Calcium
Calcium is the most prevalent mineral in the human body. About 99% of the body's calcium resides in the bones, 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
|
Age Group
(in years) |
Adequate Intake | |
|---|---|---|
| Females | Males | |
| 1-3 | 500 mg | 500 mg |
| 4-8 | 800 mg | 800 mg |
| 9-13 | 1,300 mg | 1,300 mg |
| 14-18 | 1,300 mg | 1,300 mg |
| 19-30 | 1,000 mg | 1,000 mg |
| 31-50 | 1,000 mg | 1,000 mg |
| 50 + | 1,200 mg | 1,200 mg |
| Pregnancy: 14-18 | 1,300 mg | n/a |
| Pregnancy: 19-50 | 1,000 mg | n/a |
| Lactation: 14-18 | 1,300 mg | n/a |
| Lactation: 19-50 | 1,000 mg | n/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.
If you don't 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:
- Inadequate mineralization of bone
- Intermittent muscle contractions
- Muscle pain
- Muscle spasms
- Numbness or tingling in the hands and feet
- Rickets in children
- Osteoporosis in adults
Calcium Toxicity
Unless doses exceed 2500 mg/day, adverse effects for adults are unlikely. 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) is set at 2500 mg daily from age one through adulthood.
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.
| Food | Serving size |
Calcium content
(mg) |
|---|---|---|
| Yogurt | 1 cup | 300-400 |
| Milk | 1 cup | 300-400 |
| Macaroni and cheese, homemade | 1 cup | 362 |
| Parmesan cheese | 1 Tbsp | 336 |
| Eggnog, nonalcoholic | 1 cup | 330 |
| Chocolate milk | 1 cup | 300 |
| Ricotta cheese | 1/2 cup | 300 |
| Powdered milk | 1/4 cup | 290 |
| Cheddar cheese | 1 ounce | 250 |
| Swiss cheese | 1 ounce | 250 |
| Provolone cheese | 1 ounce | 215 |
| Cheese pizza | 1/6 frozen pizza | 210 |
| Mozzarella cheese | 1 ounce | 175 |
| American cheese | 1 ounce | 160 |
| Cottage cheese | 1 cup | 120 |
| Frozen yogurt, soft serve | 1/2 cup | 100 |
| Ice cream | 1/2 cup | 80 |
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 labels on tofu and fortified products to determine specific calcium levels of these foods.
| Food | Serving size |
Calcium content
(mg) |
|---|---|---|
| Tofu, regular, processed with calcium | 1/2 cup | 435 |
| Calcium-fortified soy milk | 1 cup | 250-300 |
| Salmon, canned with edible bones | 3 ounces | 212 |
| Calcium-fortified orange juice | 3/4 cup | 200 |
| Blackstrap molasses | 1 Tbsp | 172 |
| Pudding, from cook & serve mix | 1/2 cup | 150 |
| Dried figs | 5 pieces | 135 |
| Tofu, regular (processed without calcium) | 1/2 cup | 130 |
| Anchovies with edible bones | 3 ounces | 125 |
| Turnip greens, boiled | 1/2 cup | 100 |
| Milk chocolate bar | 1.5 ounce | 85 |
| Okra, boiled | 1/2 cup | 77 |
| Tempeh | 1/2 cup | 77 |
| Kale, boiled | 1/2 cup | 70 |
| Mustard greens, boiled | 1/2 cup | 65 |
| Orange | 1 medium | 50 |
| Pinto beans | 1/2 cup | 45 |
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 35. 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. In fact, a study reported that taking 1,200 mg a day of calcium helped to increase bone mineral density in men.
If not prevented or if left untreated, osteoporosis can progress painlessly until a bone breaks. These broken bones occur typically in the hip, spine, and wrist. Even when a person has osteoporosis, though, proper calcium and vitamin D intake can help to delay further bone loss.
Other Health Problems
Consuming enough calcium can also help protect you from high blood pressure, heart disease, and possibly colon cancer. Calcium supplementation (1500 mg/day) during pregnancy can also significantly reduce the risk of:
- Pre-eclampsia —a condition that can lead to severe seizure and blood pressure disorder that can be life threatening to both mother and baby
- Premature birth
The relationship of calcium intake to kidney stones is complicated and variable between persons. Lowering calcium intake may not reduce the risk of kidney stones because the end result may be a lesser amount of calcium absorption, but a greater tendency for the calcium that is in the urine to form stones.
Many people do increase their risk of kidney stones by consuming excess calcium—usually in supplements. This risk can probably be decreased by taking calcium supplements with meals and perhaps by limiting intake of salt (sodium). When your diet contains more sodium daily than the currently recommended 2300 grams (about 1 teaspoon of table salt), then the kidneys respond by excreting more calcium into the urine. Not only does this lead to greater calcium loss (and risk of osteoporosis), but it exposes the kidneys to a greater risk of stone formation.
Dealing With Lactose Intolerance
Some people have difficulty digesting lactose, the main sugar in milk and some dairy products. This occurs when the body does not produce enough of the enzyme lactase to properly digest lactose. People with this condition, called lactose intolerance, may experience nausea, cramping, bloating, abdominal pain, gas, and diarrhea anywhere from 15 minutes to several hours after eating milk or milk products.
People with lactose intolerance can take the following steps to be sure they meet their calcium needs:
- Eat dairy foods along with a meal rather than alone; the presence of other foods in the digestive tract can make it easier for your body to tolerate the lactose.
- Eat smaller portions of dairy foods. Most people find that they are able to tolerate 1/2 cup or 3/4 cup of milk at a time, several times during the day, rather than 1 cup or more in one sitting.
- Choose aged cheeses, such as Swiss, Colby, Parmesan, and cheddar, which have most of their lactose removed during processing.
- Try dairy foods made with live, active cultures, such as yogurt and buttermilk. The "friendly" bacteria in these foods help to digest the lactose. These foods should have a "Live and Active Cultures" label.
- Be sure to include non-dairy sources of calcium in your daily diet.
- Consider the addition of a lactase enzyme supplement, such as Lactaid (or a generic product). For many people, taking an enzyme supplement can increase the amount of lactose that can be tolerated.
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.
- Ask your doctor if you should take a supplement.
- 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
- Do not take more than 500 mg of calcium at a time. Taking the calcium with food can help absorption.
Resources
American Dietetic Association
Canadian Resources:
Canadian Council on Food and Nutrition
Dietitians of Canada
References:
Bowes A, Pennington J, Church H. Bowes & Church Food Values of Portions Commonly Used. Philadelphia, PA: Lippincott Williams & Wilkins; 1998.
Domrongkitchaiporn S, Sopassathit W, Stitchantrakul W, Prapaipanich S, Ingsathit A, Rajatanavin R. Schedule of taking calcium supplement and the risk of nephrolithiasis. Kidney Int. 2004 ;65:1835-1841.
Food and Nutrition Information Center. US Department of Agriculture website. Available at: http://fnic.nal.usda.gov/nal_display/index.php?tax_le...=1&info_center=4. Accessed August 17, 2009.
Garrison RH, Somer E. The Nutrition Desk Reference. New Canaan, CT: Keats Publishing; 1995.
Groff JL, Gropper S. Advanced Nutrition and Human Metabolism. Belmont, CA: West Publishing Company; 1995.
Hofmeyr GJ, Atallah AN, Duley L. Calcium supplementation during pregnancy for preventing hypertensive disorders and related problems. Cochrane Database Syst Rev. Jul 19, 2006;3:CD001059.
Villar J, Abdel-Aleem H, Merialdi M, et al. World Health Organization randomized trial of calcium supplementation among low calcium intake pregnant women. Am J Obstet Gynecol. 2006;194:639-649.
11/19/2008 DynaMed's Systematic Literature Surveillance DynaMed's Systematic Literature Surveillance: Reid IR, Ames R, Mason B, et al. Randomized controlled trial of calcium supplementation in healthy, nonosteoporotic, older men. Arch Intern Med. 2008;168:2276-2282.
7/6/2006 DynaMed's Systematic Literature Surveillance DynaMed's Systematic Literature Surveillance: Villar J, Abdel-Aleem H, Merialdi M, et al. World Health Organization randomized trial of calcium supplementation among low calcium intake pregnant women. Am J Obstet Gynecol. 2006;194:639-649.
7/6/2009 DynaMed's Systematic Literature Surveillance http://www.ebscohost.com/dynamed/what.php: Kumar A, Devi SG, Batra S, Singh C, Shukla DK. Calcium supplementation for the prevention of pre-eclampsia. Int J Gynaecol Obstet. 2009;104:32-36.
Last reviewed June 2008 by Dianne Scheinberg MS, RD, LDN
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.