Selenium is a chemical element with the atomic number 34 and the symbol Se. Selenium performs numerous tasks in the human body. For example, it serves to activate thyroid hormones or prevents premature cell aging.
What is selenium?
Selenium is an essential trace element. Essential means that the body needs selenium but cannot produce it itself. It must be supplied in the diet. Selenium was discovered in 1817 by a Swedish chemist. For a long time it was considered extremely toxic. It was not until the 1950s that the researchers Foltz and Schwarz discovered that selenium is essential for life and that selenium deficiency can lead to diseases. Selenium is only needed in small quantities. That is why it belongs to the trace elements.
Function, effect and tasks
Selenium has many different functions. It is a component of numerous proteins (proteins). These are also called selenoproteins. Selenoproteins perform important functions in protective and defense processes. The selenoproteins carry selenium as an active site and can thus react quickly. They act as antioxidants in oxidative stress. A particularly important selenoprotein is gluthation peroxidase. It protects the cells of the body from the attacks of free radicals. Free radicals are formed during metabolic processes involving oxygen. External factors such as smoking, stress or UV radiation also lead to an increase in free radicals. In their chemical structure, these free radicals are incomplete. They are missing an electron. They try to take this electron away from other cells. In doing so, they damage the cell membranes and, under certain circumstances, the entire cell. Free radicals are suspected of playing a crucial role in the development of cancer. Gluthation peroxidase can render the harmful radicals harmless. Another selenoprotein is iodothyronine deiodase. This enzyme is responsible for the balance of thyroid hormones. In addition to these two proteins, there are many other important selenoproteins. However, the trace element also plays an important role in inflammatory processes. Inflammatory processes in the body can be intensified by selenium. At the same time, however, selenium also stimulates the immune system. It is essential for the detoxification of heavy metals such as mercury, lead or cadmium. Selenium also seems to have a positive influence on heart health. It keeps blood vessels elastic and can prevent arteriosclerosis.
Formation, occurrence, properties, and optimal levels
The human body contains an average of 10 to 15 milligrams of selenium. Most of it is found in the muscles, liver, kidneys and heart. Selenium cannot be produced by the body itself, but must be absorbed with food. Absorption takes place in the upper parts of the small intestine. Too much absorbed selenium is excreted in the urine. An adequate intake of selenium is about 0.8 to 1 μg per kilogram of body weight. For an adult, the intake should therefore be approximately between 30 and 70 µg. Selenium is mainly found in animal and vegetable protein. Meat, fish, offal, nuts, legumes and cereals are particularly rich in selenium. Products from organic farming usually contain more selenium because they are not sprayed with sulfur-containing fertilizers. With the simultaneous intake of vitamins A, C and E, the bioavailability of selenium in the body can be improved.
Diseases and disorders
Not all people manage to get enough selenium in their diet. Selenium deficiency occurs, for example, in long-term artificial nutrition, in dialysis patients, during lactation, in alcohol abuse, in vegetarian diets, and in heavy metal exposure. Selenium deficiency can be detected in whole blood and serum. Selenium status, on the other hand, should not be determined from hair or fingernails. Hair and nails do not actively participate in metabolism. Thus, no conclusion about selenium status can be made based on the selenium content of hair and nails. Selenium deficiency can be associated with numerous diseases. For example, a deficiency of selenium leads to a weakening of the immune system. The result is an increased susceptibility to infections. Those affected suffer more from colds or flu-like infections. Chronic inflammatory diseases can also be the result of a selenium deficiency. A connection between selenium deficiency and Crohn’s disease or ulcerative colitis is conceivable.Some studies also suggest a link between high blood pressure and low selenium levels. Low selenium levels can also lead to lipometabolic disorders and promote the development of arteriosclerosis. There is also evidence that a lack of selenium can have a negative effect on fertility. For example, women who had a miscarriage showed very low selenium levels in their blood. In men, on the other hand, selenium deficiency leads to reduced motility and impaired maturation of sperm. But it is not only a deficiency of selenium that can have consequences for the body. Selenium can also be overdosed. Normally, the body excretes the excess selenium in the urine via the kidneys and the draining urinary tract. However, if larger amounts of selenium are taken over a long period of time, the body can no longer completely excrete the excess selenium and symptoms occur. However, an excess of selenium can actually only be achieved through dietary supplements. As a result, hair loss and restlessness occur. In extreme cases, the liver can be damaged. Nerve disorders and even cardiac muscle weakness can also be the result of selenium excess. Before substitution, therefore, blood values should always be determined by a doctor.
