The researchers, led by Prof Stephen Boué from the US Agricultural Research Service, New Orleans, have identified a group of compounds called glyceollins that have been shown to stop the growth of hormone-dependent breast cancer cells in the laboratory.
Population studies have shown that a diet rich in soy is associated with fewer cases of breast cancer, linked to the presence of soy isoflavones. China has the world's lowest incidence and mortality from breast cancer - a disease that has over one million new cases every year worldwide.
The concentration of glyceollins in commercial soybeans is very low since the compounds are only produced by soy as a defence mechanism from disease or infection, which Boué says is not common in today's clean, disease-free soy fields.
The research suggests possibilities for both the health food and pharmaceutical sectors, with talk of glyceollin-rich soy protein bars.
Talking to NutraIngredients.com, co-researcher Ed Cleveland said: "We are hoping to set up an industrial partnership, but because this research is very cutting edge there has been limited interest so far."
"We haven't reached the point where it's a manufacturing process yet. We are still talking lab-scale," added Stephen Boué. "It's very difficult to produce the glyceollins from seed."
Boué explained that the methodology used to produce the glyceollin-rich soybeans involves challenging just-germinated soybeans with the food-safe fungus Aspergillus sojae. The soybean believes it is under attack and starts producing the glyceollins as a defence mechanism.
There is a growing body of research that supports the cancer-protecting properties of soy.
A recent animal study published in the journal Cancer Research (Vol. 66, Issue 2) reported that high dietary intake of soy protected against breast cancer in postmenopausal monkeys.
This supports another study from the University of Ulster that focussed on the inverse link between soy and breast cancer. In this study, funded by the EU's "Quality of Life and Management of Living Resources" project, soy isoflavones were reported to inhibit breast cancer cell invasion in vitro.
The safety of the isoflavones was questioned however by a conflicting study that reported breast cancer cells in mice were stimulated by the compounds.
Toxicology studies involving primates for glyceollins are ongoing with no negative effects reported to date, but all aspects of the research have suffered setbacks due to Hurricane Katrina.
A US patent is pending, while several research articles have been submitted to peer-review journals concerning toxicology tests. NutraIngredients.com has not seen these results.
More information on Prof. Boué's research was published in the USDA's Agricultural Research magazine (January 2006, pp. 8-10).