Soy and Cancer - Part 2

Isoflavones : Agent in Cancer Prevention

Isoflavones are literally plant estrogens, but unlike human estrogen, which can have deadly effects, isoflavones are about 1/100,000 the strength of human estrogen. In this case, weaker is better. Although human estrogen is essential in the development and function of vital organs, an overabundance of human estorgen actually increases cancer risk. For example, human estrogen binds to breast cells and stimulates health7 cell growth, but if cancer invades the breast tissue, human estrogen also stimulates the growth of cancerous cells. Because the structure of isoflavones is almost identical to that of human estrogen, but less potent, isoflavones encourage healthy cell growth while inhibiting cancerous growth. By binding to cells where human estrogen typically binds, isoflavones mimic the positive roles of human estrogen without the deadly effects.

Isoflavones have an obvious impact in all hormone-related cancers, but because breast cancer is the most common, scientists are anxiously working to lower the risks of this widely spread cancer. Research indicates that soy consumption significantly lowers the risk of breast cancer. Scientists have been intrigued by the differences they notice in comparing US white women with Asian women. The Japanese breast cancer rate, for example, is only one-fourth that of the United States, and a recent study in Singapore discovered that those women who rarely consumed soy products had twice the risk of developing cancer than those who regularly ate soy foods.

Though this reduction in breast cancer is significant alone, the reduction of other hormone-related cancers that attack both men and women is also notable. Once again, lower cancer rates among Asians who regularly consume soy products indicate that there may be a correlation between soy and cancer prevention. In 1989, the Institute of Cancer Research studied 8,000 Hawaiian men with Japanese ancestry and found that the men who ate the most soy products had lower rates of prostate and colon cancer.  

While soy exhibits positive effects in hormone-related cancers, it also performs several anticarcinogenic roles active in a variety of cancers. In 1987, Japanese researchers showed that genistein, a specific soy isoflavone, inhibited the activity of tyrosine protein kinase (TPK), an enzyme which controls cell growth. Because TPK aids the spread of cancer, any factor that hinders the activity of this enzyme is considered anticarcinogenic. Since this finding, researchers have discovered that genistein represses TPK and other enzymes involved in cell growth, and over one hundred studies show that genistein discourages the growth of breast, colon, lung, leukemia, and prostate cancer cells. In addition, isoflavones act as antioxidants, substances that neutralize free radicals. The isoflavones is soy attack free radicals before they can mutate DNA and thereby initiate cancer.

A Hopeful and Healthy Future

Many factors are associated with good health, and diet is certainly one of the most important ones.

Data suggests that genistein may even have a role in cancer treatment. Studies show that this isoflavone inhibits angiogenesis, or new blood vessel growth, which is essential for tumor growth. Scientists are also realizing that genistein increases the effectiveness of cancer drugs. Findings such as these, though still speculative, are astounding scientists to the degree that the National Cancer Institute is currently studying the possibility of using purified genistein as an anticancer drug.