Role: Component of the antioxidant enzyme glutathione peroxidase. Works synergistically with vitamin E. Involved in immune function and thyroid metabolism.
Deficiency: Impaired immunity. Susceptibility to Keshan disease (a heart disorder).
Sources: Brazil nuts; tuna fish, seafood, meats and poultry, other fish; whole-grain products.
Toxicity: Fatigue, “garlic body odor”, irritability, abnormal fingernails, hair loss, skin lesions.