Calcium is the most abundant mineral in your body. It is essential for the development and maintenance of strong bones and teeth, and that’s where about 99% of the body's calcium is found. Calcium also helps the heart, nerves, muscles, and other body systems work properly. It is probably best known for helping prevent osteoporosis.
Your body needs several other nutrients in order for calcium to be absorbed and used properly, including magnesium, phosphorous, and especially vitamins D and K.
The best way to get calcium is through food (see "Dietary Sources" section). Many foods are fortified with calcium, but some people may still need to take calcium supplements to get enough. It is especially important for children to get enough calcium in their diet as they are growing and forming bone, and for older people as they start to lose bone.
Postmenopausal women, people who consume large amounts of caffeine, alcohol, or soda, and those who take corticosteroid medications may need calcium supplements. Calcium deficiency can be found in people who don’t absorb enough calcium, as can happen with Crohn's disease, celiac disease, and some intestinal surgeries.
Getting enough calcium may help prevent or treat the following conditions:
Your body needs calcium to help build and maintain healthy bones and strong teeth. People start to lose more bone than their bodies make in their 30s, and the process speeds up as they get older. Studies have shown that calcium, particularly in combination with vitamin D, may help prevent bone loss associated with menopause. It may also help prevent bone loss in older men. If you do not get enough calcium in your diet, your doctor may recommend a supplement.
People with this condition have underactive parathyroid glands. These four small glands sit on the four corners of the thyroid in the neck and produce a hormone that regulates calcium, phosphorous, and vitamin D levels in the body. People with this condition should follow a high-calcium, low-phosphorous diet as prescribed by their doctor. Often, they will also need to take calcium supplements.
Premenstrual Syndrome (PMS)
One large, well-designed study showed that women who took 1,200 mg of calcium per day reduced their symptoms of PMS by 50%, including headache, moodiness, food cravings, and bloating. A smaller study suggested that calcium may help reduce menstrual pain.
High Blood Pressure
People who do not get enough calcium may be at higher risk for hypertension or high blood pressure. Some studies suggest that increasing calcium levels may lower blood pressure slightly. However, not all studies have been positive. And researchers aren’t sure whether calcium supplements would have any benefit, or whether it’s the effects of a diet that includes low-fat dairy products (which contain calcium) that is responsible.
If you want to try calcium supplements, do not stop taking your blood pressure medication. Instead, talk to your health care provider about the right amount of calcium for you. You may need to take calcium for 6 - 8 weeks before you see any improvement in blood pressure.
Some studies suggest that calcium supplements may play a role in the prevention of high blood pressure during pregnancy and preeclampsia, a combination of high blood pressure, fluid retention, and high levels of protein in the urine that some women develop during the last trimester of pregnancy. However, not all studies show the same benefit. Taking a prenatal vitamin, with magnesium, folic acid, and many other nutrients, and getting enough calcium in food, may lower the risk of developing high blood pressure during pregnancy.
Obesity and Weight Loss
Some animal and human studies have found that eating low-fat dairy products may help you lose weight or stay at a healthy weight. However, researchers aren’t sure whether the calcium in the dairy products affects weight, or whether it’s some other nutrient -- or even a combination of nutrients. In addition, not all studies have been positive. And there’s no sound evidence that taking calcium supplements, as opposed to eating low-fat dairy products, would help with weight loss. More research is needed.
Preliminary studies in animals and people suggest that calcium supplements, in the range of 1,500 - 2,000 mg per day, may help to lower cholesterol slightly. From these studies, it seems that calcium supplements, along with exercise and a healthy diet, may be better at keeping cholesterol at normal levels than at lowering already high cholesterol. More research is needed.
Rickets causes softening and weakening of the bone in children. Although very rare in North America and Western Europe, where children drink a lot of milk, it still happens in many parts of the world. Researchers thought rickets was caused by a vitamin D deficiency. But a study in 2000 showed that taking calcium supplements is an effective treatment.
Stroke -- In a population-based study, in which large groups of people were followed over time, women who took in more calcium, both through food and supplements, were less likely to have a stroke over a 14-year period. More research is needed.
Colon Cancer -- Although not all studies agree, some show that people who have higher amounts of calcium, vitamin D, and milk in their diets are less likely to develop colorectal cancer than those who have low amounts. But researchers are not sure whether calcium supplements would have the same effect, or even whether calcium itself is making the difference.
The richest food sources of calcium include cheeses, such as parmesan, Romano, gruyere, cheddar, American, mozzarella, and feta; low-fat dairy products, such as milk and yogurt; tofu; and blackstrap molasses. Some other good sources of calcium include almonds, brewer's yeast, bok choy, Brazil nuts, broccoli, cabbage, dried figs, kelp, dark leafy greens (such as dandelion, turnip, collard, mustard, kale, and Swiss chard), hazelnuts, oysters, sardines, and canned salmon.
Foods that are fortified with calcium, such as juices, soy milk, rice milk, tofu and cereals, are also good sources of this mineral.
There are many forms of calcium available as dietary supplements. They differ in the amount of calcium they have, how well the body absorbs them, and how much they cost. The two most popular forms are calcium citrate and calcium carbonate.
- Calcium citrate: Easily absorbed and digested by the body. It does not contain as much elemental calcium -- the amount your body actually absorbs -- as calcium carbonate. It is more expensive than calcium carbonate. Also, calcium citrate should not be used with aluminum-containing antacids (see "Possible Interactions" section).
- Calcium carbonate: Less expensive than calcium citrate and contains more elemental calcium. Requires a certain amount of stomach acid to be absorbed, so it is usually taken with a glass of orange juice. Many antacids contain calcium carbonate.
Calcium supplements that are derived from oyster shells, dolomite, and bone meal are best avoided as they may contain lead, a toxic metal that can harm the brain and kidneys, cause anemia, and raise blood pressure.
How to Take It
Calcium supplements should be taken in small doses (no more than 500 mg at a time) in divided doses during the day with 6 - 8 cups of water to avoid constipation.
The following are daily dietary recommendations from the Institute of Medicine.
Talk to your pediatrician before giving a child any nutritional supplement, including calcium.
- Birth - 6 months: 200 mg
- 7 months - 1 year: 260 mg
- 1 - 3 years: 700 mg
- 4 - 8 years: 1000 mg
- 9 - 18 years: 1,300 mg
- 19 - 50 years: 1,000 mg
- Women 51 years and older: 1,200 mg
- Men 51 - 70 years: 1,000 mg
- Men older than 70: 1,200 mg
- Pregnant and breastfeeding women under 19 years: 1,300 mg
- Pregnant and breastfeeding women 19 years and older: 1,000 mg
For prevention of colon cancer, 1,800 mg per day may be required.
Because of the potential for side effects and interactions with medications, you should take dietary supplements only under the supervision of a knowledgeable health care provider. Total calcium intake, from combined dietary and supplemental sources, should not exceed 2,500 mg per day.
Side effects can include constipation and stomach upset. Very high doses can cause nausea, vomiting, loss of appetite, increased urination, kidney damage, confusion, and irregular heart rhythm.
People with hyperparathyroidism, kidney failure, sarcoidosis, or cancer could be at risk for high levels of calcium and should not take calcium supplements.
People with a history of kidney stones should not take calcium supplements. However, some research suggests that calcium in foods may not increase the risk of kidney stones. If you have or have had kidney stones, talk to your doctor about whether you should limit calcium in your diet.
Some population studies suggest that getting high amounts (more than 2,000 mg per day) of calcium through the diet may increase the risk of prostate cancer. Two of these studies found that low-fat and nonfat milk -- but not other dairy foods -- was associated with a higher risk of advanced prostate cancer. But these studies don’t prove that drinking low-fat or nonfat milk causes an increased risk of prostate cancer. And some research suggests that the amount of calcium in the diet isn’t associated with prostate cancer risk. If you have prostate cancer, or are concerned about dairy products and prostate cancer risk, talk to your doctor.
The Institute of Medicine sets the tolerable upper level of daily calcium intake at 2,500 mg. Some studies have suggested that getting amounts higher than 1,000 - 1,200 mg/day may be associated with an increased risk of heart attack, but right now the research can’t say whether high calcium actually causes an increased risk.
When figuring out how much calcium you need, be sure to take into account the calcium-rich foods you eat -- such as cheese, yogurt, milk -- along with any supplements.
If you are being treated with any of the following medications, you should not use calcium supplements without first talking to your health care provider.
Biphosphates -- These medications are used to treat osteoporosis and some other bone conditions. Calcium may interfere with how your body absorbs them, so calcium-containing products should be taken at least 2 hours before or after bisphosphonates. Bisphosphonates include:
- Alendronate (Fosamax)
- Etidronate (Didronel)
- Ibandronate (Boniva)
- Risedronate (Actonel)
- Tiludronate (Skelid)
- Zoledronic acid (Reclast)
Antacids that contain aluminum -- When calcium citrate is taken with these antacids, the amount of aluminum absorbed into the blood may go up. For people with kidney disease, the aluminum levels could be toxic.
Blood pressure medications -- Taking calcium with a beta-blocker may interfere with blood levels of both the calcium and the beta-blocker. Study results aren't clear, however. It also has been reported that calcium interferes with calcium channel blockers, but these study results are also mixed. If you take a beta-blocker or calcium-channel blocker, do not take calcium supplements without your health care provider's supervision. Beta-blockers include atenolol (Tenormin), metoprolol (Lopressor, Toprol-XL), and propranolol (Inderal, Inderal LA), among others. Calcium-channel blockers include amlodipine (Norvasc), diltiazem (Cardizem), and nifedipine (Procardia).
Cholesterol-lowering medications -- A type of medication known as bile acid sequestrants, used to treat high cholesterol, may interfere with calcium absorption and raise the amount of calcium that leaves the body in urine. Your doctor may recommend taking calcium and vitamin D supplements. These drugs include cholestyramine (Questran), colestipol (Colestid), colesevelam (Welchol).
Calcipotriene (Dovenex) -- Taking calcium supplements while using calcipotriene, a topical medication for psoriasis, could increase the risk of having calcium levels that are too high (hypercalcemia).
Corticosteroids (prednisone) -- If you take corticosteroids on a long-term basis, you may need to take calcium supplements.
Digoxin -- High levels of calcium may raise the risk of a toxic reaction to digoxin, a medication used to treat irregular heart rhythms. On the other hand, low levels of calcium keep digoxin from working. If you take digoxin, your health care provider should monitor your calcium levels closely.
Diuretics (water pills) -- Different types of diuretics interact with calcium in opposite ways.
- Thiazide diuretics can raise calcium levels in the blood. These drugs include chlorothiazide (Diuril), hydrochlorothiazide, ghlorthalidone (Hygroton), indapamide (Lozol), metolozone (Zaroxolyn), and polythiazide (Renese), among others.
- Loop diuretics can decrease calcium levels. These drugs include furosemide (Lasix) and bumetanide (Bumex).
- Amiloride (Midamor) is a type of diuretic called a potassium-sparing diuretic. It may reduce the amount of calcium your body gets rid of in urine and raise calcium levels in the blood, especially in people with kidney stones.
Estrogens -- Estrogens may contribute to an overall increase in calcium blood levels. Taking calcium supplements with estrogens improves bone density.
Gentamicin -- Taking calcium during treatment with the antibiotic gentamicin may increase the potential for toxic effects on the kidneys.
Sotalol (Betapace) -- Sotalol is used to treat an irregular heartbeat. Calcium may decrease how much sotalol is absorbed by the body.
Thyroid hormone -- Calcium can decrease the amount of thyroid hormone medication that your body absorbs.
Antibiotics -- Different types of antibiotics interact with calcium.
- Quinolones: Calcium can interfere with the body's ability to absorb quinolone antibiotics. These drugs include ciprofloxacin (Cipro), levofloxacin (Levaquin), norfloxacin (Noroxin), and ofloxacin (Floxin). Take calcium supplements 2 - 4 hours before or after taking quinolone antibiotics.
- Tetracyclines: Calcium can interfere with the body's ability to absorb tetracycline antibiotics, including doxycycline, minocycline, and tetracycline. Take calcium supplements 2 - 4 hours before or after taking tetracycline antibiotics.
Anti-seizure medications -- Some seizure medications, such as phenytoin (Dilantin), carbamazepine (Tegretol), phenobarbitol, and primidone (Mysoline), may lower levels of calcium in the body. Some doctors recommend taking vitamin D along with anti-seizure drugs to try to keep calcium levels up. You should take doses of calcium and anti-seizure medications at least 2 hours apart because each interferes with the absorption of the other.
Avgerinos DV, Leitman IM, Martinez RE, Liao EP. Evaluation of markers for calcium homeostasis in a population of obese adults undergoing gastric bypass operations. J Am Coll Surg. 2007;205(2):294-7.
Bauman WA, Shaw S, Jayatilleke E, Spungen AM, Herbert V. Increased intake of calcium reverses vitamin B12 malabsorption induced by metformin. Diabetes Care. 2000;23(9):1227-1231.
Bendich A. The potential for dietary supplements to reduce premenstrual syndrome (PMS) symptoms [review]. J Am Coll Nutr. 2000;19(1);3-12.
Bonithon-Kopp C, Kronborg O, Giacosa A, Rath U, Faivre J. Calcium and fibre supplementation in prevention of colorectal adenoma recurrence: a randomised intervention trial. European Cancer Prevention Organisation Study Group. Lancet. 2000;356:1300-1306.
Boonen S, Lips P, Bouillon R, Bischoff-Ferrari HA, Vanderschueren D, Haentjens P. Need for additional calcium to reduce the risk of hip fracture with vitamin d supplementation: evidence from a comparative metaanalysis of randomized controlled trials. J Clin Endocrinol Metab. 2007 Apr;92(4):1415-23.
Borghi L, Schianchi T, Meschi T, et al. Comparison of two diets for the prevention of recurrent stones in idiopathic hypercalciuria. N Engl J Med. 2002;346(2):77-84.
Bostick RM, Fosdick L, Grandits GA, Grambsch P, Gross M, Louis TA. Effect of calcium supplementation on serum cholesterol and blood pressure. Arch Fam Med. 2000;9:31-39.
Caan B, Neuhouser M, Aragaki A, Lewis CB, Jackson R, LeBoff MS, et al. Calcium plus vitamin D supplementation and the risk of postmenopausal weight gain. Arch Intern Med. 2007 May 14;167(9):893-902.
Chan JM, Stampfer MJ, Ma J, Gann PH, Gaziano JM, Giovannucci EL. Dairy products, calcium, and prostate cancer risk in the Physicians' Health Study. Am J Clin Nutr. 2001;74(4):549-554.
Consensus Opinion. The role of calcium in peri- and postmenopausal women: consensus opinion of the North American Menopause Society. Menopause. 2001;8:84-95.
Dagnelie PC, Schuurman AG, Goldbohm RA, Van den Brandt PA. Diet, anthropometric measures and prostate cancer risk: a review of prospective cohort and intervention studies. BJU Int. 2004;93:1139-50.
Davies KM, Heaney RP, Recker RR, et al. Calcium intake and body weight. J Clin Endocrinol Metab. 2000;85(12):4635-4638.
Giovannucci E, Liu Y, Stampfer MJ, Willett WC. A prospective study of calcium intake and incident and fatal prostate cancer. Cancer Epidemiol Biomarkers Prev. 2006;15:203-10.
Gonnelli S, Campagna MS, Montagnani A, Caffarelli C, Cadirni A, Giorgi G, Nuti R. Calcium bioavailability from a new calcium-fortified orange beverage, compared with milk in healthy volunteers. Int J Vitam Nutr Res. 2007;77(4):249-54.
Grau MV, Baron JA, Sandler RS, Wallace K, Haile RW, Church TR, et al. Prolonged effect of calcium supplementation on risk of colorectal adenomas in a randomized trial. J Natl Cancer Inst. 2007 Jan 17;99(2):129-36.
Gulson BL, Mizon KJ, Palmer Jm, Korsch MJ, Taylor AJ. Contribution of lead from calcium supplements to blood lead. Environ Health Perspect. 2001;109(3):283-288.
Heaney RP, Dowell SD, Bierman J, Hale CA, Bendich A. Absorbability and cost effectiveness in calcium supplementation. J Am Coll Nutr. 2001;20(3):239-246.
Hermensen K. Diet, blood pressure and hypertension. Br J Nutr. 2000;83(Suppl 1):S113-S119.
Hiller JE, Crowther CA, Moore VA, Willson K, Robinson JS. Calcium supplementation in pregnancy and its impact on blood pressure in children and women: follow up of a randomised controlled trial. Aust N Z J Obstet Gynaecol. 2007 Apr;47(2):115-21.
Hofmeyr G, Duley L, Atallah A. Dietary calcium supplementation for prevention of pre-eclampsia and related problems: a systematic review and commentary. BJOG. 2007 Jun 12; (Epub ahead of print)
Jänne PA, Mayer RJ. Chemoprevention of colorectal cancer. N Engl J Med. 2000;342(26):1960-1968.
Kampman E, Slattery ML, Caan B, Potter JD. Calcium, vitamin D, sunshine exposure, dairy products and colon cancer risk (United States). Cancer Causes Control. 2000:11:459-466.
Krall EA, Wehler C, Garcia RI, et al. Calcium and vitamin D supplements reduce tooth loss in the elderly. Am J Med. 2001 Oct 15;111(6):452-456.
Krauss RM, Eckel RH, Howard B, et al. AHA dietary guidelines. Revision 2000: A statement for healthcare professionals from the Nutrition Committee of the American Heart Association. Circulation. 2000;102:2284-2299.
Lappe JM, Travers-Gustafson D, Davies KM, Recker RR, Heaney RP. Vitamin D and calcium supplementation reduces cancer risk: results of a randomized trial. Am J Clin Nutr. 2007 Jun;85(6):1586-91.
Lin Y-C, Lyle RM, McCabe LD, et al. Dairy calcium is related to changes in body composition during a two-year exercise intervention in young women. J Am Coll Nutr. 2000;19(6):754-760.
Martin BR, Davis S, Campbell WW, Weaver CM. Exercise and calcium supplementation: effects on calcium homeostasis in sportswomen. Med Sci Sports Exerc. 2007;39(9):1481-6.
Myers VH, Champagne CM. Nutritional effects on blood pressure. Curr Opin Lipidol. 2007 Feb;18(1):20-4.
NAMS Consensus. Consensus Opinion: the role of calcium in peri-and postmenopausal women: consensus opinion of The North American Menopause Society. Menopause. 2001;8(20):84-95.
Napoli N, Thompson J, Civitelli R, Armamento-Villareal RC. Effects of dietary calcium compared with calcium supplements on estrogen metabolism and bone mineral density. Am J Clin Nutr. 2007 May;85(5):1428-33.
NIH Consensus Development Panel. Osteoporosis prevention, diagnosis, and therapy. JAMA. 2001;285(6):785-795.
Ochner CN, Lowe MR. Self-reported changes in dietary calcium and energy intake predict weight regain following a weight loss diet in obese women. J Nutr. 2007;137(10):2324-8.
Palacios C, Benedetti P, Fonseca S. Impact of calcium intake on body mass index in Venezuelan adolescents. P R Health Sci J. 2007;26(3):199-204.
Park SY, Murphy SP, Wilkens LR, Stram DO, Henderson BE, Kolonel LN. Calcium,vitamin D, and dairy product intake and prostate cancer risk: the Multiethnic Cohort Study. Am J Epidemiol. 2007;166(11):1259-69.
Park Y, Leitzmann MF, Subar AF, Hollenbeck A, Schatzkin A. Dairy food, calcium, and risk of cancer in the NIH-AARP Diet and Health Study. Arch Intern Med. 2009 Feb 23;169(4):391-401.
Park Y, Mitrou PN, Kipnis V, Hollenbeck A, Schatzkin A, Leitzmann MF. Calcium, dairy foods, and risk of incident and fatal prostate cancer: the NIH-AARP Diet and Health Study. Am J Epidemiol. 2007 Dec 1;166(11):1270-9.
Peacock M, Liu G, Carey M, et al. Effect of calcium or 25OH vitamin D3 supplementation on bone loss at the hip in men and women over the age of 60. J Clin Endocrinol Metabol. 2000;85(9):3011-3019.
Petti S, Cairella G, Tarsitani G. Nutritional variables related to gingival health in adolescent girls. Community Dent Oral Epidemiol. 2000 Dec;28(6):407-413.
Ross EA, Szabo NJ, Tebbett IR. Lead content of calcium supplements. JAMA. 2000;284(11):1425-1429.Sacks FM, Svetkey LP, Volmer WM, et al. Effects on blood pressure of reduced dietary sodium and the Dietary Approaches to Stop Hypertension (DASH) Diet. N Engl J Med. 2001;344:3-10.
Shahar DR, Schwarzfuchs D, Fraser D, Vardi H, Thiery J, Fiedler GM, Blüher M, Stumvoll M, Stampfer MJ, Shai I. Dairy calcium intake, serum vitamin D, and successful weight loss. Am J Clin Nutr. 2010 Nov;92(5):1017-22.
Straub DA. Calcium supplementation in clinical practice: a review of forms, doses, and indications. Nutr Clin Pract. 2007 Jun;22(3):286-96.
Tang BM, Eslick GD, Nowson C, Smith C, Bensoussan A. Use of calcium or calcium in combination with vitamin D supplementation to prevent fractures and bone loss in people aged 50 years and older: a meta-analysis. Lancet. 2007;370(9588):657-66.
Tavani A, Bertuccio P, Bosetti C, et al. Dietary intake of calcium, vitamin D, phosphorus and the risk of prostate cancer. Eur Urol. 2005 Jul;48(1):27-33.
Thys-Jacobs S. Micronutrients and the premenstrual syndrome: the case for calcium. J Am Coll Nutr. 2000;19(2):220-227.
Torkos S. Drug-nutrient interactions: a focus on cholesterol-lowering agents. Int J Integrative Med. 2000;2(3):9-13.
Varenna M, Binelli L, Casari S, Zucchi F, Sinigaglia L. Effects of dietary calcium intake on body weight and prevalence of osteoporosis in early postmenopausal women. Am J Clin Nutr. 2007;86(3):639-44.
Wagner G, Kindrick S, Hertzler S, DiSilvestro RA. Effects of various forms of calcium on body weight and bone turnover markers in women participating in a weight loss program. J Am Coll Nutr. 2007;26(5):456-61.
Zemel MB, Shi H, Greer B, Dirienzo D, Zemel PC. Regulation of adiposity by dietary calcium. FASEB. 2000;14:1132-1138.
- Last reviewed on 4/12/2011
- Steven D. Ehrlich, NMD, Solutions Acupuncture, a private practice specializing in complementary and alternative medicine, Phoenix, AZ. Review provided by VeriMed Healthcare Network.
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