Calcium is the most common mineral in the human body, with over 90% of it forming the structure of the bones and teeth. There is also a small amount of calcium circulating in the bloodstream, and this amount must stay within a narrow limit in order to keep your body functioning properly. If you don't have enough calcium available in your diet to maintain the amount you need in your blood, your body will start to break down and circulate the calcium in your bones and teeth.

Most kidney stones are made up of calcium phosphate or calcium oxalate. People with high levels of calcium in their urine are at a greater risk of developing these kidney stones. Calcium in the diet doesn't have a huge effect on the levels in your urine, but a high intake of sodium, protein or caffeine can raise the level of calcium in the urine, contributing to this type of kidney stones.

The name phosphorus comes from the Greek word phosphoros, which means lightbearing. The element phosphorus is never found free in nature. It is always combined with other minerals.

Phosphorus taken in high amounts can interfere with calcium absorbtion. This is why replacing milk in the diet with sodas, which are high in phosphorus, can be very detrimental to teenagers who are building up their bone structure.

In its natural form magnesium is a strong, lightweight, silvery-white metal. It is named after a region of Greece called Magnesia.

Two common products containing magnesium are epsom salts (magnesium sulfate) and Milk of Magnesia (magnesium hydroxide).

"Hard" water, which contains more minerals, can be a dietary source of magnesium.

The iron in your diet comes in two forms: heme and nonheme. Heme iron is the form in red blood cells, and is found in meat products. This form is most easily absorbed. Plant foods and iron fortified foods (such as breads and cereals) contain nonheme iron, which is not absorbed as easily. You can help your body to absorb nonheme iron by taking it with Vitamin C, such as a glass of orange juice.

Manganese is a pinkish gray, hard, very brittle metal. It is a very common element that can be found everywhere on the earth, and every species requires manganese to stay alive.

Manganese is toxic if too much is ingested. Symptoms of manganese poisoning are hallucinations, forgetfulness, nerve damage, lung embolism bronchitis and impotence.

Most of the world's iodine is found in oceans. Soils in different areas have very different amounts of iodine. Mountainous regions and flooded river valleys contain very little iodine, and people living on produce from those regions will be iodine deficient.

Some foods contain goitrogens, which can inhibit the bodies absorbtion of iodine. These include cassava, millet, cruciferous vegetables such as cabbage, cauliflower and brussels sprouts, and some compounds in soybeans. However, this doesn't usually cause a problem unless the foods are eaten in very large quantities, or the diet is already very low in iodine.

Selenium was discovered in 1817, and the name comes from the Greek word for moon, Selênê.

High levels of selenium in the blood can cause selenosis, with symptoms of stomach upset, hair loss, blotchy nails, garlic breath, fatigue, irritability and nerve damage. Luckily this is rare, except in cases or industrial poisoning or a mistake in the levels of a supplement.

China and Russia have low levels of selenium in their soil, and this is where you most often find a deficiency of this mineral.

We get most of our sodium in the form of salt, or sodium chloride. The sodium and chloride are both important electrolytes that are essential for life.

The minimum amount of sodium needed to function is 500 mg/day. However people who eat highly processed foods and add a lot of salt to their diet can be getting as much as 5000 mg/day! Americans, you know who you are! Low sodium levels may occur when extreme heat or physical activity causes you to perspire excessively.

Prolonged diarrhea and vomiting can cause a sodium deficiency that goes along with dehydration. This is a problem in impoverished countries where diseases result from contaminated water supplies.

Zinc was discovered in Germany in 1500, and the name is derived from the German word zink, which means of obscure origin.

There have been many studies done testing whether zinc lozenges can shorten the duration of the common cold. About half of the studies have shown cold symptoms reduced or shortened with zinc lozenges, and the other half have shown the same effects for a placebo. Therefore there isn't any evidence that zinc can help to shorten cold symptoms. Because of problems with taking too much zinc, discussed below, it's not recommended that you take zinc lozenges for more than 3-5 days, especially if your cold symptoms don't improve during that time.

Too much zinc can be harmful. Large doses taken even for a short period can cause stomach cramps, nausea and vomiting. In the long term, large doses of zinc can interfere with copper absorption and cause a copper deficiency. It isn't recommended to exceed the RDA if you take zinc supplements.

Potassium is one of the electrolytes, along with sodium and chloride. Electrolytes change into ions when they are in a solution (blood), and then they are capable of conducting electricity. They are vital for regulating the fluid volume and ph of the blood.

Hyperkalemia is too much potassium in the blood; hypokalemia is too little potassium. Hypokalemia can be caused by excessive vomiting and diarrhea, anorexia and bulemia, magnesium deficiency, alcoholism and certain medications that deplete potassium levels.

Eating large amounts of black licorice for long periods of time can cause hypokalemia, or not enough potassium in the blood. Black licorice contains a substance which causes you to excrete potassium in the urine.

Hippocrates was said to have prescribed copper compounds to treat diseases as far back as 400 B.C. In ancient Egypt, copper was used to promote wound healing, treat headaches and epilepsy, and sterilize water. Romans, ancient Indians and Persians also used copper for a range of skin, lung, and inflammatory disorders.

Many people wear copper bracelets to relieve the pain of arthritis. Proponents of this treatment claim that you actually absorb copper through the skin to get the therapeutic effect. There has been a study done which showed positive effects for the people wearing copper bracelets, and another study which showed no effect. There isn't any danger in wearing a copper bracelet, if you aren't allergic to the metal. However, these bracelets can also be expensive, so be careful not to spend a lot of money based on health claims that may not be true. (Mayo Clinic Study: "http://www.cancerpage.com/news/article.asp?id=5149", Walker and Keats study: "http://www.ncbi.nlm.nih.gov/pubmed/961545")

Flouride is not essential to grow and sustain life. It is mainly needed to prevent dental caries, and this is how it gets its status as an essential element. Ninety five percent of the fluoride in the human body is found in the bones and teeth.

Fluoride consumed in drinking water can strengthen children's teeth before they erupt, and also has a topical effect to help strengthen the teeth of older children and adults. Studies have shown that adding fluoride to drinking water has lowered the amount of dental cavities by 40% or more. Many dentists prescribe fluoride supplements for children living in areas where fluoride is not added to the water.

Chromium's name comes from the Greek word chroma, which means color. All compounds containing chromium are colored.

The amount of chromium in foods depends a lot on the way the food is grown and processed, and sometimes a sample can even be contaminated with chromium before it is analyzed. This makes it hard to come up with a definitive list of good sources. However it is widely available in the food supply. Foods that are not high in chromium are simple sugars (see macronutrients).

Nearly all life forms need molybdenum to survive. It is also an essentail element for the global ecosystem, since it is needed to facilitate the natural cycles of carbon, nitrogen and sulfur.

Blood and other body fluids have almost the same concentration of chloride as sea water.