Submitted to: Journal of Trace Elements in Medicine and Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/29/2009
Publication Date: 6/1/2009
Citation: Hawkes, W.C., Hwang, A., and Alkan, Z. 2009. The Effect of Selenium Supplementation on DTH Skin Responses in Healthy North American Men. Journal of Trace Elements in Medicine and Biology. Vol.23:272-280.
Interpretive Summary: Our previous study of high-selenium foods suggested that selenium may improve immune system memory. Clinical trials indicate selenium supplementation can protect against prostate cancer. Improved immune function may be one way selenium protects against cancer. We tested the health effects of taking 300 micrograms of selenium as high-selenium yeast tablets for one year in 42 healthy, free-living men. Most parts of the immune system were neither improved nor degraded by selenium supplementation. The placebo yeast unexpectedly decreased skin hypersensitivity responses, and this decrease was prevented by the addition of selenium to the yeast. Our research shows that there are no adverse effects of selenium on immune function at intakes up to the upper tolerable intake set by the National Academy of Sciences. This research may be useful to cancer researchers studying the mechanisms of cancer prevention with selenium.
Technical Abstract: TThe essential nutrient selenium is required in microgram amounts (RDA=55 µg/d, 699 nmol/d) and has a narrow margin of safety (upper tolerable intake limit = 400 µg/d, 5080 nmol/d). We conducted a randomized placebo-controlled study of high-selenium yeast, the form used in most supplements, (300 µg/d, 3.8 µmol/d) administered to 42 free-living healthy men for 48 w. Dietary intakes of selenium, macronutrients and micronutrients were not different between groups and did not change during the study. Supplementation more than doubled urinary selenium excretion from 69 to 160 µg/d (876 to 2032 nmol/d). Urinary excretion was correlated with recent selenium intake estimated from 3-d diet records: urinary selenium excretion = 42 µg/d (533 nmol/d) + 0.132 × dietary selenium intake, p<0.001. Dietary selenium intake was not significantly correlated with the other indicators of selenium status, presumably because urinary selenium excretion reflected recent intake and tissue selenium was homeostatically controlled. After 48 w of supplementation, plasma selenium was increased 60% from 142 to 228 µg/L (1.8 to 2.9 µmol/L) and erythrocyte selenium was approximately doubled from 261 to 524 µg/L (3.3 to 6.6 µmol/L). Selenium concentrations increased more modestly in hair (56%) and platelets (42%). Platelets were the only blood component in which glutathione peroxidase activity was significantly related to selenium content. Selenium levels decreased rapidly after the end of supplementation and there were no significant differences in selenium status indicators between groups by week 96. The absorption, distribution and excretion of selenium from high-Se yeast were similar to selenium in foods.