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 by-products of metabolism, but they can cause cell damage.
What Does Selenium Do?
Selenium's functions include:
How Much Should I Take?
What If I Do Not Get Enough Selenium?
Symptoms of selenium deficiency may include:
Groups of people who may be at risk for selenium deficiency include:
Can Too Much Selenium Be Toxic?
The government has set the tolerable upper intake level (UL) for selenium at 400 mcg for people ≥ 14 years of age. Selenium toxicity is rare in the United States. However, when it occurs, symptoms may include:
Where Can I Find Selenium?
Major food sources of selenium include:
How Can Selenium Affect My Health?
Some studies that have examined selenium intakes and blood selenium levels effect on cancer. Some of these studies 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. However, other studies have not found selenium to be protective for cancers. If selenium affects cancer, it is thought to be due to its action as an antioxidant. Also, it may be that 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 a greater incidence of heart disease, while those with higher selenium intakes have lower risks for heart disease.
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.
Tips for Increasing Your Selenium Intake
Academy of Nutrition and Dietetics
United States Department of Agriculture
Canadian Cancer Society
Dietitians of Canada
Dietary supplement fact sheet: selenium. Office of Dietary Supplements. National Institutes of Health. National Institutes of Health website. Available at: http://ods.od.nih.gov/factsheets/selenium.asp . Accessed September 19, 2012.
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Selenium. EBSCO Natural and Alternative Treatments website. Available at: http://www.ebscoho.... Updated July 2012. Accessed September 19, 2012.
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1/13/2009 DynaMed's Systematic Literature Surveillance http://www.ebscohost.com/dynamed/what.php : Lippman SM, Klein EA, Goodman PJ, et al. Effect of selenium and vitamin E on risk of prostate cancer and other cancers: the Selenium and Vitamin E Cancer Prevention Trial (SELECT). JAMA. 2009;301:39-51. Epub 2008 Dec 9.
Last reviewed September 2012 by Brian Randall, MD