Dietary consumption of isoflavones — a subtype of phytoestrogen including genistein, daidzein, and glycitein found in foods such as soybeans, peas, and teas — may increase the risk of advanced prostate cancer, according to a study published in the International Journal of Cancer.

Previous studies have demonstrated that a diet high in phytoestrogens reduces serum testosterone levels and may modulate the risk of certain hormone-mediated cancers such as prostate cancer

For this prospective study, researchers analyzed an intervention arm of the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial that included 27,004 men. Patients were asked to complete a sex-specific baseline questionnaire and a food frequency questionnaire. Patients in the intervention arm were offered annual digital rectal exams and prostate-specific antigen (PSA) blood tests for the first 6 years of the trial and had an additional 7 years of follow-up.

After a median follow-up of 11.5 years, 2598 patients were found to have prostate cancer.