ABSTRACT
Selenium (Se) was first suspected to be an essential nutrient in the diets of rodents in 1957 when Klaus Schwarz identified the element as the active component of “Factor 3,” which protected rats fed yeast-based diets from liver necrosis. In some studies, diets containing high levels of this element have been fed to determine the toxicity of various organic and inorganic forms of Se and to examine the cancer chemopreventive effects of those forms. The use of corn oil or lard at 5% as the fat source is standard in Se-deficient diets. In certain studies of Se deficiency, it is desirable to induce a concomitant deficiency of vitamin E. This is done by omitting vitamin E from the vitamin mix and substituting vitamin E-stripped corn oil or lard as the fat source. The repeated demonstration of Se’s cancer chemopreventive effects has renewed interest in examining the biological effects of Se when fed at high levels.
