis—a network of nerves, hormones, immune signals, and microbes. One of the most important players here is the vagus nerve, which links your brainstem to your heart, lungs, and digestive tract.

🍬 Did you know? That “butterflies in the stomach” feeling before something nerve-wracking is your vagus nerve relaying signals between your gut and brain.

This isn’t just about digestion. The messages sent through this system also shape mood, focus, and stress responses. So when people talk about a “gut feeling,” they’re describing a real biological process.

Why your gut microbiome matters for mental health

Inside your gut lives a vast ecosystem of microbes - your gut microbiome. These trillions of bacteria don’t just help break down food; they also influence your brain chemistry.

• Around 90–95% of serotonin (a key mood-regulating neurotransmitter) is produced in the gut, not the brain.

• Other microbes contribute to dopamine (motivation and reward) and GABA (a calming chemical linked to reduced anxiety).

When the microbiome is in balance, this chemical communication supports emotional wellbeing. But if balance is lost - a state called dysbiosis - it can affect sleep, mood, and digestion.

☝ Fun fact: Early studies suggest that certain probiotics may reduce anxiety and depression symptoms, showing just how tightly linked microbes and mood can be.

How stress disrupts the gut-brain connection

The gut and brain influence each other in both directions. Stress, anxiety, and trauma don’t just affect your thoughts, they can also:

• Shift the balance of your microbiome

• Contribute to inflammation

• Influence the gut lining, making it more “leaky”

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🧠 Think about it: feeling nauseous before a job interview or craving carbs after a stressful day isn’t “all in your head” - it’s your gut-brain axis reacting.

The problem is that this can become a vicious cycle: stress affects the gut, which influences the brain, which in turn creates more stress.

Signs your gut-brain axis might be off balance

Because the gut and brain are so intertwined, an imbalance often shows up as both physical and emotional symptoms, such as:

• Persistent digestive discomfort (bloating, irregular bowels)

• Brain fog or difficulty concentrating

• Low mood, anxiety, or irritability

• Sleep disturbances

• Ongoing fatigue

🗒️ If you’ve been treating digestive, mood, or sleep issues separately, they may actually share the same root cause: an imbalanced gut-brain axis.

Everyday ways to nurture gut and brain health

The good news: this system is highly adaptable. Small, consistent changes can help restore balance and improve how you feel day to day.

Eat for diversity

Aim for at least 30 different plant-based foods per week. Variety in fruits, vegetables, legumes, nuts, herbs, and whole grains nourishes a more diverse microbiome, which benefits both digestion and mental health.

Add fermented foods

Foods like kefir, live-culture yoghurt, sauerkraut, kimchi, and miso introduce beneficial probiotics. Certain strains, such as Lactobacillus rhamnosus, have even been shown to lower cortisol (the stress hormone).

Relax with stress

Choose stress-relief practices that feel kind and realistic, whether journaling, yoga, deep breathing, or simply walking outside.

🫶 Reminder: Chronic stress reduces microbiome diversity. Calming your mind also nurtures your gut.

Prioritise sleep

Sleep and gut health are linked in a feedback loop. Protecting your rest supports microbial balance, which in turn supports restorative sleep.

Move your body

Exercise doesn’t have to mean hours in the gym. Brisk walks, dancing, or cycling all increase microbial diversity and boost mood.

🏃 Try this: A 10-minute walk after meals supports digestion, stabilises blood sugar, and helps clear your mind.

Final thoughts

Your gut and brain are constant collaborators. If you’ve been battling digestive discomfort, brain fog, or mood swings, it might not be a pile of separate issues but one ongoing conversation between belly and brain. Supporting your gut health means supporting your mental clarity, emotional balance, and resilience too.

Key takeaways

• The gut-brain axis links digestion and mental health through nerves, hormones, and microbes.

• The gut microbiome produces important brain chemicals like serotonin, dopamine, and GABA.

• Stress disrupts this system, and gut imbalances can worsen mood and sleep.

• Signs of imbalance can include bloating, fatigue, anxiety, and trouble concentrating.

• Daily habits - such as eating a varied diet, including fermented foods, reducing stress, getting enough sleep, and staying active - have a positive effect on the gut-brain connection.

References:

Arneth, B. M. (2018). Gut–brain axis biochemical signalling from the gastrointestinal tract to the central nervous system: gut dysbiosis and altered brain function. Postgraduate Medical Journal, 94(1114), 446–452. https://doi.org/10.1136/postgradmedj-2017-135424

Bistas, K. G., & Tabet, J. P. (2023). The Benefits of Prebiotics and Probiotics on Mental Health. Cureus, 15(8), e43217. https://doi.org/10.7759/cureus.43217

Dandamudi, B. J., Dimaano, K. A. M., Shah, N., AlQassab, O., Al-Sulaitti, Z., Nelakuditi, B., & Mohammed, L. (2024). Neurodegenerative Disorders and the Gut-Microbiome-Brain Axis: A Literature Review. Cureus. https://doi.org/10.7759/cureus.72427

Makris, A. P., Karianaki, M., Tsamis, K. I., & Paschou, S. A. (2020). The role of the gut-brain axis in depression: endocrine, neural, and immune pathways. Hormones, 20. https://doi.org/10.1007/s42000-020-00236-4