Gut Health and Mental Wellbeing: The Gut–Brain Axis Connection

Why This Matters

If you’ve ever felt your mood drop after a bout of bloating or noticed brain fog during digestive discomfort, you’re not imagining it. The connection between gut health and mental health is real, and it’s gaining scientific attention. Known as the gut–brain axis, this communication system links your digestive system to your brain in surprising ways. Supporting gut health might not only help with digestion but also ease anxiety, improve focus, and support emotional resilience.

The Gut–Brain Conversation

Your digestive tract is home to trillions of microbes collectively known as the gut microbiome. These bacteria help digest food, but they also interact with your brain through a complex web of nerves, hormones, and immune signals. Together, this system is called the microbiota–gut–brain axis.

People with conditions like anxiety or depression often show differences in their gut bacteria compared to those without these conditions. Early studies also suggest that improving gut balance may positively affect how we feel, think, and respond to stress.

How the Gut Affects Mood and Cognition

Let’s break down how gut health can shape mental wellbeing:

Vagus Nerve Signalling

The vagus nerve is a direct line of communication between your gut and brain. When stimulated by certain gut bacteria, it can help regulate mood and emotional balance. Disruptions in this pathway may weaken that signal and increase vulnerability to anxiety.

Inflammation and Immunity

Around 70% of your immune system lives in your gut. If the gut is inflamed or imbalanced, the immune system may release inflammatory markers that affect the brain, potentially contributing to brain fog or low mood. A balanced microbiome can help reduce these signals.

Microbial Metabolites: SCFAs

When gut microbes ferment fibre, they produce short-chain fatty acids (SCFAs) like butyrate. These metabolites are linked to improved brain health; they reduce inflammation, protect brain cells, and may even influence learning and memory.

Serotonin and Tryptophan

Gut microbes help regulate how your body processes tryptophan, an amino acid needed to make serotonin. Imbalances in this pathway may reduce serotonin production or divert tryptophan into metabolites linked to low mood.

Stress and the HPA Axis

The HPA (hypothalamic–pituitary–adrenal) axis controls the stress response. Gut microbes influence this system, helping to regulate how much cortisol (your main stress hormone) is released. A healthy gut may help your body respond to stress more calmly and recover more quickly.

Everyday Gut Health Habits

The good news is that everyday habits can support a healthier microbiome and, by extension, mental wellbeing. Here are a few simple ways to help:

• Eat more plants. A fibre-rich diet (vegetables, fruits, legumes, whole grains) feeds the beneficial gut bacteria.
• Include fermented foods. Yoghurt, kefir, kimchi, and sauerkraut introduce helpful bacteria into your gut.
• Manage stress. Stress affects digestion and gut balance. Daily movement, nature time, and breathing exercises can help.
• Stay hydrated. Water supports healthy digestion and microbial function.
• Use antibiotics wisely. Only take them when necessary; they can wipe out helpful gut bacteria.

Final Thoughts

Gut health isn’t a cure-all for mental health conditions — but it’s a growing area of science that reinforces what many of us instinctively feel: when your digestion is off, your mood can be too. Taking small steps to nurture your gut may support clarity, calm, and overall well-being.

If you’re experiencing persistent anxiety, low mood, or cognitive changes, speak with a healthcare professional. Gut health can be one piece of a larger picture — and looking after it is a step in the right direction.

References

1. Cryan, J. F., et al. (2019). The Microbiota-Gut-Brain axis. Physiological Reviews, 99(4), 1877–2013. https://doi.org/10.1152/physrev.00018.2018

2. Jiang, H., et al. (2015). Altered fecal microbiota composition in patients with major depressive disorder. Brain Behavior and Immunity, 48, 186–194. https://doi.org/10.1016/j.bbi.2015.03.016

3. Doenyas, C., Clarke, G., & Cserjési, R. (2025). Gut–brain axis and neuropsychiatric health: recent advances. Scientific Reports, 15(1). https://doi.org/10.1038/s41598-025-86858-3

4. Zheng, P., et al. (2019). The gut microbiome from patients with schizophrenia modulates the glutamate-glutamine-GABA cycle and schizophrenia-relevant behaviors in mice. Science Advances, 5(2). https://doi.org/10.1126/sciadv.aau8317

5. Frankiensztajn, L. M., Elliott, E., & Koren, O. (2020). The microbiota and the hypothalamus-pituitary-adrenocortical (HPA) axis, implications for anxiety and stress disorders. Current Opinion in Neurobiology, 62, 76–82. https://doi.org/10.1016/j.conb.2019.12.003

6. Zhang, R., Ding, N., Feng, X., & Liao, W. (2025). The gut microbiome, immune modulation, and cognitive decline: insights on the gut-brain axis. Frontiers in Immunology, 16. https://doi.org/10.3389/fimmu.2025.1529958