Selenium in natural environment and food chains. A Review.

The analytical review attempts to summarize the results of numerous scientific research conducted by scientists around the world on selenium scattering and accumulation in natural environment, with considerable attention paid to the concentration of this trace element in soils, natural waters and plants. It is shown that selenium content in agricultural products is caused by the processes of physico-chemical and biogenic migration of this element in the biogeochemical food chain. According to the modern classification of trace elements, which is based on their biological significance for living organisms, selenium belongs to the vital group or biogenic elements. As a biotic element, it has unique physicochemical and biochemical properties and with adequately absorbed into the human body has a positive effect on a number of physiological processes. Various research shows that the majority of the world population (except in some regions) today consumes less selenium with the food than necessary and its consumption decreases every year. Insufficient selenium intake in the human body (less than 15-30 mu g/day) leads to the development one of the hypomicroelementosis - hyposelenosis. Selenium deficiency is considered as a possible etiological factor in some cardiovascular, cancer, osteoarticular and neurodegenerative diseases that threaten to human life. Providing the human body with selenium in optimal amounts is one of the important conditions of nutrition. A number of countries have developed recommended selenium intake standards for the adults, which range from 55 to 120 mu g/day. We can calculate the physiological need for selenium in children and adolescents by extrapolation. The most safe and effective way to maintain the necessary level of selenium for the human body can be achieved only through the poultry and livestock products by mandatory introduction of premixes containing highly effective biologically available selenium forms into animal feed. This will ensure a relatively high level of trace element in meat, eggs, and milk and would eliminate the cases of toxicosis in human population due to buffer effect of animal tissues.