Written by Greg Arnold, DC, CSCS. In 28 healthy Japanese volunteers, researchers found an 11.7% increase in a substance that stops prostate cell growth.
As the number one cancer killer of American men, there are an estimated 234,460 new cases of prostate cancer each year. In 2006, prostate cancer resulted in an estimated 27,350 deaths (1). If found early, there is 100% five-year survival rate (at a cost of nearly $43,000 per patient) (2). But if the cancer has spread, there is only a 34% survival rate (1). So prevention is a priority.
Now a new study (3) has found that soy isoflavones may help with prostate health. In the study, 28 healthy Japanese volunteers between 30 and 59 years of age were given soy isoflavones (60 mg daily of which 19.1 mg was daidzin and 3.5 mg was genistein) or placebo for 3 months. The researchers collected both blood and urine samples before and after the study and measured levels of daidzein, genistein, and a protein called equol. The researchers looked at equol because lab studies have found it to bind to a protein called SHBG (sex hormone-binding globulin) (4) and stop the growth of prostate cells (5).
By the end of the 3 months, the researchers found a significant increase in SHBG (11.7% increase – 52.2 to 61.2 nanmoles/Liter). This has implications for prostate health, since SHBG binds to testosterone, thereby lowering free testosterone levels which, according to 2004 study, “should theoretically halt cancer cell [spread], [stop tumor growth] and reduce the tumor volume” (6). As expected, the increase in SHBG coincided with a 5% decrease in free testosterone levels (74.9 to 70.9 pg/mL).
Regarding the isoflavone levels, there was a 230% increase in daidzen (40.5 to 133.8 nanograms/milliliter), a 12.1% increase in genistein (81.7 to 91.6 ng/mL), and a 208% increase in equol (21.0 to 64.7 ng/mL) The implication here for prostate health is that genistein has been found to stop the growth of prostate cancer cell lines (7) and stop the development of prostate-related cancers in rat studies (8).
Finally, the researchers noted significant increases in HDL cholesterol 7.9% increase (55.4 to 59.8 miligram per milliliter) and significant decreases in LDL cholesterol 10.7% decrease (132.2 to 118 mg/mL) in the soy group. These results demonstate an association between soy isoflavones and prostate health. Hopefully further research will be done to clarify this association.
Source: Tanaka, M., et al. “Isoflavone supplements stimulated the production of serum equol and decreased the serum dihydrotestosterone levels in healthy male volunteers.” Prostate cancer and prostatic diseases 12.3 (2009): 247-252.
© 2009 Nature Publishing Group
Posted October 16, 2009.
References:
- What Are The Key Statistics For Prostate Cancer?” posted on the American Cancer Society Website.
- Long-Term Financial Costs Associated With Prostate Cancer Treatment” posted on the Medical News Today website.
- Tanaka M. Isoflavone supplements stimulated the production of serum equol and decreased the serum dihydrotestosterone levels in healthy male volunteers. Prostate Cancer and Prostatic Diseases (2009) 12, 247–252; doi:10.1038/pcan.2009.10; published online 14 July 2009
- Déchaud H, Ravard C, Claustrat F, de la Perrière AB, Pugeat M. Xenoestrogen interaction with human sex hormone-binding globulin (hSHBG). Steroids 1999; 64: 328–334.
- Lund TD, Munson DJ, Haldy ME, Setchell KD, Lephart ED, Handa RJ. Equol is a novel anti-androgen that inhibits prostate growth and hormone feedback. Biol Reprod 2004; 70: 1188–1195.
- Kumar NB, Cantor A, Allen K, Riccardi D, Besterman-Dahan K, Seigne J et al. The specific role of isoflavones in reducing prostate cancer risk. Prostate 2004; 59: 141–147.
- Peterson G, Barnes S. Genistein and biochanin A inhibit the growth of human prostate cancer cells but not epidermal growth factor receptor tyrosine autophosphorylation. Prostate 1993; 22: 335–345.
- Pollard M, Wolter W, Sun L. Prevention of induced prostate-related cancer by soy protein isolate/isoflavone-supplemented diet in Lobund-Wistar
