Selenium

Selenium occurs in all tissues. Selenium works with vitamin E as an antioxidant. It helps protect cells against damage by free radicals, which are reactive by-products of normal cell activity. Selenium is also necessary for the thyroid gland to function normally.

Selenium Deficiency

Selenium deficiency is rare, even in New Zealand and Finland, where selenium intake is much lower than in the United States and Canada. In China, where selenium intake is even lower, selenium deficiency occurs in association with Keshan disease, a viral disease that affects mainly children and young women. Keshan disease damages the heart, resulting in cardiomyopathy.

In selenium deficiency, antioxidants are lacking in the heart and muscles. As a result, cardiomyopathy and muscle weakness may occur.

Doctors suspect selenium deficiency on the basis of the person's circumstances and symptoms. Treatment with a selenium supplement may result in a complete recovery.

Selenium Excess

Taking more than 1 milligram of a nonprescription selenium supplement each day can have harmful effects. Symptoms include nausea and vomiting, loss of hair and nails, a skin rash, and nerve damage. The diagnosis is based on symptoms, particularly rapid hair loss. Treatment involves reducing selenium consumption.