Calcium, an essential mineral found in the body, represents the building block of bone and plays an important role in many physiologic processes (Table 1). Calcium is primarily associated with its role in osteoporosis, a disease characterized by low bone mass and fragility, which can predispose an individual to fractures. Osteoporosis is linked to many risk factors, such as family history, gender, age, and cigarette smoking. Yet, adequate calcium intake with vitamin D, which enhances the absorption of calcium, is crucial to keeping ideal bone mass.
Calcium requirements vary throughout a patient's lifetime (Table 2), and it is believed that calcium deficiency can be harmful at any stage in life. Even if a patient is on prescription medication for the prevention or treatment of osteoporosis, calcium and vitamin D supplementation is essential, with the greatest demand occurring later in adult life.
Foods are by far the best source of calcium, yet most people find it difficult to follow a daily diet that provides all the required vitamins and minerals, so calcium supplementation may be necessary. Calcium-rich foods include dairy foods (milk, yogurt, cheese), sardines, salmon, and leafy green vegetables. For example, an 8-oz glass of milk provides ~300 mg of calcium, and 1 cup of collards provides ~360 mg.
Calcium consumed from foods or as a supplement is absorbed by the body in the small intestine, although the amount actually absorbed depends on the type of calcium. Elemental calcium refers to the amount of actual calcium in a formulation that the body can absorb. Calcium carbonate has the most elemental calcium but requires an acidic environment; since the production of acid increases with food, calcium carbonate should be taken with food. Calcium citrate, on the other hand, has less elemental calcium but does not require the presence of acid and may be taken with or without food. This form of calcium is preferred for patients with a tendency toward kidney stones. Calcium phosphate may also be taken without regard to meals. It is suggested that calcium be taken in doses of 500 mg to maximize absorption.
Available Calcium Supplements
In addition to calcium carbonate, citrate, and phosphate, calcium is also available as calcium lactate and calcium gluconate. Calcium supplements that contain bone meal or dolomite should be avoided as they may contain toxic substances such as lead and mercury.
Some supplements on the market also include magnesium and other minerals (Table 3). Magnesium is important for maintaining strong bones. Zinc, manganese, and copper have an effect on skeletal development and help the body utilize calcium. Phosphorus works by helping merge calcium into bone. Premcal, a product consisting of calcium carbonate, magnesium oxide, and vitamin D, has an indication for the alleviation of premenstrual symptoms.
Calcium supplementation and its role in preventing and treating osteoporosis provide a pharmacist with an excellent opportunity for patient education (Table 4). Pharmacists should be familiar with the various calcium formulations in order to provide effective patient counseling. Pharmacists should take advantage of every opportunity to provide valuable information on disease management.
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Dr. Pelegrin is the pharmacy manager of a Publix Pharmacy in Miami, Fla.