Selenium is a trace element essential to our metabolism, a vital constituent of certain antioxidant enzymes that plays a role in the fight against free radicals that “attack” our cells and DNA. Selenium also stimulates the immune system and promotes proper functioning of the thyroid hormone.
However, in very large doses, selenium can become toxic. To pose a significant risk would require more than 900 thousandths of a milligram of selenium per day, over 16 times the daily recommended dose of 55 thousandths of a milligram per day for adults. Such an overdosage is highly unlikely.
In France, for instance, consumption of selenium is 40 thousandths of a milligram per day, two to three times less than in certain countries of North and South America. In these regions, there are far higher levels of selenium in the soil than in Europe.
Found naturally in soil and rocks, selenium enters the food chain via the plants in which it accumulates and the animals that consume those plants. Foods richest in selenium are meat products (such as raw beef), dried fruits and nuts, fish, shellfish and cereals.