The truth about soy: latest research confirms its benefits

Perhaps, in these distrustful times, a backlash was to be expected: Thirty years after being introduced as a miracle food in North America--and 5,000 years after its discovery in Asia as an important source of protein--the once-unassuming soybean is suddenly a 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 [B.sub.6], 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 grains 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 if 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 Metabolism, round 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 tire 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.