Body composition may be analyzed in terms of molecular type e. In terms of tissue type, the body may be analyzed into water, fat, muscle, bone, etc. All 11 are necessary for life. Essential trace elements pdf all elements which are found in the human body in trace quantities play a role in life.
Functions have been proposed for trace amounts of cadmium and lead, although these are almost certainly toxic in amounts very much larger than normally found in the body. There is evidence that arsenic, an element normally considered a toxic in higher amounts, is essential in ultratrace quantities, in mammals such as rats, hamsters, and goats. One study has found bromine to be necessary to collagen IV synthesis in humans. About 29 of these elements are thought to play an active positive role in life and health in humans.