Selenium is an essential trace mineral that acts as an antioxidant—a substance that protects the body's cells against the effects of free radicals. Free radicals are normal byproducts of metabolism, but they can cause cell damage. Selenium can function alone or as part of enzyme systems.
What Does Selenium Do?
Selenium's functions include:
- Acting as a cofactor for the antioxidant enzyme glutathione peroxidase
- Aiding the metabolism of sulfur-containing amino acids
- Binding heavy metals and possibly reducing toxicity from mercury contamination
- Allowing for normal fetal development during pregnancy
- Stimulating immune function
- Ensuring proper function of the thyroid gland
- Aiding cell growth
How Much Should I Take?
Recommended Dietary Allowance
Adequate Intake (AI) = 15
AI = 15
AI = 20
AI = 20
|14 years and older||55||55|
What If I Don't Get Enough Selenium?
Symptoms of selenium deficiency may include:
- Muscle pain
- Muscle wasting
- Enlarged heart
- Heart disease
- Liver damage
- Altered thyroid function
Groups of people who may be at risk for selenium deficiency include:
- People living in areas where the soil is very low in selenium, such as parts of China and Russia
- People with gastrointestinal disorders, such as Crohn's disease, that may decrease absorption of selenium
- People receiving total parenteral nutrition (TPN); however these people now routinely receive selenium supplementation
Can Too Much Selenium Be Toxic?
The government has set the tolerable upper intake level (UL) for selenium at 400 mcg. Selenium toxicity is rare in the US. However, when it occurs, symptoms may include:
- Garlicky breath
- Hair loss
- General weakness
- Liver disease
- White, blotchy nails
- Mild nerve damage
Where Can I Find Selenium?
The major food sources of selenium are seafood, eggs, and meats, especially organ meats. Seeds and grain products are also good sources. The amount of selenium these plant foods provide depends on the level of selenium in the soil they were grown in. This level varies by region. Fruits and vegetables generally don't have much selenium.
|Brazil nuts, dried, unblanched||1 ounce||840|
|Tuna, canned in water||3 ounces||68|
|Liver, beef, pan-fried||3.5 ounces||58|
|Pork tenderloin, separated lean, roasted||3.5 ounces||48|
|Oysters, cooked||6 medium oysters||43|
|Shrimp, frozen, cooked||3 ounces||40|
|Cod, baked||3 ounces||33|
|Salmon, sockeye, canned||3 ounces||33|
|Macaroni and cheese, from mix||1 cup||31|
|Turkey, light meat, no skin, roasted||3.5 ounces||31|
|Beef, ground, lean, broiled||3.5 ounces||29|
|Macaroni, boiled||1 cup||29|
|Chicken breast, no skin, roasted||3 ounces||25|
|Sunflower seed kernels, dry roasted||1 ounce||22|
|Special K®||1 cup||17|
|Cream of wheat, instant, cooked||1 packet||16|
|Brown rice, cooked||½ cup||13|
|Egg, large||1 egg||13|
|Rye bread||1 slice||10|
|Whole wheat bread||1 slice||10|
|Walnuts, black||1 ounce||5|
How Can Selenium Affect My Health?
Many studies that have examined selenium intakes and blood selenium levels have suggested that people with greater intakes of selenium are less likely to develop cancer or to die from cancer if they already have it. The types of cancer that selenium may help prevent include:
Selenium's effects on cancer are believed to be due to its action as an antioxidant. In addition, selenium helps stimulate the immune system, making it better able to fight cancer.
In population studies, people with low intakes of selenium have been found to have heart damage, while those with higher selenium intakes have lower risks for heart disease. In addition, a selenium deficiency has been associated with lower levels of HDL cholesterol—the "good" cholesterol.
Again, selenium's action as an antioxidant is likely the means by which it protects the heart. Selenium and other antioxidants help limit the oxidation of LDL ("bad") cholesterol. This oxidation leads to plaque build-up on artery walls, and subsequently, heart disease.
Free radicals can promote inflammation and destroy cartilage and collagen in joints, contributing to the pain of rheumatoid arthritis. As an antioxidant, selenium can help limit free radical production and therefore ease the pain of arthritis. Selenium is also believed to affect other biochemical pathways that lead to arthritis. Studies of people with rheumatic diseases, including arthritis, have found these people to have low tissue levels of selenium.
Tips for Increasing Your Selenium Intake
- For a simple lunch, open a can of tuna or salmon and make a sandwich on whole wheat bread.
- Choose fish or seafood for dinner 2-3 times per week.
- Choose lean meats for entrees.
- Select a breakfast cereal that is rich in nutrients. Check the nutrition facts label on the side.
- Choose brown rice over white, and whole wheat or rye bread over white.
American Dietetic Association
United States Department of Agriculture
Canadian Cancer Society
Dietiticans of Canada
Dietary supplement fact sheet: selenium. NIH Clinical Center. National Institutes of Health website. Available at: http://ods.od.nih.gov/factsheets/selenium.asp. Accessed July 6, 2008.
Duyff RL. The American Dietetic Association's Complete Food & Nutrition Guide. 3rd ed. John Wiley and Sons, Inc.: Hoboken, NJ; 2006.
Garrison Jr R, Somer E. The Nutrition Desk Reference. 3rd ed. Keats Publishing: New Canaan, CT; 1995.
Wardlaw GM, Insel PM. Perspectives in Nutrition. 2nd ed. Mosby: Philadelphia, PA; 1993.
Last reviewed July 2008 by Maria Adams, MS, MPH, RD
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.
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