Books

Go to the archives

The Science of Yoga: The Risks and the Rewards

William Broad

By Lorraine Kreahling
Published: Mar 14, 2012
Category: Health and Fitness

Guest Butler Lorraine Kreahling has contributed regularly to the New York Times, including writing about yoga for the science section. She recently completed “The Green Hotel,” a memoir that explores the archetype of house and home and the process of rebuilding an historic house destroyed by a propane explosion.

If you’ve spent as much time in a yoga studio as I have, you’ve heard a lot about what yoga can do for you. Some of it seems true, but some seems like a Blue State version of faith-based thinking — which is why William Broad, a Pulitzer Prize-winning science reporter for The New York Times, set out to compare the claims about yoga’s benefits with the hard scientific facts. The result is “The Science of Yoga: The Risks and Rewards.”
 
I’ve been doing yoga seriously for more than three decades, and I’ve got a couple of shelves full of yoga books. But this is the most important one I have read. [To buy the book from Amazon, click here. For the Kindle edition, click here.]
 
Broad’s headline comes down to: Yogis Beware, But Take Heart! Like all worthwhile athletic undertakings, yoga can be dangerous. It can also make you stronger and saner, while improving your posture and sex life.
 
Broad, himself a yogi of more than four decades, spent six years combing through research journals and talking to just about everyone who has ever looked closely at yoga and studied its science. His findings are sometimes startling — in both the good and bad sense.
 
Take, for example, the claim that yoga “pumps up” the body’s oxygen supply. The American College of Sports Medicine has determined that for exercise to build aerobic fitness, it must draw on 50 to 85 percent of the body’s oxygen reserve. But Hatha yoga uses only 15 percent of the body’s oxygen reserves, and even the “sun salutations” of Ashtanga yoga — one of the most demanding styles — use just 35 percent. Yoga alone, it turns out, will not make you aerobically fit.
 
Nor does yoga increase yogis’ metabolic “burn.” Multiple studies show that the metabolic rate of fit and long-practicing yogis actually slows markedly, along with the heart rate. This is why trained yogis can last for long periods with a lot less of what the rest of the human race needs — air, water, food.  Documented instances of yoga masters being “buried alive” or locked away in caves for weeks suggest that rather than stopping the heart, these men go into a kind of animal-like hibernation in which everything slows down. The rest of us can actually gain weight from yoga because it slows metabolism.
 
Broad rightly points out that yoga is a physical exercise with spiritual underpinnings. Instructors often draw on the guru archetype to teach: They lead, you follow, and don’t question what the master’s says. But the charisma and confidence yoga teachers exude can mask a lack of knowledge of the physiological realities of joints, bones and muscles. Unlike physical therapists or chiropractors, yoga instructors are not licensed. Some training, like the kinesiology-focused Iyengar method, takes years for certification. But other teachers can train for a couple of weeks. That instructor who is trying to convince you to kick your feet skyward into a headstand actually may have put in fewer yoga studio hours than you!
 
Perhaps the most troubling fact which Broad reports — and which most yogis will find difficult to accept — is that yoga has caused strokes. Apparently excessive pressure on certain fragile blood vessels — usually in the neck in inverted postures like the shoulder stand and the “plow” — can cause blood clots that migrate to the brain. There are yogis out there who are permanently disabled by the stroke brought on by what they did in yoga class. Statistically, Broad reckons, a minimum of 300 yogis annually face the risk of stroke — 15 of which may prove fatal.
 
So why bother? Consider: Broad seems to knows more than just about anyone about yoga’s dangers, and he still practices regularly. And he practices for the simplest of reasons: yoga is good for you. Because his book is so objective and hard-hitting, you feel you can trust the good news here.
 
For example, studies have shown that yoga reduces cholesterol and fatigue, lowers blood pressure, and improves sleep. It counters osteoporosis and improves balance. Better balance may not be of much interest to youngsters, but as you get older, not falling or tripping gets a lot more important. Researchers have also found that yoga has a measurable anti-aging affect. Broad explains telomerase — the microscopic whorls of DNA at the tips of chromosomes —cause us to age as they shorten over time. But one study of 24 men who did yoga for 3 months showed a 30-percent increase of their telomerase.
 
And Broad confirms what every yogi knows: yoga really does calm you down. Research shows yoga lowers levels of that well-known indicator of stress, cortisol. Meanwhile, it raises the neurotransmitter GABA, a kind of natural Valium, that reduces excitability. Yoga also increases hormones that counter depression. 
 
Then there’s better sex. This was of paramount interest to Stephen Colbert:
 
 
Talk about burying the lead. Readers who don’t skip ahead must wait until the next-to-last chapter to learn about “divine sex.” Yoga began and endured for some four thousand millennia as a regimen to fire up the body to make it more sexually receptive, responsive, and, well, potent. But when yoga migrated to the United States. about a hundred years ago, it was sanitized for our still-Puritanical culture. Have you ever wondered why you press down on your pelvic bone in the “cobra”? And what about the rapid breathing exercises your yoga teacher challenges you to imitate? Can you think of another experience that involves fast deep gasps of air? 
 
I won’t spoil all the surprises of Broad’s wonderful reporting about yogis who have learned through Kundalini yoga to “think off” — and who were willing to perform mental arousal to let their brains be scanned by researchers.
 
Suffice to say that William Broad’s book is the richest, most complete portrait of yoga in our time and one that every yogi and potential yogi should read.  If I wanted a new guru, I’d choose William Broad.