Controversy over this thoughtful new book on the pros and cons of yoga, the Hindu-based breathing and posture practice that's been sweeping America for over a decade -- written by noted New York Times science writer William J. Broad -- broke out even before the 300-page volume reached the sales counters in March -- and it's unlikely to die down any time soon.

Apparently, Broad's editors at the Times thought it might be clever to publish two highly provocative excerpts from the book prior to its release, as a sales promo. It's a common enough strategy but it backfired. Many of the country's 15 million yoga devotees -- a huge part of the anticipated sales market -- were so put off by those excerpts that they've dismissed the book out of hand, refusing to buy or even to read it. And many of those that have read the book, Broad's seventh, tend to be drawn to very same parts they found so objectionable to begin with -- and continue to criticize Broad and the Times for what they consider a "sensationalist" and indeed, "unscientific," portrait of their industry.

As a result, a well-researched and carefully reasoned analysis that, on balance, powerfully validates yoga's extraordinary healing potential -- and could even help mitigate the industry's growing reputation for bizarre guru cultism and Hollywood style glitz -- isn't getting the positive reception and wide reading it so richly deserves. And that's a shame.

In fact, the bulk of The Science of Yoga: Risks and Rewards isn't even devoted to the two issues that initially caused so much outrage. For example, the chapter on yoga injuries follows an initial chapter on yoga's contribution to fitness, and is far more nuanced and informative than the published excerpt. Broad does seem to suggest that certain yoga postures are inherently dangerous, and shouldn't be pushed on yoga newcomers, but his main concern isn't with the postures but with the pushers -- the thousands of "certified" yoga teachers roaming around America who, in his view, are too poorly trained in anatomy to teach and who, being young and unusually bendy and aggressive, have an unfortunate tendency to "amp up" their yoga pedagogy to a level that makes debilitating injuries -- their numbers confirmed by data on annual hospital emergency room visits -- more likely than they need be.

Some of his statistics, like his anecdotes, are truly eye-opening. In one study conducted in Finland, a whopping 62 percent of the survey respondents reported suffering one or more yoga injuries sufficiently grave to put them out of commission for a month. Broad even unearths a little-known survey of American yoga teachers conducted in 2007 in which two-thirds of the respondents freely admitted that poorly-trained yogis -- their own colleagues, in other words -- were placing students at risk. For an industry that still routinely denies that these injuries occur as often as they do -- or worse, tries to blame over-eager consumers for them -- Broad's focus on the quality of yoga instruction seems spot on.

Broad also casts doubt on some of the industry's more extreme and recurring health claims -- for example, that yoga has major "weight-loss" benefits. In recent years, Tara Stiles and Sadie Nardini, two of the industry's emerging pop celebrities, have continued to hype the yoga weight-loss connection, which Broad suggests, based on the evidence, simply doesn't exist. Yoga can certainly make you sweat but it also lowers your metabolic rate; even its more intense "Power" versions won't burn off calories like jogging or aerobics -- or even a brisk evening walk -- might. At the same time, yoga's ability to improve flexibility and balance may be unsurpassed, Broad notes, and the practice can also have real body strengthening and toning benefits, especially for specific muscle groups. But as with yoga injuries, and weight loss, even here Broad suggests that the industry adhere to stricter "truth-in-advertising" guidelines, and not claim more for yoga than actual science can sustain.

Broad does detect many impressive health benefits from yoga in specific areas. For example, yoga appears to be a uniquely effective treatment for rheumatoid arthritis and osteoporosis, two bone illnesses that afflict hundreds of millions of people (especially women) worldwide. And practiced regularly, in a meditative setting, yoga's calming effects can relieve stress and hypertension, two of the more serious risk factors for heart attacks and strokes (rather ironic, perhaps, given that Broad also argues that some yoga postures can cause these same conditions). There's even evidence that yoga can slow down the aging process, while stimulating the parts of the brain most associated with artistic imagination and creativity, a tantalizing prospect that Broad suggests might one day turn yoga into a "cultural force of some consequence."

Broad seems especially fascinated with yoga's demonstrated ability to alter mood and to elevate self-esteem, suggesting that it may give yoga wide application in the mental illness field, with problems ranging from addiction to depression. He takes delight in highlighting the work of contemporary yoga industry pioneers like Amy Weintraub, who claims to have overcome her own debilitating clinical depression not through drugs or counseling but on the basis of her yoga practice. Elsewhere, he hails the work of Glenn Black, and Mel Robin, veteran yogis who have helped educate the yoga industry, often against its own will, to create more science-based teaching guidelines, as well as brilliant Indian scientists like Jagannath Gune, who in 1924, at the ripe old age of 40, opened the first national ashram devoted exclusively to the experimental testing of yoga.

While some of these early scientists perpetuated myths about yoga that survive to this day, they also legitimized the idea of subjecting yoga to traditional, even "Western," scientific scrutiny, Broad argues. And that tradition, he suggests, desperately needs to be revived, to ensure that yoga's potential application to modern health problems is explored as widely as possible, rather than the practice left dangling in the foggy realm of perpetual myth and industrially manufactured half-truth.

And what of the other controversial topic that landed the author in so much trouble -- yoga and sex? Broad waits until the end of the book to address it, and like his treatment of injuries, his analysis here is more restrained and nuanced. Yes, he does repeat what many in the yoga world consider a flat-out canard -- that "yoga began as a sex cult" -- and he seems intent on arguing that because yoga so easily stimulates sexual arousal, and can enhance a practitioner's sex drive, that must also be its primary purpose. That said, Broad is making a critical point that too many of his hostile readers are still ignoring -- yoga, in the context of a hyper-sexualized culture like our own, can easily lead many teachers and practitioners astray.

In fact, for those who think that hyper-sexuality and sexual abuse aren't a problem, Broad sets the record straight. It is, and has been, a serious problem, ever since yoga first arrived on American shores, he shows. Many famous yoga celebrities, Indian and non-Indian, including founders of major yoga schools and leaders of important yoga training centers and ashrams, have exploited their followers for sexual gain. Broad cites the experience of the California Yoga Association in the 1990s which received so many reports of rampant sex between yoga students and their teachers that senior leaders were forced to intervene, in a desperate attempt to establish ethical guidelines to protect members of the state's yoga community. And of course, the still-unfolding Anusara yoga sex scandal involving John Friend, which has captivated the yoga blogosphere for weeks on end, has only confirmed this painfully recurring cycle.

What's the solution? Yoga needs to "grow up," Broad says, and focus more squarely on its healing mission. And the best way to start is to create a more professionally trained and licensed teaching corps, operating under some form of public authority, with the power to ride herd on the industry and to crack heads on abusers and charlatans, if necessary. Many countries in Europe, and even in India, the yoga motherland, take their yoga so seriously that they treat it as a collective public good, and like all such goods, subject it to state guidelines and to at least a modicum of regulation. But not in America, Broad notes. Free market fundamentalism and a near-hysteria over religious "freedom," two of the hallmarks of our conservative political culture, have also, oddly enough, suffused the yoga movement. As Broad documents, organized yoga "lobbyists" have already beaten back legislation in New York and Virginia that would have imposed state vocational training guidelines on yoga teachers, just as it does on nurses, chiropractors, and other healing professionals. And more recent legislation in Texas and elsewhere that would require yoga studios to pay sales taxes is also under siege.

Broad suggests that this defensive posture is a dead-end for yoga. Defending an esoteric sub-culture prevents yoga from fully embracing the American mainstream, and sets the interests of the yoga studios and their teachers against the needs of their students and the broader public. In his Epilogue, Broad envisions a time when yoga has moved beyond its traditional know-nothing attitude toward science while the mainstream health and medical establishment has also become increasingly open to "non-traditional" medicine. Government authorities would agree to fund large-scale clinical trials to more thoroughly document yoga's manifold contributions to "disease prevention and treatment". And yoga, with the help of professional accreditation, and a more sober and mature attitude toward its own corporate and social responsibility, could become more accepted as a modern, time-tested "wellness" practice, accessible to the broad masses, not just to a relatively privileged few.

A convergence of science and spirituality? That sounds like a powerful "yoking of opposites," the very essence of yogic philosophy. But that convergence won't happen, Broad suggests, as long as the industry clings to its worst eccentricities, and refuses to subject itself to public scrutiny and oversight. If yoga really wants to grow -- and to "serve," one of its cherished ambitions -- it can't, like a rebellious infant, stay in "Child's Pose" forever. It needs to embrace the world like a trusted friend, rather than indulging its penchant for hollow consumerism and seduction. Only then, he suggests, can yoga truly "soar."