Selenium is a trace mineral, which means that it is only needed in small amounts in the diet. Proper selenium intake is needed to make certain proteins, and there is some evidence that selenium can help treat or prevent certain conditions. But getting too much selenium can cause health problems, so you should talk to your doctor before taking supplemental selenium.
Selenium in Food
According to the Office of Dietary Supplements, most adults should get 55 mcg of selenium each day, except for lactating or pregnant women, who need 60 and 70 mcg of selenium, respectively. The predominant source of selenium in the diet is foods made from plants, though their selenium intake may vary depending on the amount of selenium in the soil where they are grown. Tuna, beef, cod, pasta and eggs are also good sources of selenium. Selenium deficiencies are rare, but can occur where selenium levels in the soil are low.
Selenium and Antixodiants
Selenium is needed primarily to make special enzymes that function as antioxidants, MedLinePlus explains. Antioxidants are able to scavenge molecules known as free radicals or reactive oxygen species, which can react with DNA, proteins and cell membranes to cause cell damage and death. These molecules are made as a byproduct of cells using energy and can also be generated in response to certain toxins. Reactive oxygen species can damage DNA, which can result in cancer, so selenium may play a role in preventing cancer.
Other Effects
Selenium also contributes to the effectiveness of vaccines, as selenium can help produce the antibodies that cause immunity, the University of Maryland Medical Center explains. Selenium also increases sperm production and the motility of sperm, so it may boost fertility in men. There is also some evidence that selenium can help protect against heart disease by improving cholesterol levels. Selenium's role in lowering levels of reactive oxygen species may also help treat arthritis, because reactive oxygen species can cause inflammation and swelling in the joints.
Selenosis
If you consume too much selenium each day, you may develop a condition known as selenosis. The tolerable upper limit for selenium, which is the maximum dose recommended to avoid developing selenosis, is 400 mcg per day, the Office of Dietary Supplements reports. In general, selenosis is rare, and it is typically caused by getting too much selenium from supplements. Selenosis can also be caused by eating too many Brazil nuts, which contain 544 mcg per ounce. Symptoms of selenosis include hair loss, gastrointestinal upset, fatigue, white blotchy nails, garlic-breath odor and mild nerve damage.
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