The Wandering Nerve
If you’ve ever made a decision based on your gut feeling, it was likely to have been informed by signals from what has been called our second brain. ‘Gut feeling’ isn’t just a colourful idiom. Hidden in our intestinal lining is our enteric nervous system: millions of nerve cells lining our whole gastrointestinal tract. This nerve centre exerts influence well beyond hunger pangs, and impacts our overall mood and mental health.
The gut nerves send signals to our brains through the amazing information superhighway that is our vagus nerve. Extending from its origins in the brainstem through the neck and thorax down to the abdomen, the long vagus nerve is the most obvious physical representation of the brain-body connection. Scientific understanding of the vagus nerve’s role in the gut-brain axis is opening up new frontiers in medical treatment and possibilities for improving wellbeing.
The vagus nerve is rather romantically named the ‘wandering’ nerve (from the Latin). By far the longest of the 12 cranial nerves, it does indeed wander from the brain to connect with many of our most critical organs - heart, larynx, liver and the organs of the digestive tract. It is better imagined not as a single nerve, but as a complex bundle of fibres branching off into numerous parts of the body. It plays a key role in our autonomic nervous system, which controls our unconscious actions: digestion, heart rate, breathing and cardiovascular activity.
The autonomic nervous system comprises two parts: sympathetic and parasympathetic. The sympathetic nervous system activates the fight, flight or freeze response during threat or perceived danger, and the parasympathetic nervous system restores the body to a state of calm, digestion and rest. The systems works in balance; the activation of one means the suppression of the other. When your sympathetic nervous system is activated (the classic example is being chased by a lion, but more modern examples might be being growled at by a dog while jogging, or giving a big presentation at work) you become alert, your heart and breathing rate speeds up and your energy mobilises. At the same time, your digestion slows and feelings of calm disappear. It is essential for our long term mental health that we are able to switch flexibly between the two systems. Crucially, once a perceived or real threat is removed, the parasympathetic nervous system should swiftly switch on, deactivating our sympathetic stress response. The vagus nerve is the main parasympathetic operator, and therefore is intimately involved in the healthy balance of the two systems.
Often we think of nerves as being the brain’s messaging system: transmitting signals from the brain to the organs. The vagus nerve does perform this function. But it is far more than a one way street. Imagine instead the vagus nerve as a ten lane motorway. Two lanes are carrying messages from the brain to the organs. But eighty percent of the nerve’s lanes are carrying messages that flow the other way: from the body - and particularly our enteric nervous system in the gut - to the brain.
Which takes our wandering back to our gut feelings. When your enteric nervous system senses that something is wrong (often well before your ‘thinking’ brain can catch up), the vagus nerve transports signals from gut to brain, and then returns new signals from brain to gut and other organs in response, forming a feedback loop. That feedback loop then helps communicate when the danger is past so that the body can switch into calm and rest mode. A 2014 Swiss study looked at what would happen if that loop was interrupted in rats. The research showed that once they became afraid, they had trouble overcoming this fear even when the danger was no longer present. This suggests that healthy functioning of the vagus nerve helps us bounce back from stressful situations and overcome fear conditioning.
Health and wellbeing solutions
Medicine is looking at how we can use the vagal nerve to support mental and brain health. Limited use of electrical stimulation of the vagus nerve (through a surgically implanted device called a Vagus Nerve Stimulator) has been approved as a therapy for patients whose chronic depression has failed to respond to other treatments. Electrical stimulus is also being used in some cases to treat severe epilepsy, again where other treatments have failed. There has also been some promising early research into whether vagal nerve stimulation can reduce the severity of rheumatoid arthritis.
A step down from the technological stimulation of the vagal nerve but in the same vein, people have been looking into how we can use the vagus nerve to boost mental well-being. There is some suggestion that strengthening the ‘tone’ of the vagus nerve can have beneficial effects, and improve overall wellness. People with a strong vagal tone may find it easier to relax after a stressful event, and their body may be better able to manage inflammation and gut issues. A number of techniques have been suggested to strengthen the vagus nerve, and influence the activity of the calming parasympathetic nervous system:
Deep rhythmic breathing stimulates your parasympathetic nervous system and lowers stress levels, while potentially increasing vagal tone. A simple breathing exercise is to breathe in to the count of 5, breathe out to the count of 5, wait for a count of 5 before breathing back in. If 5 feels too much, simply lower the breath count to allow you to breathe deeply but with ease.
Acute cold exposure activates the vagus nerve. Your sympathetic system decreases when your body adjusts to cold, while your parasympathetic system increases. Cold exposure ignites your body’s natural healing powers and leaves you relaxed and refreshed. If you aren’t used to cold exposure, adapt to it gently.
A healthy microbiome is important for the optimal function of the enteric nervous system and vagal functioning. Research suggests that gut microorganisms can activate the vagus nerve, and improve the feedback loop of the gut-brain axis. Consider adding fermented foods to your diet for their probiotic effect, and prebiotics to benefit the growth of healthy bacteria. Our Vegan Collagyn collection contains inulin which is one of the most well researched prebiotic fibres.