Fungus spurs development of disease-fighting compounds in soy.

There's good reason for soy's recent surge in popularity. Inside the seed are dozens of plant chemicals that could be a boon to health. Some of these compounds may protect the heart, halt postmenopausal bone loss and stave off certain cancers.

It's soy's phytoestrogens--estrogen-like compounds--that could play an important role in human health. For instance, because hormonal fluctuations in postmenopausal women can put them at an increased risk for developing cancer or experiencing bone loss, some plant-derived estrogens could reduce that risk if they are included in the diet.

The soy compounds of greatest interest to scientists are the glyceollins. Investigators determined that glyceollins can block the growth of hormone-dependent breast cancer cells. But you won't find any glyceollins in soy products

now on the market. That is because today's soybean plants aren't getting enough stress. They are grown in clean, relatively disease-free fields and are not challenged by the pathogens and insects they'd normally encounter in nature. When confronted with disease or stress, soybeans will increase their natural defenses and pump out protective compounds. It's these plant-guarding chemicals that are showing such potential in human health studies.

Scientists have found a way to elicit this chemical response in the laboratory . They are using a fungus--Aspergillus sojae--that mimics the kind of disease threat needed to force soybean plant cells to produce glyceollins. After soaking soybeans for a few hours to get the seeds close to germination, the researchers sprinkled dried A. sojae onto cut surfaces of the legumes.

Just a couple of days after treatment, investigators saw the soybeans' wound surfaces turn a deep red. A biochemical reaction was taking place, and glyceollins were developing. The scientists isolated enough of the compounds from the laboratory procedure for use in health studies. For their research, investigators injected mice with breast cancer cells and then treated the animals with glyceollins. So far, results from the medical studies are promising.

The glyceollins are stopping cancer cells from proliferating, according to scientists. The colleagues also produced a soy protein isolate from their induced soybeans. Also containing glyceollins, the isolate could be the basis for future health foods, like soy protein bars. If collaborators continue to unveil positive results, the next step will be to devise an effective method for treating soybean seeds on a large scale. This may involve finding the genes involved in glyceollin production, or developing sprays or elicitor treatments that can be safely applied to soybean plants themselves.

FYI: An American Heart Association committee recently reviewed a decade of studies on soy's benefits and came up with results that are now casting doubt on the health claim that soy-based foods and supplements significantly lower cholesterol. The findings could lead the FDA to re-evaluate rules that allow companies to tout a cholesterol-lowering benefit on the labels of soy-based food. The heart panel also found that neither soy nor the soy component isoflavone reduced symptoms of menopause, and that isoflavones don't help prevent breast, uterine or prostate cancer. Results were mixed on whether soy prevented postmenopausal bone loss.

Further information. Stephen Boue, USDA-ARS Southern Regional Research Center, Food and Feed Safety Research , Room NPURU, P.O. Box 8048, University, MS, 38677; phone: [phone]; fax: [phone]; email: [e-mail].