Viva Las Vagus: The Vagus Nerve
Anyone who practises yoga can have no doubt about the power of the mind-body connection. Even non-yogis know that a few deep breaths can calm us if we’re stressed or in an anxious state. But did you know that just one nerve – the vagus nerve – is largely responsible for this complex symbiotic relationship?
As part of the autonomic nervous system which controls the things the body does automatically, the vagus nerve – which connects the brain stem to nearly all major organs in the body – monitors information from our senses to gauge threat levels.
You can think of the vagus nerve as a two-way radio communication system helping you stay in touch with your sensations and emotions: it is behind your gut instinct, the knot in your throat and the butterflies in your stomach.
When the vagus nerve senses any threat it activates the sympathetic nervous system responsible for our adrenaline and cortisol-fuelled “fight or flight” response. Adrenaline surges through the body making the heart beat faster, expanding the air passages of the lungs and altering the body’s metabolism. Cortisol, the primary stress hormone, curbs the immune system responses and suppresses the digestive system, the reproductive system and growth processes – all non-essential in a fight or flight situation.
It’s been a vital part of the toolkit for human survival since we first evolved.
Stress, as a by-product of a body being in fight-or-flight mode, is a helpful short-lived response. These days stress is primarily psychological – we’re never actually going to be attacked by a sabre-toothed tiger – but our physical response to it remains the same. And in our constantly over-stimulated society, stress levels – induced by anything from noisy neighbours to exam stresses to the constant demands of social media – are on the rise.
As a result, stress has even been labelled “public health enemy no. 1“.
Part and parcel of your body preparing to face (or flee) the threat it senses is that it releases a load of cortisol. One of the three stress hormones, it enables your body to tap into protein stored in the liver and give your body an energy boost.
And although cortisol reduces inflammation in the short term, chronic stress causes cortisol levels to keep rising and, over time, become less effective in managing inflammation in the body. Eventually inflammation becomes unregulated and, as inflammation is closely linked to your immune system, you can be susceptible to all sorts of physical and mental health issues. Problems ranging from mental health and anxiety issues to heart disease, immune system-related health problems, obesity, Alzheimer’s and Type 2 Diabetes have all been linked to excess levels of cortisol in your body.
Stimulating the vagus nerve
Regulation of the vagus nerve – or vagal toning as it is sometimes referred to – can have a profound and immediate effect on the body, as taking those deep breaths when stressed prove. As the vagus nerve controls heart rate and blood pressure, regulating it activates the parasympathetic nervous system, lowering cortisol levels, heart rate and blood pressure.
Less apparent but equally important effects include helping with digestive issues. Vagal toning increases stomach acidity and digestive juice secretion, releasing bile in the gallbladder and controlling blood glucose levels in the liver and pancreas.
This is what’s known as the “rest-and-digest” response system (as opposed to “fight-or-flight”).
Things that work
Sound complicated? It isn’t. The good news is that if you practise yoga, most likely you’ll be doing all of this on a regular basis. A really effective way of stimulating the vagus nerve is through adopting a regular and deep breathing pattern – which yogis do all the time. Diaphragmatic breathing will stimulate the nerve, as will chanting or practising Brahmari (humming or bee breath). Another really easy way is to splash cold water on your face (or use a washcloth): the vagus nerve responds to the cold by activating the mammalian dive reflex which, in an effort to conserve oxygen, slows your heart rate.
So while we know that yoga relaxes you, the physiological effect of it is that by practising it you lower your heart rate and reduce cortisol levels. Doing so on a regular basis will reduce your risk of heart disease and help keep stress levels in balance – which I’m sure we all agree is a Very Good Thing.
This post is an edited version of an article that appears in this month’s Om Yoga & Lifestyle magazine.