What Is It?
Health Benefits
Recommended Intake
If You Get Too Little
If You Get Too Much
General Dosage Information
Guidelines for Use
General Interaction
Evidence Based Rating Scale


What Is It?

The most abundant mineral in the human body, calcium has long been recognized for its ability to keep bones healthy and strong. New research indicates that it may also be an effective weapon against high blood pressure, heart attack, PMS (premenstrual syndrome), and colon cancer. Unfortunately, most Americans consume only about half the dietary calcium their bodies require.

For people who find it difficult to incorporate calcium-rich foods into their diet, there are a number of supplements widely available, including calcium carbonate, calcium gluconate, calcium citrate, calcium citrate malate, calcium lactate, and calcium phosphate. The amount of elemental (pure) calcium in a supplement depends on the compound it's combined with. Calcium combined with carbonate supplies 40% elemental calcium, for example, while calcium combined with gluconate provides only 9%. Recent findings indicate that the amount of elemental calcium you ultimately absorb (and use) differs from compound to compound as well. Most people appear to better absorb the elemental calcium in calcium citrate supplements, for example, than the elemental calcium in calcium carbonate.

Health Benefits

Most of the body's calcium is stored in the bones and teeth, where it is instrumental in keeping them strong. The small amount of calcium circulating in the bloodstream helps to produce the hormones and enzymes that regulate energy release, digestion, and metabolism. Calcium also facilitates the movement of nutrients across cell membranes. In addition, this mineral helps nerve cells to communicate normally, aids muscle contraction, and promotes blood clotting. To perform these essential functions, the body simply takes as much calcium as it needs from the bones. Unfortunately, if there's too little calcium in your diet to replenish this supply, your bones will eventually suffer, and become porous, weak, and prone to breaking.

Calcium is often taken in supplement form in combination with vitamin D and magnesium. The body actually makes vitamin D when the skin is exposed to sunlight; vitamin D is also readily available through food (fortified milk is an excellent source). Between 200 and 400 IU of vitamin D are needed daily to ensure that calcium will be properly absorbed and used. And because calcium can inhibit the absorption of magnesium--an important healing mineral in its own right--many conditions, from depression to anxiety, should be treated with a calcium and magnesium combination.

Specifically, calcium may help to:

  • Maintain healthy bones and prevent or slow osteoporosis. Getting enough of this mineral every day, over a lifetime, will help prevent this bone-thinning disease, which can gradually lead to bone fractures, stooped posture, and loss of height. Although the body is best equipped to absorb calcium and establish adequate bone mass (mineral content) before age 35, everyone can benefit from high calcium intake to maintain the health of bones (and teeth). In fact, studies of people over age 65 show that adding calcium-rich foods and calcium supplements to their diet reduces their risk of bone loss and fractures. A three-year study of 176 men and 213 women over age 65 taking either 500 mg of calcium plus 700 IU of vitamin D3 daily found the supplementation moderately reduced bone loss in the femoral neck, spine and total body and reduced the incidence of nonvertebral fractures (1).  


  • Relieve back pain. If you suffer from back problems, try calcium, alone or in combination with magnesium, to help strengthen your bones and cartilage.

  • Treat high blood pressure. Some studies have found that calcium supplements can keep blood pressure in check. A few studies even indicate that a diet rich in calcium derived from low-fat dairy products, fruits, and vegetables may be as effective as some prescription medications at lowering high blood pressure (2). Because calcium helps muscles to contract, it also keeps the heart and blood vessels performing efficiently.

  • Prevent colon cancer. Recent studies suggest that individuals who are susceptible to colon cancer are less likely to develop the disease if they follow a calcium-rich diet or take calcium supplements. The mineral seems to reduce the irritating effects of bile acids and fatty acids in the colon, which, if left unchecked, can cause abnormal cell growth.

  • Ease the symptoms of PMS and endometriosis. A growing body of research indicates that calcium supplements may relieve irritability, mood swings, depression, and other PMS symptoms. The theory is that low calcium levels contribute to PMS-related hormonal imbalances. A recent study of hundreds of women reported that daily calcium supplements (two 750 mg tablets twice a day) reduced the severity of PMS symptoms by nearly 50%, compared with only a 30% reduction for women taking a placebo. And for women who suffer from painful cramps as a result of endometriosis, research indicates that taking magnesium along with calcium during menstruation may bring some relief.

  • Reduce heartburn. Taking calcium carbonate in the form of antacid tablets such as Tums can neutralize gastric acid and relieve the burning sensation and other symptoms of heartburn. The chewable tablets provide the fastest relief.

  • Fight insomnia. Some people experience sleep problems due to low levels of calcium. Supplementing the diet with calcium as well as magnesium--another nutrient that may be depleted in insomnia sufferers--may ultimately lead to sounder slumber.

  • Prevent migraines. Taking calcium and magnesium on a long-term basis may thwart these debilitating headaches. Both minerals help to maintain healthy blood vessel function throughout the body, including the brain.

  • Prevent kidney stonesResearch shows patients who get the recommended amount of calcium in addition to restricting intake of animal protein and salt, have greater protection against recurrent kidney stones than those with a low-calcium diet (8).


  • Note: Calcium has also been found to be useful for a number of other disorders. For information on these additional ailments, see our Dosage Recommendations Chart for Calcium.

  • Forms

    • tablet
    • softgel
    • powder
    • liquid
    • capsule

    Recommended Intake

    The government recently established new goals for the daily intake of calcium for men and women. Called AI (Adequate Intake), the figures below supplant the old RDA (Recommended Daily Allowance) and represent the amount of daily calcium that all individuals in the following age groups should try to meet:

  • For men and women ages 19 to 50: 1,000 mg a day.

  • For men and women ages 50 to 70: 1,200 mg a day.

    For more information on Adequate Intake and other dietary guidelines, see Government Dietary Guidelines.

  • If You Get Too Little

  • Over time, a calcium deficiency can cause thinning of the bones, which can result in osteoporosis or other bone problems.

  • Insufficient amounts of calcium in the blood can provoke muscle spasms.

  • If You Get Too Much

  • Even at daily doses as high as 2,500 mg from both food and supplement sources, calcium appears to be safe.

  • The absorption of zinc, iron, and magnesium may be hindered by calcium, particularly when calcium is taken in high doses. Take a multimineral supplement to ensure balanced absorption of these other nutrients.

  • Very high doses from calcium supplements (in the range of 2,500 mg a day) can cause kidney stones, a complication apparently due to dehydration. Be sure get plenty of fluid when taking calcium at any dosage level.

  • Calcium carbonate may cause gas and constipation in some cases. If this happens, switch to calcium citrate. This should resolve the problem.

  • General Dosage Information

    Special tips: Your body can't absorb more than about 500 mg of calcium at a time, so divide a daily dose of 1,000 mg, for example, into two doses of 500 mg and take them at different times of the day.

    In addition, when calculating your dose, make sure to look at the amount of "pure" or "elemental" calcium, not just the weight of each pill. The packaging will usually provide this information. For example, a 600 mg calcium carbonate tablet contains 240 mg of elemental calcium.

  • For osteoporosis: Take 600 mg elemental calcium twice a day.

  • For the prevention and treatment of the majority of conditions mentioned: Every day, get 1,000 to 1,200 mg of elemental calcium from foods, supplements, or a combination of the two.

    Be sure to check out our Dosage Recommendations Chart for Calcium, which lists therapeutic dosages for specific ailments at a glance. Dosages for calcium/vitamin D and calcium/magnesium combinations are listed as well.

  • Guidelines for Use

  • Make sure to get l,000 to l,200 mg of elemental calcium daily.

  • Take calcium with food--it's best absorbed that way. Orange juice and other foods with calcium citrate mixed right in can now easily be found on grocery store shelves.

  • Avoid calcium supplements made from bone meal, oyster shells, or dolomite; they may contain high levels of lead.

  • People over age 65 are advised to use calcium citrate because they may not have enough stomach acid to absorb calcium carbonate.

  • General Interaction

  • Don't consume calcium within one to three hours of taking an antibiotic such as doxycycline, minocycline, or tetracycline. It may decrease the absorption of the drug.

  • If you use thiazide diuretics, consult your doctor before taking calcium supplements. When taken together, they can cause dangerously high calcium levels in the body, possibly resulting in kidney failure.

    Note: For information on interactions with specific generic drugs, see our WholeHealthMD Drug/Nutrient Interactions Chart.

  • Cautions

  • If you have thyroid or kidney disease, consult your doctor before taking calcium supplements.
  • Evidence Based Rating Scale 

    The Evidence Based Rating Scale is a tool that helps consumers translate the findings of medical research studies with what our clinical advisors have found to be efficacious in their personal practice. This tool is meant to simplify which supplements and therapies demonstrate promise in the treatment of certain conditions. This scale does not take into account any possible interactions with any medication/ condition/ or therapy which you may be currently undertaking. It is therefore advisable to ask your doctor before starting any new treatment regimen.












    Back Pain












    Small studies have shown efficacy. More research is needed to confirm or refute these findings


     Eating Disorders  


    Large studies have proved calcium along with Vitamin D to be essential to building bone and mass strength. Dosage: 500-800 mg twice a day (10-21)








    Calcium Carbonate is FDA-Approved for this use (9) 


    Date Published: 04/18/2005
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