America's Compounding Center says the following about selenium:
"Selenium is an essential element found in trace amounts throughout the body. It is an antioxidant and may have anticancer and anti-aging effects. Selenium also helps maintain immune system and thyroid function. Dietary sources of selenium include nuts (particularly Brazil nuts), fish, shellfish, meats, and whole grain breads and cereals. Selenium deficiency is rare, but can occur in patients with malabsorption syndromes, genetic and mitochondrial disease, and in alcoholics. Complications of selenium deficiency include changes in the fingernails and nail beds, muscle weakness or pain, bleaching of the skin and hair, and heart problems. The UMDF recommends taking 25-50 micrograms (mcg) of selenium daily. Patients should not receive more than 400 mcg of selenium per day due to risk of selenium toxicity, which can result in fatigue, hair loss, and skin lesions. "