New Study: Soy May Offer Hope When Conventional Prostate Cancer Treatment Proves Unsuccessful

ST. LOUIS, Dec. 12, 2011 /PRNewswire/ -- New research points to soy as a potential solution for men with prostate cancer that is unresponsive to the conventional treatment of surgery and radiation.  For many men in this situation, no standard therapeutic option exists, and the most common choice has sexual and other side effects that worsen quality of life. In this pilot study, conducted at Pennsylvania State University by Monika Joshi and colleagues and published in the Southern Medical Journal in November 2011, fifty percent of participants benefitted from soy (three servings a day, for two years) either permanently or short-term. Prostate cancer is the most common cancer among U.S. men and the second most common cause of cancer death, according to American Cancer Society statistics.

When Conventional Prostate Cancer Treatment Fails
In prostate cancer prevention and treatment, health professionals monitor men's prostate-specific antigen (PSA) levels. PSA is a protein produced by the prostate that is measurable in the blood and not only reflects risk of developing prostate cancer but also measures treatment success. The ten men in this study decided to participate as a result of their PSA levels continuing to rise after surgery and radiation. The cancer had not spread to other parts of the body, but was still present in the prostate.

When this happens, no standard therapy exists. One possible option is called androgen deprivation therapy (ADT), which suppresses testosterone levels. However, ADT is controversial. There's no clear proof it works, and quality of life issues range from common sexual side effects (loss of libido, erectile dysfunction and hot flashes) to less common gynecomastia (enlarged breasts in men), changes in body composition (weight gain, reduced muscle mass, increase in body fat) and changes in lipids. These problems may exacerbate more serious conditions, such as high blood pressure, diabetes and heart disease.

Studying a Soy Solution
For these reasons, researchers seek new options for prostate cancer patients, including changes to the diet. In Joshi's study, men consumed three servings of soy per day for two years.  A serving is equivalent to one cup soymilk, three ounces of tofu or one ounce of soynuts. Nine study participants chose to drink three glasses of soymilk each day, while one ate soy snacks.

Overall, five men benefited from soy consumption as demonstrated by PSA levels either permanently or temporarily declining or remaining stable. Among the three men in this study who opted for ADT, only one favorably responded to soy; in contrast, among the seven patients who did not use ADT, four responded favorably to soy. Thus, the researchers concluded that "soy supplementation using commercially available soy products can have durable beneficial effects on PSA levels...in some men with prostate cancer." 

Noted oncologist Omer Kucuk, MD – Georgia Cancer Coalition's distinguished cancer scholar and chief of genitourinary medical oncology at Emory University's Winship Cancer Institute – added, "The results from Pennsylvania State University appear consistent with a considerable amount of published research showing that soy may help to prevent prostate cancer and may be useful in its treatment." Dr. Kucuk continued, "For men unresponsive to surgery and radiation for prostate cancer, it is critically important to find ADT alternatives, such as soy as a dietary intervention. While this study is small, it's important because it takes place in real-life conditions in a clinical setting."

Additionally, Lisa Kelly, a registered dietitian for the United Soybean Board, noted, "With the wide availability and variety of soyfoods on the market, it is relatively easy to eat three servings of soy each day." Since this study only evaluated one level of soy consumption, she also suggested that future research examine whether somewhat lesser amounts are still effective. For information on soy and nutrition, or recipes to enjoy soy daily, visit www.soyconnection.com.

About USB
USB is made up of 69 farmer-directors who oversee the investments of the soybean checkoff on behalf of all U.S. soybean farmers. Checkoff funds are invested in the areas of animal utilization, human utilization, industrial utilization, industry relations, market access and supply. As stipulated in the Soybean Promotion, Research and Consumer Information Act, USDA's Agricultural Marketing Service has oversight responsibilities for USB and the soybean checkoff.

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SOURCE United Soybean Board