Director of the Integrative Medicine Unit at Rabin Medical Center, Dr. Opher Caspi explains:

People the world over rely on soy as a major source of protein, especially in Asia. Beyond being a vital nutritional resource, soy also contains a group of chemicals called phytoestrogens. These are similar to estrogen, an important female sex hormone, and have been said to stimulate the estrogen receptors of breast cancer cells and make them grow. This has created concern that soy consumption may lead to progression of breast cancer in women who have breast cancer positive estrogen receptors (ER+) and women with increased risk of breast cancer. It was therefore, recommended to these women to avoid excessive daily consumption of soy.

New research from China found that increased soy consumption was not associated with breast cancer disease progression and, on the contrary, that it brought about a decrease of up to 30% in mortality and morbidity from this disease.  However, soy food produced in America also tends to be genetically modified and heavily processed. Overall, the results of this study could be quite different if conducted with participants from Western countries. Therefore, unequivocal conclusions regarding the protective effort of soy for breast cancer can only be made after a long-term, well-controlled research study which includes women with breast cancer or in the high risk group from a variety of cultures. Until then, there seems no reason to avoid a varied diet rich in soy from plants.