The vagus nerve has quietly shaped how our bodies function for thousands of years. Recently, it has moved into the spotlight, especially in wellness culture, where manipulating it is often described as a way to calm the body, reset the nervous system or even treat a wide range of conditions.

As someone who researches the vagus nerve in clinical settings, I think it is important to explain what it actually does, what we know so far and where claims run ahead of the evidence.

The vagus nerve is one of 12 cranial nerves that emerge directly from the brain. It is the longest of them, extending from the brainstem through the neck and into the chest and abdomen. Along the way it connects to the heart, lungs, gastrointestinal tract and liver. You cannot see or feel it directly, but it helps regulate everything from your heartbeat to digestion.

Its name comes from the Latin word for “wanderer”, reflecting its long route through the body. One of the most important things to understand is that it is primarily a sensory nerve. Roughly 80% of its fibres carry information from the body back to the brain, acting as a constant internal monitoring system. Only about 20% of the fibres send signals from the brain to the organs.

In practice, this means the vagus nerve continually informs the brain about what is happening inside the body, including heart rate, digestion and inflammation.

The vagus nerve is a major component of the autonomic nervous system, which controls functions we do not consciously regulate. This system has two main branches.

The sympathetic nervous system drives the fight-or-flight response. It increases heart rate, raises blood pressure and prepares the body for action.

The........

© The Conversation