Can Your Gut Affect Your Mood?

What is the gut-brain axis?

The gut-brain axis is the two-way communication network between your gut and your brain. They’re linked through nerves, including the vagus nerve, immune signals, hormones and chemicals influenced by your gut microbiome. This means your brain can affect your gut, which is why stress can upset your stomach, and your gut can send signals back to your brain, which is why gut health is increasingly linked to mood. It’s a genuine physical connection, not just a figure of speech.

How does your gut affect your mood?

Your gut may influence your mood through the chemical messengers it helps regulate, the signals it sends to the brain, and its effects on immune and inflammatory pathways:

• Neurotransmitters: Gut bacteria can produce or influence chemical messengers involved in gut-brain signalling, including serotonin, dopamine and GABA. Most of the body’s serotonin is produced in the gut, although mood regulation is more complex than serotonin alone.
• The vagus nerve: This nerve is one of the main signalling routes between your gut and brain, helping information travel in both directions.
• Inflammation: Gut imbalance can affect immune and inflammatory signalling, which is one pathway researchers are studying in relation to mood and brain health.

These work together, which is why gut balance is thought to influence mood as a whole rather than through any single pathway.

Can an unhealthy gut cause anxiety or low mood?

An unhealthy gut has been linked to anxiety and low mood, but it is one factor among many rather than a sole cause. Research suggests that gut microbiome imbalance may influence mood through inflammatory signalling, the stress-response system, gut barrier function and microbial metabolites such as short-chain fatty acids and tryptophan-related compounds. People with major depressive disorder also often show differences in gut bacteria involved in inflammation and metabolite production. This does not prove that gut imbalance directly causes mood problems, but it does suggest gut health can be part of the wider mental wellbeing picture.

What are the signs your mood issues might be gut-related?

There's no certain way to tell, but some possible indicators that your mood and gut could be connected include:

• Low mood or brain fog that appears alongside digestive symptoms like bloating or irregular bowel movements
• Mood dips that seem to follow periods of poor diet or disrupted routine
• Feeling worse during times of high stress, which can affect gut balance and barrier function as well as mood
• Mental fog or fatigue that doesn't have an obvious cause

These are soft indicators rather than proof, but if several apply, your gut may be worth considering as part of the wider picture.

How can you support your mood through your gut?

Supporting your gut may help support your mood, and the steps are the same ones that build a healthy gut:

• Eat more fibre and variety to feed a diverse range of good bacteria
• Add fermented foods like yoghurt, kefir, and sauerkraut
• Limit sugar and ultra-processed food, which can drive inflammation
• Prioritise sleep, which supports both gut balance and mental wellbeing
• Manage stress, since it affects the gut-brain connection in both directions

These changes work gradually, so consistency matters more than quick fixes.

How can a gut microbiome test help?

A gut microbiome test can show you the balance of bacteria in your own gut, which is useful because everyone's gut is different. It won't diagnose a mood condition or tell you why you feel a certain way, but it can give you a clearer picture of your gut as a starting point, so any changes you make are based on your own body rather than general advice.

→ Explore the Gut Microbiome Test
→ How to Improve Your Gut Health: The Complete Guide
→ What Is the Gut Microbiome?
→ What Causes an Unhealthy Gut?
→ Can Your Gut Affect Your Skin?
→ Best Foods for Gut Health: What to Eat (and Why)