David R Hamilton, Ph.D. – There’s a lot of buzz around the vagus nerve these days, but many people still don’t fully understand what it is, how it works, or why it matters so much for health.
So this week’s Better You, Backed by Science is dedicated to why “toning” your vagus nerve can make such a difference – and how to do it.
What is the vagus nerve — and what does “toning” it mean?
The vagus nerve plays a central role in maintaining balance and stability across your body’s systems – a state known as homeostasis. When that balance is off, we’re more vulnerable to illness, inflammation, and emotional dysregulation.
Having a healthy vagus nerve is associated with:
♦ Better cardiovascular health
♦ Lower resting heart rate and blood pressure
♦ Reduced inflammation
♦ Improved emotional resilience
“Vagal tone” refers to the activity (or efficiency) of the vagus nerve. Higher vagal tone = greater capacity to regulate and support health.
You don’t have one vagus nerve — you have thousands
Despite the singular name, the vagus nerve is actually made up of about 200,000 fibres – bundling from the brainstem, with around 100,000 running down each side of your neck and into the body. These fibres reach into the face, major organs, the gut, and the immune system.
Here’s what’s fascinating:
About 80% of these fibres are afferent – meaning they carry information from the body to the brain, constantly reporting on your internal state.
The brain then responds by sending signals back out to adjust and regulate – like applying brakes or changing gears depending on what’s needed.
How breathing can increase vagal tone
The vagus nerve acts like a brake on the heart – and it’s the reason your heart rate naturally slows when you exhale.
Here’s how it works:
When you inhale, your lungs stretch. Stretch receptors detect this and send signals (via the vagus nerve) to the brain.
The brain responds by easing off the vagal “brake” – your heart rate speeds up.
When you exhale, the brain increases vagus nerve output to the heart – slowing it down.
So:
Inhale = heart rate speeds up
Exhale = heart rate slows down
Thanks to the vagus nerve.
The longer and slower the exhale, the more sustained the vagal activation.
That’s why deep, slow, diaphragmatic breathing increases vagal tone.
In fact, in an 8-week Harvard and Beijing Normal University study, this kind of breathing not only increased vagal tone — it also improved cognitive function, boosted mood, and reduced negative emotions.
The vagus nerve helps control inflammation
One of the vagus nerve’s most powerful roles is through what’s called the Inflammatory Reflex – a biological circuit that lets the brain detect and regulate inflammation.
When inflammation rises, vagus nerve fibres carry the signal to the brain.
The brain responds by sending a message back through the vagus nerve, telling immune cells to turn the inflammation down.
This is why higher vagal tone = better inflammation control.
In one study of people with stage 4 cancer, those with the highest vagal tone lived longer than those with the lowest. Researchers suggested it was the vagus nerve’s anti-inflammatory effect that made the difference – especially when medications were less effective.
There’s even a clinical technique called Vagus Nerve Stimulation (VNS) – where the vagus nerve is electrically stimulated – currently being studied for conditions like rheumatoid arthritis, Crohn’s disease, epilepsy, and depression.
Try this: Two simple vagus nerve practices
Spend just 5 minutes a day this week doing either of these:
1. The 3-7 breath
Breathe in for 3 seconds, then out for 7.
This is a go-to for Kevin Tracey, the scientist who discovered the inflammatory reflex. The extended exhale increases vagus nerve activation to the heart.
2. Sigh on the outbreath
According to research, sighing on your outbreath activates the vagus nerve and can improve mood.
Take a comfortable breath in, then let out a long, audible sigh.
References (if you’re curious):
Harvard and Beijing breathing study
For more, read “The Great Nerve” by Kevin Tracey
SF Source David R Hamilton Jul 2025