When soy burst onto the Western food scene in the early 1990s, the possibilities for the bean seemed boundless. The protein-packed legume had potential to prevent breast cancer, increase bone mass and alleviate hot flashes. It seemed to lower cholesterol, and thus to help prevent heart disease.
Millions of dollars were poured into research, and technologists plopped soy into every food imaginable. They ground it into burgers, hot dogs and sausages. Tofurky was born. They processed it into cheese, milk and ice cream. Manufacturers added it to baby formula, and baristas foamed it into lattes.
Purists consumed soy in its traditional Asian forms -- as tofu, tempeh or edemame -- while hard-core health nuts sought out soy protein powder or isoflavone-packed supplements.
Fifteen years later, more soy products are available than ever, and conspicuous soy consumption is a cultural shorthand for "Hey, I'm health-conscious!"
But the tides are turning against the Asian wonder food. Call it the "soy backlash."
A crop of books and articles is warning about the dangers, not benefits, of the bean.
Soy has its very own tell-all, penned by nutritionist Kaayla T. Daniels: The Whole Soy Story: The Dark Side of America's Favorite Health Food.
Soy is being tracked by an international watchdog group, the Soy Online Service, whose mission is to "uncover the truth about soy" and inform consumers about "the plethora of criminal and dangerous lies that issue from the soy industry."
Soy, we are warned, can do terrible things should we overdose on tofu or soysauge, suggests the men's magazine, Best Life: "Grow man boobs! Shed muscle tone! Boost estrogen! Saps your sex drive!"
These reactions are extreme, but even mainstream scientists are pulling back on once-heady health predictions for the bean. New research is showing that soy is not the magic bullet researchers once hoped it might be.
Yet these scientists also see soy's fall from grace as the latest casualty in Americans' endless -- and unrealistic -- search for a single substance that can change your life.
"It's just food!" says soy guru Mark Messina, an adjunct professor of nutrition at Loma Linda University in California, who has written books on its health effects and works as a consultant for the soy industry. "We are talking about diet here. Not the fountain of youth."
The vegetable in the hairy pod is a pretty complicated bean. Native to China and Japan, it is termed the "king of legumes" because it has the most complete protein of any member of the pea family. It is high in calcium, magnesium and vitamin B, and contains estrogen-like chemicals -- isoflavones.
It was in the 1990s that evidence of soy's possible benefits began to mount -- as books and magazines ran with the science. During the past 10 years, the average growth rate of soy products has been about 14 percent a year, says Peter Golbitz, president of Soyatech, a soy industry information company.
Even now, he says, soy sales continue to grow, albeit less briskly. "We have been selling to baby boomers and hippies for the past 20 years," he says. "Now it is time to embrace the changing demographic of the American consumer."
That, he said, includes Latinos, Gen X-ers and Y-ers.
Perhaps no food could withstand the hype heaped on soy. But with more rigorous scientific examination, the bean's starry promise seems to be crumbling.
In January, the American Heart Association published an advisory pulling back on its earlier, 2000 stance on soy, which had recommended "including soy protein foods in a diet low in saturated fat and cholesterol."
January's statement said that a review of 22 studies showed that soy protein with isoflavones did not, after all, improve cholesterol. Thus, the association said, it "could not recommend the use of isoflavone supplements in pills or food for the prevention of heart disease."
Alice Lichtenstein, a nutrition scientist at Tufts University and chairwoman of the heart association's nutrition committee, says the scientific cart simply got ahead of the horse.
"Soy is good," she says. "Soy as a food is very good" -- but only because it has healthier fats and vitamins than, say, meat. If you eat a soy burger, you are not eating a hamburger. If you are eating a tofu pup, you are not eating a hot dog.
Last month, there was more bad news for soy. Although many women consume soy or soy supplements in the hope of preventing breast cancer, a study in the Journal of the National Cancer Institute found their hopes may be unfounded.
After analyzing 18 studies, the authors concluded that eating soy may very slightly reduce the risk of breast cancer -- but not enough to recommend soy foods or supplements.
For breast cancer survivors, taking soy supplements (as opposed to eating foods made from soy) could actually be ill-advised, says study co-author Robert Clarke, a professor at Georgetown University's Lombardi Comprehensive Cancer Center.