Activating the Vagus Nerve, Through Breathing, to Relax Your Body from Flight-or-Fight Response

I read about the vagus nerve first in the book "The Ultramind Solution", I highly recommend that book. In the book the author says that through a deep breath into your stomach you activate the vagus nerve. It will then turn off stress response and activate the parasympathetic stress response.

To quote the book:

"Right now take a deep breath into your belly to the count of five, pause for one second, then breathe out slowly to the count of five. Keep your belly soft. Put down the book and do this five times. Notice how you feel in your body and mind. Then keep reading.

You have just activated the vagus nerve, which flows from your brain through your neck, right into your chest, and through your diaphragm. So when you are a deep breath and relax and expand the diaphragm, your vagus nerve is stimulated, you instantly turn on the parasympathetic nervous system, your cortisol levels are reduced, and your brain heals."​

I then talked to a Indian doctor (in my home country) about the vagus nerve, and he said you can even swallow the air for getting a stronger activation. By breathing in swallow the air, and then inhale more, then swallow it, then inhale more etc. This will activate the vagus nerve even more. This relaxes the body from "flight-or-fight" response.