You have more calcium in your body than any other mineral. Most is in your bones and teeth, where it provides structure and strength. About 1 percent of your body's calcium is in your blood and soft tissues. It is so important to cellular functioning that your body will steal it from your bones if the level in your blood drops too low. This can cause bones to become weak and brittle.
Regulation of Calcium Levels
The amount of calcium in blood and extracellular fluid is controlled by hormones. When calcium levels fall, the parathyroid glands secrete parathyroid hormone. It causes the kidneys to convert vitamin D to calcitriol, a potent steroid hormone and the active form of vitamin D. Calcitriol helps your body absorb calcium through the small intestine and, with the help of the parathyroid hormone, releases calcium from bones and decreases its excretion in urine.
Calcium and Your Cells
Calcium levels in blood and the fluid surrounding cells must remain at an optimal level for cells to function. Calcium is necessary for the constriction and relaxation of blood vessels, secretion of hormones -- including insulin, transmission of nerve impulses and contraction of muscles. Symptoms of low blood calcium levels include abdominal cramps, muscle spasms and tingling of the hands and feet. Low blood calcium is usually due to an impaired parathyroid gland, kidney disease, vitamin D deficiency or low magnesium, all of which affect the body's regulation and use of calcium.
Bones and Teeth
To build strong bones and teeth, you need calcium over and above what is needed by the rest of your body. Bones and teeth harbor approximately 99 percent of your body's total supply of calcium. Bone is living tissue that your body breaks down and rebuilds throughout your life. Because calcium is so important for survival, your body will sacrifice the strength of your bones in order to supply calcium to the rest of your body, resulting in low bone density that can ultimately lead to fractures.
Recommended Intakes
From birth to six months, babies need 200 mg of calcium daily and from 6 to 12 months, they need 260 mg. Children from 1 to 3 need 700 mg and from 4 to 8, they need 1,000. From ages 9 to 18, children and teens, including pregnant or breast-feeding teens, need 1,300 mg. Both men and women from 19 to 50 need 1,000 mg, but from 51 to 70, women need 1,200 mg. After age 70, both men and women need 1,200 mg of calcium daily.
Dietary Sources
You are likely aware that food made from cow's milk is an excellent source of calcium, but calcium is present in a variety of foods. Good sources include tofu, blackstrap molasses, broccoli, cabbage, bok choy, brewer's yeast, dried figs, kelp, oysters, sardines and canned salmon with bones. Dark green leafy vegetables, such as dandelion, collard, turnip and mustard greens, Swiss chard and kale, are good sources of calcium. Many nuts, including almonds, Brazil nuts and hazelnuts contain calcium. In addition, some juices, cereals, soy milk and rice milk are calcium-fortified.
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