ABSTRACT
Trace elements are required to maintain normal human physiology but are present in small quantities, with less than 4 g in the entire body (1). Nine trace elements-iron, zinc, manganese, copper, selenium, chromium, molybdenum, iodine, and cobalt-are considered essential in humans. The only known function of cobalt is as a component of vitamin B12 (2). Experimental evidence suggests that five other trace elements-boron, nickel, silicon, arsenic, and vanadium-may be essential in humans; however, definitive evidence is lacking (3).
