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Home Minerals Calcium
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Renowned for preventing – or at least minimizing – the devastating effects of osteoporosis, calcium is now thought to lower blood pressure and prevent colon cancer.  Unfortunately, this important mineral is often seriously lacking in the modern Australian and New Zealand diet.

What it is?

Although calcium is the most abundant mineral in the body, most adults get about half the amount they need each day.  Eating enough calcium-rich foods may be difficult, but you can prevent a deficiency by taking supplements.  A wide array of products is available.  The most common forms are calcium carbonate, calcium citrate, calcium hydroxyapatite, calcium gluconate, calcium phosphate and calcium lactate.  A supplement's elemental (or pure) calcium depends on its accompanying compound.  Calcium carbonate (useful in antacids to relieve heartburn) provides 40% elemental calcium, while calcium gluconate supplies 9%.  The lower the calcium content, the more pills you need to meet recommended amounts.

What it does?

The majority of the body's calcium is stored in the bones and teeth, where it provides strength and structure.  The small amount circulating in the bloodstream helps move nutrients across cell membranes and plays a role in producing the hormones and enzymes that regulate digestion and metabolism.  Calcium is also needed for normal communication among nerve cells, for blood clotting, for wound healing and for muscle contraction.  To have enough of this mineral available in the blood to perform vital functions, the body will 'steal' it from the bones.  Over time, many calcium 'withdrawals' leave bones porous and fragile.  Only an adequate daily calcium intake will maintain healthy levels in the blood and provide an ample reserve for the bones.


Getting enough calcium throughout life is a central factor in preventing osteoporosis, the bone-thinning disease that increases the risk of hip and vertebrae fractures, spinal deformities and loss of height.  The body is best equipped to absorb calcium and build up bone mass before the age of 35, but it's never too late to increase your intake.  Several studies show that, even in people over the age of 65, taking calcium supplements and eating calcium-rich foods help to maintain bone density and reduce the risk of fractures.

Additional Benefits

By limiting the irritating effects of bile acids in the colon, calcium may reduce the incidence of colon cancer.  Other research indicates that diets that include plenty of calcium – as well as fruits and vegetables – may actually help to lower blood pressure as much as some prescription medications do.

Common Uses

  • Maintains bones and teeth.
  • Helps to prevent progressive bone loss and osteoporosis.
  • Aids heart and muscle contraction, nerve impulses and blood clotting.
  • May help to lower blood pressure in people with hypertension.
  • Eases heartburn.


  • Tablet.
  • Capsule.
  • Soft gel.
  • Powder.
  • Liquid.


  • People who have thyroid or kidney disease should check with their doctor before taking calcium.  Also, calcium may interact with some drugs, notably the tetracycline antibiotics.
  • Reminder:  If you have a medical condition, talk to your doctor before taking supplements.

How much you need?

The RDI is 800 mg for adults, and 1000 mg for women after menopause.  Many nutritionists, however, would recommend a minimum intake of 1200 mg for all adults.

If you get too little: 
A prolonged calcium deficiency can lead to bone abnormalities, such as osteoporosis.  Muscle spasms can result from low levels of calcium in the blood.

If you get too much: 
A daily calcium intake as high as 2500 mg from a combination of food and supplements appears to be safe.  However, taking calcium supplements may impair the body's absorption of the minerals zinc, iron and magnesium.  At very high doses of calcium from supplements might lead to kidney stones.  Calcium carbonate may cause wind or constipation; in this case, switch to calcium citrate.

How to take it?

Be sure to get the recommended amount of 800-1000 mg of elemental calcium a day from foods, supplements or both.  When taking supplements, it's vital that the additional calcium be balanced by magnesium (at least half the dose of calcium), zinc, silicon, and, preferably, boron.  Combined formulations containing these minerals are available.  (Those including boron are available only on prescription in Australia.)

Guidelines for use: 
To enhance absorption, divide your supplement dose so that you don't consume more than 600 mg of calcium at any one time, and be sure to take the supplements with food.

Other Sources

While dairy products (preferably low-fat) are usually recommended as the most plentiful sources of calcium, some nutritionists think that the pasteurization process may reduce the absorption of calcium.  Yoghurt, being predigested, may be the best dairy source of 'bioavailable' calcium.  Good nondairy sources include canned salmon and sardines (eaten with the soft bones), broccoli and almonds.

Facts and Tips

  • Avoid calcium supplements made from dolomite, oyster shells or bone meal – these compounds may contain unacceptable levels of lead.
  • Calcium cannot be absorbed without vitamin D, which is made by the skin in response to sunlight.  Because your body's ability to convert sunlight to vitamin D declines with age, your safest bet is to get 200-400 IU of vitamin D a day in your diet or in supplement form.  To be effective, supplements should contain vitamin D3 (cholecalciferol), not vitamin D2 (ergocalciferol).  You can also buy calcium supplements with vitamin D.
  • Spinach is not a good source of calcium.  It contains high levels of substances called oxalates, which lock up the calcium and limit the amount available to the body.  The oxalates don't interfere with calcium absorption from other foods eaten at the same time, however.

Shopping Hints

  • If you are over 65, buy calcium citrate.  People over this age often lack sufficient stomach aid to absorb calcium carbonate.

Did you know?

You'd have to eat about 50 florets of broccoli to get the 800 mg of calcium you need to meet the RDI.