Calcium

What It Is
Calcium and phosphorus--the two most abundant minerals in our bodies--work together to keep our bones and teeth healthy. Calcium is found in many foods--most notably dairy products--and is also available as natural and synthetic supplements. You will need a prescription for certain forms of calcium; others can be purchased over the counter.

What It Does
Fully 99 percent of our calcium deposits are stored in the bones. In response to the body's needs, calcium moves out of the bones into the bloodstream and then back into the bones for continued storage. Most of the remaining 1 percent of our calcium supply is located in body fluids, where it helps transmit nerve impulses. Calcium also promotes blood coagulation and plays an essential role in enabling muscles, such as the heart, to relax and contract.

Why You Need It
Calcium is essential to a child's normal growth and development, and everyone needs an adequate supply to keep bones and teeth strong and healthy. Because of the part it plays in muscle activity, some people take it to prevent muscle cramps; others use it to alleviate their severe muscle spasms that accompany a disorder called tetany.

   One of calcium's more recently--and widely--publicized benefits is its ability to stave off the brittle-bone disease osteoporosis when used in combination with estrogen.

Can You Take Too Much?
Doses above 2,000 milligrams per day can lead to potentially serious problems, including development of kidney stones. A loss of appetite, constipation, drowsiness, dry mouth or a metallic taste in the mouth, headache, and a feeling of fatigue or weakness could be early warning signs that there is too much calcium in your system. Later signs may include confusion, depression, nausea, vomiting, pain in bones or muscles, high blood pressure, increased thirst or urination, increased sensitivity of the eyes or skin to light, itchy skin or rash, and a slow or irregular heartbeat. If you notice any of these symptoms and you think the amount of calcium you have been taking could be the source of the problem, stop using the supplements and call your doctor. If you think your heartbeat is either irregular or slow, seek medical attention immediately.

Recommended Daily Allowances
ADULTS

The basic allowance for everyone 18 years of age and older is 800 milligrams.

   Women need an additional 400 milligrams of calcium each day during pregnancy and as long as they breastfeed. Do not take megadoses of calcium during pregnancy or while breastfeeding. Calcium does pass into the breast milk.

   Many experts believe that we need more calcium than the official recommendation and suggest the following amounts: 1,000 milligrams of calcium per day for premenopausal women and, due to the risk of osteoporosis, 1,500 milligrams for postmenopausal women and for both elderly men and women past the age of 65.

All calcium supplements are not created equal. The body only absorbs part of the calcium it takes in, and different forms of calcium provide varying amounts of this mineral. Calcium citrate may provide a bit more usable calcium than other forms, and is less likely to have side effects. Calcium carbonate is often recommended because it contains the highest percentage of absorbable calcium. It is also the cheapest and has the added advantage of acting as an antacid. Two 1,250- or 1,500-milligram tablets of calcium carbonate per day will provide 1,000 milligrams of what is called "available" calcium to the body.

   To get the same 1,000 milligrams from other forms of calcium, you need to take up to 12 tablets a day. Divide the following amounts into more than one dose and take them after meals: two 1,600-milligram tablets of calcium phosphate, five 950-milligram tablets of calcium citrate, eleven 1,000-milligram tablets of calcium gluconate, twelve 650-milligram tablets of calcium lactate, and 12 teaspoons of calcium glubionate. Chelated calcium tablets and combinations of calcium and other vitamins and minerals such as vitamin D and magnesium offer no special advantage. Also avoid bone meal and dolomite--they may contain toxic lead, mercury, and arsenic.

   Whichever supplement you choose, check the information supplied with it to determine the dosage that will supply the amount of calcium you need. Remember too, that smoking and drinking alcohol, coffee, or tea increases the amount of calcium that your body will lose.

Best Dietary Sources
Calcium is found in dairy products, shrimp, canned salmon and sardines, green leafy vegetables, Brazil nuts and almonds, molasses, soybeans, and tofu.

   One cup of yogurt contains up to 415 milligrams of calcium. There are 300 milligrams in 1 cup of skim milk, and 290 milligrams in 1 cup of whole milk. One slice of Swiss cheese provides 270 milligrams; 1 cup of cottage cheese, 230 milligrams; 1 ounce of cheddar cheese, 200 milligrams; 1 stalk of broccoli, cooked, 160 milligrams; and one 4-ounce piece of tofu, 150 milligrams.

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Revised: June 10, 2006 .