Prostatic and Peripheral Blood Selenium Levels After Oral Supplementation

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Abstract
The dietary trace element selenium has been proposed to be a potential chemopreventive agent for prostate cancer. Epidemiological studies have suggested an inverse association between blood selenium and prostate cancer incidence. However, to our knowledge no study to date has examined selenium absorption by the prostate. Therefore, we determine whether oral selenium supplementation alters selenium levels within the prostate and/or peripheral blood. In this prospective trial 51 men undergoing transurethral resection of the prostate for benign prostatic hyperplasia were randomly assigned to serve as controls or receive 200 μg selenium daily orally for 1 month. Sample size was calculated to detect a difference of 30 ng/gm in prostate tissue with a power of 80%. Peripheral blood was obtained at enrollment and subsequently at surgery, when prostate tissue was also sampled. Selenium levels were determined using inductively coupled plasma mass spectrometry. Baseline erythrocyte selenium was within the standard reference range. Supplementation increased erythrocyte (initial median 173 and final median 209 ng/ml, p = 0.008) and prostate (supplement median 241 and control median 196 ng/gm, p = 0.016) levels. Erythrocyte levels at surgery correlated poorly with prostate levels in the control (r = 0.18) and supplement (r = 0.07) groups. Oral selenium supplementation increases prostatic and peripheral blood levels in men in a nonselenium deficient population. Blood and prostate levels correlated poorly, suggesting that peripheral blood measurements are a poor indicator of prostatic selenium content.