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Take a deep breath—how does it feel? If you’re like most people, you probably haven’t given much thought to the way you breathe. In this book, Breath, James Nestor shares why the way we breathe is so pivotal, and how it touches every aspect of our existence. In this free Breath summary, you’ll learn how breathing affects your health, performance, and even your lifespan. You’ll also find out why so many of us are breathing incorrectly, and how you can transform your life simply by breathing better.

Breath: Nestor’s Journey of Discovery

This book started out as a personal quest by James Nestor to address his own breathing and sleep challenges. He spent 10 years researching, travelling, and self-experimenting with a wide range of techniques, from ancient breathing practices to the latest scientific solutions.

Along the way, Nestor consulted many experts and enthusiasts on respiratory science and breathing, including free divers, scientists, researchers, medical professionals, Yogis, healers, and more.

This book synthesizes Nestor’s findings, including the biological processes involved in breathing, how human breathing patterns have evolved over time, and how this affects our health, performance, and lifespan. In our Breath summary, we’ll be presenting the insights in 2 key sections:

• The Basics of Breathing; and

• The Art and Science of Optimal Breathing.

The Basics of Breathing

Breath and Human Evolution

Breathing is essential to life. It’s much more than the exchange of oxygen and carbon dioxide. Ancient civilizations believe that our breath affects our overall health and vitality. Modern science has further uncovered how breathing affects physiological and metabolic processes to impact physical and mental well-being.

Over the millennia, the way we breathe has changed due to evolution in our diet, lifestyle, and facial structures. Around 1.7 million years ago, our ancestors began to mash food. Then, around 800,000 years ago, they discovered fire and began to cook food. These allowed them to consume and absorb calories more easily, leading to larger brains with less space for our mouths, sinuses, and airways.

This worsened from the Industrial Age when humans primarily ate soft, processed foods that didn’t require hard chewing. In the past, hunter-gatherers had to chew unprocessed foods (like raw grains, fruits, vegetables, and tough meats) on a daily basis, which naturally expanded their jaws. As we chewed less, our faces, jaws and mouths shrank further, so much so that most of us can no longer accommodate all our teeth. Dental malocclusions (misaligned or improperly positioned teeth) were virtually non-existent among hunter-gatherers, but common among modern humans.

Such evolutionary changes meant narrower respiratory passages and less efficient breathing, making modern humans one of the worst breathers in the animal kingdom. Ancient human skulls had a straight facial profile with a broad mouth, wide sinuses, and ample room for their teeth. By contrast, modern humans have compressed sinuses, narrower airways, and smaller mouths. Here’s a visual summary:

Breath summary - overview of evolutionary changes
In short, such evolutionary changes have altered our breathing dynamics, leading to breathing issues such as sleep apnea, sinusitis and other breathing disorders.

The Stanford Experiment

James Nestor went on to describe how the human nose works. He also shared in detail about the 20-day breathing experiment that he participated in together with breath trainer, Anders Olsson. They were guided by Dr. Jayakar Nayak, a researcher and otolaryngologist at Stanford University.  The goal was to study the effects of nose breathing versus mouth breathing.

Effects of Mouth Breathing

For the first 10 days, Nestor and Olsson plugged their noses with silicon nose clips which forced them to breathe exclusively through their mouths. After 10 days:

• Both subjects had higher levels of stress hormones, elevated blood pressure and reduced heart rate variability.

• At night, both men experienced severe snoring, with Nestor developing sleep apnea. Nestor also developed a bacterial infection in his nose.

• There were no changes in blood sugar levels, most blood markers, or ionized calcium levels. Yet, both men had trouble concentrating, sleeping, and generally felt weak and exhausted. They also felt shaky and nauseous post-exercise.

Effects of Nose Breathing

For the next 10 days, they breathed exclusively through their noses. Within 10 days, the effects were reversed:

• Sleep apnea vanished. Snoring decreased instantly by about 85%, and stopped after 2 nights for both subjects.

• Nestor’s blood pressure dropped back to a healthy range, and his nasal bacterial infection cleared without medical intervention.

• Both men felt more energetic, and enjoyed better focus and mental clarity. They also reported 5-10% improvements in stationary bike performance at the gym.

The Stanford experiment showed how far mouth breathing or nose breathing can affect us in just 10 days. The findings corroborate with other studies which found harmful effects of chronic mouth breathing. Do check out our full 13-page Breath summary to learn more about (i) nasal features, functions, and nasal cycles, and (ii) other research findings about nose-breathing vs mouth-breathing.

The Art and Science of Optimal Breathing

Fortunately, we can counteract generations of evolutionary changes and habits to breathe more optimally. Research suggests that proper breathing can significantly reduce symptoms for respiration-related ailments like anxiety, asthma, ADHD, and psoriasis. James Nestor shares various breathing principles and techniques that can be tailored to your lifestyle and personal needs. Here’s a visual summary:

Breath summary - how to breathe optimally

In our complete Breath summary bundle, we’ll be elaborating on each of these areas, including: (i) breathing techniques and exercises (e.g. Buteyko method, breath-holding, Tummo technique, Wim Hof method, Breathwork), (ii) research insights on the impact of breathing (on diseases, cognitive/sports performance, and longevity), (iii) application tips, and (iv) other ancient wisdoms and practices. In a nutshell:

Breathe through your nose, not your mouth. Consider taping your mouth at night.

• Inhale deeply and exhale fully to expand your lung capacity. There are a host of lung-expanding exercises and techniques we can learn from free divers and celebrated breathing coach Carl Stough.

• Carbon dioxide is not just a metabolic waste product—it’s actually crucial for respiration (and we explain why in our full Breath summary). To optimize carbon dioxide levels, you should breathe less + breathe slower. The ideal rate of relaxed breathing is 5.5 seconds for each inhale and 5.5 seconds for each exhale.

• You can potentially use carbon dioxide therapy to manage anxiety rather than address the issues psychologically.

• Occasionally, use controlled bursts of heavy breathing to enhance resilience and consciously regulate bodily functions.

• Use hard chewing and “mewing” to reshape your face and jawline to improve airflow, and adopt a J-posture for better breathing.

Getting the Most from Breath

Optimal breathing can enhance physical and mental health, boost athletic and cognitive performance, and possibly extend life. And, it can be mastered through patience and practice. However, don’t try to rush or short-cut the process. If you’d like to zoom in on the ideas above and get more detailed insights, examples and actionable tips to breathe more heathily, do check out our full book summary bundle which includes an infographic, 13-page text summary, and a 29-minute audio summary.

Breath summary - Book Summary Bundle

The book is packed with stories and anecdotes of Nestor’s self-experiments and his engagements with breathing experts and enthusiasts. You can purchase the book here or visit for more details.

Keen to learn more about your body and health?  Do also check out our Why We Sleep summary to improve healthy sleep, or learn about dysevolution in The Story of the Human Body summary.

About the Author of Breath

Breath: The New Science of a Lost Art was written by James Nestor—an American author and journalist best known for his scientific and anthropological explorations. His writing has appeared in publications such as The New York Times, Scientific American, The Atlantic, and National Public Radio. The book Breath was one of his most notable works, winning the Best General Nonfiction Book of 2020 by the American Society of Journalists and Authors, and was translated into more than 35 languages as of 2022.

Breath Quotes

“This book is a scientific adventure into the lost art and science of breathing.”

“The nose is the silent warrior: the gatekeeper of our bodies, pharmacist to our minds, and weather vane to our emotions.”

“Breathing is so much more than just getting air into our bodies. It’s the most intimate connection to our surroundings.”

“The optimum breathing rate is about 5.5 breaths per minute. That’s 5.5-second inhales and 5.5-second exhales. This is the perfect breath.”

“The key to optimum breathing…is to breathe, but to breathe less.”

Click here to download the Breath infographic & summary

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