Health Encyclopedia

Calcium

General Description

Calcium is the most abundant mineral in the human body, making up 1.5 to 2 percent of total body weight. Approximately 99 percent of the body's calcium is located in the bones and teeth. Calcium is essential for bone development and maintenance, and plays important roles in much of the body's enzyme activity. It is required for muscle contraction, blood clotting, transmission of nerve signals, and regulation of heartbeat. Supplemental forms of calcium include bone meal, dolomite, refined calcium carbonate, unrefined calcium carbonate (derived from limestone or oyster shells), and calcium chelates (such as aspartate, citrate, gluconate, or lactate).

Food Sources

The best food sources of calcium include milk and dairy products, kale, spinach, swiss chard, and members of the cabbage family.

Health Applications

  • Bone health
  • Bone growth/development
  • Cardiovascular health
  • Prenatal nutrition

Chemical Composition

Dosage/Toxicity

The optimum daily intake of calcium varies with age and gender. The recommendations from a 1994 consensus statement issued by the National Institutes of Health are:

From birth to six months:
400 mg/day
Ages six to twelve months: 600 mg/day
Ages one to five years: 800 mg/day
Ages six to ten years: 800-1,200 mg/day
Ages 11 to 24 years 1,200-1,500 mg/day
Women 25-50 years: 1,000 mg/day
Pregnant or lactating women: 1,200-1,500 mg/day
Postmenopausal women on
estrogen replacement therapy: 		1,000 mg/day
Postmenopausal women not on
estrogen replacement therapy: 		1,500 mg/day
Men age 25-65: 1,000 mg/day
Men and women over 65: 1,500 mg/day

Calcium intake of 2,000 mg/day appears to be safe in most people. These guidelines are based on calcium from diet plus any calcium taken in supplemental form. Adequate vitamin D is essential for optimal calcium absorption. New guidelines recommend that adults between the ages of 51 and 70 consume at least 400 IU of vitamin D per day and that those over 70 consume 600 IU per day. For best absorption, calcium supplements should be taken with meals. Complications from excessive calcium intake are rare, as excess calcium is usually not absorbed. Patients with hyperparathyroidism or cancer should not take calcium supplements unless under a physician's supervision.

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