Science of soy: the latest word on this versatile bean

The scientific evidence continues to mount: Soy food is good food--and it might be even better than many nutrition experts are willing to admit.

During the past decade, universities and specialty laboratories around the world have conducted thousands of research studies on soy and its effects on the body. Consistently, those studies have shown that the little legume packs a potent nutritional punch.

In 1999, the US Food and Drug Administration (FDA)--based on long-term studies--allowed soy purveyors to make this unprecedented health claim: Eating soy as part of a low-fat, plant-based diet will help reduce cholesterol. Since then, sales of soy products have soared. From soymilks to imitation meats, soy has been moving steadily--albeit slowly--from the confines of hippie health food hangouts to the tables of the American heartland.

Functional Food

Now soy devotees are making more health claims--not approved by a government agency but based on dozens of scientific studies--that soy cuts a wide swath of health benefits flint shouldn't be ignored. These include reducing the intensity of hot flashes for women in menopause; providing nutrients that battle prostate and breast cancers; offering protein that enhances athletic performance; providing the body with autioxidants that help fight everything from diabetes to kidney disease to memory loss; and contributing to bone health for women. One study even suggests that eating soy might reduce hair loss!

Conservative nutritionists caution that more long-term research is needed before they'll cozy up to all these claims. But many others who have watched the health of patients and clients improve with a steady diet of soy foods are convinced that the bean needs to occupy more room on our plates.

Mounting Evidence

One of soy's biggest promoters is Aaron Tabor, MD, the owner of Revival Soy. The company makes soy bars, shakes, pasta, chips and nuts. Tabor first learned of soy's health benefits after being prodded by his mother to help her find relief from menopause-induced hot flashes. Being the good son, he started doing research and found a smorgasbord of research studies that showed that Asian women experience far less menopause discomfort than women in the West, and they have a lower incidence of breast cancer. He also found that Asians have a vastly lower incidence of heart disease.

The key, he believes, is the amount of soy that Asians eat--as ninny as six servings per day.

"Hundreds of human clinical trials have been completed on soy protein and soy isoflavones ... [that] show statistically significant results with soy," Tabor says. "We continue to learn more about soy's benefits each year."

One of the largest soy studies ever is now in progress. The US National Institute on Aging, an agency of the National Institutes of Health, is sponsoring a 5-year, $8 million research effort that's being led by Bill Helferich, a professor of nutrition at the University of Illinois. Scientists from around the country will study the effects of high doses of soy nutrients on breast, brain and fat tissue. Helferich believes the work will provide insights that will be especially helpful for post-menopausal women and the elderly.

Much of the study will look at safety issues, which are the major concern of nutritionists. Many makers of soy foods and supplements are telling consumers to eat amounts of soy products that are far greater than most nutritionists recommend. Scientists hope to determine which levels are safe for consumption, Helferich explains.

Active Ingredients

The main ingredient of soy that researchers have their eyes on is isoflavones. These are phytochemicals with renowned antioxidant properties that may help prevent various diseases, including cancer.

So why are some scientists nervous about isoflavones? They mimic the effects of estrogen, a group of hormones unique to women. Scientists are concerned that women who consume high amounts of isoflavones could be inadvertently encouraging the growth of breast cancer cells.

"Soy in its whole-food form is beneficial," says Dave Grotto, a nutritionist from Chicago. "We just don't have good research on the effects of [large amounts] of isoflavones on the human body."

Mark Messina, a professor of nutrition at Loma Linda University in California, is nationally known for his soy research and advocacy. He says that a regular diet should be rich in soy foods. And he believes that soy supplements are appropriate if used wisely.

He tries to eat enough soy to give him about 50-75 milligrams Crag) of isoflavones every day, which requires eating two or three servings of various soy foods. That's more titan most people will eat. So be recommends supplements that can provide 25-50 mg of isoflavones. He does caution against supplements that provide 100 mg or more of isoflavones.

"We don't know if that amount is harmful, but we just don't have any historical precedent for consuming that amount," Messina says. Studies show that Asians' soy diet gives them 40-80 mg of isoflavones per day.