Selenium excess is rare and is caused by consuming too much of the mineral selenium.
(See also Overview of Minerals.)
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 may help protect against some cancers. Selenium is also necessary for the thyroid gland to function normally.
Taking more than 900 micrograms of a nonprescription selenium supplement each day can have harmful effects. Symptoms of selenium toxicity are mainly gastrointestinal upset, including nausea, vomiting, and diarrhea. Other symptoms include hair loss, abnormal nails, a rash, fatigue, and nerve damage. The breath may smell like garlic.
The diagnosis of selenium excess is based on symptoms. Blood or urinaryselenium levels can be measured.
Treatment of selenium excess involves reducing selenium consumption.
