Selenium is an essential trace mineral, needed for repair of DNA. You only need a small amount, but even the smallest amount is not part of the average daily diet.
Selenium comes from plant sources, and the amount provided is directly related to the quality of the soil the plants grow in. The use of pesticides, insecticides, fungicides and artificial fertilizers - these fertilizers contain practically no trace minerals except for nitrogen - have diminished the quality of agricultural land up to the point that many parts are almost devoid of selenium.
As a result selenium deficiency is very common. Symptoms include:
- Hair loss and skin and fingernail discoloration
- Low immunity
- Difficulty concentrating
- Reproductive problems
Scientists recommend two Brazil nuts a day for your daily requirement of selenium, they say it's better than a supplement.
For the study published in the American Journal of Clinical Nutrition: