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.

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

A multivariate analysis revealed that there was an increased risk of prostate cancer associated with an intake of total isoflavones (hazard ratio [HR], 1.91; 95% CI, 1.25-2.92), genistein (HR, 1.51, 95% CI, 1.02-2.22), daidzein (HR, 1.80; 95% CI, 1.18-2.75), and glycitein (HR, 1.67; 95% CI, 1.15-2.43) (P-trend for all associations less than 0.05). There were, however, no statistically significant associations between total isoflavone or phytoestrogen intake and prostate cancer.

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The results demonstrate that a higher intake of isoflavones may increase the risk of advanced prostate cancer. The authors concluded, “[t]he findings of the present study need to be confirmed in a more prospective cohort or nested case-control studies to be conducted by measuring both dietary intake of phytoestrogens and their biomarkers among populations with diverse dietary habits.”


Reger MK, Zollinger TW, Liu Z, Jones JF, Zhang J. Dietary intake of isoflavones and coumestrol and the risk of prostate cancer in the Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial [published online November 8, 2017]. Inter J Cancer. doi: 10.1002/ijc.31095

This article originally appeared on ONA