Such a dangerous and such useful selenium

For many years selenium was considered a poison. It is reality! But of course only in certain doses. That's the main challenge: a little bit more harmful, slightly less - too bad. And these "little" so small! Health we need to get daily 0,00001 g of selenium. In our body its just 0.2 parts by 1 million
Selenium toxicity discovered in 1933, when it was noticed that the wheat from the fields that are rich in this mineral has a poisoning effect on cattle. Already 1 mg per 1 kg of weight of cattle causes symptoms of poisoning, and in high doses cattle is sick and wrong develops. Even chickens birds vyluplivajutsja bad eggs, horses go blind, and poultry are killed the content of selenium in rates of up to 3 PPT.
And suddenly in the 60-ies of the rose enthusiastic boom about this trace: Without selenium no health! Selenium together with vitamin E saves heart! Selenium prolong youthfulness! Selenium will deliver us from cancer! Opening of selenium as a factor of health is a turning point in medicine, and in cattle!
For example, in New Zealand, and Turkey revealed a great lack of this element in the soil. There it was discovered that inexplicable and mysterious sudden death of babies (or young pigeons), especially males, are caused by lack of selenium.
In Scotland, where Selena is also too little, newborn calf after birth inject salts of selenium or within a few weeks they get a small dose of this element. A similar, although somewhat worse, the effect of vitamin E.
But the excess selenium harmful. In Colombia, in areas with a high content of selenium, people lose their hair and nails; the disease is called "selenas" (selenosis). Animals also appear typical signs of the disease, including diseases of the gastrointestinal tract, tooth decay, gum disease, skin, damage to limbs, hair loss.
Selenium is exceptionally interesting item. It is used in the manufacture of glass, to make it crystal clear. It is part of a solar cell. Under the action of light getting enough selenium sustainable electric charges that are used, for example, in xerography on selenium plates.
The truth is, we need only "traces" of selenium. However, the more carefully handled the soil, the more we lose that item. Selenium washed with water (and eventually taken out to sea), carried by wind, and it becomes smaller. Interestingly, some plants have the ability to accumulate selenium, sometimes even in excess, such as tropical plant Neptunia amplexicaulis, which was determined to 4 g of selenium per 1 kg of dry mass. Fortunately, there are also plants that selenium exactly what we need.
In General, we can say that there is no food, completely devoid of selenium, in it there are always at least its "footprints".