Calcium is critical to the development and maintenance of bones and teeth. It
also plays an important role in controlling the heartbeat, maintaining proper
blood pressure, clotting blood, transmitting nerve impulses, contracting and
relaxing muscles, maintaining the integrity of mucosal membranes and cell walls,
and activating enzymes such as lipase, adenosine triphosphatase (ATPase),
succinate dehydrogenase, and choline acetylase.
Calcium comprises approximately 2% of an adult's body weight, more than any
other mineral; the amount of calcium in an infant's body is approximately 0.8%.
The rate of absorption is greatest in childhood (50% to 70% of the calcium
ingested), decreasing in adults to 10% to 40%. As the intake of calcium
increases, the percent absorbed decreases. Vitamin D (especially D3, or
cholecalciferol) is the most important vitamin for assisting in the absorption
of calcium. The antioxidant vitamins A, C, and E are also important. Lactose
aids absorption, improving the value of milk as a source of calcium. Magnesium
and phosphorus are significant in assisting in proper absorption. Recommended
ratios of calcium to each of these minerals range from 1:2 to 2:1, but are
currently under review. Iron, zinc, and manganese play a less important role.
Stress and lack of exercise can cause negative calcium balances.
Parathyroid hormone (PTH), vitamin D, and the thyroid hormone calcitonin act
to maintain normal blood calcium levels of 9 to 11 mg/100 ml. PTH stimulates the
release of calcium from bone and decreases excretion from the kidney, and it
acts with vitamin D to increase the rate of absorption, if blood levels are
reduced. Calcitonin lowers blood calcium levels that are too high by inhibiting
calcium release from bone.
Average dietary calcium intakes in Americans are lower than recommended
levels; the problem is particularly acute with women. Calcium deficiency has
been linked to stunted growth, bone deformities, rickets, osteoporosis,
osteomalacia, muscle spasms, leg cramps, high blood pressure, and colon cancer.
Recent studies question the role of calcium in decreasing the incidence of colon
cancer. Although kidney stones can result from toxic levels of calcium in
certain susceptible individuals, high calcium intake can actually decrease the
risk of kidney stones, and large calcium supplements are accepted therapy for
kidneys stones associated with intestinal hyperoxalosis.
- Rich sources: cheeses (especially Parmesan, Romano, Gruyère, Swiss,
provolone, Monterey Jack, Edam, cheddar, Muenster, Gouda, Tilsit, Colby,
caraway, brick, Roquefort, Port du Salut, Cheshire, Havarti, fontina,
mozzarella, feta), wheat-soy flour, blackstrap molasses, rennin
- Good sources: almonds, Brazil nuts, caviar, dried figs, dark greens
(turnip, dandelion, collard, mustard), hazelnuts, ice cream, kale, bok choy,
broccoli, cabbage, milk, oysters, sardines, soybean flour, yogurt. (Milk and
dairy products account for about 75% of dietary calcium in Americans; butter,
cream cheese, and other high-fat dairy products contain little or no calcium.)
- Many herbs, spices, and seaweeds supply calcium (e.g., basil,
chervil, cinnamon, dill weed, fennel, fenugreek, ginseng, kava kava, kelp,
marjoram, oregano, parsley, poppy seed, sage, savory).
The mineral calcium is the fifth most prevalent element in the biosphere. The
calcium ion (Ca2+) can form bonds with up to 12 oxygen atoms and is
nearly unique in its ability to interact with the peptide chain.
Calcium citrate: soluable (optimizing absorption); most bioavailable; safe
levels of lead; easily digested. It is recommended for elderly patients and
persons taking acid-lowering medications, and it may be more effective in
hypertension control than calcium carbonate. The citrate effects may inhibit
kidney stone formation.
Calcium carbonate: Lead levels are safe if it is a refined product. Some
antacids (Rolaids/Tums) contain 500 mg of calcium carbonate.
Calcium gluconate and calcium lactate: soluble; safe levels of lead
Calcium chloride: not recommended (irritates the gastrointestinal tract)
Homeopathic calcium medications and their uses:
- Calcarea carbonica: backache, pain
- Calcarea fluorica: tissue elasticity
- Calcarea phosphorica: fatigue, discontentment, discomfort,
- Calcarea sulfurica: sores, wounds, abscesses, boils,
- Osteoporosis: to preserve adequate mineral mass, prevent loss of
structural bone components, maximize repair of damaged bones, prevent loss of
- Hypertension: to reduce blood pressure (most effective in elderly,
African-Americans, and salt-sensitive hypertension patients, but not in
salt-resistant hypertensive patients)
- Premenstrual syndrome (PMS): to relieve menstrual cramps,
irritability or apprehension, muscle cramps
- Pregnancy: to reduce pregnancy-induced hypertension and prevent
- Menopause: to reduce headaches, irritability, insomnia,
- Dental: to improve loose teeth, gingivitis, periodontal disease
- Cardiovascular: to reduce heart irregularity, lower cholesterol
|Dosage Ranges and Duration of
Recommendations for adequate calcium intakes promulgated by the National
Academy of Science Food and Nutrition Board in 1997:
- birth to 6 months: 210 mg/day
- 6 months to 1 year: 270 mg/day
- 1 to 5 years: 500 mg/day
- 6 to 8 years: 800 mg/day
- 9 to 18 years: 1,300 mg/day
- 19 to 50 years: 1,000 mg/day
- Over 50 years: 1,200 mg/day
Lactating or pregnant women:
- 14 to 18 years: 1,300 mg/day
- 19 years and older: 1,000 mg/day
Ideally, supplements should be taken in small doses throughout the day, and
six to eight 8-oz. glasses of water should be consumed to avoid
Nutritional toxicity is an increase in blood calcium levels (hypercalcemia)
because intake is too high, or an increase of urine calcium excretion resulting
in calcification of the kidneys or development of renal stones. Results of
hypercalcemia include decreased gastrointestinal and muscle tone, kidney
failure, emotional deterioration, large urine volumes, constipation, nausea,
confusion, coma, and ultimately death. Doses of 5,000+ mg/day are
toxic. Osteopetrosis may result from continuous high calcium
- Unrefined calcium carbonate, especially if derived from limestone or
oyster shells, dolomite, and bone meal calcium supplements may contain toxic
levels of lead.
- Doses above 2,000 mg/day may increase the risk of kidney stones and
- Calcium chloride is contraindicated in hypocalcemia caused by renal
Because calcium supplements may interfere with alendronate absorption, they
should be taken two hours before or after the drug (PDR
In a study with eight male subjects, 5 mL of aluminum hydroxide gel (2.4 gm
qid) coadministered with calcium citrate (950 mg qid) for three days increased
urinary aluminum excretion (Coburn et al. 1991). The finding of enhanced
aluminum excretion is consistent with another study involving 30 healthy women
who were given calcium citrate (800 mg elemental calcium/day) (Nolan et al.
1994). Urinary and plasma aluminum levels were increased significantly. This
effect may have been related to aluminum derived only from dietary sources
because the women were not receiving aluminum-based
Two doses of amiloride (2.5 mg/day) reduced urinary calcium in subjects with
kidney stones (Leppla et al. 1983). This decrease in calciuresis was enhanced
when amiloride was coadministered with two doses of hydrochlorothiazide (25
Oral administration of 500 mg calcium salts (lactate, gluconate, and
carbonate) with atenolol (100 mg) reduced plasma levels of atenolol by 51% in
six healthy subjects (Kirch et al. 1981). Long-term coadministration increased
the elimination half-life and led to atenolol accumulation. Subsequent studies
did not confirm an interaction between atenolol and calcium antacids (Gugler and
Allgayer 1990). Until more is known, individuals on beta-blockers should have
their blood pressure checked before and after the addition of calcium antacids
or supplements to their atenolol
Hypocalcemia can negate the therapeutic effects of digoxin, while
hypercalcemia may predispose a patient to arrhythmias and digoxin toxicity
(Hines Burnham et al. 2000). In one study, patients with digoxin-induced
cardiotoxicity had serum concentrations of the drug that were within therapeutic
range but they had higher calcium to potassium ratios (Sonnenblick et al. 1983).
Normal levels of calcium should be maintained during digoxin treatment. Patients
taking digoxin should have calcium blood levels monitored
Conjugated estrogens lower calcium excretion (Lobo et al. 1985) and increase
calcium absorption in postmenopausal women (Gallagher et al. 1980). The enhanced
absorption appears to be due to an increase in serum 1,25(OH)2D. Early
postmenopausal women taking calcium supplements with estradiol (or conjugated
estrogens) have been shown to have significantly greater gains in bone mineral
density than women taking HRT alone (Pines et al. 1999). Calcium supplementation
is highly recommended in all postmenopausal women. For women 51 years or older,
the Dietary Reference Intake (DRI) for calcium is 1200 mg/day (Institute of
In a retrospective study, coronary artery bypass graft patients who received
both a bypass prime with a high calcium concentration and gentamicin
perioperatively had a higher incidence of renal failure compared with those who
received only the prime, gentamicin alone, or neither (Schneider et al. 1996).
Concomitant administration of calcium may potentiate gentamicin-induced
Quinolone antibiotics form chelates with metal cations, such as aluminum,
magnesium, calcium, iron, zinc, copper, and manganese (Kara et al. 1991; Li et
al. 1999), which significantly reduces the absorption of these medications
(Balfour and Wiseman 1999; Brouwers 1992; Campbell and Hasinoff 1991). Dietary
supplements and antacids containing aluminum and magnesium should be taken two
to four hours before or after administration of these antibiotics (Hines Burnham
et al. 2000; Li et al.
Tetracyclines form chelates with divalent and trivalent cations, including
iron, aluminum, magnesium, and calcium (Neuvonen 1976). These chelates are
poorly soluble and can significantly reduce the absorption and efficacy of
tetracyclines (Hines Burnham et al. 2000; Neuvonen 1976). Calcium salts should
be administered at least two hours before or after tetracyclines (Hines Burnham
Thiazide diuretics may cause hypercalcemia by decreasing calcium excretion
(Hines Burnham et al. 2000). Treatment with a combination of hydrochlorothiazide
(50 mg/day) and vitamin D in six postmenopausal women with osteoporosis for six
months reduced urinary calcium excretion by 22% (Sakhaee et al. 1984). In this
study, it was noted that the combination of hydrochlorothiazide and vitamin D
also decreased calcium absorption by 25%.
However, the ability of thiazide diuretics to decrease urinary calcium
excretion has been associated with less risk of hip fractures in patients taking
these medications (Rejnmark et al. 1998).
It has been reported that calcium salts may reverse the clinical effects and
toxicities associated with verapamil (Hines Burnham et al. 2000). However,
pretreatment with intravenous calcium in patients with supraventricular
arrhythmias reduced the incidence of hypotensive side effects without
compromising the antiarrhythmic effect of verapamil (Haft and Habbab 1986; Weiss
et al. 1983). Calcium also influenced blood pressure by restoring it to control
values when administered after treatment with verapamil (Weiss et al. 1983).
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enhances aluminum absorption from aluminum hydroxide. Amer J Kidney Dis.
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Garrison RH Jr, Somer E. The Nutrition Desk Reference. 3rd ed. New
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drugs. An update. Clin Pharmacokinet. 1990;18(3): 210-219.
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Kara M, Hasinoff BB, McKay DW, et al. Clinical and chemical interactions
between iron preparations and ciprofloxacin. Br J Clin Pharmacol.
Kirch W, Schäfer-Korting M, Axthelm T, et al. Interaction of atenolol with
furosemide and calcium and aluminum salts. Clin Pharm and Ther.
Leppla D, Browne R, Hill K, Pak C. Effect of amiloride with or without
hydrochlorothiazide on urinary calcium and saturation of calcium salts. J
Clin Endocrinol Metab. 1983;57(5):920-924.
Li RC, Lo KN, Lam JS, et al. Effects of order of magnesium exposure on the
postantibiotic effect and bactericidal activity of ciprofloxacin. J
Lobo RA, Roy S, Shoupe D, et al. Estrogen and progestin effects on urinary
calcium and calciotropic hormones in surgically-induced postmenopausal women.
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