Soybeans contain compounds that can manipulate estrogen as well as directly inhibit the growth of cancerous cells, theoretically reducing the risk of breast cancer in women of all ages. One soybean compound, in fact, is quite similar chemically to the drug tamoxifen, given to certain women to help prevent breast cancer and its spread. Animal studies have shown that the soybean's phytoestrogens counteract cancer-promoting estrogen much the same way tamoxifen does. Researchers believe that soybean's most active anticancer agent is genistein. This was found to prevent breast tumors in animals. Human studies are in progress.