Gut-brain axis
A two-way communication system between the gut (and its microbiome) and the brain, linking digestion, emotions, mood and cognitive functions.
The gut-brain axis is a constant dialogue between the digestive tract and the brain, through several channels: the vagus nerve (a direct nerve highway), gut hormones, the immune system, and microbiome metabolites (SCFAs, neurotransmitters).
The original angle (the gut, a neurotransmitter factory): a spectacular fact: the gut produces or modulates many neurotransmitters:
- ~90-95% of the body’s serotonin (the « feel-good hormone ») is made in the gut, not in the brain! The microbiome directly influences this production
- The gut also produces dopamine, GABA (calming) and acetylcholine
- The microbiome makes precursors and regulates these molecules
This explains the deep link between gut health and mood. Dysbiosis is associated with anxiety and depression. Studies on « psychobiotics » (probiotics with a psychological aim) show promising effects on mood.
The vagus nerve, a direct line: this nerve links the gut to the brain and carries ~80-90% of its signals from the gut TO the brain (and not the other way round). The gut massively « informs » the brain. Chronic stress disrupts this dialogue.
Practical implications:
- Looking after your microbiome (fibre, fermented foods, diversity) can support mood
- Stress and emotions directly affect digestion (hence the « knots in the stomach », stress-related IBS)
- Heart coherence breathing, meditation and sleep act on this axis via the vagus nerve
The gut-brain axis breaks down the artificial separation between « physical » and « mental » health: the two are intimately linked via the gut.