Calcium is the most abundant mineral in the human body and one of the most important. The calcium topic is huge and complex. This mineral constitutes about 1.5-2.0 percent of our body weight. Almost all (98 percent) of our approximately three pounds of calcium is contained in our bones, about 1 percent in our teeth, and the rest in the other tissues and the circulation.

It is mainly the calcium in your diet that spares, or protects, the calcium in your bones. In addition to their structural role, your bones are your emergency supply of calcium. Your body actually tears down and builds bone all of the time in order to make its calcium available for your body’s functions. If you don’t get enough calcium from the food you eat, your body automatically takes the calcium you need from your bones. If your body continues to tear down more bone than it replaces over a period of years to get calcium, your bones become weak and break easily. This leads to the crippling bone disease called "osteoporosis." Approximately 25 million American women have some degree of osteoporosis; the disease will affect one-third to one-half of post-menopausal women, and 5 million American men suffer from osteoporosis.

The most available source of calcium in our food supply comes from milk and foods made with milk. Because these dairy products are one of the easiest ways to meet your calcium needs, the food pyramid recommends 2-3 servings from the Milk, Yogurt and Cheese Group every day. The pyramid is an outline of what to eat each day to get the nutrients you need. Each food group provides a unique combination of nutrients. Foods in one group can't replace those in another. For good health, you need them all. The Milk, Yogurt and Cheese Group is one piece of the pyramid that needs rebuilding. Most Americans do not eat the recommended number of servings to get the calcium they need. Calcium is also found in foods such as dark green vegetables, nuts, grains, beans, canned salmon and sardines (if you eat the bones). These foods can help contribute to your calcium quota. But without dairy in your diet, it may be difficult to meet your daily calcium requirements.

Calcium and magnesium are the "earth alkali" minerals found in the earth's crust, usually as salts that are fairly insoluble. (The word calcium comes from the Latin calc, meaning "lime," as in limestone, a calcium carbonate substance.) Dolomite, a calcium-magnesium earth mineral combination that is a little more soluble and usable by the body than some other forms, is a commonly used calcium supplement.

Many other nutrients, vitamin D, and certain hormones are important to calcium absorption, function, and metabolism. Phosphorus as well as calcium is needed for normal bones, as are magnesium, silicon, strontium, boron possibly, and the protein matrix-all part of our bone structure. The ratio of calcium to phosphorus in our bones is about 2.5:1; the best proportions of these minerals in our diet for proper metabolism are currently under question.

Prolonged bone re-absorption from chronic dietary deficiency results in osteoporosis - from either too little bone mass accumulation during growth or higher rate of bone loss at menopause. Dietary calcium deficiency also has been associated with increased risk of hypertension, and colon cancer. When it is in short supply, a variety of symptoms from aching joints, eczema, elevated blood cholesterol, heart palpitations, brittle nails, hypertension (high blood pressure) and insomnia can become evident. Muscle cramps, nervousness, numbness in the arms and legs, rheumatoid arthritis, convulsions, depression and delusions have also been noted.

According to recent USDA surveys, average calcium intakes for women and younger men are below their RDA. The average calcium intake by women 20 to 29 years of age was about 778 milligrams per day, and the intake by women 30 to 50 years of age was about 719 milligrams. Average calcium intake by men 20 to 29 years of age was 1075 milligrams. Calcium absorption is dependent upon the calcium needs of the body, the foods eaten, and the amount of calcium in the foods eaten. Vitamin D, whether from diet or exposure to the ultraviolet light of the sun, increases calcium absorption. Calcium absorption tends to decrease with increased age for both men and women.

Excess calcium supplementation has been associated with some mineral imbalances such as zinc, but combined with a magnesium deficiency it may cause deposits to form in your kidneys, which could cause kidney stones. It is recommended to take one to two parts of calcium and phosphorus to one part of magnesium. Vitamin D and vitamin A are beneficial to have with this nutrient and it is great when taking a supplement that it is chelated with amino acids.

More calcium may be needed if you suffer from osteoporosis, are lacking in Vitamin D, if you have a gum disease or eat processed foods, ingest excess protein, fat, sugar or caffeine, salt or fizzy soda drinks. Drinking bottled water with a low mineral content could require more dietary calcium and so may the consumption of alcohol, taking a birth control pill, diuretic (water pill), antacids or if you are on hormone replacement therapy.

Phosphorus, sodium, alcohol, coffee and white flour aid the loss of calcium from the body, while too much protein, fat and sugars can have a negative effect with the absorption thereof. Tetracycline and calcium bond together which impairs the absorption of both.

Milk, milk products, beans, nuts, molasses and fruit contain good amounts of calcium. Fish and seafood, as well as green leafy vegetables, supply good amounts of calcium.