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.
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 regulate the heart beat
- Plays a role in normal nerve function, transfers nerve impulses
- Helps blood clot during bleeding
- Builds healthy teeth (in kids)
The Institute of Medicine offers these recommendations:
|Recommended Dietary Allowance or •Adequate Intake (mg/day)|
|Birth to 6 months||200 milligrams (mg)||200 mg|
|7-12 months||260 mg||260 mg|
|1-3 years||700 mg||700 mg|
|4-8 years||1,000 mg||1,000 mg|
|9-18 years||1,300 mg||1,300 mg|
|19-50 years||1,000 mg||1,000 mg|
|51-70 years||1,200 mg||1,000 mg|
|71 years and older||1,200 mg||1,200 mg|
|Pregnant or lactating teens||1,300 mg||n/a|
|Pregnant or lactating adults||1,000 mg||n/a|
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
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.
|Upper Level Intake (mg/day)|
|Birth to 6 months||1,000 milligrams (mg)||1,000 mg|
|7-12 months||1,500 mg||1,500 mg|
|1-8 years||2,500 mg||2,500 mg|
|9-18 years||3,000 mg||3,000 mg|
|19-50 years||2,500 mg||2,500 mg|
|51 years and older||2,000 mg||2,000 mg|
|Pregnant or lactating teens||3,000 mg||n/a|
|Pregnant or lactating adults||2,500 mg||n/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.
|Yogurt, plain, low fat||1 cup||415|
|Milk, nonfat||1 cup||299|
|Cheddar cheese||1.5 ounces||307|
|Mozzarella cheese, part skim||1.5 ounces||333|
|Cottage cheese, 1% milkfat||1 cup||138|
|Frozen yogurt, soft serve||½ cup||103|
|Ice cream||½ cup||84|
|Sardines, canned in oil with bones||3 ounces||313-384|
|Salmon, pink, canned solids with bone||3 ounces||181|
|Bread, white||1 slice||73|
|Pudding, chocolate, ready to eat||4 ounces||55|
|Orange juice, calcium-fortified||6 ounces||261|
|Soymilk, calcium-fortified||8 ounces||299|
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.
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.
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.
Department of Agriculture
Eat Right—Academy of Nutrition and Dietetics
Dietitians of Canada
Calcium. EBSCO Natural and Alternative Treatments website. Available at: http://www.ebscohost.com/biomedical-libraries/natural-alternative-treatments. Updated December 2015. Accessed April 29, 2016.
Calcium. Office of Dietary Supplements website. Available at: https://ods.od.nih.gov/factsheets/Calcium-HealthProfessional. Updated February 11, 2016. Accessed April 29, 2016.
Calcium intake and supplementation. EBSCO DynaMed website. Available at: http://www.ebscohost.com/dynamed. Updated November 4, 2015. Accessed April 29, 2016.
Dietary reference intakes for calcium and vitamin D. Institute of Medicine website. Available at: http://www.nationalacademies.org/hmd/Reports/2010/Dietary-Reference-Intakes-for-Calcium-and-Vitamin-D/Report-Brief.aspx?page=1. Accessed April 29, 2016.
Hypocalcemia. EBSCO DynaMed website. Available at: http://www.ebscohost.com/dynamed. Updated June 2, 2014. Accessed April 29, 2016.
Last reviewed April 2016 by Michael Woods, MD Last Updated: 4/29/2016