Epidemiologic studies have suggested that consumption of phytoestrogen-rich foods may protect against breast cancer, and phytoestrogens such as genistein have been reported to both inhibit and stimulate the growth of some human breast cancer cells. The phytoestrogens genistein, daidzein, biochanin A, and coumestrol were tested and found to inhibit serum-stimulated growth in both T-47D and MCF-7 breast cancer cells at 10-100 microM. Extracts of several estrogenic herbs, including hops, black cohosh and vitex, inhibited growth of T-47D cells. These in vitro results suggest that certain herbs and phytoestrogens may have potential in the prevention of breast cancer.
