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, particularly in prostate cancer. 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.

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 enhance immune system function, 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.



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

Breastfeeding women

75 mcg

 Photo of a loaf of wheat bread

Food source

Nutrient content per 100 grams

Wheat germ

106.6 mcg

Brazil nuts

96 mcg

Whole wheat bread

63 mcg


53.3 mcg

Brown rice

36.6 mcg

Orange juice

18.3 mcg


not available


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 (range in which the most therapeutic benefit is 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 include lightening of the 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 (weakness of the heart muscle).

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 developing liver and heart disease.

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

Women who are pregnant or breastfeeding 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 interactions.  Selenium can interact with certain antibiotics and some medications used to treat osteoporosis. Be sure to discuss any supplements, including selenium, with your doctor before taking them.  

Additional information

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