Selenium speciation in edible tissues of animal origin

Selenium is an essential element playing a vital role in many metabolic functions and showing some cancer preventive properties. The main source of Se intake is food. However, the concentration of food production in regions with low soil selenium content has led to decline in the amount of this element in human food supply which poses potential health risk. Among selenium food sources, particular attention is paid to edible animal tissues of animal origin such as meat and eggs due to their nutritional importance. Strategies of Se supplementation aimed at increasing its uptake by animals (broilers and layers) were proposed resulting in higher Se content in respective foodstuffs. The interest in species selective determination of selenocompounds results from their different bioavailability in humans and potential importance for the stability and quality of the marketed products. The study presented concerned chicken meat (breast and leg) and eggs from animals fed with selenium enriched (both inorganic and organic) and control diets. Size-exclusion HPLC ICP MS of sequential foodstuffs extracts (aqueous followed by SDS) was used to study selenium speciation. Additional information on the selenium incorporation into proteins was obtained by quantification of selenoaminoacids by RP HPLC-ICP MS after proteolytic digestion of meat and egg samples. Significantly higher selenium content was observed in edible tissues of animals fed with organic selenium rich diet. The supplementation with organic selenium is accompanied by a relative increase in the high-molecular selenium species and an increase in the selenomethionine concentration with no change in the selenocysteine level. No such phenomenon was observed for the samples supplemented with inorganic selenium.