It is an element with atomic mass 78.96 and its atomic number is 34. It is related to tellurium and sulphur and its chemical symbol is Se. This mineral is found in soil and rocks in many allotropic forms and rarely occurs in nature in its elemental state.
It helps in the neutralization of free radicals created in oxidative reactions in the course of energy production in biological processes. This trace mineral enhances the immunological process protecting us from diseases. It is an important factor in the production of enzymes.
Numerous health benefits are being found and attributed to Se, an essential trace mineral, including protection from cardiovascular diseases, protection from cancers (especially prostate cancer), enhancement of immunity, slowing down of progress of HIV/AIDS ...
Throughout the world, most of the rich sources of Se are of plant origin. Animals raised on natural plants and fodder containing high levels of selenium also yield meat and dairy products containing high levels of this trace mineral.
Brazil nuts tree (Bertholletia excelsa) is a native of South America found in the rainforests of Brazil, Bolivia, Colombia, Guiana, Peru and Venezuela. One ounce of these fruits are found to contain as much as 550 mcg of Se which is ten times the U.S.Recommended Dietary Allowances (US RDA).
Its natural form shows higher degree of absorption and metabolism than the inorganic form. It is the integral part of the selenoprotein and antioxidant enzyme, glutathione peroxidase (GPx), and is vital for reducing the destruction of cells in free radical peroxidative reactions.
Selenium yeast is the enriched organic form mostly containing selenomethionine. Attempts were made to enrich Se in yeast by fermenting a cane molasses medium with higher levels of inorganic salts of this trace mineral.
The availability of this mineral in nutrition depends upon its presence in the soil. Plants take it up from soil and animals feeding on the plants get their requirements fulfilled. However soils in different regions of the world have different amount of its presence with many regions having adequate or higher concentrations.
Exceeding the upper tolerable levels of selenium is fraught with many side effects. When blood levels of this essential trace mineral exceed 100 μg (mcg or micrograms) per one deciliter (dL) of blood, selenosis, an excess condition with many side effects is caused.
People living in selenium deficient soils and sourcing locally grown food become chronically deficient and develop the deficiency diseases. In such specific conditions (found in China and Russia) they require to take the essential trace mineral in sufficient level to remain healthy.
Selenium sulfide is the commercial name for Selenium disulfide, an inorganic compound with antibiotic, fungicidal and anti infective properties, widely used in topical preparations for treating fungal infection like dandruff, seborrheic dermatitis and tinea versicolor.
Its inorganic salts like sodium selenite and selenate are used as dietary supplements in animal feeds as well as human nutrient supplement formulations. As an chemical it has many industrial uses and in glass industry it is used to manufacture colorless glass.
Selenomethionine is a naturally occurring amino acid containing the essential trace mineral. Selenomethionine is an organic form of selenium, with IUPAC name (International Union of Pure and Applied Chemistry nomenclature) 2-amino-4-methylselanyl-butanoic acid.
This trace mineral is very important for the synthesis of antioxidant enzymes containing selenoproteins. For the proper function of thyroid hormones as well as many organs like heart, prostate glands and thyroid glands this mineral is required in trace quantities.
Initially there may be symptoms like diarrhea, vomiting, fever and body pains. The initial symptoms include heart inflammation, Arrhythmia, Cardiac insufficiency and enlargement accompanied by loss of heart muscle tissues. Advanced stage is characterized by pulmonary edema and heart failure.
The antioxidants vitamin C and vitamin E reduce the free radicals and protect the tissues from their damage. Well documented evidence is available on the preventive effects of vitamin E and vitamin C on the cardiac problems. In the case of selenium conflicting results have been obtained towards its use for prevention of cardiac problems.
In the treatment of AIDS the focus is now shifting towards nutrient supplements like Se in addition to antiretroviral therapy so as to improve the quality of life of the affected. It is found that dietary supplement with this mineral can reduce the viral load and help in boosting immune system.
Selenium as such is not an antioxidant. It has the vital role in catalyzing the reduction activity as an enzyme. The cellular and subcellular membrane integrity depends totally on glutathione peroxidases. Further the protective catalyst function of glutathione peroxidase itself depends on the presence of this mineral.
The proper utilization of hormones, thyroxine (T4 or C15H11I4NO4) and triiodothyronine (T3 or C15H12I3NO4) and the conversion of T4 to active T3 is mediated and influenced by the quantities of selenium available in the body.
It is believed that one of the main reason for the occurrence of malignancy, especially of prostate glands, is the damage of the genetic components of the cells by free radicals. Se containing enzymes (selenoproteins) have been found to catalyze many antioxidant activities.
SELECT trial was also to assess the impact of vitamin E and Se on colon and lung cancers as well as to collect the details of total incidences and survival rate.The objective of the trial was to determine whether either or both could prevent tumor of prostate gland and other diseases with no toxicity in healthy men.