Food...

Soy is similar to the best animal sources of protein without all the saturated fat. Soybeans contain minerals, including iron and, if the processing method is correct, calcium. Soy foods are rich in isoflavones. Isoflavones are unique plant compounds that match human hormone receptors and aid in special health benefits.

Soy protein combined with isoflavones lower cholesterol, provide some protection against cancers of the prostate and uterus, contain antioxidants, inhibit blood clotting, improve the elasticity of blood vessels (benefits blood flow and lowers blood pressure) and aids in the building of bone. For women, it may also ease hot flashes suffered during menopause.

Men
For men, the most direct cancer protection you receive from soy foods relates to the way isoflavones interfere with hormone-related cancers of the prostate. Isoflavones inhibit testosterone from turning into a form that promotes prostate cell growth, and thus, cancer.

Women
The breast cancer story is more complex. There is some evidence that soy foods rich in isoflavones may help protect against endometrial, breast and other hormone-related cancers, but the data is conflicting. While many experts believe that soy foods are health-protective for all women, several raise concerns about isoflavone supplements. However, in the uterus, isoflavones work much as they do for the prostate in men.

Report released April 4th, 2006 by AICR: New Soy-Breast Cancer Study Finds Small but Significant Protective Effect