Michael Downey

Perhaps, in these distrustful times, a backlash was to be expected: Thirty years after being introduced as the miracle food in North America — and 5,000 years after it’s discovery in Asia as an important source of protien — the once-unasuming soybean is suddenly the subject of controversy. For example, one book warns of “the ploy of soy,” implying sinister motives on the part of those who grow, market and defend it. Contrary to popular opinion, the naysayers assert, soy can actually be harmful.

Fortunately, this just isn’t so, as any reasonably objective survey of the evidence attests. Not even the critics doubt that soy packs a wide-ranging nutritional wallop and furnishes superior protein.

Reduced to its simplest terms, the case against soy—such as it is—is rooted in the fact that soy is high in phytoestrogen, or plant-based estrogen, and that high estrogen levels are a risk factor for breast cancer. But the latest studies demonstrate that cautions about “too much” soy are groundless.

Protein Power
Repeatedly lost in all this talk about soy’s risks lies a basic fact: Soy is not merely a meat alternative for vegetarians. Research continues to show that soy is nature’s only plant source of complete protein. A complete protein provides all eight of the essential amino acids that foods must supply because the human body can’t make them itself. Like meat and dairy products, soy furnishes the full protein profile—but with a difference.

Unlike meat and dairy, soy is extremely low in cholesterol and saturated fat, an artery-clogging cause of coronary heart disease, which is North America’s leading cause of death. Add in soy’s high fiber and vitamin B6 content, and it’s clear: Soy is the healthiest protein source. No other plant food can make that claim. In fact, no other food can make that claim.

Wouldn’t any bean do? Nope. No other bean offers all eight essential amino acids. And besides offering higher-quality protein, the soybean’s protein makes up 35–38 percent of its total calories, compared to about 20–30 percent for other beans.

Heart Health
Other soy advantages come from its rich source of isoflavones—beneficial, estrogen-like plant hormones. Soy’s isoflavones lower low-density lipoprotein (LDL), or “bad” cholesterol. Isoflavones also decrease thrombosis, or blood clotting. And together, these results reduce the risk of heart attack and stroke. In October 1999, the US Food and Drug Administration (FDA) officially recognized this health benefit by allowing foods containing at least 6.25 grams of soy per serving to state: “Diets low in saturated fat and cholesterol that include 25 grams of soy protein per day may reduce the risk of heart disease.” And there’s more.

Soy’s isoflavones also reduce plaque in arteries, improve blood pressure, increase brain and nerve-cell function and lower high blood pressure. Even people with low cholesterol benefit from soy because it boosts high-density lipoprotein (HDL), the “good”cholesterol.

Blood Bean
And research that the Beth Israel Deaconess Medical Center in Brookline, Massachusetts, reported in November 2002 concluded that a handful of roasted soy nuts daily produces the same reductions in blood pressure that some medications do.

The favorable studies keep piling up. The August 2002 issue of Stroke, a journal of the American Heart Association, reported that the essential fatty acid known as omega-6—an essential polyunsaturated fat that must come from the diet because the body cannot make it—protects against strokes. Another essential fat, omega-3, also protects against heart disease. And soy contains both types of omegas.

A study conducted by the University of Toronto and St. Michael’s Hospital, both located in Toronto, and published in the December 2002 issue of Metab olism, found that diets combining soy, nuts and oat-based fibers drop LDL levels by a dramatic 29 percent. That matches the reduction that some pharmaceutical drug treatments achieve. “This opens up the possibility that diet can be used much more widely to lower blood cholesterol and possibly spare some individuals from having to take drugs,” which may cause side effects, said lead author David Jenkins, MD, PhD.

Cancer Concepts
Then there is soy’s supposed cancer link. The isoflavones and protein in soy provide antioxidants, which are compounds that neutralize free radicals—the toxic, oxygen-based molecules that damage cell membranes and DNA. Antioxidants reduce free-radical damage, which includes cancer and aging. And soy’s soluble fiber reduces the risk of many digestive cancers such as colon and rectal cancer. The water-absorbing fiber may dilute intestinal carcinogens and usher them out of the body, as well as spur growth of bifidobacteria, the good bacteria that help prevent colon cancer.

Isoflavones are the primary ingredients in the “smart bomb,” a drug that University of Minnesota scientists believe may cure childhood leukemia. And isoflavones guard the body against many hormone-related cancers such as breast, uterine and prostate cancer.

Numerous early studies showed that consumption of tofu, soybeans and soymilk lowered the incidence of dense breast tissue, which is considered a high risk for breast cancer.

Contrary to the popular soy scare, women who consume soy foods are less susceptible to breast cancer, but the exact mechanism is unknown. Here’s one theory: Once digested, the soybean’s phytoestrogens mimic the activity of a woman’s natural estrogen hormones. Some of the body’s receptors accept the phyto estrogens—which are significantly weaker than natural estrogens—instead of the body’s own estrogens. Thus, a woman’s overall estrogen level is lower. Because high estrogen levels are linked to breast cancer, a reduced level lessens a woman’s risk of cancer.

Menopause Relief
Holistic health practitioners have long recommended the use of phyto estrogen-filled soy foods to help prevent hormone-related can cers and to aid women in relieving symptoms of menopause such as hot flashes. Some perimenopausal and menopausal wom en receive prescriptions from their physicians for soy-based hormone replacement therapy. These therapies are derived from soy and yam and have the same chemical structure as hormones manufactured by the human body. Because they replicate the behavior of natural estrogen, they are known as bio-identical hormone replacement therapy (BHRT).

Taking BHRT is not the same as relying on soy foods alone to aid in symptom relief because BHRT contains a higher concentration of phytoestrogens. Many wo men have had great success with BHRT. Even better, a woman may have a soy allergy but may still be able to tolerate BHRT.

Although men don’t produce estrogen, the addition of soy and phytoestrogen to their diets can help improve their cardiovascular health, and soy appears to help prevent prostate cancer by inhibiting the growth of cancer cells. In fact, a key study—published in the December 2002 issue of Cancer Epidemiology Biomarkers and Prevention—concludes that a supplement containing four iso-flavones, two of which are found in soy, causes pre-cancerous prostate cancer cells to die in numbers five times greater than normal. This finding likely explains why soy-consuming Asian men, who get pre-cancerous cells at rates similar to US men, develop only 3.4 percent of the number of prostate cancers that US men do.

Bean Bashing
In recent years, some scientists suggested that soy’s estrogenic compounds might possibly interfere with hormone levels and actually encourage the growth of some estrogen-dependent breast tumors. Critics feared that soy phytoestrogens could increase a woman’s total estrogen level. Articles began cautioning that soy should be taken “in moderation.” The debate lacked sound scientific evidence, but many people backed away from soy.

Most of the original concerns about soy isoflavones such as daidzein and genistein focused on extracted and concentrated forms in soy supplements—not necessarily on whole soy foods. These
extracted compounds, which are available over the counter in pills and powders, are often advertised as supplements that help women ease menopausal symptoms.

Concerns about these supplements persist, but research presented in July 2002 proved conclusively that soy foods do not increase breast-cell proliferation. According to researchers at three institutions—Cancer Research UK, based in London, the National University of Singapore and the US National Cancer Institute in Bethesda, Maryland—soy reduces breast-cancer risk. Women consuming the most soy are a full 60 percent less likely to have high-risk breast tissue than women eating the least soy.

Also, an April 2000 finding at the University of Toronto concludes that soy does not increase the risk of breast cancer. Study leader David Jenkins, MD, PhD, reported, “The concerns had been whether soy estrogen might lead to hormone-dependent breast cancer or abnormal sexual development in children—but we found no evidence of this.”

And isoflavones, by delivering phytoestrogens, give the body a hormone boost that helps lower cholesterol, build bone mass, and aid nerve and brain function. This is especially important for women whose bodies reduce production of estrogen just before and during menopause.

Asian cultures have integrated soy as a substantial part of their diets for thousands of years, and Asian women, as compared to their American counterparts, tend not to suffer the effects of menopause. In fact, hot flashes are so rare among Japanese women that their language does not include a word for the phenomenon.

Allergies Among Us
It’s true that some individuals are allergic to soy—but not many. Only 1 or 2 percent of all adults are allergic to foods or food additives. And the foods most likely to cause a fatal reaction are peanuts, tree nuts and shellfish. Eggs, wheat, milk and soy are the most common sources of food allergies in children. And although 2–8 percent of children have food allergies, many children outgrow their allergies as they age.

Many commercial foods today contain soy. If you’ve never had a reaction to mayonnaise, margarine, salad dressings or vegetable shortenings before, chances are you won’t with soy. For example, soybean oil accounts for 79 percent of the edible fats used in the United States, according to the United Soybean Board.

Positive Conclusions
Despite the overwhelming evidence of soy’s benefits, some authors warn about soy’s so-called anti-nutrients, a term used to describe compounds—such as trypsin inhibitors and phytates—that interfere with normal nutrient absorption. Both of these components are also found in numerous other common foods, but critics single out soy foods.

Phytates do bind to, and prevent the absorption of, some minerals such as zinc, magnesium and iron. Critics such as Sally Fallon and Mary Enig, authors of The Ploy of Soy, claim soy’s phytates will prevent our bodies from absorbing these important minerals from any other foods eaten at the same time as soy.

However, Karl Weingartner, a soy specialist at the University of Illinois, finds that soy contains just enough phytates to bind the few minerals present in the soy itself—and no more. We still absorb all the minerals present in other foods we eat, even foods eaten with soy. Besides, phytates are antioxidants and have numerous healthful effects, from cancer prevention to boosting immunity. And fermented soy foods—such as tempeh—contain very few phytates, which are also found in other beneficial legumes such as whole wheat, oats, barley, rye, parsnips and split peas.

Raw soybeans contain trypsin inhibitors, which do indeed interfere with trypsin, an enzyme needed for protein digestion. But soaking and cooking soybeans for a long time—a necessity for all forms of soybean preparation—inactivates trypsin inhibitors.

Soy may well be a perfect food. It’s a good source of fiber and important nutrients such as B vitamins, calcium, and omega-3 and omega-6 fatty acids. Soy foods lower the risk of heart disease, cancer, osteoporosis, diabetes and kidney disease. With so many benefits, it’s easy to forget where we started—with the simple fact that soy is clearly nature’s healthiest source of quality protein.