Eating to beat breast cancer: potential role for soy supplements.

BACKGROUND The study reviews the anticancer properties of natural isoflavones which occur in especially high concentration in soybeans. It considers the suitability of soybean products for clinical trials aiming to reduce the progression of breast cancer. METHODS Evidence is reviewed that plant isoflavones such as genistein show cytostatic activity against human mammary cancer cell lines in vitro and can also suppress carcinogen-induced mammary cancer in young and mature rats. RESULTS Plant isoflavones are converted in the bowel to compounds with potential antioestrogenic and antioxidative properties. These compounds show cytostatic activity for both oestrogen receptor-positive and negative human mammary cancer cell lines, and also inhibit growth and progress of the rat mammary cancer model. The high content of soybean products in the diet of Asian women has been postulated as one reason for their relatively low breast cancer incidence. CONCLUSION Preclinical studies suggest that soybean products be given priority for clinical trials in breast cancer protection. A pilot study could test soy protein supplements as long-term adjuvant dietary treatment after primary surgery for early breast cancer, looking for a decrease in the risk of recurrence or of second primary tumours.