Scientists in University of California reported on Tuesday that their new research has shown how the healing power of these vegetables works at the cellular level.

While it has been known for some time that eating cruciferous vegetables, such as broccoli, can help prevent breast cancer, the mechanism by which the active substances in these vegetables inhibit cell proliferation was unknown -- until now.

Scientists in University of California reported on Tuesday that their new research has shown how the healing power of these vegetables works at the cellular level.

The study results was published in this month's journal Carcinogenesis.

"Breast cancer can be protected against by eating cruciferous vegetables such as cabbage and near relatives of cabbage such as broccoli and cauliflower," said author Olga Azarenko. "These vegetables contain compounds called isothiocyanates which we believe to be responsible for the cancer-preventive and anti- carcinogenic activities in these vegetables."

Their research focuses on the anti-cancer activity of one of these compounds, called sulforaphane, or SFN. It has already been shown to reduce the incidence and rate of chemically induced mammary tumors in animals. It inhibits the growth of cultured human breast cancer cells.

The researchers made the surprising discovery that SFN inhibits the proliferation of human tumor cells by a mechanism similar to the way that the anticancer drugs inhibit cell division. However SFN is much weaker than these other plant-based drugs, and thus much less toxic.

"SFN may be an effective cancer preventive agent because it inhibits the proliferation and kills precancerous cells," said the authors. It is also possible that it could be used as an addition to anticancer drugs to increase effective killing of tumor cells without increased toxicity.