Four key elements make up most of the human body. These are oxygen (65.5%), carbon (18.5%), hydrogen (9.5%), and nitrogen (3.2%).
Other essential elements include
Iron - Deficiency of iron contributes to poor oxygen absorption, ADD, and ADHD
Zinc - Deficiency affects thyroid functionality, loss of smell and taste, fatigue, arthritus, and low libido. Excess iron can lead to scoliosis, nausea, and vomiting.
Lead - Excess leads to hormonal disorders, developmental disorders, mental disorders, hearing loss, constipation, headaches, brain damage, kidney damage, and reproductive issues.
Copper - Excess copper causes vomiting, hypotension, melena, coma, depression, anemia, panic attacks, ADD, schizoprhrenia, and damage to liver and kidneys.Aluminum - Excess cause digestive disorders, brain disorders, blood disorders, and Alzheimers.
Even though these elements are found in only trace amounts in the human body, they play significant roles in the maintenance of the body. An example of these important elements include iron, which is used in the blood for carrying oxygen from the lungs to the rest of the body. Copper, another important element (but only in very small amounts), combines with proteins for proper enzyme production. Zinc is significant to a number of key enzymes, and selenium is essential to antioxidant enzyme activity.
As is often the case in life, too much of a good thing is not always good. Iron becomes toxic in higher accumulations. Copper toxicity, known as copperiedus, is a consequence of excessive copper in the body and is linked to physical and psychiatric symptoms similar to those of mercury and lead.
You can find some useful information about elements in the human body here. Composition of the human body
The acceptable levels of some of the trace elements found in the human body continue to be studied, though it is known that excess amounts of these elements (mostly metals) in the body can be toxic. Toxic Elements