your gut has a brain.
and it's talking to your head.

The gut-brain axis isn't wellness woo — it's peer-reviewed neuroscience. Here's what the research actually says.

95%

of serotonin made in gut

500M

neurons in your gut

70%

of immune system in gut

the vagus nerve: your body's information highway

Your gut and brain communicate constantly through the vagus nerve — the longest nerve in your body, running from your brainstem to your abdomen.

This isn't a one-way street. While your brain sends signals down to your gut, 80% of the communication actually travels upward — from gut to brain. Your gut is constantly reporting on its state, and your brain is listening.

The enteric nervous system (your "second brain") contains over 500 million neurons — more than your spinal cord. It can operate independently, but it's in constant dialogue with your central nervous system.

Furness, J.B. (2012). The enteric nervous system and neurogastroenterology. Nature Reviews Gastroenterology & Hepatology.

90% of your serotonin is made in your gut

Serotonin — the neurotransmitter most associated with mood regulation — isn't primarily produced in your brain. Approximately 90% is synthesised in your gastrointestinal tract, produced by specialised cells called enterochromaffin cells.

While gut-derived serotonin doesn't cross the blood-brain barrier directly, it influences the vagal signals sent to your brain and affects systemic inflammation — both of which impact how you feel mentally.

Studies have found significant correlations between gut microbiome composition and symptoms of depression and anxiety. While causation is still being established, the association is consistent across multiple research groups.

Valles-Colomer, M. et al. (2019). The neuroactive potential of the human gut microbiota. Nature Microbiology.

chronic inflammation: the silent disruptor

When your gut barrier is compromised (often called "increased intestinal permeability"), bacterial products can enter your bloodstream, triggering low-grade systemic inflammation.

This inflammatory response doesn't just affect your gut. Pro-inflammatory cytokines can cross the blood-brain barrier, affecting neurotransmitter metabolism and contributing to symptoms like brain fog, fatigue, and mood disturbances.

Brain fog — difficulty concentrating, memory issues
Fatigue — tiredness that sleep doesn't fix
Mood changes — anxiety, irritability, low mood
Bloating — digestive discomfort and distension
Sleep disruption — difficulty falling or staying asleep

These symptoms can have many causes. If you're experiencing persistent symptoms, consult a healthcare professional.

your microbiome: 100 trillion reasons to care

You're home to approximately 100 trillion microorganisms — bacteria, fungi, and viruses that collectively weigh about 2kg. This ecosystem, your microbiome, influences everything from digestion to immune function to mental health.

Diversity matters. Research consistently shows that a more diverse microbiome is associated with better health outcomes. Modern lifestyles — processed foods, antibiotics, stress — tend to reduce this diversity.

Germ-free mice (raised without any gut bacteria) show significantly altered stress responses and behaviour compared to normal mice. When given bacteria from anxious mice, previously calm mice develop anxious behaviours.

Cryan, J.F. & Dinan, T.G. (2012). Mind-altering microorganisms. Nature Reviews Neuroscience.

supporting the gut-brain axis

The gut-brain axis can be influenced through several evidence-based approaches:

Probiotics

Certain probiotic strains have shown promise in clinical trials for improving mood and reducing anxiety symptoms. These are sometimes called "psychobiotics."

Prebiotics

Fibre that feeds beneficial bacteria, helping them thrive and produce beneficial metabolites like short-chain fatty acids.

Adaptogens

Compounds that may help the body adapt to stress, potentially supporting both gut function and the stress response system.

Gut-Supportive Nutrients

Minerals, vitamins, and compounds that support gut barrier integrity and reduce inflammation.

This is the foundation of Symflory's approach: supporting gut health through targeted nutrition, with the understanding that gut health and mental wellbeing are connected.