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Page 52
| mechanisms that enable them to do this involve estrogen-receptor-binding modulation of sex-hormone-binding globulin (SHBG), and inhibition of the enzymes protein tyrosine kinase (PTK) and 5-alpha reductase, a key enzyme involved in prostate cancer. Thus, soy foods have particularly beneficial effects on breast cancer, prostate cancer, and other hormone receptor-type cancers. Genistein and other soy isoflavones also have an antiangiogenesis effect on tumors. As noted in chapter 2, angiogenesis is the process that generates new capillary blood vessels, a critical step in the growth and proliferation of solid tumors. Genistein inhibits angiogenesis by neutralizing vascular endothelial growth factor (VEGF), a substance put out by tumors to encourage blood vessel nourishment. |
| Isoflavones also exert a mild estrogenic effect that may help relieve or eliminate the symptoms of menopause. The isoflavones present in soybeans are greatly enhanced and become more available during the fermentation process. Thus, one should be sure to eat fermented soybean foods such as tempeh, miso, shoyu (soy sauce), and natto along with the nonfermented soybean foods like tofu and soy milk. Studies of Japanese women have shown that those who consume miso soup daily have a significantly reduced risk for all types of cancer compared with those who consume little or none. |
| However, there are also findings that show miso consumption may be associated with a somewhat increased risk of digestive tract cancers, although some believe that faulty refrigeration is the culprit because it leads to bacterial growth in miso. |
| In addition, soy foods are a source of lignans, coumestans, saponins, plant sterols, phytates, and protease inhibitors, all of which contribute to the anti-cancer effects of soy. |
| It is important that dietary studies involving soy be carried out using whole soybeans rather than isolated compounds, since soybeans appear to contain several potential anticarcinogens. Unfortunately, studies continue to be carried out using genistein alone in cancer therapy. |
| Foods That Are Good for You |
| Vegetables |
| In 1996, the largest controlled study ever done to date on diet and breast cancer confirmed that high vegetable intake conferred a 30 to 50 percent protection against not only breast cancer but virtually all cancer sites and types. 6 |
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