Calcium
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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 found in 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:

Age Group (in years) Recommended Dietary Allowance or •Adequate Intake (mg/day) FemalesMalesBirth to 6 months200 milligrams (mg)200 mg7-12 months260 mg260 mg1-3 years700 mg700 mg4-8 years1,000 mg1,000 mg9-18 years1,300 mg1,300 mg19-50 years1,000 mg1,000 mg51-70 years1,200 mg1, 000 mg71 years and older1,200 mg1,200 mgPregnant or lactating teens1,300 mgn/aPregnant or lactating adults1,000 mgn/a
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 as an adult.

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 or cramps
  • 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.

Age Group (in years) Upper Level Intake (mg/day) FemalesMalesBirth to 6 months1,000 milligrams (mg)1,000 mg7-12 months1,500 mg1,500 mg1-8 years2,500 mg2,500 mg9-18 years3,000 mg3,000 mg19-50 years2,500 mg2,500 mg51 years and older2,000 mg2,000 mgPregnant or lactating teens3,000 mgn/aPregnant or lactating adults2,500 mgn/a
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.

FoodServing size Calcium content (mg) Yogurt, plain, low fat1 cup415Milk, nonfat1 cup299Cheddar cheese1.5 ounces307Mozzarella cheese, part skim1.5 ounces333Cottage cheese, 1% milkfat1 cup138Frozen yogurt, soft serve½ cup103Ice cream½ cup84Sardines, canned in oil with bones3 ounces313-384Salmon, pink, canned solids with bone3 ounces181Bread, white1 slice73Pudding, chocolate, ready to eat4 ounces55Orange juice, calcium-fortified6 ounces261Soymilk, calcium-fortified8 ounces299
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
Bone Health and Osteoporosis Prevention
Calcium is essential to build and maintain strong bones at all stages of life. Bone growth begins at conception, and bones grow longer and wider until well into the 20s. After this type of growth is complete, bones gain in strength and density as they continue to build up to peak bone mass by about age 30. From this point on, as a natural part of the aging process, bones slowly lose mass. Calcium is essential to slow this natural loss and stave off the onset of osteoporosis—a disease in which bones become fragile and more likely to break.

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.



RESOURCES:
Academy of Nutrition and Dietetics

The Nutrition Source
Harvard School of Public Health

CANADIAN RESOURCES:
Dietitians of Canada


References:
Calcium. EBSCO Natural and Alternative Treatments website. Available at: http://www.ebscohost.com/biomedical-libraries/natural-alternative-treatments. Updated August 2013. Accessed July 15, 2014.

Calcium. Office of Dietary Supplements website. Available at: http://ods.od.nih.gov/factsheets/Calcium-HealthProfessional/#h8. Updated November 21, 2013. Accessed July 15, 2014.

Calcium intake and supplementation. EBSCO DynaMed website. Available at: http://www.ebscohost.com/dynamed. Updated July 7, 2014. Accessed July 15, 2014.

Dietary reference intakes for calcium and vitamin D. Institute of Medicine website. Available at: http://www.iom.edu/Reports/2010/Dietary-Reference-Intakes-for-Calcium-and-Vitamin-D/Report-Brief.aspx?page=1. Published November 30, 2010. Accessed July 15, 2014.

Last Reviewed July 2014



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