Second to skin cancer, prostate cancer is the most common malignancy in American men. Even though the American Cancer Society reports that there are uncertainties surrounding the value of early detection and treatment of prostate cancer, many men who are diagnosed with this disease opt for surgical, radiation or medical therapy. Following initial treatment, men must undergo regular surveillance for cancer recurrence. Those who suffer relapse sometimes turn to alternative remedies, such as soy, although such treatments have not been proven to cure recurrent prostate cancer.
Soy Is a Rich Source of Isoflavones
A 2009 review in "American Family Physician" reports that breast and prostate cancers are much less common in populations where soy consumption is high. Thus, soy has been closely scrutinized by scientists investigating alternative treatments for cancer. The soy constituents that have garnered the most attention are two isoflavones, or phytoestrogens, called genistein and daidzein. Phytoestrogens exert weak estrogen-like effects in the human body.
Soy Isoflavones Attach to Cellular Receptors
Genistein and daidzein weakly bind to both types of known estrogen receptors in human tissue, which, according to the National Cancer Institute, accounts for their observed estrogenic effects in experimental situations. However, these isoflavones also exert other effects, including regulation of cell division and reduction of oxidative damage. A 2011 study in "The Journal of Steroid Biochemistry and Molecular Biology" demonstrates the presence of estrogen receptors in prostate tissue and suggests that these receptors play a major role in a man's risk for prostate cancer.
Soy Decreases PSA in Recurrent Prostate Cancer
Although soy and soy isoflavones have not been proven to prevent or treat prostate cancer, at least two clinical trials have shown that isoflavones reduce the prostate specific antigen, or PSA, in men with prostate cancer, including those who have suffered recurrence. PSA is a test commonly used to screen for prostate cancer, to survey for recurrence and to monitor response to treatment. A 2004 study in "Urology" demonstrated that genistein either prevented an increase or induced a reduction of PSA levels in men with prostate cancer, and a 2008 study at the University of Florida showed that soy isoflavones exerted positive effects on PSA profiles in men with recurrent prostate cancer.
Considerations
Soy isoflavones have not been proven to be beneficial in men with recurrent prostate cancer. However, preliminary trials suggest that soy products may exert positive biological effects in prostate cancer. No optimal intake of soy or soy isoflavones has been established, although one phase II clinical trial utilized a soy milk formula containing 47 mg of isoflavones, and this preparation was administered three times daily for one year. If you have prostate cancer, talk to your doctor before you add soy to your daily regimen.
References
- "CA, A Cancer Journal for Clinicians"; American Cancer Society Guideline for the Early Detection of Prostate Cancer; Andrew M. D. Wolf, MD, et al.; March 3, 2010
- "American Family Physician"; Soy: A Complete Source of Protein; A.J. Michelfelder; January 2009
- "Journal of the National Cancer Institute"; Addressing the Soy and Breast Cancer Relationship: Review, Commentary, and Workshop Proceedings; M. Messina, et al.; September 2006
- "The Journal of Steroid Biochemistry and Molecular Biology"; 17ß-Estradiol Regulates Oxidative Stress in Prostate Cancer Cell Lines According to ERalpha/ERbeta Ratio; A.M. Miro, et al.; February 2011
- "Urology"; Effects of a Genistein-Rich Extract on PSA Levels in Men with a History of Prostate Cancer; R.W. deVere White, et al.; February 2004
- "BMC Cancer"; Phase II Trial of Isoflavone in Prostate-Specific Antigen Recurrent Prostate Cancer after Previous Local Therapy; J.M. Pendleton, et al.; May 2008
