As consumers have pursued healthier lifestyles in recent years, consumption of soy foods has risen steadily, bolstered by scientific studies showing health benefits from these products. Last October, the Food and Drug Administration gave food manufacturers permission to put labels on products high in soy protein indicating that these foods may help lower heart disease risk.

As with health claims for oat bran and other foods before it, this health claim provides consumers with solid scientific information about the benefits of soy protein and helps them make informed choices to create a "heart healthy" diet. Health claims encourage food manufacturers to make more healthful products. With soy, food manufacturers have responded with a cornucopia of soy-based wares.

No sooner had FDA proposed the health claim regulation, however, than concerns arose about certain components in soy products, particularly isoflavones. Resulting questions have engulfed the regulation in controversy.

While the controversy may seem confusing to the consumer giving it casual consideration, a careful review of the science behind the rule reveals a strict divide between what FDA allows as a health claim based on solid scientific research and related issues that go well beyond the approved statements about health benefits of soy protein.

What's known is that all foods, including soy, are complex collections of chemicals that can be beneficial for many people in many situations, but can be harmful to some people when used inappropriately. In that simple fact lies much of the scientific dilemma--when do data show a food is safe and when do they show there could be problems?

Scientists agree that foods rich in soy protein can have considerable value to heart health, a fact backed by dozens of controlled clinical studies. A yearlong review of the available human studies in 1999 prompted FDA to allow a health claim on food labels stating that a daily diet containing 25 grams of soy protein, also low in saturated fat and cholesterol, may reduce the risk of heart disease.

"Soy by itself is not a magic food," says Christine Lewis, acting director of the Center for Food Safety and Applied Nutrition's Office of Nutritional Products, Labeling and Dietary Supplements. "But rather it is an example of the different kinds of foods that together in a complete diet can have a positive effect on health." Much of the research to date has examined dietary soy in the form of whole foods such as tofu, "soymilk," or as soy protein added to foods, and the public health community mostly concurs that these whole foods can be worthwhile additions to a healthy diet. The recently raised concerns, however, focus on specific components of soy, such as the soy isoflavones daidzein and genistein, not the whole food or intact soy protein. These chemicals, available over the counter in pills and powders, are often advertised as dietary supplements for use by women to help alleviate menopausal symptoms such as hot flashes.

The team from the Pennington Biomedical Research Center reports in the April 5 issue of the Journal of the American Medical Association on a six-month study of men and women between 25 and 50 who were placed on a calorie restriction diet that lowered their daily caloric intake by about 25 percent. The researchers compared those on calorie restriction to subjects who either had not been on a diet, had cut calories by about 12.5 percent and increased the energy they burned through exercise by a like amount, or had spent six months on a standard low-calorie diet of about 1,800 to 2,000 calories per day until they had lost 15 percent of their body weight.

The problem, researchers say, is that isoflavones are phytoestrogens, a weak form of estrogen that could have a drug-like effect in the body. This may be pronounced in postmenopausal women, and some studies suggest that high isoflavone levels might increase the risk of cancer, particularly breast cancer. Research data, however, are far from conclusive, and some studies show just the opposite--that under some conditions, soy may help prevent breast cancer. It is this scientific conundrum, where evidence simultaneously points to benefits and possible risks, that is causing some researchers to urge caution. Unlike the controversy surrounding soy isoflavones, available evidence on soy protein benefits is much clearer. That's why FDA limited its health claim to foods containing intact soy protein. The claim does not extend to isolated substances from soy protein such as the isoflavones genistein and daidzein.

"The story's not all in yet," says Margo Woods, D.Sc., associate professor of medicine at Tufts University, who has studied soy's effects in postmenopausal women. "There's a lot of emerging data and it's confusing. In the meantime, we should be cautious." She says her concerns are centered mainly on isoflavone supplements and that she's "much more comfortable" recommending soy as a whole food. "There are probably hundreds of protective compounds in soy [foods]. It's just too big a leap to assume that a pill could do the same thing."

Daniel Sheehan, Ph.D., director of the Estrogen Knowledge Base Program at FDA's National Center for Toxicological Research, also urges caution in consumption of soy isoflavones. In formal comments submitted to the public record of his own agency while FDA was reviewing the health claim, Sheehan, along with colleague Daniel Doerge, Ph.D., wrote, "While isoflavones may have beneficial effects at some ages or circumstances, this cannot be assumed to be true at all ages. Isoflavones are like other estrogens in that they are two-edged swords, conferring both benefits and risks."

Soy Benefits

Soy protein products can be good substitutes for animal products because, unlike some other beans, soy offers a "complete" protein profile. Soybeans contain all the amino acids essential to human nutrition, which must be supplied in the diet because they cannot be synthesized by the human body. Soy protein products can replace animal-based foods--which also have complete proteins but tend to contain more fat, especially saturated fat--without requiring major adjustments elsewhere in the diet.

While foreign cultures, especially Asians, have used soy extensively for centuries, mainstream America has been slow to move dietary soy beyond a niche market status. In the United States, soybean is a huge cashcrop, but the product is used largely as livestock feed.

With the increased emphasis on healthy diets, that may be changing. Sales of soy products are up and are projected to increase, due in part, say industry officials, to the FDA-approved health claim. (U.S. retail sales of soyfoods were $.852 billion in 1992 and are projected to rise to $3.714 billion in 2002. See attached chart.) "We've seen this before with other claims FDA has approved," says Brian Sansoni, senior manager for public policy at the Grocery Manufacturers of America. "It brings attention to products; there are newspaper and TV stories and information on the Internet."

To qualify for the health claim, foods must contain at least 6.25 grams of soy protein per serving and fit other criteria, such as being low in fat, cholesterol, and sodium. The claim is similar to others the agency has approved in recent years to indicate heart benefits, including claims for the cholesterol-lowering effects of soluble fiber in oat bran and psyllium seeds.

FDA determined that diets with four daily soy servings can reduce levels of low-density lipoproteins (LDLs), the so-called "bad cholesterol" that builds up in blood vessels, by as much as 10 percent. This number is significant because heart experts generally agree that a 1 percent drop in total cholesterol can equal a 2 percent drop in heart disease risk. Heart disease kills more Americans than any other illness, while disorders of the heart and blood vessels, including stroke, cause nearly 1 million deaths each year.

FDA allowed the health claim for soy protein in response to a petition by Protein Technologies International Inc., a leading soy producer that tracks its origins to soybean studies sponsored by Henry Ford in the early 1930s. The company was acquired by E.I. du Pont de Nemours & Company (DuPont) in 1997. In considering the petition, FDA reviewed data from 27 clinical studies submitted in the petition, as well as comments submitted to the public record and studies identified by FDA. The available research consistently showed that regular soy protein consumption lowered cholesterol to varying degrees.

One of the studies, conducted over nine weeks at Wake Forest University Baptist Medical Center and reported in the Archives of Internal Medicine in 1999, found that soy protein can reduce plasma concentrations of total and LDL cholesterol but does not adversely affect levels of HDL, or "good" cholesterol, which at high levels has been associated with a reduction in heart disease risk. Another often-quoted study, published in the New England Journal of Medicine in 1995, examined 38 separate studies and concluded that soy protein can prompt "significant reductions" not only in total and LDL cholesterol, but also in triglycerides, a fat linked to health problems when present at elevated levels.

Other studies hint that soy may have benefits beyond fostering a healthy heart. At the Third International Symposium on the Role of Soy in Preventing and Treating Chronic Disease, held in late 1999, researchers presented data linking soy consumption to a reduced risk of several illnesses. Disorders as diverse as osteoporosis, prostate cancer, and colon cancer are under investigation.

Soy's Many Faces

Though soy may seem like a new and different kind of food for many Americans, it actually is found in a number of products already widely consumed. For example, soybean oil accounts for 79 percent of the edible fats used annually in the United States, according to the United Soybean Board. A glance at the ingredients for commercial mayonnaises, margarines, salad dressings, or vegetable shortenings often reveals soybean oil high on the list.

But the health claim only covers the form that includes soy protein. This form can be incorporated into the diet in many ways to help reach the daily intake of 25 grams of soy protein considered beneficial.

While not every form of the following foods will qualify for the health claim, these are some of the most common sources of soy protein:

Tofu is made from cooked pureed soybeans processed into a custard-like cake. It has a neutral lavor and can be stirfried, mixed into "smoothies," or blended into a cram cheese texture for use in dips or as a cheese substitute. It comes in firm, soft and silken textures.

"Soymilk," the name some marketers use for a soy beverage, is is produced by grinding dehulled soybeans and mixing them with water to form a milk-like liquid. It can be consumed as a beverage or used in recipes as a substitute for cow's milk. Soymilk, sometimes fortified with calcium, comes plain or in flavors such as vanilla, chocolate and coffee. For lactose-intolerant individuals, it can be a good replacement for dairy products.

Soy flour is created by grinding roasted soybeans into a fine power. The flour adds protein to baked goods, and, because it adds moisture, it can be used as an egg substitute in these products. It also can be found in cereals, pancake mixes, frozen desserts, and other common foods.

Textured soy protein is made from defatted soy flour, which is compressed and dehydrated. It can be used as a meat substitute or as filler in dishes such as meatloaf.

Tempeh is made from whole, cooked soybeans formed into a chewy cake. It is commonly used as a meat substitute.

Miso is a fermented soy bean paste used for seasoning and in soup stock.

Soy protein is also found in many "meat analog" products, such as soy sausages, burgers, franks, and cold cuts, as well as soy yogurts and cheese, all of which are intended as substitutes for their animal-based counterparts.

Adding Soy Protein to the Diet

For consumers interested in increasing soy protein consumption to help reduce their risk of heart disease, health experts say they need not completely eliminate animal-based products like meat, poultry, and dairy foods in order to reap soy's benefits. While soy protein's direct effects on cholesterol levels are well documented, replacing some animal protein with soy protein is a valuable way to lower fat intake.

"If individuals begin to substitute soy products, for example, soy burgers, for foods high in saturated fat, such as hamburgers, there would be the added advantage of replacing saturated fat and cholesterol [in] the diet," says Alice Lichtenstein, D.Sc., professor of nutrition at Tufts University.

Whole soy foods also are a good source of fiber, B vitamins, calcium, and omega-3 essential fatty acids, all important food components. The American Heart Association recommends that soy products be used in a diet that includes fruits, vegetables, whole grains, low-fat dairy products, poultry, fish, and lean meats. The AHA also emphasizes that a diet to effectively lower cholesterol should consist of no more than 30 percent of total daily calories from fat and no more than 10 percent of calories from saturated fat.

Nowadays, a huge variety of soy foods is on shelves not only in health food stores, but increasingly in mainstream grocery stores. As the number of soy-based products grows, it becomes increasingly easy for consumers to add enough soy to their daily diets to meet the 25-gram amount that FDA says is beneficial to heart health. According to soybean industry figures, the numbers add up quickly when you look at the protein contained in typical soy foods. For example:

• Four ounces of firm tofu contains 13 grams of soy protein.
• One soy "sausage" link provides 6 grams of protein.
• One soy "burger" includes 10 to 12 grams of protein.
• An 8-ounce glass of plain soymilk contains 10 grams of protein.
• One soy protein bar delivers 14 grams of protein.
• One-half cup of tempeh provides 19.5 grams of protein.
• A quarter cup of roasted soy nuts contains 19 grams of soy protein.

Though some consumers may try soy products here and there, it takes a sustained effort to eat enough to reach the beneficial daily intake. This is especially true for those who have elevated cholesterol levels.

Dietary interventions that can lower cholesterol are important tools for physicians," says Antonio Gotto, M.D., professor of medicine at Cornell University, "particularly since diet is usually prescribed before medication and is continued after drug therapy is begun." He emphasizes that in order to succeed, such diets must have enough variety that patients don't get bored and lapse back into old eating habits. He says his experience with patients suggests that it's important to learn how to "sneak" soy into the diet painlessly.

"People think it's challenging to get a high concentration of soy into your diet," says chef and cookbook author Dana Jacobi. "But it's actually easy to consume 25 grams [of soy protein], once you realize what a wide range of soy products is available." For those new to soy, she recommends what she calls "good-tasting" soy foods such as smoothies, muffins made with soy flour, protein bars, and soy nuts.

The American Dietetic Association recommends introducing soy slowly by adding small amounts to the daily diet or mixing into existing foods. Then, once the taste and texture have become familiar, add more. Because some soy products have a mild or even neutral flavor, it's possible to add soy to dishes and barely know it's there. Soy flour can be used to thicken sauces and gravies.

Soymilk can be added to baked goods and desserts. And tofu takes on the flavor of whatever it is cooked in, making it suitable for stews and stir-fries. "Cook it with strong flavors such as garlic, crushed red pepper, or ginger," says Amy Lanou, a New York-based nutritionist. "One of my favorites is tofu sauteed with a spicy barbecue sauce." She also suggests commercial forms of baked tofu, which she says has a "cheese-like texture and a mild, but delicious, flavor." For soy "newbies," she also recommends trying a high-quality restaurant that really knows how to prepare soy dishes--just to see how professionals handle soy.

Soy chefs and nutritionists suggest the following further possibilities for adding soy to the diet:

• Include soy-based beverages, muffins, sausages, yogurt, or cream cheese at breakfast.
• Use soy deli meats, soy nut butter (similar to peanut butter), or soy cheese in sandwiches.
• Top pizzas with soy cheese, pepperoni, sausages, or "crumbles" (similar to ground beef).
• Grill soy hot dogs, burgers, marinated tempeh, and baked tofu.
• Cube and stir fry tofu or tempeh and add to a salad.
• Pour soymilk on cereal and use it in cooking or to make "smoothies."
• Order soy-based dishes such as spicy bean curd and miso soup at Asian restaurants.
• Eat roasted soy nuts or a soy protein bar for a snack.

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