A case cohort study by Kristal AR, et al looked at the baseline selenium status of patients from the SELECT trial who developed prostate cancer and were matched to a cohort of 3117 men without prostate cancer. The men in the trial took 200 mcg of selenium and 400 I.U. of vitamin E. Out of 1739 cases of prostate cancer, 489 cases of prostate cancer were aggressive forms of the disease with poor prognosis. Selenium status was determined by using the toenails of men sent for analysis. The authors found that (12):
- Men with high toenail selenium who took a selenium supplement or selenium plus vitamin E had a 91% higher risk of aggressive prostate cancer calculated as a hazard ratio.
- Neither selenium supplementation alone, nor selenium supplementation plus vitamin E reduced the risk of prostate cancer in men with a low selenium status.
- Vitamin E increased the risk of prostate cancer in men with low selenium toenail content.
- The authors concluded that selenium should not be consumed in higher doses than the recommended daily allowance.
Also, please see the selenium section in Preventive Health Advisor to research benefits of selenium intake and foods high in selenium.