Soyfoods may help reduce the risk of developing prostate cancer - the most common cancer among U.S. men. Clinical and epidemiologic evidence suggests that eating soyfoods such as tofu and edamame may not only help reduce the risk of developing prostate cancer, but also may help improve the prognosis of men with this disease.
In soyfood-consuming countries such as Japan and China, prostate cancer incidence and mortality rates are very low. In the U.S., age-adjusted prostate cancer incidence rates are about ten times higher than Japanese rates. Researchers have found that Asian men who consumed higher amounts of soy (one-and-a-half to two servings per day) were about 50 percent less likely to have prostate cancer than Asian men who consumed little soy.
“Men are becoming increasingly conscious about maintaining good health as they age, and soy is one of the foods that can help them accomplish that goal,” says A. Elizabeth Sloan, PhD, president of Sloan Trends.
Through its public education initiative, USSEC shares research and highlights the work of experts who have conducted studies on the health benefits of eating soy. Ömer Küçük, M.D., conducted the first clinical trials demonstrating that soy isoflavones may benefit prostate cancer patients. He also was the first to report that isoflavones prevent the adverse effects of radiation in prostate cancer patients. Soyfoods are uniquely rich sources of isoflavones.
Dr. Küçük is professor of Hematology-Oncology and Urology, leader of the Prostate Cancer Research Program and chief of Genitourinary Medical Oncology at Winship Cancer Institute at Emory University. He and his research team found that soy isoflavones reduce or stabilize serum prostate specific antigen (PSA) levels in patients with prostate cancer. They also decrease the side effects of radiation therapy in prostate cancer patients. Regarding dietary recommendations, Dr. Küçük says, “I recommend a diet rich in vegetables, fruit and legumes, including soy products, as a cancer preventive and healthy diet. This is true for prostate cancer patients as well as people without cancer.”
Raymond Bergan, M.D., began working with soy because epidemiological data suggested that people whose diet is soy-based, such as those from China, had a lower incidence of metastatic prostate cancer. He is currently head of Hematology and Medical Oncology in the Oregon Health & Science University (OHSU) School of Medicine and associate director of Medical Oncology for the OHSU Knight Cancer Institute. Dr. Bergan’s research suggests that isoflavones, and specifically the main isoflavone in soybean genistein, may help inhibit the growth and spread of prostate tumors. He explains, “The key to understanding this is to understand the importance of concentration. With dietary consumption of soy, a certain concentration is achieved in the blood. Scientifically, we say ‘low nanomolar concentrations,’ but I like to think of them as dietary concentrations. At dietary concentrations, genistein will stop the spread of prostate tumors.”
Ongoing research studies continue to investigate the possible health benefits of soy. Both Dr. Küçük and Dr. Bergan have ideas for the direction of future research. Dr. Bergan suggests conducting a phase III randomized placebo controlled study to determine whether genistein can benefit men who are at high risk for developing prostate cancer. Dr. Küçük would like to see studies evaluating the effects of soy isoflavones in conjunction with chemotherapy and immunotherapy in the treatment of prostate cancer.
Finally, according to Mark Messina, PhD, MS, “Because soyfoods contain numerous biologically active compounds that provide a number of health benefits and are excellent sources of high-quality protein, all men, not just those concerned about prostate health, should try to incorporate soy into their diet.