Soy, the world's most important bean, has been cultivated in many Asian countries for at least 5,000 years. The valued portion of the plant is the seeds, which contain about 20 percent oil and 40 percent high-quality protein, called soy protein. Unlike other vegetables, soy provides all nine of the essential amino acids, making this legume a high-protein meat substitute. Another promising area for soy is breast cancer prevention, although scientists are not fully sure as to whether soy prevents or promotes breast cancer. Therefore, check with your doctor before you decide to take soy in connection with breast cancer.
Soy Isoflavones and Other Constituents
Soy is the most concentrated source of naturally occurring phytoestrogens, called isoflavones. Soy isoflavones can both mimic the action of human estrogen, a reproductive hormone, and block it. In fact, soy isoflavones are the most researched components of soy for their health-promoting properties. Soy also contains two essential fatty acids, linoleic and linolenic acids; mucilage fiber; carbohydrate; fat; vitamins such as folic acid, ascorbic acid and vitamin B-6; and minerals such as magnesium, potassium and iron.
Estrogen-Dependant Breast Cancer
Breast cancer is a malignant tumor inside the breast. It is generally agreed upon in the scientific community that the body's own estrogen increases cell proliferation in mammary glands and therefore could increase cancer risk in these milk-producing glands. Thus, lifelong exposure or increased estrogen levels put women at a higher risk of developing estrogen-responsive breast cancer.
Negative Effects of Soy Isoflavones on Breast Cancer
Soy isoflavones have many similarities to human estrogen, so these molecules can act like estrogen and bind to estrogen receptors found in the bones and cardiovascular system. It is likely that soy isoflavones augment the effects of the body's natural estrogen and therefore spur the development of existing estrogen-dependant breast tumors, according to the Sprecher Institute at Cornell University.
Beneficial Effects of Soy Isoflavones on Breast Cancer
Proponents of soy argue that soy could alter the outcome for breast cancer. Soy isoflavones are weak forms of estrogens, and therefore could have anti-estrogenic properties. They can actually compete with the more potent, naturally occurring endogenous estrogens in the regulation of breast tissue development that may lead to cancer. This has important implications in lowering breast cancer risk, according to Anne Weaver, a research specialist at the University at Buffalo.
References
- University of Maryland Medical Center: Soy
- Cornell University, Sprecher Institute: Phytoestrogens and Breast Cancer
- University at Buffalo, State University of New York: Soy Isoflavones Decrease Risk of Invasive Breast Cancer, Large Breast Tumors, Study Shows; Anne Weaver; 2010
- Columbia University Health Sciences: Estrogen's Role in Cancer; Susan Conova; 2010
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