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 cellular damage.
Selenium's functions include:
Recommended Dietary Allowance
Adequate Intake (AI) = 15
AI = 15
AI = 20
AI = 20
|14 years and older||55||55|
Symptoms of selenium deficiency may include:
Groups of people who may be at risk for selenium deficiency include:
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:
Major food sources of selenium include:
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 adequate 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.
Department of Agriculture
Eat Right—Academy of Nutrition and Dietetics
Canadian Cancer Society
Dietitians of Canada
Dietary supplement fact sheet: selenium. Office of Dietary Supplements website. Available at: https://ods.od.nih.gov/factsheets/Selenium-HealthProfessional. Updated February 11, 2016. Accessed July 7, 2016.
Selenium. EBSCO Natural and Alternative Treatments website. Available at: http://www.ebscohost.com/biomedical-libraries/natural-alternative-treatments. Updated December 15, 2015. Accessed July 7, 2016.
Selenium. Oregon State University Linus Pauling Institute website. Available at: http://lpi.oregonstate.edu/mic/minerals/selenium. Updated June 2015. Accessed July 7, 2016.
1/13/2009 DynaMed's Systematic Literature Surveillance http://www.ebscohost.com/dynamed: 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(1):39-51.
Last reviewed July 2016 by Michael Woods, MD
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.