Calcium

Related Terms

• AdvaCAL®, Alka-Mints®, Apo-Cal®, atomic number 20, Bica®, Bo-Ne-Ca®, bone meal, bovine cartilage, Ca, Cal-100®, Calcanate®, Calcefor®, Calci Aid®, Calci-Fresh®, Calcigamma®, Calcilos®, Calcimax®, Calcit®, calcitonin, Calcitridin®, calcitriol, calcium acetate, calcium aspartate, calcium carbonate, calcium chelate, calcium chloride, calcium citrate, calcium citrate malate, Calcium Dago® (Germany), calcium formate, calcium glucepate, calcium gluconate, Calcium Klopfer® (Austria), calcium lactate, calcium lactate gluconate, calcium lactogluconate, calcium orotate, calcium oxalate, Calcium Pharmavit® (Hungary), calcium phosphate, calcium pyruvate, Calcium-Sandoz Forte® (Bulgaria), Calcuren® (Finland), Caldoral® (Colombia), Calmate® 500 (Philippines), CalMax®, Calmicid®, Cal-Quick®, Calsan® (Mexico, Peru, Philippines), Calsup®, Cal-Sup® (New Zealand), Caltab® (Thailand), Caltrate®, Caltrate® (Puerto Rico, Colombia, Malaysia, Mexico, South Africa), Caltrate 600® (Canada, Colombia, Costa Rica, Dominican Republic, Ecuador, El Salvador, Guatemala, Honduras, Nicaragua, Panama, Peru, Venezuela), Cantacid® (Korea), Cartilade®, CC-Nefro 500® (Germany), Chooz®, Chooz Antacid Gum 500® (Israel), Citrical®, coral calcium, dairy products (milk, cheese, yogurt, etc.), dicalcium phosphate, Dimacid®, dolomite, Estroven®, Fixical® (France), Gaviscon®, heated oyster shell-seaweed calcium, hydroxyapatite, (oral 44Ca and intravenous 42Ca), isotopically enriched milk, LeanBalance®, Living Calcium®, Maalox®, Maalox® Quick Dissolve (Canada), magnesium, Netra® (Israel), Neutralin®, Noacid® (Uruguay), nonfat milk, Orocal® (France), Os-Cal®, Os-Cal® (Canada), Ospur® Ca 500 (Germany), Osteocal® 500 (France), osteocalcin, osteocalcin concentration, Osteomin® (Mexico), OsteoPrime®, Osteo Wisdom®, oyster shell calcium, oyster shell electrolysate (OSE), Pepcid® Complete, Pluscal® (Argentina), Posture-D®, Renacal (Germany), Rocaltrol®, Rolaids®, salmon calcitonin, Sandocal®, Sandocal (India), shark cartilage, tricalcium phosphate, Tums®, Tums® (Israel, Mexico), Tums Ultra Assorted Berries® (Israel), Tums Ultra Spearmint® (Israel), Tzarevet X® (Israel), Viactiv®.

Background

• The Romans used lime (calcium oxide), clacked lime (calcium hydroxide), and hydraulic cement in construction works. Calcium (Latin calx, meaning "lime") was first isolated in its metallic form by Sir Humphrey Davy in 1808 through the electrolysis of a mixture of calcium oxide and mercury oxide.
• Chelated calcium refers to the way in which calcium is chemically combined with another substance. Calcium citrate is an example of such a chelated preparation. Calcium may also be combined with other substances to form preparations such as calcium lactate or calcium gluconate. Calcium carbonate can be refined from limestone, natural elements of the earth, or from shell sources, such as oyster. Shell sources are often described on the label as a "natural" source. Calcium carbonate from oyster shells is not "refined" and can contain variable amounts of lead.
• Calcium is the most abundant mineral in the human body and has several important functions. More than 99% of total body calcium is stored in the bones and teeth where it supports the structure. The remaining 1% is found throughout the body in blood, muscle, and the intracellular fluid. Calcium is needed for muscle contraction, blood vessel constriction and relaxation, the secretion of hormones and enzymes, and nervous system signaling. A constant level of calcium is maintained in body fluid and tissues so that these vital body processes function efficiently.
• The body gets the calcium it needs in two ways. One method is dietary intake of calcium-rich foods including dairy products, which have the highest concentration per serving of highly absorbable calcium, and dark, leafy greens or dried beans, which have varying amounts of absorbable calcium. Calcium is an essential nutrient required in substantial amounts, but many diets are deficient in calcium.
• The other way the body obtains calcium is by extracting it from bones. This happens when blood levels of calcium drop too low and dietary calcium is not sufficient. Ideally, the calcium that is taken from the bones will be replaced when calcium levels are replenished. However, simply eating more calcium-rich foods does not necessarily replace lost bone calcium, which leads to weakened bone structure.
• Hypocalcaemia is defined as a low level of calcium in the blood. Symptoms of this condition include sensations of tingling, numbness, and muscle twitches. In severe cases, tetany (muscle spasms) may occur. Hypocalcaemia is more likely to be due to a hormonal imbalance, which regulates calcium levels, rather than a dietary deficiency. Excess calcium in the blood can cause nausea, vomiting, and calcium deposition in the heart and kidneys. This usually results from excessive doses of vitamin D and can be fatal in infants.
• The Surgeon General's 2004 report "Bone Health and Osteoporosis" stated that calcium has been singled out as a major public health concern today because it is critically important to bone health and the average American consumes levels of calcium that are far below the amount recommended. Vitamin D is important for good bone health because it aids in the absorption and utilization of calcium. There is a high prevalence of vitamin D insufficiency in nursing home residents, hospitalized patients, and adults with hip fractures.
• Calcium supplements are widely used to reduce bone resorption in osteoporosis, and many studies support this use. Calcium supplementation is also used for colorectal neoplasia and in pregnancy.

Evidence

*Key to grades:

A: Strong scientific evidence for this use;
B: Good scientific evidence for this use;
C: Unclear scientific evidence for this use;
D: Fair scientific evidence against this use (it may not work);
F: Strong scientific evidence against this use (it likely does not work).

For full grading rationale, click here.

Safety

The U.S. Food and Drug Administration does not strictly regulate herbs and supplements. There is no guarantee of strength, purity or safety of products, and effects may vary. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare professional before starting a new therapy. Consult a healthcare professional immediately if you experience side effects.

Allergies

• Avoid in individuals with a known allergy/hypersensitivity to calcium supplements or any of their ingredients. Some people are lactose intolerant. Dairy products contain lactose and dairy products are a common food source of calcium. Lactose intolerance can cause cramping, bloating, gas, and diarrhea. Lactose intolerance affects the population in varying degrees.
• Avoid calcium supplementation in those who are very sensitive to any component of a calcium-containing supplement, or who have hypercalcaemia (high levels of calcium in the blood). Conditions causing hypercalcaemia include sarcoidosis (inflammation in the lymph nodes and other organs), hyperparathyroidism (high levels of parathyroid hormone), and hypervitaminosis D (high levels of vitamin D).

Side Effects and Warnings

• Calcium supplementation is likely safe when used orally and intravenously, as recommended by a qualified healthcare professional. It is also likely safe when used orally and appropriately in pregnancy and lactation, as recommended by a qualified healthcare professional. Routine dietary intake and supplementation in recommended doses are not associated with significant adverse effects.
• Avoid calcium supplements made from dolomite, oyster shells, or bone meal because such compounds may contain unacceptable levels of lead. Avoid in patients with hypercalcaemia (high blood levels of calcium), hypercalciuria (high levels of calcium in urine), hyperparathyroidism (high levels of parathyroid hormone), bone tumors, digitalis toxicity, ventricular fibrillation (ventricles of the heart contract in unsynchronized rhythm), kidney stones (renal calculi), kidney disease or disorders, and sarcoidosis (inflammation of lymph nodes and various other tissues).
• Excretion of abnormally large amounts of calcium in the urine is a well-established side effect of administration.
• Low levels of calcium in the blood and tissues can cause sensations of tingling, numbness, muscle twitches, and muscle spasms (tetany). This condition is more likely to be due to a hormonal imbalance in the regulation of calcium rather than a dietary deficiency.
• Excess calcium in the blood can be without symptoms or it can cause loss of appetite, nausea, vomiting, constipation, abdominal pain, dry mouth, thirst, frequent urination, and calcium deposition in the heart and kidneys. More severe hypercalcaemia may result in confusion, delirium, coma, and if not treated, death. Hypercalcaemia has been reported only with the consumption of large quantities of calcium supplements usually in combination with antacids, particularly in the past when peptic ulcers were treated with large quantities of milk, calcium carbonate (antacid) and sodium bicarbonate (absorbable alkalai).
• Avoid high doses of calcium without food in those who are prone to the formation of calcium-containing kidney stones, as calcium supplementation in the absence of food may be associated with an increased risk of calcium oxalate stone formation. Consult a qualified healthcare professional if you are prone to kidney stones before using calcium supplements.
• Use cautiously in those with achlorhydria (absence of hydrochloric acid or HCl in gastric juices) as low levels of gastric acid during digestion reduces urinary phosphate and calcium excretion. It may be advisable to take calcium carbonate with food to stimulate gastric acid production. Consult a qualified healthcare provider.
• Avoid cigarette smoking, as this decreases intestinal calcium absorption and may lead to decreased bone mineral density.
• Use cautiously if taking large amounts of vitamin D. Excess calcium in the blood (hypercalcaemia) can cause nausea, vomiting and calcium deposition in the heart and kidneys. This usually results from excessive doses of vitamin D and can be fatal in infants. Consult a qualified healthcare provider.
• Use cautiously in individuals with heart arrhythmias and ventricular fibrillation (irregular heart beating). Large fluctuations in free calcium during intravenous calcium infusion can cause the heart to slow down or beat too rapidly. Although calcium appears to have benefits on bone density and osteoporosis, calcium should be used cautiously in postmenopausal women due to an increased possibility of cardiovascular side effects. Consult a qualified healthcare provider.

Pregnancy and Breastfeeding

• The Standing Committee on the Scientific Evaluation of Dietary Reference Intakes, Food, and Nutrition Board suggests that current calcium recommendations for non-pregnant women are also sufficient for pregnant women because intestinal calcium absorption increases during pregnancy.
• Pregnant women are especially vulnerable to accelerated bone turnover due to the physiologic stress of pregnancy and lactation. Studies indicate that pregnant women should take calcium supplements to prevent bone density loss. The National Academy of Sciences recommends that women who are pregnant or breastfeeding consume calcium each day. For pregnant teens, the recommended intake is higher.
• Consult a qualified healthcare professional to determine dosing during pregnancy and breastfeeding.

Interactions

Most herbs and supplements have not been thoroughly tested for interactions with other herbs, supplements, drugs, or foods. The interactions listed below are based on reports in scientific publications, laboratory experiments, or traditional use. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare professional before starting a new therapy.

Interactions with Drugs

• Intestinal aluminum absorption is increased in healthy and kidney failure patients taking even small amounts of calcium citrate. As a result, all citrate-containing preparations are contraindicated in chronic renal failure patients taking aluminum-containing compounds.
• Anticonvulsants decrease calcium absorption by increasing the metabolism of vitamin D. Anticonvulsant intake can lead to hypocalcaemia (low blood calcium) and softening of the bones (osteomalacia).
• Intake of a bisphosphonate and calcium may decrease the absorption of the bisphosphonate. Patients should take bisphosphonates at least 30 minutes before calcium. Optimally, the two would be consumed at different times of the day.
• Caffeine may increase urinary calcium excretion and has been implicated in osteoporosis; however, research is still conflicting. Caffeine has a small effect on calcium absorption.
• Calcitriol is a form of vitamin D that is used to treat and prevent low levels of calcium in the blood of patients whose kidneys or parathyroid glands (glands in the neck that release natural substances to control the amount of calcium in the blood) are not working normally.
• When given intravenously, calcium can reverse the effects of calcium channel blockers (commonly used for high blood pressure). Calcium channel blockers include: nifedipine (Adalat®, Procardia®), verapamil (Calan®, Isopin®, Verelan®), diltiazem (Cardizem®), isradipine (DynaCirc®), felodipine (Plendil®), and amlodipine (Norvasc®).
• Cholestyramine (commonly used for high cholesterol) can reduce the absorption of vitamin D, which, in turn, reduces the absorption of calcium.
• Corticosteroids (commonly used for inflammation) can cause significant bone loss (osteoporosis) if the recommended level of calcium and vitamin D intake is not met.
• Calcium levels should be monitored if taking the heart rhythm medication digoxin due to the potential for interaction with high blood levels of calcium and the need for adequate blood levels of calcium. Patients taking digoxin should consult with a qualified healthcare professional before using calcium supplements.
• Alcohol can affect calcium status by reducing the intestinal absorption of calcium. It can also inhibit enzymes in the liver that help convert vitamin D to its active form, which in turn reduces calcium absorption. However, the amount of alcohol required to affect calcium absorption is unknown. Evidence is currently conflicting on whether moderate alcohol consumption is helpful or harmful to bone.
• Fluroquinolone antibiotics form complexes with calcium in the gastrointestinal tract, which can lead to reduced absorption of both if taken at the same time.
• Use of H₂ blockers (like ranitidine commonly used to treat acid reflux) at the same time as calcium carbonate or calcium phosphate may interfere with the absorption of these calcium salts.
• Hormone replacement therapy (HRT) alone may be associated with a fall in calcium absorption efficiency. However, the bone-preserving effects of estrogen treatment are increased by calcium supplementation. Estrogen increases supplemental calcium absorption in postmenopausal women.
• Use of inositol hexaphosphate (phytic acid) and calcium may decrease the absorption of calcium.
• Mineral oil or stimulant laxatives (cascara, senna and bisacodyl), when used for prolonged periods, can reduce dietary calcium and vitamin D absorption often causing osteomalacia (bone softening).
• Intake of levothyroxine (synthroid, levothroid, levoxyl) at the same time as calcium carbonate has been found to reduce levothyroxine absorption and to increase serum thyrotropin levels. Levothyroxine may adsorb (stick) to calcium carbonate in an acidic environment, which may block its absorption.
• Loop diuretics, including furosemide (Lasix®), bumetanide (Bumex®), ethracrynic acid (Edecrin®), and torsemide (Demadex®), at high doses, may reduce serum calcium levels because they increase urinary calcium excretion.
• Orlistat (Xenical®) has been shown to induce a relative increase in bone turnover (increased resorption or bone loss), which may be due to the malabsorption of vitamin D and/or calcium.
• The effect of dietary phosphorus on calcium is minimal. Some researchers speculate that the detrimental effects of consuming foods high in phosphate such as carbonated soft drinks is due to the replacement of milk with soda rather than the phosphate level itself.
• Increasing dietary potassium intake in the presence of a low sodium diet may help decrease calcium excretion particularly in postmenopausal women.
• Use of proton pump inhibitors (like esomeprazole used to treat ulcers) and calcium carbonate or calcium phosphate at the same time can cause decreased absorption of these calcium salts.
• Typically, dietary sodium and protein increase calcium excretion as their intake is increased. However, if a high protein, high sodium food also contains calcium, this may help counteract the loss of calcium.
• Calcium may form complexes with sotalol (a beta-blocker drug used to treat irregular heartbeats), reducing its absorption. A physician should be contacted in order to determine optimal timing of doses. Patients taking sotalol should consult a qualified healthcare professional before using calcium supplements.
• Intake of a tetracycline and calcium may decrease the absorption of the tetracycline, including doxycycline, minocycline, and tetracycline. Two to four hours between tetracyclines and calcium supplements should be allowed.
• Thiazides are diuretics that reduce calcium excretion by the kidneys. These diuretics include: chlorothiazide (Diuril®), hydrochlorothiazide (HydroDIURIL®, Esidrix®), indapamide (Lozol®), metolazone (Zaroxolyn®), and chlorthalidone (Hygroton®).
• An interaction between levothyroxine (a thyroid hormone) and calcium carbonate is also possible.

Interactions with Herbs and Dietary Supplements

• Calcium carbonate and aluminum hydroxide taken together have produced a significant rise in serum and urine aluminum levels.
• Combined use of inositol hexaphosphate (phytic acid) and calcium may decrease the absorption of calcium.
• Inulin, found in fresh cheese, does not appear to acutely affect serum ionized calcium concentrations.
• Stimulant laxatives (cascara, senna, and bisacodyl) when used for prolonged periods can reduce dietary calcium and vitamin D absorption often causing osteomalacia (bone softening).
• Combining calcium salts may increase absorption or alter efficacy.
• Large doses of magnesium salts can cause hypocalcaemia (low levels of blood calcium). Oral magnesium supplements do not affect calcium absorption.
• Combined use of iron and calcium may not inhibit the absorption of iron over long periods of time. Combined use of fluoride, magnesium, or zinc and calcium may decrease the absorption of these minerals. However, these possible mineral interactions have not been shown to be of clinical significance.
• Mineral oil can interfere with calcium utilization and retention by reducing the absorption of calcium and vitamin D.
• Combined use of non-digestible fructo-oligosaccharides or inulin and calcium may increase the absorption of calcium in the colon.
• Calcium taken orally can bind with phosphate in the gut, preventing its absorption and reducing the hyperphosphatemia (high levels of phosphate in the blood) associated with renal failure. Calcium carbonate or calcium acetate is used for this purpose, whereas calcium citrate is not recommended because it increases aluminum absorption.
• While the effects of high phosphorus intakes on calcium balance and bone health are presently unclear, the substitution of large quantities of soft drinks for milk or other sources of dietary calcium is cause for concern with respect to bone health in adolescents and adults. The effect of dietary phosphorus on calcium is minimal.
• Reports show that increased sodium intake results in increased loss of calcium in the urine suggesting that an effect of reducing bone loss by increasing calcium supplementation can also be achieved by halving daily sodium excretion.
• Intake of sodium alginate and calcium may decrease the absorption of calcium.
• Excessive vitamin A use has also been found to alter bone turnover. Too much preformed vitamin A can promote fractures. Avoid vitamin supplements that have large amounts of vitamin A as preformed vitamin A, unless prescribed by a doctor. Vitamin A in the form of beta-carotene does not appear to increase one's fracture risk.
• Use of vitamin D and calcium increases the absorption of calcium. Vitamin D is important and recommended for optimal calcium absorption.

Authors

• This information is based on a professional level monograph edited and peer-reviewed by contributors to the Natural Standard Research Collaboration (www.naturalstandard.com).

Selected References

Natural Standard developed the above evidence-based information based on a systematic review of the available scientific articles. For comprehensive information about alternative and complementary therapies on the professional level, go to www.naturalstandard.com. Selected references are listed below.

1. Bolland MJ, Barber PA, Doughty RN, et al. Vascular events in healthy older women receiving calcium supplementation: randomised controlled trial. BMJ 2008 Feb 2;336(7638):262-6.
2. Checa MA, Garrido A, Prat M, et al. A comparison of raloxifene and calcium plus vitamin D on vaginal atrophy after discontinuation of long-standing postmenopausal hormone therapy in osteoporotic women. A randomized, masked-evaluator, one-year, prospective study. Maturitas 9-16-2005;52(1):70-77.
3. Day GM, Chance GW, Radde IC, et al. Growth and mineral metabolism in very low birth weight infants. II. Effects of calcium supplementation on growth and divalent cations. Pediatr Res 1975;9(7):568-575.
4. Devine A, Dick IM, Heal SJ, et al. A 4-year follow-up study of the effects of calcium supplementation on bone density in elderly postmenopausal women. Osteoporos Int 1997;7(1):23-28.
5. Domrongkitchaiporn S, Ongphiphadhanakul B, Stitchantrakul W, et al. Risk of calcium oxalate nephrolithiasis in postmenopausal women supplemented with calcium or combined calcium and estrogen. Maturitas 2-26-2002;41(2):149-156.
6. Elders PJ, Lips P, Netelenbos JC, et al. Long-term effect of calcium supplementation on bone loss in perimenopausal women. J Bone Miner Res 1994;9(7):963-970.
7. Hanzlik RP, Fowler SC, Fisher DH. Relative bioavailability of calcium from calcium formate, calcium citrate, and calcium carbonate. J Pharmacol Exp Ther 2005;313(3):1217-1222.
8. Hyman J, Baron JA, Dain BJ, et al. Dietary and supplemental calcium and the recurrence of colorectal adenomas. Cancer Epidemiol Biomarkers Prev 1998;7(4):291-295.
9. Jorde R, Szumlas K, Haug E, et al. The effects of calcium supplementation to patients with primary hyperparathyroidism and a low calcium intake. Eur J Nutr 2002;41(6):258-263.
10. Luengo M, Pons F, Martinez de Osaba MJ, et al. Prevention of further bone mass loss by nasal calcitonin in patients on long term glucocorticoid therapy for asthma: a two year follow up study. Thorax 1994;49(11):1099-1102.
11. Mazokopakis EE, Giannakopoulos TG, Starakis IK. Interaction between levothyroxine and calcium carbonate. Can Fam Physician 2008 Jan;54(1):39.
12. McDonough RP, Doucette WR, Kumbera P, et al. An evaluation of managing and educating patients on the risk of glucocorticoid-induced osteoporosis. Value Health 2005;8(1):24-31.
13. Reid I, Ames RW, Evans MC, et al. Effect of calcium supplementation on bone loss in postmenopausal women. N Engl J Med 2-18-1993;328(7):460-464.
14. Rudnicki M, Hojsted J, Petersen LJ, et al. Oral calcium effectively reduces parathyroid hormone levels in hemodialysis patients: a randomized double-blind placebo-controlled study. Nephron 1993;65(3):369-374.
15. Thys-Jacobs S, Ceccarelli S, Bierman A, et al. Calcium supplementation in premenstrual syndrome: a randomized crossover trial. J Gen Intern Med 1989;4(3):183-189.

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