Other name(s):

selenious acid, selenium methylselenocysteine, selenomethionine, sodium selenite

General description

Selenium is an essential trace element and antioxidant. It’s a cofactor in enzyme regulation. It also helps maintain the health of tissue and muscle. Selenium may help treat and prevent prostate cancer.

Selenium has antioxidant effects. It may serve some of the same antioxidant functions as vitamin E.

Medically valid uses

Selenium is needed to maintain the heart and blood vessels. It also keeps the heart muscle and skin tissue healthy. It may also aid in the treatment and prevention of cancer.

Selenium compounds are used in some shampoos. An example is selenium sulfide. It’s used in this form to treat seborrhea and dandruff.

Unsubstantiated claims

There may be benefits that have not yet been proven through research.

Selenium may prevent aging of the skin. It also slows the aging process. It may enhance immune system function. It may also protect against heart disease. It may also bind to heavy metals and reduce the toxicity of mercury.

Recommended intake

Selenium is measured in micrograms (mcg). It’s available as 50 mcg to 200 mcg tablets. The RDA is the recommended dietary allowance.



Infants (0 to 6 months)

15 mcg*

Infants (7 months to 1 year)

20 mcg*

Children (1 to 3 years)

20 mcg

Children (4 to 8 years)

30 mcg

Children (9 to 13 years)

40 mcg

Children (14 to 18 years)

55 mcg

Adults (19 years and older)

55 mcg


60 mcg


70 mcg

*Adequate Intake (AI)

Food source

Selenium content per 100 grams

Wheat germ

79 mcg

Brazil nuts

1912 mcg

Whole wheat bread

25.6 mcg

Oats, dry

28.8 mcg

Brown rice

5.8 mcg

Orange juice

0.1 mcg

*mcg = microgram

The amount of selenium in vegetables and grains depends on the soil in which they are grown.

Selenium is suggested in doses of no more than 200 mcg per day. The treatment range for selenium is narrow. You shouldn’t take too much. The recommended dose is 100 mcg to 200 mcg per day.

Selenium deficiency can cause symptoms. These can include:

  • Lightening of fingernail beds

  • Muscle weakness

  • Muscle discomfort

In parts of the world where selenium isn’t found in the soil and water, people may develop Keshan disease. This is a form of cardiomyopathy. This condition is weakness of the heart muscle. Selenium deficiency has also been seen in children with Kwashiorkor, a protein malnutrition disorder.

Side effects, toxicity, and interactions

Getting selenium from food sources doesn’t seem to cause side effects. However, having more than 200 mcg of selenium per day from supplements for an extended period of time may cause side effects. These can include:

  • Itchy skin

  • Diarrhea

  • Weakening and loss of fingernails and hair

  • Discolored teeth

  • Nausea

  • Vomiting

  • Peripheral neuropathy

  • Severe tiredness (fatigue)

  • A garlic-like odor to your breath

Adults who work in industrialized areas with high selenium content have a higher chance of liver and heart disease.

Even though optimal amounts of selenium may reduce the risk of cancer, having too much can be harmful. It may increase the risk for cancer.

Women who are pregnant or breastfeeding should talk to their healthcare providers before taking any supplements. Too much selenium can lead to bone and cartilage problems in unborn babies.

Kidney problems can cause high selenium levels in the body.

There are no known food interactions with selenium. It can interact with some antibiotics. It can also interact with some medicines used to treat osteoporosis.

Talk to your healthcare provider about selenium before taking it.

Online Medical Reviewer: Bianca Garilli MD
Online Medical Reviewer: Jessica Gotwals RN BSN MPH
Online Medical Reviewer: Tennille Dozier RN BSN RDMS
Date Last Reviewed: 8/1/2023