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. Selenium can function alone or as part of enzyme systems.
What Does Selenium Do?
Selenium's functions include:
- Acting as a co-factor 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:
- Enlarged heart
- Heart disease
- Bones and joints disease
- Altered thyroid function
- Mental retardation
- Weak immune system
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 for people ≥ 14 years of age. Selenium toxicity is rare in the United States. However, when it occurs, symptoms may include:
- Garlicky breath
- Hair loss
- General weakness
- 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||544||780|
|Tuna, light, canned in oil, drained, 3 ounces||63||95|
|Beef, cooked, 3½ ounces||35||50|
|Spaghetti w/ meat sauce, frozen entrée, 1 serving||34||50|
|Cod, cooked, 3 ounces||32||45|
|Turkey, light meat, roasted, 3½ ounces||32||45|
|Beef chuck roast, lean only, roasted, 3 ounces||23||35|
|Chicken breast, meat only, roasted, 3½ ounces||20||30|
|Noodles, enriched, boiled, ½ cup||17||25|
|Macaroni, elbow, enriched, boiled, ½ cup||15||20|
|Egg, whole, 1 medium||14||20|
|Cottage cheese, low fat 2%, ½ cup||12||15|
|Oatmeal, instant, fortified, cooked, 1 cup||12||15|
|Rice, white, enriched, long grain, cooked, ½ cup||12||15|
|Bread, whole wheat, commercially prepared, 1 slice||10||15|
|Walnuts, black, dried, 1 ounce||5||8|
|Bread, white, commercially prepared, 1 slice||4||6|
|Cheddar cheese, 1 ounce||4||6|
*DV = Daily Value. DVs are reference numbers developed by the Food and Drug Administration (FDA) to help consumers determine if a food contains a lot or a little of a specific nutrient. The DV for selenium is 70 micrograms (ug). Most food labels do not list a food's selenium content. The percent DV (%DV) listed on the table indicates the percentage of the DV provided in one serving. A food providing 5% of the DV or less is a low source while a food that provides 10-19% of the DV is a good source. A food that provides 20% or more of the DV is high in that nutrient. It is important to remember that foods that provide lower percentages of the DV also contribute to a healthful diet. For foods not listed in this table, please refer to the U.S. Department of Agriculture's Nutrient Database Web site: http://www.nal.usda.gov/fnic/cgi-bin/nut_search.pl.
Source: Dietary Supplement Fact Sheet: Selenium. Office of Dietary Supplements. National Institutes of Health.
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 effects 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. 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
Dietitians of Canada
Dietary supplement fact sheet: selenium. Office of Dietary Supplements. National Iinstitutes of Health. National Institutes of Health website. Available at: http://ods.od.nih.gov/factsheets/selenium.asp. Accessed July 2, 2010.
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.
¹1/13/2009 DynaMed's Systematic Literature Surveillance DynaMed's Systematic Literature Surveillance : 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 July 2010 by ]]>Brian Randall, 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.
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