As a book, Breath works because it sneaks physiology in through storytelling. Nestor uses explorers, monks, athletes, dentists, and oddball experiments to make one simple point: "how we breathe now is not how humans evolved to breathe — and it’s costing us health." He sometimes leans too hard on anecdote, but he never loses sight of the central truth: breathing is a trainable biological system, not an automatic afterthought.
What makes the book especially effective is that it doesn’t treat breathing as wellness fluff. It ties breath to:
* facial structure and crooked teeth
* inflammation and nitric oxide
That’s a surprisingly wide map for something most people do 20,000 times a day without thinking.
Where Nestor is strongest is in showing that "over-breathing" — fast, shallow, mouth-based breathing — is now the default in industrial societies, and that this alone can drive fatigue, nervousness, poor sleep, and reduced oxygen delivery. You don’t need to buy every historical claim he makes to see that the modern chest-breathing, mouth-open pattern is maladaptive.
The practical side of the book is what gives it staying power. You can read it as a story, but you walk away with concrete, testable habits: nasal breathing, slower exhalations, tolerance of mild air hunger, and attention to nighttime breathing. None of that is mystical. It’s nervous-system regulation and gas chemistry.
Breath doesn’t promise immortality. It promises something more believable: that "if you stop fighting your own respiratory system, a lot of things quietly get better." That’s a rare combination of entertainment and usefulness. Nestor made something most of us never think about — breathing — feel like a lost technology.
It’s not a medical textbook. It’s part history, part journalism, part self-experiment. Some of its claims get overstated, but the "core" is solid: how you breathe affects your nervous system, sleep, blood pressure, endurance, anxiety, and even how your face and jaw develop.
And most modern people breathe badly.
What he gets right:
1. Nasal breathing matters
Breathing through your nose:
* warms and filters air
* produces nitric oxide (which improves oxygen uptake)
* keeps airways open
* reduces snoring and apnea
Mouth breathing, especially at night, is linked to:
* poor sleep
* dry mouth and cavities
* higher blood pressure
* anxiety
* worse endurance
If you do "one" thing from that book, it should be: sleep with your mouth closed.
That’s why he pushes mouth tape — weird but effective. I use it now.
2. Slow breathing calms your nervous system
Long exhales activate the vagus nerve. That shifts your body from “fight or flight” into “rest and repair.” It’s not mystical — it’s physiology.
A simple rule:
* Inhale ~4 seconds
* Exhale ~6–8 seconds
Do that for 5 minutes and your heart rate, cortisol, and blood pressure drop.
3. Overbreathing is the modern disease
Most of us breathe too much, too fast, and too shallow. That:
* lowers CO₂
* reduces oxygen delivery to tissues
* increases anxiety and fatigue
The irony: breathing less makes you feel better.
That’s why techniques like Buteyko and “box breathing” work.
4. CO₂ tolerance = endurance and calm
Your urge to breathe is driven by CO₂, not oxygen. Training yourself to tolerate higher CO₂:
* improves athletic performance
* reduces panic
* increases breath efficiency
Simple test: how long you can hold your breath after a normal exhale. Under 20 seconds = poor. Over 40 = very good.
5. You don’t need all the crazy stuff
Some of the book’s “ancient breathing secrets” are romanticized. You don’t need Tibetan monks or Wim Hof ice baths to get the benefit.
Good things:
* nasal breathing
* slower breathing
* deeper diaphragm movement
* better sleep breathing
Breath is a fun read with a lot of good information.
