“Gut instinct” isn’t just a random turn of phrase. It hints at the bidirectional connection between the gut and the brain. We often talk about your gut and feelings in the same sense without realising it. If you’re anxious, you might say you’ve got “butterflies in your stomach,” you “go with your gut,” or find a traumatic experience “gut-wrenching.”

The common theme is that they’re borderline instinctual. They communicate core, practical information to your brain. This isn’t just a nice idea, the gut-brain axis is a genuine connection.

But how does the gut affect the brain? What does this relationship look like day to day? And why gut microbiome testing can help support your brain? Find out below.

What Is the Gut-Brain Axis?

The gut-brain axis is a two-way biochemical signalling pathway taking place between the gut and the nervous system. There’s also a third component; the gut microbiome. Information is constantly passed between these two systems, including physical and emotional messages.

In fact, your gut is sometimes known as the ‘second brain.’ It contains more nerve cells than anywhere else in your body outside of your brain.

How the Gut and Brain Communicate

The Vagus Nerve (Direct Line of Communication)

If the gut has an urgent message, it gives your brain a call. The vagus nerve is the main link between the gut nerves (enteric nervous system) and the brain. It’s one of the twelve cranial nerves.

The vagus nerve carries sensory information from inside your gut in response to chemical changes or the presence of food. The gut microbiome can even activate the vagus nerve by releasing specific molecules.

Chemical Signalling and Neurotransmitters

Slower messages are sent by the body’s version of the post. Gut bacteria, in particular, release or influence neurotransmitters like serotonin and GABA. These hormones have a direct effect on gut performance, regulating food movement and sensation.

But there’s a behavioural and mood component.

Changes in the gut microbiome are linked to depression, anxiety, and bipolar disorder, which is perhaps due to the effect on serotonin and other neurotransmitters.

The Role of the Immune System

The immune system is an indirect link between the brain and the gut. Gut bacteria can influence levels of inflammation. For example, certain bacteria turn fibre into short-chain fatty acids (SCFAs), which can downregulate inflammation.

Systemic inflammation is known to alter mood and cognitive function. When chronic inflammation occurs, people often notice brain fog or low mood.

The Role of the Microbiome in Brain Function

Your gut is home to trillions of bacteria, viruses, and other microbes, which form the gut microbiome. They play an active role in brain function, altering neurotransmitters and regulating inflammation.

You’ll notice changes in:

• Mood regulation

• Stress response

• Sleep quality

• Cognitive clarity (focus, brain fog)

What Happens When the Gut-Brain Axis is Disrupted

Dysbiosis, or harmful changes in the gut microbiome, can occur due to antibiotics, chronic stress, or a highly processed diet. You’ll often notice immediate changes in your brain function.

Common effects include anxiety and low mood, brain fog, stress-related digestive issues, and increased inflammation.

People often think it’s the foods themselves. Or they might wonder why they don’t feel suddenly better when they change bad habits. The reason is that gut bacteria play the mediating role.

How to Support a Healthy Gut-Brain Axis

Diet and the Microbiome

The easiest way to support the gut-brain axis is to help the gut microbiome. Fibre feeds beneficial bacteria, increasing numbers and protecting against harmful bacteria. Eating a range of different fibre sources helps support a greater diversity of bacterial species.

Fermented foods contain helpful bacteria. If you’ve just taken a hit from antibiotics or chronic stress, these foods can help restore your gut to normal.

Managing Stress

Stress is kryptonite to your gut-brain axis. It causes cortisol levels to spike, which negatively impacts beneficial bacteria, lowers your immune system, and allows harmful bacteria to proliferate.

Tackling stress doesn’t have to be complicated. Just going for a walk, practicing mindfulness, or taking some downtime can make a big difference.

Lifestyle Foundations

Most of the time, the problem is the basics. People don’t get enough sleep, exercise, or eat too much processed food. Ensure you get your 7-8 hours of sleep per night, exercise around 3 times per week, and eat a healthy, balanced diet.

You’ll notice the beneficial effects on your gut-brain axis within a few days. But the real results are felt after a few weeks or months.

Get Your Microbiome Tested

If you’re dealing with brain fog, low mood, or stress alongside digestive issues, it may be worth looking at your gut more closely.

The Functional Gut Clinic offers personalised microbiome testing, along with clear guidance on what to change. It’s a simple way to move from guesswork towards a plan that actually works for you.

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