Selenium is a mineral found in soil, water, and some foods. It is important for making many body processes work correctly.
Most of the selenium in the body comes from the diet. The amount of selenium in food depends on where it is grown or raised. Crab, liver, fish, poultry, and wheat are generally good selenium sources. The amount of selenium in soils varies a lot around the world, which means that the foods grown in these soils also have differing selenium levels. In the U.S., the Eastern Coastal Plain and the Pacific Northwest have the lowest selenium levels. People in these regions naturally take in about 60 to 90 mcg of selenium per day from their diet. Although this amount of selenium is adequate, it is below the average daily intake in the U.S., which is 125 mcg.
Selenium is used for diseases of the heart and blood vessels, including stroke, "hardening of the arteries" (atherosclerosis), complications from statin drugs, abnormal cholesterol levels, and high blood pressure during pregnancy. It is also used for various cancers including cancer of the prostate, colon and rectum, stomach, esophagus, lung, ovaries, bladder, and skin.
Selenium is also used for alcohol-related liver disease, asthma, eczema, enlarged prostate, liver disease, hepatitis C, diabetes, Kashin-Beck disease, low birth weight, muscular dystrophy, pancreas infection, swelling after surgery, itchy and scaly skin (psoriasis), selenium deficiency, blood infection, inflammatory bowel disease, Kashan disease, and Osgood-Schlatter disease.
Some people take selenium by mouth for under-active thyroid, thyroid inflammation, osteoarthritis, rheumatoid arthritis (RA), an eye disease called macular degeneration, hay fever, infertility, cataracts, gray hair, abnormal pap smears, chronic fatigue syndrome (CFS), mood disorders, arsenic and mercury poisoning, and preventing miscarriage.
Selenium is also taken by mouth for preventing serious complications and death from critical illnesses such as head injury and burns. It is also used for preventing bird flu, swine flu, treating HIV/AIDS, and reducing side effects from cancer chemotherapy and radiation.
Selenium is given through an IV when someone has experienced a trauma and is critically ill.
How it works
Selenium is important for making many body processes work correctly. It seems to increase the action of antioxidants.
Likely EffectiveSelenium deficiency
Taking selenium by mouth is effective for preventing selenium deficiency.
Selenium is LIKELY SAFE for most people when taken by mouth in doses less than 400 mcg daily, short-term
Selenium is POSSIBLY UNSAFE when taken by mouth in high doses or for long-term. Taking doses above 400 mcg can increase the risk of developing selenium toxicity. Taking lower doses long-term can increase the risk of developing diabetes. High doses of selenium can cause significant side effects including nausea, vomiting, nail changes, loss of energy, and irritability. Poisoning from long-term use is similar to arsenic poisoning, with symptoms including hair loss, white horizontal streaking on fingernails, nail inflammation, fatigue, irritability, nausea, vomiting, garlic breath odor, and a metallic taste.Selenium can also cause muscle tenderness, tremor, lightheadedness, facial flushing, blood clotting problems, liver and kidney problems, and other side effects.
Children: Selenium isPOSSIBLY SAFEwhen taken by mouth appropriately. Selenium seems to be safe when used in the short-term in doses below 45 mcg daily for infants up to age 6 months, 60 mcg daily for infants 7 to 12 months, 90 mcg daily for children 1 to 3 years, 150 mcg daily for children 4 to 8 years, 280 mcg daily for children 9 to 13 years, and 400 mcg daily for children age 14 years and older.
Pregnancy and breast-feeding: Selenium use is POSSIBLY SAFE during pregnancy and breast-feeding when used short-term in amounts that are not above 400 mcg daily. Selenium is POSSIBLY UNSAFE in pregnancy and breastfeeding when taking by mouth in doses above 400 mcg daily, as this might cause toxicity, and in HIV-positive women, as this might increase virus levels in breast milk.
Autoimmune diseases: Selenium might stimulate the immune system. In theory, selenium might make autoimmune disease worse by stimulating the activity of the disease. People with autoimmune diseases such as multiple sclerosis, systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), and other should avoid taking selenium supplements.
Hemodialysis: Blood levels of selenium can be low in people undergoing hemodialysis. Using a dialysis solution with selenium might increase selenium levels, but selenium supplementation might be needed for some people.
Under-active thyroid (hypothyroidism): Taking selenium can worsen hypothyroidism especially in people with iodine deficiency. In this case, you should take iodine along with selenium. Check with your healthcare provider.
Fertility problems in men: Selenium might decrease the ability of sperm to move, which could reduce fertility. If you are trying to father a child, don't take selenium supplements.
Skin cancer: Long-term use of selenium supplements might slightly increase the risk of skin cancer recurrence, but this is controversial. Until more is known about the possible increase in skin cancer risk, avoid long-term use of selenium supplements if you have ever had skin cancer.
Surgery: Selenium might increase the risk of bleeding during and after surgery. Stop taking selenium at least 2 weeks before a scheduled surgery.
Selenium might stimulate the immune system. By stimulating the immune system, selenium might decrease the effectiveness of medications that decrease the immune system.Some medications that decrease the immune system include azathioprine (Imuran), basiliximab (Simulect), cyclosporine (Neoral, Sandimmune), daclizumab (Zenapax), muromonab-CD3 (OKT3, Orthoclone OKT3), mycophenolate (CellCept), tacrolimus (FK506, Prograf), sirolimus (Rapamune), prednisone (Deltasone, Orasone), and other corticosteroids (glucocorticoids).Selenium might slow blood clotting. Taking selenium along with medications that also slow blood clotting might increase the chances of bruising and bleeding.Some medications that slow blood clotting include aspirin, clopidogrel (Plavix), dalteparin (Fragmin), enoxaparin (Lovenox), heparin, ticlopidine (Ticlid), warfarin (Coumadin), and others.Taking selenium, beta-carotene, vitamin C, and vitamin E together might decrease the effectiveness of some medications used for lowering cholesterol. It is not known if selenium alone decreases the effectiveness of medications used for lowering cholesterol.Some medications used for lowering cholesterol include atorvastatin (Lipitor), fluvastatin (Lescol), lovastatin (Mevacor), and pravastatin (Pravachol).Taking selenium along with vitamin E, vitamin C, and beta-carotene might decrease some of the beneficial effects of niacin. Niacin can increase levels of good cholesterol. Taking selenium along with these other vitamins might decrease how well niacin works for increasing good cholesterol.Sedative medications (Barbiturates)
The body breaks down medications to get rid of them. Selenium might slow how fast the body breaks down sedative medications (barbiturates). Taking selenium with these medications might increase the effects and side effects of these medications.Warfarin (Coumadin)
Selenium might thin the blood. Selenium might also increase the effects of warfarin in the body. Taking selenium along with warfarin might increase the chances of bruising and bleeding.