Copper is an essential nutrient required for energy metabolism, redox reactions, immune function, gene transcription and iron metabolism. 

Iodine is required for thyroid function. 

Iron is required for proper oxygen transport through blood (in the form of hemoglobin) and muscle tissue (in the form of myoglobin).  Iron is also required for energy metabolism (e.g., electron transport chain), antioxidant functions, and DNA synthesis.  Including a vitamin C rich food with an iron-rich food improves absorption of iron.  Using cast-iron cookware with a vitamin C rich food also helps increase absorption (e.g., tomato-based products in cast-iron cookware). 

Selenium is required for selenoproteins.  These specialized selenium-containing proteins act in various functions associated with amino acid and protein synthesis, immune function, reproduction and cellular growth regulation. 

Zinc plays an important role in immune function, cellular growth and development, neurological function, and reproduction.