While the benefits of soy for women have been widely acknowledged, men may also learn eventually that soy can benefit their prostate.
Two studies have used changes in PSA levels to assess reduction, stabilization, or progression of prostatic cancer, according to the United Soybean Board. The first study fed 38 grams of soy protein containing either 70 mg or 4 mg of total isoflavones to 34 men with elevated PSA. Half of the subjects in the six-week crossover study had biopsies before the study, and none had prostate cancer. The other half declined to have biopsies. Neither of the soy preparations altered blood PSA levels.
In a second study of 41 patients with confirmed prostate cancer, patients took pills containing 10 mg of soy isoflavones twice daily for a median period of six months. All of the patients had progressive or recurrent cancer based on increasing concentrations of serum PSA or PSA concentrations greater than 10 ug per liter.
Overall, soy isoflavone treatment slowed prostate cancer growth, as assessed by a slowing of the rise in PSA levels. Four patients had not received treatment prior to the study, and in three of these men, consumption of soy isoflavones stabilized PSA levels, indicating a slowing of the prostate cancer growth. In addition, in 15 out of 18 patients who previously had surgery or radiation therapy, but whose serum PSA was increasing before the study, consumption of soy isoflavones resulted in stabilized PSA levels.
Additional clinical studies are under way and are expected to help clarify the potential of soy and soy isoflavones to inhibit prostate cancer. But while more research is needed, there is sufficient strength in overall data to recommend eating soy to help reduce prostate and colon cancer risk, according to the United Soybean Board.
(Source: Nutritional Outlook magazine, September 2003.)