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Selenium is a mineral that is considered to be essential for human health. It can be found in small amounts throughout the body and functions as an antioxidant, particularly when taken in conjunction with vitamin E. Selenium helps fight free radicals in the body. Free radicals are particularly problematic to human health as they can damage cells and DNA, and are thought to contribute to several conditions including aging, heart disease, and cancer. Selenium is known for its role in thyroid function and helping with immune function.

People at risk of selenium deficiency include those who have rheumatoid arthritis and certain types of cancer. Other populations at risk of deficiency include those who smoke cigarettes, drink alcohol, take birth control pills, or have conditions such as Crohn's disease or ulcerative colitis which lead to difficulty absorbing selenium. In addition, selenium acts in synergy with the antioxidant vitamins, vitamin C (ascorbic acid) and vitamin E (α-tocopherol), by regenerating them from their oxidized forms and promoting maximal antioxidant protection.

Also known as:  Dioxyde de Sélénium, Ebselen, L-Selenomethionine, L-Sélénométhionine, Levure Sélénisée, Numéro Atomique 34, Selenio, Selenite, Sélénite de Sodium, Sélénium, Selenium Ascorbate, Selenium Dioxide, Selenized Yeast, Selenomethionine, Sélénométhionine, Sodium Selenite

Diseases and Conditions

Taking selenium orally has been shown to be effective for treating selenium deficiency, and it may also be effective for improving the symptoms and quality of life of people suffering from autoimmune thyroiditis, as well as for treating dyslipidemia and sepsis, as well as other conditions.

The risk of selenium deficiency may be increased following bariatric surgery or in severe gastrointestinal conditions, such as Crohn's disease. Some specialized medical diets like those used to treat certain metabolic disorders, including phenylketonuria, homocystinuria, and maple syrup urine disease, need to be supplemented with selenium to ensure optimum selenium status in patients.


Selenium is FDA-approved and is likely safe when taken orally and appropriately. Research shows that it is possibly safe for children and pregnant women. However, selenium may not be safe when taken long-term, and doses over 400 mcg increase the risk for selenium toxicity.


Medication Interactions

Patients who are taking selenium should use caution when combining it with anticoagulants, barbituates, contraceptives, gold salts, immunosuppressants, niacin, and warfarin.

Supplement and Food Interactions

Selenium may increase a person's risk of bleeding when combined with herbs, foods, or supplements which act as an anticoagulant. Selenium may affect copper absorption, while omega-3 fatty acids, zinc, and vitamin C might affect selenium absorption. Since astralagus contains selenium, it should not be taken at the same time as a selenium supplement.


The right amount of selenium depends on a variety of factors such as age, gender, medical history, DNA, and lifestyle. A recommended daily allowance (RDA) of selenium for an adult 19-50 years of age is 55 mcg. This number increases to 60 mcg per day for pregnant women and 65 mcg per day for women who are breastfeeding.


Selenium is found in some foods, including beef, turkey, ham, some fish, rice, eggs, spinach, peas. The levels and chemical forms of selenium in plant-based food vary according to the composition and selenium content of soil in which the plants are grown. Selenium-rich food sources include Brazil nuts, grains, seafood, organ meats, poultry, and dairy products.

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