The gut–brain axis: how the gut "talks" to the mind and what it means for how you feel
"I've got butterflies in my stomach." "My stomach tightened with nerves." Everyday language has long known that the gut and the mind are connected. In the last two decades, research has begun to describe how this connection actually works. The results are fascinating, but also often exaggerated.
In short
The gut–brain axis is the two-way communication network between the digestive system and the brain. It includes the vagus nerve, the enteric nervous system in the gut wall, the immune system, hormones and the compounds produced by gut bacteria, the microbiota. Stress can influence digestion, and the state of the gut can in turn influence mood and the response to stress. Research in humans is still developing, and many spectacular results come from studies in animals. What realistically helps: a varied, fibre-rich diet, fermented foods, sleep, movement and managing stress.
What the gut–brain axis is
The gut has its own nervous system, called the enteric nervous system, with hundreds of millions of neurons. For this reason, it's sometimes called the "second brain". It communicates constantly with the brain through several routes:
- the vagus nerve: the main "motorway" between the gut and the brain; most of its fibres carry information from the organs to the brain;
- the immune system: a large share of immune cells is located in the gut;
- hormones: the gut produces hormones that influence appetite and overall state;
- the microbiota: the trillions of bacteria in the gut produce compounds that can influence the body and, indirectly, the brain.
Communication in both directions
From the brain to the gut
Stress and anxiety can influence:
- the movements of the gut, hence diarrhoea or constipation in hard periods;
- the secretion of stomach acid;
- the gut's sensitivity to pain;
- the composition of the microbiota.
From the gut to the brain
The state of the gut can influence, according to research:
- the response to stress;
- mood;
- the perception of discomfort and pain.
The gut doesn't just digest. It constantly sends information about the state of the body to the brain.
The microbiota and mood: what we know and what we don't
What's promising
- some gut bacteria produce short-chain fatty acids, with anti-inflammatory effects;
- the microbiota is involved in the metabolism of some neurotransmitter precursors;
- studies in animals without a microbiota show differences in the stress response;
- some observational studies in humans associate the composition of the microbiota with depression.
What remains uncertain
- many results come from studies in mice and don't transfer directly to humans;
- serotonin produced in the gut doesn't pass directly into the brain;
- studies on "psychobiotics", probiotics for mood, have mixed results and small samples;
- we don't yet know what exact composition of the microbiota is "ideal".
Irritable bowel syndrome: a clear example
Irritable bowel syndrome is one of the most common digestive conditions and a good example of the gut–brain axis. Stress can make the symptoms worse, and psychological interventions, such as cognitive behavioural therapy or gut-directed hypnotherapy, have good evidence for reducing them.
Habits that support the gut–brain axis
Fibre and variety
Vegetables, fruit, pulses, whole grains, nuts and seeds. A large study, the American Gut Project, associated eating more than 30 different plants a week with a more diverse microbiota.
Fermented foods
Yoghurt, kefir, sauerkraut, brine pickles, kimchi. A 2021 Stanford study observed that a diet rich in fermented foods increased the diversity of the microbiota and reduced some inflammatory markers.
Fewer ultra-processed foods
They're associated with a less diverse microbiota.
Regular sleep
Disrupted sleep can also influence the microbiota.
Movement
Regular physical activity is associated with a more diverse microbiota.
Managing stress
Slow breathing, breaks, nature, relationships. Breathing with a longer out-breath activates parasympathetic mechanisms, including through the vagus nerve.
Antibiotics only when necessary
Antibiotics are essential when they're needed, but they temporarily affect the microbiota.
When to see a doctor
Persistent digestive symptoms, blood in the stool, unexplained weight loss, intense pain or sudden changes in bowel habits require a medical assessment. Don't automatically put them down to stress.
How NeuroFit complements your routine
The vagus nerve is one of the main pathways of the gut–brain axis. NeuroFit by Emmanuel CliniX, in Bucharest, uses taVNS, transcutaneous stimulation of the auricular branch of the vagus nerve, as part of its relaxation and recovery experiences.
- Relax (CES, taVNS, neurofeedback): for periods when stress is also felt "in your stomach";
- Reset (taVNS, tPBM, CES): after demanding weeks;
- Longevity (tPBM, neurofeedback, taVNS): as part of a long-term routine.
Each circuit is set after a safety screening. The first experience costs 190 lei. Bookings: +40 790 099 070.
NeuroFit is brain wellness, not medical treatment.
Frequently asked questions
What is the gut–brain axis?
It's the two-way communication network between the digestive system and the brain, through the vagus nerve, the enteric nervous system, the immune system, hormones and the compounds produced by the gut microbiota.
Can stress affect digestion?
Yes. Stress can influence the movements of the gut, stomach secretion and the gut's sensitivity, which explains the digestive symptoms in hard periods.
Do probiotics help with anxiety or depression?
Studies on probiotics for mood have mixed results and small samples. There isn't yet enough evidence to recommend them as a treatment.
How do I support my gut–brain axis?
Through a varied, fibre-rich diet, fermented foods, fewer ultra-processed foods, regular sleep, movement and managing stress.
Brain wellness information. It is not medical advice and does not replace specialist assessment, diagnosis or treatment.