It contributes to thyroid hormone metabolism and DNA synthesis, and it helps protect against oxidative damage and infection, according to the United States (U.S.) Office of Dietary Supplements.
It is present in human tissue, mostly in skeletal muscle.
Dietary sources are varied. They include Brazil nuts, seafood, and meats.
The amount of selenium in food often depends on the selenium concentration of the soil and water where farmers grew or raised the food.
Fast facts on selenium
Here are some key points about selenium. More detail is in the main article.
- Selenium is a mineral that plays a role in many bodily functions.
- It may protect against cancer, thyroid problems, cognitive decline, and asthma, but more research is needed.
- Brazil nuts, some fish, brown rice, and eggs are good sources.
- The best source of nutrients is food. Any supplement use should first be discussed with a doctor.
- Cardiovascular disease: According to the Office for Dietary Supplements, selenoproteins can protect against cardiovascular disease, because they prevent the oxidative modification of lipids, or fats, in the body.This reduces inflammation and prevents the buildup of platelets.However, clinical evidence does not support the use of selenium supplements for this purpose.Cognitive decline: Selenium’s antioxidant activity may help reduce the risk of cognitive, or mental, decline, as people get older.Evidence from studies is mixed, however, and selenium supplements are not yet prescribed for people at risk of diseases such as Alzheimer’s, although it may have a role in prevention that is still under investigation.
Thyroid disorders: Selenium has an important role in producing and metabolizing thyroid hormone.
There is some evidence that women with higher selenium levels have fewer thyroid problems, but this has not been proven for men, and other studies have produced mixed results.
More studies are under way to decide whether selenium supplements might support thyroid health.
Cancer: The role played by selenium in DNA repair and other functions may mean that is can help prevent cancer. However, studies have produced mixed results.
The U.S. Food and Drug Administration (FDA) concluded in 2003:
“Some scientific evidence suggests that consumption of selenium may reduce the risk of certain forms of cancer.”