Breath

The argument

James Nestor is a science journalist. Breath grew out of a breathing class that a doctor recommended for his recurring pneumonia, and out of his earlier reporting on freediving, where he met people who held their breath for minutes at a time. He came to believe that breathing is a neglected lever on health. His claim is that modern humans breathe through the mouth, too fast, and too much, and that this contributes to snoring, sleep apnea, high blood pressure, anxiety, and crooked teeth.

The book mixes three strands. The first is a self-experiment at Stanford. The second is history and anthropology: skulls, lost texts, and forgotten researchers. The third is a tour of breathing practices, from yoga to Wim Hof, that Nestor tries himself.

Nestor calls breathing a lost art. His point is that the knowledge was never secret. Ancient Chinese medical texts, yoga manuals, and 19th-century writers such as the painter George Catlin, who urged Americans to shut their mouths and breathe through the nose, all described it. Modern medicine, in his view, treats breathing as automatic and therefore ignores it. He estimates that a large share of adults breathe through the mouth at least part of the time, and that most have never been told it matters.

The Stanford experiment and the nose

Nestor and a Swedish breathing coach, Anders Olsson, agree to a two-part test under the supervision of Jayakar Nayak, a rhinologist at Stanford. For ten days they block their nostrils with silicone plugs and tape so they can only breathe through the mouth. For the next ten days they breathe only through the nose and practice slow breathing exercises.

The mouth-breathing phase goes badly for Nestor. His blood pressure rises. His heart rate variability drops. He snores for hours each night, and his sleep apnea events multiply. He feels foggy and anxious. Nayak's team finds that his nasal passages become inflamed and colonized by bacteria. He describes it as feeling sick without being sick.

In the nasal phase the numbers reverse. Snoring falls sharply and apnea events almost disappear. Blood pressure comes down. Nestor uses the two phases as the spine of the book. He presents them as a demonstration, not a controlled study, since the sample size is two.

Why the nose matters. Nestor explains what the nose does that the mouth cannot. It filters, warms, and humidifies air. Its tissues release nitric oxide, a molecule that widens blood vessels and increases oxygen uptake. He cites research that nasal breathing raises nitric oxide levels several times over mouth breathing. The nose also slows the breath, which increases the pressure in the lungs and improves gas exchange.

He describes the nasal cycle: the nostrils alternate dominance every few hours, which some yoga traditions use to shift arousal. He also covers erectile tissue in the nose, which swells with congestion, and the way sleeping position affects it.

Mouth breathing, in his account, dries the airway, promotes snoring, and lets the tongue fall back during sleep. Over years it changes the face. He cites the work of the orthodontist Marianna Evans and others who argue that a mouth-breathing child grows a longer, narrower face with a smaller jaw and crowded teeth.

He spends time on mouth taping: a small strip of tape over the lips at night to force nasal breathing. He reports that it reduced his own snoring and that some dentists and sleep specialists recommend it. He also describes nasal dilators and the idea that chronic congestion can be trained away.

The shrinking face

A large part of the book is anthropology. Nestor visits the Morton Collection of skulls at the University of Pennsylvania and the catacombs under Paris. Ancient skulls, he reports, show wide jaws, straight teeth, and large nasal openings. Modern skulls show narrower faces and crooked teeth.

His explanation follows the dentist Weston Price and later researchers. For most of human history, people chewed tough food for hours each day. Chewing built the jaw and widened the airway. Industrial food is soft. Infants bottle-fed on formula and children raised on processed food do not develop their jaws, so the airway narrows, the tongue has less room, and mouth breathing follows.

Nestor argues that this is reversible to a degree, even in adults. He tries a device that applies pressure to the palate to widen it, and he describes studies in which chewing gum or hard foods increased bone density in the jaw. His practical advice is simple: eat food that requires chewing, and chew more.

Slow and less

The most useful chapter for most readers is about rate. Nestor reports research by Luciano Bernardi, who studied people reciting the Latin rosary and the yoga mantra om mani padme hum. Both practices produce a rate of about six breaths per minute. At that rate, heart rate, blood pressure, and brain blood flow enter a rhythm Nestor calls coherence.

From this and other studies he arrives at what he calls the perfect breath: inhale for about 5.5 seconds, exhale for about 5.5 seconds, for about 5.5 breaths per minute. He argues that this rhythm improves oxygen delivery and calms the nervous system, and that it is embedded in prayer traditions across cultures. He also notes that many people breathe at 12 to 20 breaths per minute, which he considers too fast.

The second idea is breathing less. Here Nestor draws on the Ukrainian physician Konstantin Buteyko, who treated asthma by training patients to breathe less air. The physiology is the Bohr effect: carbon dioxide in the blood helps hemoglobin release oxygen to tissues. Breathing too much blows off carbon dioxide, which constricts blood vessels and makes oxygen harder to deliver. Buteyko's exercises raise tolerance for carbon dioxide. Nestor describes the control pause, a measure of how long you can hold your breath after a normal exhale before the urge to breathe arrives, and reports it as a rough marker of breathing health.

Nestor applies this to exercise as well. Olsson has him cycle with the mouth closed. At first it feels like suffocation. Over the nasal phase, his output at the same effort improves, and he argues that athletes who train the nose gain endurance because they use oxygen more efficiently. He ties this to the Bohr effect again: more carbon dioxide tolerance means more oxygen delivered to working muscle.

He also profiles Carl Stough, a choir director who taught emphysema patients and Olympic runners to exhale fully, and whose method, Breathing Coordination, improved lung function in patients that doctors had written off. Nestor argues that a full exhale is more important than a deep inhale.

Breathing hard: Tummo, Wim Hof, and Holotropic Breathwork

The later chapters move to intense techniques that stress the body on purpose. Nestor calls them "breathing plus."

Tummo is a Tibetan Buddhist practice of forceful breathing and breath holds that generates body heat. He tells the story of Alexandra David-Néel, a French explorer who reported seeing monks dry wet sheets with their bodies in the cold, and of the French yogi Maurice Daubard, who practices in snow in his eighties. The best known modern version is the Wim Hof Method: rounds of deep breaths followed by breath holds, plus cold exposure. Nestor cites a study at Radboud University in which trained volunteers suppressed an immune reaction to an injected toxin.

Holotropic Breathwork was developed by the psychiatrist Stanislav Grof as a legal substitute for LSD after the drug was banned. Participants breathe fast and deep for an hour or more to music and report visions, emotional release, and altered states. Nestor tries it and reports a mild experience. He also describes Sudarshan Kriya, a rhythmic breathing practice taught by the Art of Living Foundation, and visits a researcher who studies carbon dioxide and the fear response in people with anxiety.

His position on these methods is that they work by pushing the nervous system hard and then letting it recover. He does not treat them as daily tools for everyone.

The appendix of techniques

Nestor closes with a short list of methods readers can try:

• Alternate nostril breathing (nadi shodhana): close one nostril, inhale, close the other, exhale, and repeat.
• Breathing coordination: Stough's method of long, full exhales while counting aloud.
• Resonant or coherent breathing: inhale and exhale for about 5.5 seconds each.
• Buteyko breathing: control pause measurements and reduced-volume breathing.
• Chewing: tough foods and gum to build the jaw.
• Box breathing: inhale, hold, exhale, hold, each for four counts.
• 4-7-8 breathing: inhale for four, hold for seven, exhale for eight.
• Breathing plus: Tummo and similar methods, with a warning not to practice them in water or while driving.

His summary rule is: shut your mouth, breathe through your nose, breathe slowly, and exhale fully.

What the critics say

Reviewers describe the science as uneven. The Stanford test involved two people and no controls. Several claims rest on small studies, animal data, or anecdotes, and the links between skull shape, soft food, and mouth breathing are debated among anthropologists. The benefits of nasal breathing and slow breathing for relaxation have better support than the stronger claims about disease. Readers should treat the book as a tour of ideas, not a clinical guide.

Who should read it

Read it if you snore, sleep badly, feel anxious, or have never thought about how you breathe. The chapters on nasal breathing and slow breathing are the practical core. Skip the Tummo and Holotropic sections unless you want the history.