Men’s Health, cue scary music, takes you one way:
The 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….
….Long the foundation of a vegetarian diet, tofu provides protein with little of the saturated fat and none of the moral indigestion that comes with meat. Moreover, in the past decade, research has emerged suggesting that scarfing down soy may also play an active role in extending our lives. In 1999,soy protein earned a highly coveted FDA-allowed health claim: Diets that include 25 grams—about a pound of tofu—a day may reduce the risk of heart disease. Add to this the number of studies showing that soy protein might also help protect against prostate cancer, and suddenly the stuff starts looking like powerful medicine for men.
Of course, most medicines have side effects. And when you consume soy protein, you’re actually courting the Mr. Hyde side of two natural drugs: genistein and daidzein. Both act so similarly to estrogen that they’re known as phytoestrogens (plant-produced estrogens). Soybeans couldn’t care less about human sex characteristics—genistein and daidzein may have evolved to act as chemical defenses against fungi and grazing animals. (They aren’t very effective deterrents, apparently, since soy meal is widely used to feed livestock.) But when humans consume these compounds in high enough quantities, they may experience gender-bending nightmares like James Price’s (TZ note: he grew breasts and cried more at movies]. What’s more, studies of these phytoestrogens in leading peer-reviewed medical journals suggest that even lower doses—such as the amount in the 25-gram soy proteintarget cited by the FDA—have the potential to wreak hormonal havoc.
And then the New York Times, cue soothing music, debunks the other way:
As far as any downside, most of the health concerns about soy stem from its concentration of phytoestrogens, a group of natural compounds that resemble estrogen chemically. Some experts have questioned whether soy might lower testosterone levels in men and cause problems for women who have estrogen-sensitive breast cancers. Animal studies have found, for example, that large doses of phytoestrogens can fuel the growth of tumors.
But phytoestrogens mimic estrogen only very weakly. A number of clinical studies in men have cast doubt on the notion that eating soy influences testosterone levels to any noticeable extent. And most large studies of soy intake and breast cancer rates in women have not found that it causes any harm, said Dr. Anna H. Wu of the Keck School of Medicine at the University of Southern California. In fact, work by Dr. Wu and others has found that women who consume the equivalent of about one to two servings of soy daily have a reduced risk of receiving a diagnosis of breast cancer and of its recurrence.
Still, some women who have developed breast cancer remain particularly worried about eating soy. But the evidence “is overwhelming that it’s safe,” said Dr. Bette Caan of the Kaiser Permanente Northern California Division of Research, who has studied soy intake and breast cancer. “If people enjoy soy as a regular part of their diet,” she said, “there’s no reason to stop.”
Confusing, no? And a perfect example of how difficult it can be to find a clear answer to a simple question. But I think I will go with the clinical trials and the New York Times, rather than anecdotal scare stories, on this one. And buy a bra.