The Nutritional Prevention of Cancer Study Group tested 1312 patients to determine whether or not 200 mcg of selenium would prevent non-melanoma skin cancer in a randomized, double-blind, placebo controlled trial. After this trial, the authors re-evaluated the findings and it was apparent that the prostate cancer risk was much lower in the selenium group. Subjects taking selenium who had the lowest two thirds of serum selenium levels or with a PSA of less than or equal to 4.0 ng/ml at the start of the trial, had a 49% lower incidence of prostate cancer (8,9).
The patients with higher baseline selenium levels at the start of the trial did not benefit from selenium (8,9).
