The research conducted by Jianjun Zhang, M.D., Ph.D. showed that higher intake of total isoflavones and some individual isoflavones (namely genistein, daidzein and glycitein) were associated with an increased risk of advanced prostate cancer.
Dr. Jianjun Zhang answers questions about soy products and prostate cancer
By Mary Hardin
Tuesday, January 30, 2018
A cohort study published in the November 2017 International Journal of Cancer finds that eating isoflavones, largely found in soy products, may play a role in the development of advanced prostate cancer. IU Simon Cancer Center researcher Jianjun Zhang, M.D., Ph.D., the lead author of the article, analyzed the dietary habits of 27,004 men participating in the National Cancer Institute’s Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial, including 2,598 men with prostate cancer. Advanced disease was defined as patients with Stage II (Gleason score of 8 or greater), Stage III, Stage IV or those who died from the disease. Dr. Zhang, associate professor in the Department of Epidemiology at the Richard M. Fairbanks School of Public Health, answered questions about the research.
What are phytoestrogens and isoflavones?
Dr. Zhang: Phytoestrogens are plant-derived xenoestrogens, which are estrogens not generated in the endocrine system. Foods high in phytoestrogens are soybeans and soy products, lentils, Mexican yams, sesame seeds, flaxseeds, tempeh, barley and products made from these grains and seeds. Isoflavones, a type of phytoestrogens, are a dietary supplement isolated from soybeans, chickpeas and other legumes. Although the mechanism of action is unclear, soy isoflavones mimic estrogen action in the body.
Did the study show that consuming isoflavones can cause prostate cancer?
Dr. Zhang: Our study showed that higher intake of total isoflavones and some individual isoflavones (namely genistein, daidzein and glycitein) were associated with an increased risk of advanced prostate cancer, but no association was found for patients with non-advanced prostate cancer or for overall prostate cancer risk. Little is known about the role of phytoestrogens in the spread of prostate cancer and our study did not investigate this question due to the nature of the study and lack of data on serum testosterone.
