Calcium

Americans may not be getting enough vitamins and minerals out of the food they eat. Over-processing, chemicals, preservatives and depleted soils have reduced the levels of natural vitamins and minerals we once received from our fruits and vegetables. Our nutrient levels are easily reduced by many factors in everyday life: stress, medications, coffee, alcohol and even exercising. As the body becomes depleted of these vitamins and minerals, it may extract them from other sources.

Osteoporosis may be related to these deficiencies. Once the body becomes low in calcium, it begins depleting the stored calcium essential for maintaining healthy bones. In the same way, when magnesium levels in the body begin to drop, muscles tighten. A deficiency in magnesium also interferes with the transmission of nerves and muscle impulses, causing irritability and nervousness.

Calcium is essential for developing and maintaining healthy bones and muscles and it also plays a major role in controlling heartbeat, blood pressure, nerve impulses and muscle function. Average dietary intake of calcium is lower than recommended for most Americans.

Calcium is found in both the extracellular and intracellular fluids; however, it is somewhat more concentrated in the extracellular fluid. Approximately 55% of serum calcium is bound to protein and 45% is free ionized calcium. It is the free calcium that is physiologically active.

The serum calcium concentration range is 4.5-5.5 mEq/L, 9-11mg/dL, or 2.23-2.57 mmol/L. A decrease in the serum calcium level is known as hypocalcemia, and an increase in serum calcium level is called hypercalcemia. Today’s blood analyzers allow the ionized calcium (iCa) level to be measured. The normal serum ionized calcium range is 2.2-2.5 mEq/L, 4.25-5.25 mg/dL, or 1.15-1.30 mmol/L. Certain changes in the blood composition can either increase or decrease the serum iCa level. When an individual is acidotic, calcium is released from the serum protein and increases the serum iCa level. During alkalosis, calcium is bound to protein and their is less iCa.

Vitamin D is needed for calcium absorption from the gastrointestinal tract. The anion phosphorus (P) inhibits calcium absorption. Thus, the actions of these two ions on the body have an opposite physiologic effect. Both calcium an phosphorus are stored in the bones and excreted by the kidneys.

The parathyroid glands secrete the parathyroid hormone (PTH), which is responsible for the homeostatic regulation of the calcium ion in body fluids. The parathyroid glands are located on the posterior thyroid gland. When the serum calcium level is low, the parathyroid glands secrete more parathyroid hormone (PTH); PTH increases the calcium level by promoting calcium release from the bone as needed. Calcitonin from the thyroid gland increases calcium return to the bone, decreasing the serum calcium level.

Calcium is needed for neuromuscular activity, contraction of the myocardium (heart muscle), normal cellular permeability, coagulation of blood, and bone and teeth formation.

  • Distribution – Ninety-nine percent of calcium is in the teeth and bones; 1% is in the extracellular fluid (ECF) and intracellular fluid (ICF), with the greater concentration of the 1% in the ECF.

  • Functions – Includes neuromuscular activity, maintaining cardiac contraction and cellular permeability, promoting blood clotting and the formation of teeth and bone.

  • Normal Serum Values – Calcium (Ca): 4.5-5.5 mEq/L, 9-11 mg/dL Ionized Calcium (iCa): 2.2-2.5 mEq/L, 4.25-5.25 mg/dL

  • Normal Excretion (Urine) – Two hundred milligrams per day.

  • Dietary Requirement – Eight hundred milligrams daily.

  • Food Sources – Milk, cheese, vegetables (baked beans, kale, greens, broccoli), meats, salmon.

  • Excretion - Urine: 200mg/day; bile-200mg/day; others: pancreatic and intestinal (feces) secretions.

Calcium and Its Functions

Body Involvement Functions

Neuromuscular

Normal nerve and muscle activity. Calcium causes transmission of nerve impulses and contraction of skeletal muscles.

Cardiac

Contraction of heart muscle (myocardium).

Cellular and Blood

Maintenance of normal cellular permeability.

Increase calcium decreases cellular permeability and decreased calcium increases cellular permeability.

Coagulation of blood. Calcium promotes blood clotting by converting prothrombin into thrombin.

Bones and Teeth

Formation of bone and teeth. Calcium and phosphorus make bones and teeth strong and durable
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