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.

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 eclampsia, a severe seizure and blood pressure disorder that can be life threatening to both mother and baby.*

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, the body can’t absorb more than 500mg at a time. Taking the calcium with food can help absorption too.