In Breath: The New Science of a Lost Art, journalist James Nestor spends years with pulmonologists, free-divers, dentists, and breathing researchers to answer a plain question: are we doing this basic thing wrong? His throughline is uncomfortable and simple — most of us breathe too much, too fast, and through the wrong opening.
1. Your nose isn't a backup for your mouth. Nasal breathing filters, warms, and humidifies air, and it releases nitric oxide — a molecule that widens blood vessels and helps the body take up more oxygen per breath. The nose produces roughly six times more of it than mouth breathing does; Nestor cites research suggesting nasal breathing can raise oxygen uptake by nearly a fifth.
2. He plugged his nose for ten days to prove it. In a study at Stanford under rhinologist Jayakar Nayak, Nestor breathed only through his mouth for ten days: his blood pressure climbed about 13 points, his snoring rose by thousands of percent, and he began logging sleep-apnea events. Ten days of nose breathing reversed nearly all of it.
3. Slower beats deeper. The book's "perfect" pace is about 5.5 seconds in and 5.5 seconds out — roughly 5.5 breaths a minute. At that rhythm, sometimes called resonant or coherent breathing, the heart rate and nervous system settle. It's close to the pace people naturally fall into when reciting prayers or mantras.
4. You probably breathe too much, not too little. Carbon dioxide isn't just waste to purge; your tolerance for it governs how efficiently oxygen actually reaches your cells. Chronic over-breathing — big, fast mouthfuls of air — can leave you feeling worse rather than more oxygenated. The counterintuitive fix is usually less air, taken more slowly.
5. Our mouths shrank, and our airways paid for it. Nestor's more provocative claim is that soft, processed modern diets gave humans smaller jaws and more crowded airways than our ancestors — part of why snoring and obstructed breathing are now so common. Chewing tougher food and keeping the mouth closed are, in his telling, partial correctives.
6. The tools are free and portable. Unlike most health advice, none of this needs equipment, a subscription, or time you don't have. You can change how you breathe in the next thirty seconds, in any chair, with no one noticing.
Right now, close your mouth and breathe in through your nose for a slow count of about 5.5 seconds, then out through your nose for the same. Do it for two minutes. It's the single most-tested exercise in the book — and it costs nothing but attention.
Nestor's point isn't that breathing cures everything; he's careful about the more sweeping claims. It's that something we do 25,000 times a day, entirely on autopilot, turns out to be adjustable — and that the smallest change, made through the nose and slowed down, is the one most likely to stick.