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The vagus nerve even affects digestion.
May 6, 2024
Margit Hiebl
He is currently making a lot of headlines: the vagus nerve. How the vagus nerve affects the mind and body and how it can be stimulated.
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"With the vagus nerve to inner balance! " "Relax at the push of a button! " "This is how you train your vagus nerve! " "The new way Stress to face! " "Activate the relaxation nerve! " Anyone scrolling through Instagram, Facebook, or TikTok can't avoid the vagus nerve right now.
The offerings range from activating Breathing exercises to humming or ice bathing to vagus meditation, and there are even devices to stimulate the nerve. According to health influencers, the vagus nerve is the patent solution to a major concern of our time: stress management.
But also in the Science now makes the nerve talk again: for example in connection with the treatment of depression , pain , inflammation, obesity, and COVID 19. But what's behind all the healing messages and what is the state of research? Here are some basic facts: The vagus nerve is the tenth of twelve cranial nerves and is actually something special.
"The vagus nerve is the main connection between the organ systems and the brain."
It does not only run in the head but also on both sides of the body – from the brainstem through the neck and chest towards the abdomen. Therefore, it is considered the longest nerve. Numerous branches and ramblings also extend from it, which earned it its name: vagus nerve, from the Latin word vagus for wandering.
Medically expressed: "The vagus nerve is the main connection between the organ systems and the brain – you can think of it as a kind of data highway," says Prof. Dr. Nils Kroemer, who researches at the University Hospitals of Bonn and Tübingen how and whether this super nerve can be influenced.
"About 80 percent of the information is transmitted from the body to the brain via the vagus nerve – a good 20 percent goes from the brain back to the body to control bodily functions based on the integration of signals that are processed in the brain."
In doing so, it is connected to all relevant organ systems: Whether breathing, heart rate, or digestion – the vagus nerve plays a role in all important processes. Also in stress regulation. Because it belongs to the parasympathetic nervous system, the counterpart of the sympathetic nervous system. The sympathetic nervous system is the part of the autonomic nervous system that prepares us to fight or flee in fear or stressful situations – heartbeat and breathing speed up, and intestinal activity is stopped.
The parasympathetic nervous system, on the other hand, helps to calm down again when the danger is over. These connections have been researched for a long time, and also how they can be used therapeutically in a targeted manner. But so far this has been limited to the so-called invasive vagus nerve stimulation (VNS):
The vagus nerve plays a role in all major processes.
For this, a type of pacemaker is implanted below the collarbone, which transmits electrical impulses via the vagus nerve. It has been a therapeutic option for patients with treatment-resistant depression for 20 years and, to some extent, emerged as a side effect from its use in the treatment of epilepsy. It was observed that not only the frequency of seizures decreased, but also the depressive symptoms.
Nevertheless, it was always difficult to draw far-reaching conclusions on exactly how and why it has an antidepressant effect," says Kroemer. In addition, the implantation is associated with a small operation and may be accompanied by side effects such as swallowing difficulties or hoarseness.
Kroemer and his research group therefore rely on a non-invasive alternative, the transcutaneous auricular vagus nerve stimulation (tVNS), which in the future may also enable broader and more flexible application. A mini-electrode is placed in the auricle, an area where a branch of the vagus nerve runs relatively close to the surface. An initial study on this, conducted in 2022, concerned the coupling between the stomach and the brain.
It was known that the vagus nerve supports the transmission of endogenous signals that help in targeted food seeking - finding what provides particularly high energy, so to speak. And also that it digestion can influence the brain. But how this control functions was not clear.
To find that out, the study combined stimulation at the ear with simultaneous recording of brain activation via MRI and an electrogastrogram, which, similar to an ECG, can make signals from the stomach visible. This was the first time it was shown not only that the brain is activated, but also which areas exhibit a stronger coupling with the rhythm of the stomach.
And that the body's own signals can be enhanced within minutes with electrical stimulation of the vagus nerve. Insights that probably play a role in feelings of satiety and hunger, Kroemer suspects. But that is still at the beginning.
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About 80 percent of the information is transmitted from the body to the brain via the vagus nerve.
It was also investigated how acutely the stimulation affects motivation and mood. Although mood-enhancing effects had already been described in patients and measured in healthy individuals, it was not yet known when they occur. The surprising result:
They do not occur during stimulation, but only about 15 minutes later. And that suggests that the effect occurs on a different time scale than digestion and motivation. These are important insights that give hope for future applications to be targeted and individualized, because vagus nerve stimulation can occur at the right time. A promising prospect for a variety of areas.
The vision is to be able to help those affected in the future by optimally timed stimulation to restore their perception of body signals.
For example, in the area of obesity: The problem here in most cases is not to consume fewer calories over a certain diet period, but to maintain this in the long term. The vision is to be able to help those affected in the future with temporally optimized stimulation to restore their perception of body signals or to bring about a behavioral change.
This could also help with depression. Vagus nerve stimulation could be established as a third pillar alongside medication and psychotherapy. For example, in patients who are more likely to have physical changes such as digestive problems. Finding this out is the subject of a currently ongoing study by Prof. Dr. Kroemer and his team.
Also on the topic Inflammation is being researched: Initial results provide hope that stimulation of the vagus nerve may help alleviate rheumatoid arthritis and reduce medication doses, as was reported at last year's rheumatology conference in Leipzig. Similarly in connection with Long COVID: For example, it has been found with ultrasound that the nerve is reduced in size – perhaps a marker of how a physical change in the system can affect the nerve, reports Kroemer. But even here it is still unclear how this finding should be classified.
What is clear is that more studies are needed. Only then can patent remedies be considered. Currently, the mentioned stimulation devices are approved and available – however, Prof. Kroemer advises restraint and medical consultation for private use, because not enough is known about dosage, application, effect, and side effects.
What can be said with some certainty: The vagus nerve cannot be trained like a muscle, as some healing messages on social media might suggest. There are indications that the vagus nerve can be influenced by massage in the ear or neck area, but no valid studies yet that definitively exclude other explanations for this effect, says Kroemer.
"Whenever you set an impulse and there is an exchange of information between the brain and body, the vagus nerve is indirectly involved," says the expert. Nevertheless, the scientist wants more restraint in neuromarketing. "One does not have to market a massage that feels good and relaxes as a vagus nerve massage and thus suggest a special effect."
And also not always make well-being after a certain intervention dependent on whether one demonstrably stimulates the vagus nerve. Health coach and osteopath Andreas Stollreiter sees it similarly. For him, it's always about the whole in daily practice – balancing the autonomic nervous system, i.e., the interplay of the sympathetic and parasympathetic systems.
As a picture of this, he uses the good old saber-toothed tiger: "If we didn't run away, it would eat us. But when it's finally gone, you also have to stop running. And being able to achieve this balance well or better and better, even in stressful everyday situations – that can actually be practiced" – whether the vagus nerve is directly involved in this or not.
