Calcium is the most prevalent mineral in the human body. About 99% of the body's calcium resides in the bones and teeth, and the remaining 1% is dispersed throughout other body fluids and cells.

Functions

Calcium's functions include:

• Builds bones, both in length and strength
• Helps bones remain strong by slowing the rate of bone loss with age
• Helps muscles contract
• Helps the heart beat
• Plays a role in normal nerve function, transfers nerve impulses
• Helps blood clot during bleeding
• Builds healthy teeth (in kids)

Recommended Intake

The Institute of Medicine offers these recommendations:

Calcium Deficiency

In childhood, not getting enough calcium may interfere with growth. A severe deficiency may keep children from reaching their potential adult height. Even a mild deficiency over a lifetime can affect bone density and bone loss, which increases the risk for osteoporosis.

If you do not consume enough calcium, your body will draw from the storage in your bones in order to supply enough calcium for its other functions: nerve transmission, muscle contraction, heartbeat, and blood clotting.

Symptoms of a calcium deficiency include:

• Intermittent muscle contractions
• Muscle pain
• Muscle spasms
• Numbness or tingling in the hands and feet
• Rickets in children
• Osteoporosis in adults

Calcium Toxicity

Very large doses over a prolonged period of time may cause kidney stones and poor kidney function. Your body may not absorb other minerals, such as iron, magnesium, and zinc, properly. These problems could occur from consuming too much through a calcium supplement, not from milk or other calcium-rich foods. The tolerable upper intake level (UL) depends on age.

Major Food Sources

Dairy foods—milk, yogurt, and some cheeses—are the best dietary sources of calcium. These foods are also rich in vitamin D, which helps the body absorb calcium.

Absorption of calcium from some other dietary sources is not as great as that from dairy foods. Specifically, dark green vegetables contain oxalates, and grains contain phytates, which can bind with calcium and decrease their absorption.

Read food labels to determine the specific calcium levels of these foods.

Health Implications

Tips for Increasing Your Calcium Intake

• When making oatmeal or other hot cereal, use milk instead of water.
• Add powdered milk to hot cereal, casseroles, baked goods, and other hot dishes.
• Make your own salad dressing by combining low-fat plain yogurt with herbs.
• Add tofu (processed with calcium) to soups and pasta sauce.
• If you like fish, eat canned fish with bones on crackers or bread.
• For dessert, try low-fat frozen yogurt, ice cream, or pudding.
• In baked goods, replace half of the fat with plain yogurt.

Taking Supplements

If you are unable to meet your calcium needs through dietary sources, consider a calcium supplement. Some points to remember when choosing and using a calcium supplement include:

• Check the label because the amount of calcium differs among products.
• Avoid supplements with dolomite or bone meal; they may contain lead.
• Check your vitamin D intake, too. This vitamin is essential for absorption of calcium. Milk is a great source of vitamin D, as is sunlight.
• If you take both calcium and iron supplements or a multivitamin with iron, take them at different times of the day. They can impair each other's absorption. This is also true of chromium, manganese, magnesium, and zinc.
• Do not take more than 500 mg of calcium at a time. Taking the calcium with food can help absorption.