Focus on Calcium

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The hard fact behind coral reefs, marble statues, antlers, tusks and bones

Lisa van de Geyn

Got milk? If the only moo juice in your diet is the splash you put in your morning coffee, you may be lacking in the most abundant mineral in the human body — yet one that’s anything but abundant in many diets. While calcium is celebrated for its role in building bones and teeth, it is, in fact, crucial to every cell in your body. It’s essential in nerve and brain function, hormone release, muscle contraction and your heart’s electrical pumping system. It also binds to and helps eliminate toxic by-products of digestion.

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The basics

Almost all — 99% — of the body’s calcium is found in the skeleton and teeth; the rest is located largely in blood, muscle and the fluid between cells. The best sources for keeping up your body’s critical calcium supply are food and drink, not supplements, says Dr. Robert Heaney, a researcher in calcium nutrition at Creighton University in Omaha, Neb. “For calcium to be effective in supporting bone health, it needs to be taken into the body with an adequate quantity of protein, phosphorus, vitamin D and a whole host of other nutrients.” 

That’s because nutrients are like the instruments in a symphony
orchestra: you need the complete  complement working together to get the maximum effect. “Supplements should be used precisely as their name suggests — as adjuncts to an otherwise good diet,” says Heaney.

Besides the calcium-rich dairy family, the white stuff can also be found in leafy greens (kale, broccoli, bok choy), legumes (lentils, beans, peas), bone-in fish (canned salmon,  sardines) and fortified orange juice and soy beverages. Seeds, almonds and pecans are decent sources, too.

Calcium is absorbed into the blood from the intestines with the crucial help of vitamin D, a fat-soluble vitamin found in fortified milk and fatty fish such as salmon, rainbow trout, Arctic char, mackerel, sardines, anchovies and tuna. Liver, egg yolk and lean beef also supply it.

How much?

Most people ages 18 to 50 should consume about 1,000 milligrams (mg) daily — which, according to Canada’s Food Guide, translates to two to three dairy servings. The amount goes up to about 1,200 mg for pregnant or nursing women under age 18, as well as people over age 51. Some at-risk older women may require up to 1,500 mg.

While it’s important to get the recommended amount daily, too much calcium can be harmful. “The tolerable upper limit for the intake of calcium is 2,500 mg a day,” says  Montreal-based registered dietitian Kim Arrey. “It’s only possible to have an intake of this magnitude if you consume supplements, drink litres of milk or eat mounds of cheese each day.” In the days before modern antacid drugs, some ulcer sufferers developed hypercalcemia by doing just that! Elevated blood levels of calcium can leave damaging deposits in the kidneys and arteries, as well as block absorption of other minerals such as zinc, magnesium and iron.

Signs of deficiency

Bad news: there’s no easy way to tell if you’re not getting enough. “Bone provides such a huge reserve of calcium that the only effect of low intake is a reduction in skeletal strength,” says Heaney. And that might go unnoticed until a fracture announces osteoporosis. “In the short term, the only way to know if you’re getting enough is by looking at what you’re eating,” says Arrey. Or by
having a bone test. Your intake could be deficient if you’re vegan, lactose- intolerant or post-menopausal.

For current Dietary Reference Intakes, go to www.canadian-health.ca. Click on Past Issues, September/October 2007, “Calcium and Vitamin D.”