The Vagus nerve is the 10th of a total of 12 cranial nerves that exit the skull. The vagus nerve is the longest cranial nerve and translates to "wondering" which refers to its many branches to most vital organs such as the heart, lungs, kidneys, stomach, and intestines. There are actually two Vagus nerves that travel down each side of the upper body. So, what does the Vagus nerve do?
The vagus nerve is the primary nerve of the parasympathetic nervous system. This system is known as "rest and digest" for its control over our mood, sleep, digestion, and stress. The Vagus nerve has an extremely long list of functions including speaking, muscles of the throat, swallowing, slowing of the heart rate, hunger, appetite control, and reducing chronic and acute inflammation. It is estimated that 20% of the vagus nerve function is efferent communication which sends information from the brain to the organs to help with peristalsis and controlling contractions to move bowel along the intestinal tract. But about 80% of the nerve function is sensory information or afferent communication from the intestines back up to the brain. This makes up the majority of the "brain and body" connection.
Symptoms of "low vagal tone" may result in a variety of symptoms. Most recently there have been studies that show low vagal tone may increase the risk of depression, stress and anxiety, cardiovascular disease, kidney malfunction, and irritable bowel disease as it helps regulate the gut microbiome. Other symptoms may include frequent illness, difficulty swallowing, anxiety, depression, gut problems, and high inflammation.
There is exciting new research that is currently being done to evaluate stimulation of the vagus nerve to help manage chronic inflammation in diseases with no known cures. Some research is being conducted with non-electrical stimulation and electrical stimulation or microcurrent to stimulate the vagal nerve and improve vagal tone. Electric muscle stimulation via acupuncture can target the auricular branch of the vagus nerve. In 2019 the first human clinical trial for electrical stimulation of the vagus nerve was performed by implanting an internal electrical stimulation device. The goal was to modify and improve treatment for active rheumatoid arthritis and the results of that study did show promising findings. This video talks about that study in detail.
There are other ways to stimulate the vagus nerve externally. The ear and abdomen are the most common. Taken directly from the Wim Hof Method, these simple techniques are ways to improve vagal tone without the use of microcurrent:
Exposure to cold. Shocking your body to acute cold conditions, such as taking a cold shower or splashing cold water on your face, increases stimulation of the vagus nerve. While your body adjusts to the cold, sympathetic activity declines, and parasympathetic activity increases. Deep breathing. You can indirectly stimulate the vagus nerve by taking deep, deliberate breaths from your belly. Deep breathing activates specific neurons that detect blood pressure. These neurons signal to the vagus nerve that blood pressure is becoming too high, and the vagus nerve in turn responds by lowering your heart rate. Meditation. Meditating is another great way to increase parasympathetic activity. It will bring your body in a state of calm, telling your vagus nerve that there is no need for a fight-or-flight response, thereby increasing vagal tone. Singing. You can also use singing, humming, and gargling to activate your vocal cords and the muscles in the back of your throat, which are connected to the vagus nerve. Incorporating these activities into your daily routine can help increase your vagal tone."