Picturing soy in its natural state, as a bean in a fuzzy green pod, makes it all that more challenging to comprehend the staggering number of foods it shows up in.
Since 1999, when the U.S. Food and Drug Administration approved a "heart healthy" labeling claim for certain soy-based foods, pantry staples like cereal and pasta have been "soy-ed up" and repackaged as health foods. But unbeknownst to most consumers, soy is added without fanfare to foods all the time.
In fact, soy ends up in everything from canned tuna to powdered lemonade mix as a "filler" or "extender," moisture retainer, texture provider, protein booster or cheap substitute for flour, eggs or milk.
Is this healthy? That depends on whom you ask, but a vocal contingent of credible sources insists the answer is no.
The FDA has been under pressure to reverse its position that 25 grams of soy protein a day, as part of a diet low in saturated fat and cholesterol, may reduce the risk of heart disease. Research findings that support this claim have been called into question by the American Heart Association and some of the FDA's own divisions.
A 2005 report on soy and health outcomes prepared by Tufts-New England Medical Center, Boston, for the government's Agency of Healthcare Research and Quality, found insufficient evidence to recommend soy for improving cardiovascular risk factors.
"More and more people are recognizing that health claims for soy are more about shrewd marketing than good science," says Kaayla T. Daniel, Albuquerque, N.M., a nutritionist who helped prepare a petition asking the FDA to revoke the health claim.
Still, there is some evidence that soy alleviates symptoms of menopause, lowers cholesterol levels and helps prevent osteoporosis and certain types of cancers.
"But the strength of the data varies," says nutritionist Gary Miller, associate professor of health and exercise science at Wake Forest University, Winston-Salem, N.C. "There is not overwhelming evidence to bear out these claims."
Traditional fermented soy products introduced to the United States from Asia, such as miso (a rich, salty paste used for seasoning and soup stock) and tempeh (whole soybeans bound together into a firm, squared-off patty) are generally accepted as healthy because the fermentation process eliminates naturally occurring plant chemicals found in soybeans that have been shown to hinder digestion and block absorption of other nutrients, says New York-based nutritionist Carol Anne Wasserman.
However, "Foods that contain soy usually contain a highly processed form of soy, which is not healthy," she adds.
Processed, un-fermented forms include soy protein isolate, soy protein concentrate, hydrolyzed plant protein and textured soy protein.
"These products have been so refined as to take away all the nutritional properties that are found in the actual soybeans," Wasserman says.
Soy's many guises as well as its presence in so many foods - including fast-food hamburgers, of all places - threatens allergy sufferers in particular.
Not everyone agrees that soy products, such as those used to make meatless "veggie" burgers, are nutritionally bankrupt.
"Soy is a wonderful low-saturated fat, protein-rich replacement for meat," says Joan Salge Blake, associate professor of nutrition, Boston University.
"Soy burgers have little if no saturated fat, whereas a 3-ounce portion of lean hamburger will contain approximately 5 grams," or about a quarter of the daily recommended allotment of 22 grams.
Daniel is concerned not only about what soy manufacturing takes out of the bean but also what it leaves behind - residues she describes as "toxic and carcinogenic" resulting from the solvents, acids and alkalis used to process soybeans.
In her book "The Whole Soy Story: The Dark Side of America's Favorite Health Food" (New Trends Publishing, 2005), Daniel cites research linking excess soy consumption to malnutrition, digestive distress, attention deficit disorder, reproductive problems, immune system breakdown, thyroid problems and certain types of cancer.
The key phrase is "excess amounts."
"For most healthy people, a little soy now and again isn't a big problem," Daniel says.
But certain people would be well-advised to steer clear of it, she says, pointing out that the Israeli, French and German governments warn that infants and women with a personal or family history of breast cancer should consume soy sparingly or not at all.
The principal concern lies with plant estrogens (phytoestrogens), which can cause hormonal changes in humans, potentially affecting infants' development and women's breast health.
Phytoestrogens "in small amounts have been shown to fight cancer but in larger amounts to actually increase tumor growth, especially if you have a predisposition to breast cancer," Wasserman says.
Dr. William Dunn, Kalamazoo, Mich., a cancer specialist, says patients frequently ask him whether soy should be off-limits. He says that "normal" soy products such as soy flour, soy nuts and soy milk are "probably safe."
"But I certainly can't tell them soy is protective," he adds.
As a rich source of protein, soy can play a role in a healthy diet as well as in weight loss or maintenance, Dunn says.
"Diets based on higher protein could lead to possible weight loss. Indirectly, this could reduce cancer incidence," he says, "but this is an indirect benefit."
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