There are a lot of claims made about the vagus nerve. The longest cranial nerve in your body, made up of 200,000 fibres, it’s been heralded as the answer to everything from how to deal with stress to how to live a longer life. Videos on TikTok and Instagram share tricks to “reset” it and open a world of calm.Others promote in-ear or skin-adhesive devices claiming to do the same. But to Dr Kevin Tracey, neurosurgeon and scientist at Northwell Health’s Feinstein Institutes for Medical Research in New York, these sound a lot like snake oil – “their claims are cheapening the real science”, he says. If anyone is able to sort fact from fiction, it’s Dr Tracey. He has spent the past 30 years researching the healing potential of the vagus nerve, and his lab was the first to show that nerve directly connects the brain and the immune system. He has since gone on to develop forms of Vagus Nerve Stimulation (VNS) therapy including an implant in the chest for epilepsy and a VNS implant to treat rheumatoid arthritis which is currently awaiting approval from the US regulator FDA. And as the title of his new book implies – The Great Nerve: The New Science of the Vagus Nerve and How to Harness Its Healing Reflexes – he believes the vagus nerve has the potential for huge healing power. (Photo: Matthew V Libassi)

What is the vagus nerve?

The vagus nerve forms the main part of our parasympathetic nervous system, known colloquially as our “rest and digest” mode as opposed to our “fight or flight” mode (the sympathetic nervous system). Signals travel along these fibres between the brain and the body and are responsible for autonomic bodily functions including digestion, immune system regulation and heart rate. One of these fibres, which connects to the spleen, was found by Dr Tracey and his team to be able to “turn off” inflammation. While acute inflammation can be healing (when your body responds to infection), chronic or low-level inflammation has been dubbed “modern life’s silent killer”. Lifestyle factors like overreliance on ultra-processed food, smoking, stress and a sedentary lifestyle all contribute to chronic inflammation, which in turn has been linked with diseases like cancer, heart disease, diabetes and dementia. (Photo: Mike Kemp/In Pictures via Getty)

'Could benefit millions with arthritis'

All of which to say, research and study around the vagus nerve has the potential to have far-reaching and even life-changing effects. There is even potential that some hacks could benefit us. But, Dr Tracey says, many being pushed online haven’t been rigorously tested. “We understand enough about the science of the vagus nerve to know that its role in stopping inflammation is potentially world-changing, and certainly could benefit millions of people with arthritis,” he says. “But at the same time there’s companies selling devices and making claims that are at best, incomplete and at worst, questionable.” He worries that people will try these devices or techniques, find them wanting, and then dismiss anything vagus nerve-related. And yet, there are still a few techniques that Dr Tracey employs in his daily life, despite the lack of definitive evidence. He describes this as his “Pascal’s Wager” where the potential reward outweighs the potential loss. “I don’t mind doing these things – maybe they help, maybe they don’t,” he says. “I believe that some of them may very well be increasing the vagus nerve fibres that go to the immune system and decrease inflammation. If that’s the case, and I live longer and healthier because I do these things, I may or may not ever know. And if it doesn’t work, I won’t know either!” (Photo: Getty)

1) Breathwork helps manage anxiety...

When you deliberately breathe deeply you engage your diaphragm, a muscle at the base of your lungs, which gives your lungs space to expand. This sends a signal up your vagus nerve to the brain, which in turn triggers other nerve fibres to slow your heart rate, lower your blood pressure, and induce a general sense of calm and well-being. Studies have corroborated that breathing can increase your vagal tone (a measure of parasympathetic nervous system activity, as calculated by changes in time between heartbeats) as well as helping manage anxiety and even improve business decisions. (Photo: Olga Rolenko/Getty/Moment RF)

...But evidence around it is not conclusive

But it’s hard to scientifically conclude that deep breathing directly stimulates your vagus nerve, which means the evidence is not conclusive, Dr Tracey explains. “If you want to know if breathing inhibits inflammation you can control how people breathe but you can’t control the fact that some people start to meditate when they breathe. You also can’t definitively measure levels of inflammation. It’s almost impossible to get a well-controlled experiment where you can draw a reasonable conclusion.” Nonetheless, Tracey will do a few minutes of cyclical breathing most days and favours the inhale for three, exhale for seven method (his “favourite, because it’s easy”). Regardless of whether it stimulates his vagus nerve, he says he certainly feels calmer and happier for it. (Photo: RealPeopleGroup/Getty)

2) Meditation can create calmness

The benefits of meditation seem to stem from the same place as those from breathwork, though meditation doesn’t always focus on the breath. As is often the case, it is very hard to prove that meditation stimulates the vagus nerve and therefore reduces inflammation. “No one can say for sure that meditation causes the brain to activate the inflammatory reflex or to influence inflammation through some pathway(s),” he writes in his book. But some studies have found that meditation enhances the meditator’s vagal tone, as well as potentially modulating the activity of brain centres, reducing anxiety and enhancing happiness. As with the breathwork, Dr Tracey aims to do focused attention meditation (where you pay attention to your breath or concentrate on a single mantra or goal) for about 10 minutes. “I have made it a habit, like brushing my teeth,” he says, and finds that he feels far more calmer and a greater sense of well-being as a result. (Photo: Malte Mueller/Getty)

3) Cold water exposure reduces inflammation

Interestingly, cold water exposure which induces hyperventilating (where you engage your fight or flight response) can also reduce inflammation, which is why Dr Tracey turns his shower to cold for a few minutes several times a week. “People talk about cold immersion stimulating your vagus nerve but it’s actually not so simple,” he explains. “When you jump into a cold bath or a cold shower, the first response you get is fight or flight and that is inflammatory. But if you get through the acute fight or flight state and then cold adapt, then the heart rate starts to slow, the body temperature starts to drop and then you are stimulating the vagus nerve. It could be that you get a dual benefit of stimulating fight or flight and ‘rest and digest’, and they are not acting in opposition.” While the immersive cold shock is never pleasant, he says he’s found that he’s now used to it, and has higher tolerance for cold – as well as feeling calmer and happier. (Photo: James Manning/PA)

4) Exercise five days a week for all-round health

Perhaps unsurprisingly, Dr Tracey is a big proponent of exercise for its “profound health effects”. Though he points out that once again, it is hard to see a clear cause and effect between exercise and stimulating the vagus nerve. “While it is certain that regular, moderate-intensity exercise improves cardiovascular fitness, decreases resting heart rate, and improves vagal tone measured by heart rate, proving that exercise is beneficial because it reduces inflammation is not so simple.” Exercising activates the sympathetic nervous system which, as with cold immersion, has anti-inflammatory effects when it is engaged for an acute period of time. But the parasympathetic nervous system also appears to be working together with fight or flight. “If you do this acute vigorous exercise, you get a fight or flight response,” he explains. “But if you do that aerobic training, where you can still have a conversation, while you work out for 45 minutes or an hour, the vagus nerve is slowing the heart rate which you can’t see because the heart’s racing (if it was unopposed, it would go even faster). That slowing is a way to enhance cardiac output and enhance the perfusion of the heart muscle, which needs more oxygen during exercise.” (Photo: MixMedia/Getty)

Why is exercise good for us?

In fact, he goes so far as to say we don’t know why exercise is so good for us. “Yeah, there’s, there’s no concrete proof. Is it because it’s sending signals to the vagus nerve to stop inflammation? Is it because you’re strengthening your muscles and getting better insulin sensitivity? Is it because you are enhancing your mood centres and have a more positive outlook, and your more positive outlook prevents cancer? No one knows for sure.” Either way, he tries to exercise in some form five days a week for 30-45 minutes, doing a mix of aerobic exercise, stretching, resistance training and yoga. (Photo: AN Studio/Getty/Moment RF)