Nutrient requirements Selenium

The toxicity of selenium (Se) belies the fact that it is a required trace-nutrient for many biological organisms. The general order of toxicity for the most... 

Vitamin E is required for normal growth and reproduction. The most important natural source is a-tocopherol found in plant oils and seeds. The ester form (e.g. vitamin E acetate) can be synthesized and is used for feed supplementation. One international unit is defined as being equivalent to the activity of 1 mg DL-a-tocopherol acetate. The nutritional role of vitamin E is closely interrelated with that of selenium and is involved mainly in the protection of lipid membranes such as cell walls from oxidative damage. Although these signs are similar to those of selenium deficiency, it is not possible to substitute selenium completely for vitamin E. Both nutrients are required in the diet. 

Interest in selenium concentrations in the environment and in foodstuffs has been due to the dual role of selenium as an essential nutrient at low concentration levels and as a toxic substance at high levels of concentration. The narrow range between the two levels requires accurate methods for measurements of selenium concentrations. Selenium can exist in a number of different chemical forms and oxidation states. Inorganic selenium can be present in the environment as selenate (Se ), selenite (Se ), elemental selenium (Se°) and selenide (Se2-). 

Even if the diet in Norway must be considered nutritionally adequate, generally covering the required essential nutrients, there could in certain groups in the population exist an insufficient supply of certain minerals. An increased knowledge about the different minerals in our diet is important, and a lot of work is done in many areas, e.g. on iron, zinc, selenium and chromium. 

Selenium-Requiring Enzymes Glutathione and Cancer Glutati ione and Aldehyde Metabolism Glutathione in the Glomerular Filtrate Selenium Nutrition Otiier Inoiganic Nutrients References Bibliography... 

Cell lines differ in the defined proteins they require for optimal cell growth. Usually, addition of insulin (I) and transferrin (T), along with the trace element selenium (S), is sufficient to enable most cell lines to grow in rich balanced nutrient media, such as the ones listed above. However, several categories of additives may enhance or be required for cell growth and/or production of the desired... 

The primary sources of selenium are volcanic emanations and metallic sulfides associated with igneous activity. Secondary sources are biological sinks in which it has accumulated. The selenium content of black shales, coal, and petroleum is 10-20 times the crustal abundance (0.05 ppm). Seleniferous black shales are the parent materials of the widespread seleniferous soils of the western plains of the United States. When burned, coal and petroleum containing selenium give rise to a redistribution of particulate Se and SeOg. The average selenium content of U. S. coal is about 3 ppm and of petroleum about 0.2 ppm. Selenium is an essential nutrient for animals and is required at a concentration of about 40 ppb in their diet at concentrations of 4000 ppb and above, however, it becomes toxic to animals. 

Plant cells and animal cells share most of the same metabolic systems, and with a few exceptions, plants require the same array of nutrients as animals. Most of this overlap occurs in the macrominerals and some microminerals. But plants also have their own special needs for elements that our livestock cannot use, like boron, which is involved in fiber metabolism, and molybdenum, which is used in nitrogen metabolism and nitrogen fixation. But what about the three minerals that plants don t need—iodine, cobalt, and selenium ... 

Recommended dietary allowances for a male adult (daily intake, in foods and food supplements) of some nutrients, usually the amounts estimated as needed to prevent overt manifestation of deficiency disease in most persons. For the substances listed in smaller amounts the optimum intake, leading to the best of health, may be somewhat greater. Not shown, but probably or possibly required, are the essential fatty acids, />aminobenzoic acid, choline, vitamin D, vitamin K, chromium, manganese, cobalt, nickel, zinc, selenium, molybdenum, vanadium, tin, and silicon. 

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