Selenium

Other Name(s):

selenious acid, selenium methylselenocysteine, selenomethionine, sodium selenite

General Description:

Selenium is an essential trace element and antioxidant. It is a cofactor in enzyme regulation, and plays a role in maintaining the health of tissue and muscle. Selenium may be helpful in cancer treatment and prevention. Selenium has antioxidant properties and may serve some of the same antioxidant functions as vitamin E .

Medically Valid Uses:

Selenium is important in the maintenance of the circulatory system, and of healthy heart muscle and skin tissue.

Selenium may be helpful in cancer treatment and prevention. Studies as early as 1969 suggested that selenium might have an anti-cancer effect. Recent research from the University of Arizona Medical School has demonstrated that selenium supplements reduce the incidence of certain types of cancer.

Selenium compounds, such as selenium sulfide, are used topically in some shampoos to treat seborrhea and associated dandruff.

Unsubstantiated Claims:

Please note that this section reports on claims that have NOT yet been substantiated through scientific studies.

Selenium reportedly prevents aging of the skin and slows the aging process. Additionally, it is said to improve the immune system, protect against heart disease, bind to heavy metals and possibly reduce the toxicity of mercury.

Recommended Intake:

As indicated below, selenium is measured in micrograms (mcg). Selenium is available as 50 to 200 mcg tablets. The RDA is the Recommended Dietary Allowance.

Group

RDA

Infants (0 to 6 months)

10 mcg

Infants (6 months to 1 year)

15 mcg

Children (1 to 6 years)

20 mcg

Children (7 to 10 years)

30 mcg

Boys (11 to 14 years)

40 mcg

Girls (11 to 14 years)

45 mcg

Boys (15 to 18 years)

50 mcg

Girls (15 to 18 years)

50 mcg

Men (19+ years)

70 mcg

Women (19+ years)

55 mcg

Pregnant women

65 mcg

Breast-feeding women

75 mcg

 

Food source

Nutrient content per 100 grams

Wheat germ

106.6 mcg

Brazil nuts

96 mcg

Whole wheat bread

63 mcg

Oatmeal

53.3 mcg

Brown rice

36.6 mcg

Orange juice

18.3 mcg

Seafood

not available

Meats

not available

*mcg = microgram

Selenium content in vegetables and grains depends on the soil in which they are grown.

Selenium is recommended in doses not to exceed 200 mcg per day. The therapeutic window (period during which the best results are achieved) for selenium is narrow. Therefore, selenium should not be taken in excess. The recommended dose for therapeutic purposes is 100 to 200 mcg per day.

Signs of deficiency are lightening in the color of fingernail beds, muscle weakness and muscle discomfort. In parts of the world where selenium is not readily found in the soil and water, people may develop Keshan disease, a form of cardiomyopathy (heart muscle disease).

Selenium deficiency has also been associated with Kwashiorkor (protein malnutrition).

Side Effects, Toxicity and Interactions:

Toxicity from selenium in normal dietary sources has not been demonstrated. However, consuming more than 200 mcg of selenium on a daily basis and for prolonged periods may lead to toxicity in humans. Symptoms of excessive selenium are itching of the skin, diarrhea and weakening and loss of the fingernails, hair and teeth. Nausea, vomiting, peripheral neuropathy and fatigue are other symptoms. Selenium can also cause the breath to have a garlic-like odor. Adults working in industrialized areas with high selenium content seem to have a higher probability of liver and heart disease.

Although optimal amounts of selenium have been shown to significantly reduce the risk for certain cancers, excessive amounts can actually increase the risk for cancer.

Women who are pregnant or breast-feeding should consult a physician before taking any mineral supplements. Too much selenium can lead to bone and cartilage abnormalities in the developing fetus.

Kidney problems or kidney disease could lead to increased selenium levels in the body.

There are no known significant food or drug interactions.

Additional Information:

Click here for a list of reputable Web sites with general information on nutrition.

References:

  1. Behrman RE, Kliegman RM, Nelson EE, Vaughan VC, eds. Nelson Textbook of Pediatrics. 14th ed. Philadelphia, PA: W.B. Saunders Co.; 1992.

  2. Braunwald E, Isselbacher KJ, Petersdorf RG, Wilson JD, Martin JB, Fauci AS, eds. Harrison's Principals of Internal Medicine. 11th ed. New York, NY: McGraw-Hill; 1987.

  3. Smolin LA, Grosvenor MB. Nutrition Science and Applications. 2nd ed. Sanders College Publishing; 1997.

  4. Clark LC, Hixson LJ, Combs GF Jr, Reid ME, Turnbull BW, Sampliner RE. Plasma selenium concentration predicts the prevalence of colorectal adenomatous polyps. Cancer Epidemiol Biomarkers Prev. 1993;2(1):41-6.

  5. Trace Elements. Facts and Comparisons. St Louis, MO: Facts & Comparisons; 1991.

  6. USP DI 19th ed. Englewood, CO: Micromedex Inc.; 1999

  7. Clark LC, Dalkin B, Krongrad A. Decreased incidence of prostate cancer with selenium supplementation: results of a double-blind cancer prevention trial. Br J Urol. 1998;81(5):730-4.

  8. Fleet JC. Dietary selenium repletion may reduce cancer incidence in people at high risk who live in areas with low soil selenium. Nutr Rev. 1997;55(7):277-9.

  9. Clark LC, Combs GF Jr, Turnbull BW. Effects of selenium supplementation for cancer prevention in patients with carcinoma of the skin. A randomized controlled trial. Nutritional Prevention of Cancer Study Group. JAMA. 1996;276(24):1957-63.

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