TweetThe unassuming soybean has silently infiltrated the American diet as what might just be the perfect protein source: It's cheap and vegetarian, and could even unclog our hearts. But there may be a hidden dark side to soy, one that has the power to undermine everything it means to be male

James Price's breasts had been painful and swollen. It looked as if gum balls were implanted underneath each nipple. The slightest touch triggered throbs.

For Price, a retired U.S. Army intelligence officer who once flew attack helicopters in Vietnam, these changes were more than just physically uncomfortable. "Men aren't supposed to have breasts," he says today in a quiet Texas drawl. "It was like my body was feminizing."

A lean and wiry man, the breast development stood in stark contrast to the rest of his body. But it was not Price's only symptom. His beard growth had slowed, he'd lost hair from his arms, chest, and legs, and he'd stopped waking up with morning erections. "My sexual desire disappeared," he says. "My penis—I won't say it atrophied, but it was so flaccid that it looked very small in comparison with the way it used to be. Even my emotions changed."

The first three doctors Price consulted diagnosed him with gynecomastia, or the abnormal enlargement of the mammary glands in men. Tests further revealed that estrogen levels in his bloodstream were eight times higher than the normal limits for men, higher even than the levels typically seen in healthy women. Price's estrogen was so high, in fact, that the doctors were at a loss to explain it. One physician became so frustrated he eventually accused Price of secretly taking estrogen. "He thought I was a mental case," says Price, still angry as he recalls the experience.

Dispirited and in pain, he decided to try one more doctor, this time a fellow military man. He made an appointment with Lieutenant Colonel Jack E. Lewi, M.D., chief of endocrinology at the San Antonio Military Medical Center. During that first meeting, neither doctor nor patient had any inkling of just how long and complex this medical mystery would prove to be. Dr. Lewi initially checked for "usual suspect" lifestyle factors known to trigger gynecomastia, from alcoholism to certain herbal ingredients, like tea-tree oils and lavender. With those ruled out, Dr. Lewi was left with a more dreaded suspect: an estrogen-secreting tumor.

Over the next few months, Dr. Lewi ran multiple tests, checking Price for cancer of the testicles, adrenal glands, chest, and lungs. The good news: When the final test came back negative, Price was in the clear on all fronts. The not-so-good news: Dr. Lewi still had no clue what was causing his patient's hormones to go haywire. But he was determined not to be the fourth doctor to leave James Price in limbo.

In the classes that Dr. Lewi teaches to medical students and residents, he has long offered this advice: If you're not finding the right answers, you're not asking the right questions. Though he'd asked Price about his lifestyle and habits innumerable times, he decided to go back once again, and this time to make his questions as specific as possible. "I said, 'Let's go over your diet, meal by meal, and you tell me every single thing you eat and drink.' He said, 'Sure, Dr. Lewi. I get up and usually have some cereal.' I said, 'Do you put anything on it?' He said 'Soy milk.' "

Price explained that he'd developed lactose intolerance in recent years and had switched to soy milk exclusively. It had, in fact, become one of his favorite drinks, a great thirst quencher in the Texas heat.

Dr. Lewi suddenly felt his excitement building. He asked Price how much soy milk, on average, he drank each day.

"He told me, 'Probably about 3 quarts,' " recalls Dr. Lewi about the moment that changed everything.

Over the past decade, soy foods and good health have become inextricably linked in the national consciousness. According to annual U.S. consumer attitude surveys by the United Soybean Board, 85 percent of those polled in 2008 rated soy products as "healthy," a significant increase from the 59 percent who in 1997 thought this was the case. Many men, to be sure, are hard pressed to explain why soy is supposed to be so healthy, but they take it on faith that they should embrace the bean.

"It's something you need to train yourself to like, you know, for the health benefits," my friend Larry, a distance runner, opined recently. "Tofu's the modern equivalent of cod liver oil," added another buddy, Bill. Three times a week, his wife stir-fries tofu with chard. "It's this gunk she calls superfood. I call it soylent green." He pauses a beat before adding, "I guess I'm grateful she gets me to eat it."

TweetCarefull, I grow alot of soybeans on my farm. lol