How you breathe changes more than you think

Breathing is the most automatic thing we do — roughly twenty thousand times a day, without thought. It seems improbable that we could be doing it badly. James Nestor's Breath, published in 2020 and an international bestseller, makes a sustained case that many of us are, and that the consequences reach further than we expect.

Nestor begins with an uncomfortable personal experiment. He and a Swedish breathing expert spent several days breathing exclusively through their mouths, their noses plugged with silicone. Within days, both experienced elevated blood pressure, disrupted sleep, snoring and reduced heart rate variability. Switching back to nasal breathing reversed these effects within days. The experiment is anecdotal, but it anchors a larger argument drawn from the literature of pulmonology, sports science and anthropology.

The book traces the history of human breathing from the fossil record — showing how the human face has changed shape over millennia in ways that have narrowed airways — through to clinical practices such as breathing retraining. Nestor argues that nasal breathing is the baseline: the nose filters, warms, pressurises and adds nitric oxide to air in ways that improve oxygen absorption and have downstream effects on blood pressure and cardiovascular function.

Nestor is a science journalist, not a clinician, and the book sits at the intersection of rigorous evidence and personal investigation. Some practices he covers, such as breathing exercises from ancient traditions, have limited clinical evidence behind them. But the core argument — that the mechanics of breathing have real physiological consequences, and that modern habits are not always optimal — is supported by a real and growing body of research.