A number of studies have concluded that soy foods may contribute to the relatively low rates of breast, colon, and prostate cancers in countries such as China and Japan. Soybeans contain a number of anti carcinogens and a recent National Cancer Institute workshop recommended that the role of soy foods in cancer prevention be investigated.
Soybeans and soy protein products are a unique dietary source of the isoflavone genistein which possesses weak estrogenic activity and has been shown to act in animal models as an anti-estrogen. Genistein is also a specific inhibitor of protein tyrosine kinases. It also inhibits DNA topoisomerases and other critical enzymes involved in signal transduction. In vitro, genistein suppresses the growth of a wide range of cancer cells. No studies reported that soy intake increased tumor development. The epidemiological data is also inconsistent, although consumption of non- fermented soy products tended to be either protective or not associated with cancer risk.
However, no consistent pattern was evident with the fermented soy products, such as "miso". Protective effects were observed for both hormone and non-hormone related cancers. Messina concludes that while a definitive statement that soy reduces cancer risk cannot be made at this time, there is sufficient evidence of a protective effect to warrant continued investigation.
Isoflavones are unique to soybeans and people who do not eat soy have virtually no isoflavone in their diet. So extensive is the research on isoflavones over the past four years that only highlights can be touched upon here. Isoflavones are quite similar to the female sex hormone, estrogen, but one hundred thousandth as potent.
As such, soy reduces breast cancer risk in women by "tying up" receptors on certain tissue cells where estrogen is known to exert a number of effects, some of which are carcinogenic.
Genistein is the main isoflavone in soy. It severely inhibits an array of key enzymes involved in the cancer process, including "tyrosine protein kinases." More amazingly, genistein causes existing cancer cells to differentiate, that is, to go from a cancer cell to a normal cell. Recently, it was discovered that genistein inhibits "angiogenesis," the growth of blood vessels. For cancer to grow, tumors need to stimulate the growth of new blood vessels so that they can receive the oxygen and nutrients they need. And finally, genistein is a good antioxidant, further aiding in the prevention of free radical damage.
Adding soy and soy isoflavones to your daily diet, you may lessen your risks of cancer, high blood pressure and other life-ending diseases.