TOKYO, March 16 (UPI) -- The largest study looking at soy-rich diets and the development of prostate cancer in Japanese men has resulted in seemingly contradictory conclusions.
The study in Cancer Epidemiology, Biomarkers & Prevention looked at 43,509 men and found the effects of isoflavones -- strong antioxidants believed to help treat cancer -- may differ according to the stage of prostate cancer.
Researchers at the National Cancer Center in Tokyo found intake of isoflavone chemicals, which are derived largely from soy foods like miso soup, decreased the risk of localized prostate cancer but increased the risk of advanced prostate cancer.
One possible explanation is that isoflavones may delay the progression of latent prostate cancer, but once tumors become aggressive, isoflavones may fail to protect against the development of advanced cancer. In this case, isoflavones might even increase the risk of progression, possibly by reducing serum testosterone, the researchers say.
