CHARACTERIZATION OF TISSUE SELENIUM PROFILES AND ANTICARCINOGENIC RESPONSES IN RATS FED NATURAL SOURCES OF SELENIUM-RICH PRODUCTS

The present report describes the biological effects associated with the feeding of three selenium-rich natural products in rats: high-selenium garlic, high-selenium onion and Brazil nut. The first two are experimental crops cultivated with selenium fertilization. Brazil nut is probably the only unadulterated high-selenium food that is available commercially. Tissue selenium profiles, liver glutathione concentrations and mammary cancer inhibition (in the dimethylbenz[a] anthracene model) were the endpoints of investigation. Parallel designs were set up to compare the three high-selenium products with selenite and selenomethionine. Previous studies have shown that treatment with selenomethionine resulted in significantly greater tissue selenium accumulation, particularly in skeletal muscle, than treatment with selenite. In contrast, selenite, but not selenomethionine, induced a modest increase in liver glutathione concentrations. The objective was to determine whether the high-selenium natural products elicited responses that were similar to that of selenite or selenomethionine. Our experiments suggested that the high-selenium garlic and onion might have some unique attributes. First, their ingestion did not lead to an exaggerated accumulation of tissue selenium, a concern that was shared by both selenomethionine and Brazil nut. Second, unlike selenite, they did not cause any perturbation in glutathione homeostasis. Third, they expressed good anticancer activity that was equal to, if not better than, that of selenite. The chemical form(s) of selenium present in the high-selenium Allium vegetables will be discussed in relation to the manifestation of the above characteristics.