Oxygen (65%) and hydrogen (10%) are predominantly found in water, which makes up about 60 percent of the body by weight. It’s practically impossible to imagine life without water.
Carbon (18%) is synonymous with life. Its central role is due to the fact that it has four bonding sites that allow for the building of long, complex chains of molecules. Moreover, carbon bonds can be formed and broken with a modest amount of energy, allowing for the dynamic organic chemistry that goes on in our cells.
Nitrogen (3%) is found in many organic molecules, including the amino acids that make up proteins, and the nucleic acids that make up DNA.
Calcium (1.5%) is the most common mineral in the human body – nearly all of it found in bones and teeth. Ironically, calcium’s most important role is in bodily functions, such as muscle contraction and protein regulation. In fact, the body will actually pull calcium from bones (causing problems like osteoporosis) if there’s not enough of the element in a person’s diet.
Phosphorus (1%) is found predominantly in bone but also in the molecule ATP, which provides energy in cells for driving chemical reactions.
Potassium (0.25%) is an important electrolyte (meaning it carries a charge in solution). It helps regulate the heartbeat and is vital for electrical signaling in nerves.
Sulfur (0.25%) is found in two amino acids that are important for giving proteins their shape.
Sodium (0.15%) is another electrolyte that is vital for electrical signaling in nerves. It also regulates the amount of water in the body.
Chlorine (0.15%) is usually found in the body as a negative ion, called chloride. This electrolyte is important for maintaining a normal balance of fluids.
Magnesium (0.05%) plays an important role in the structure of the skeleton and muscles. It also is necessary in more than 300 essential metabolic reactions.
Iron (0.006%) is a key element in the metabolism of almost all living organisms. It is also found in hemoglobin, which is the oxygen carrier in red blood cells. Half of women don’t get enough iron in their diet.
Fluorine (0.0037%) is found in teeth and bones. Outside of preventing tooth decay, it does not appear to have any importance to bodily health.
Zinc (0.0032%) is an essential trace element for all forms of life. Several proteins contain structures called “zinc fingers” help to regulate genes. Zinc deficiency has been known to lead to dwarfism in developing countries.
Copper (0.0001%) is important as an electron donor in various biological reactions. Without enough copper, iron won’t work properly in the body.
Iodine (0.000016%) is required for making of thyroid hormones, which regulate metabolic rate and other cellular functions. Iodine deficiency, which can lead to goiter and brain damage, is an important health problem throughout much of the world.
Selenium (0.000019%) is essential for certain enzymes, including several anti-oxidants. Unlike animals, plants do not appear to require selenium for survival, but they do absorb it, so there are several cases of selenium poisoning from eating plants grown in selenium-rich soils.
Chromium (0.0000024%) helps regulate sugar levels by interacting with insulin, but the exact mechanism is still not completely understood.
Manganese (0.000017%) is essential for certain enzymes, in particular those that protect mitochondria – the place where usable energy is generated inside cells – from dangerous oxidants.
Molybdenum (0.000013%) is essential to virtually all life forms. In humans, it is important for transforming sulfur into a usable form. In nitrogen-fixing bacteria, it is important for transforming nitrogen into a usable form.
Cobalt (0.0000021%) is contained in vitamin B12, which is important in protein formation and DNA regulation.