Side Effects:

Selenium deficiency is rare in people in the United States. However, selenium deficiency may occur when a person is fed through a vein (IV line) for long periods of time.

Keshan disease is caused by a deficiency of selenium. This leads to an abnormality of the heart muscle. Keshan disease caused many childhood deaths in China until the link to selenium was discovered and selenium supplements were provided.

Two other diseases have been linked to selenium deficiency:

• Kashin-Beck disease, which results in joint and bone disease
• Myxedematous endemic cretinism, which results in mental retardation

Severe gastrointestinal disorders may also affect the body's ability to absorb selenium.

Too much selenium in the blood can cause a condition called selenosis. Selenosis can cause loss of hair, nail problems, nausea, irritability, fatigue, and mild nerve damage. However, selenium toxicity is rare in the United States.