Definition
Calcium is the most plentiful mineral found in the human body. The teeth and bones contain the most calcium (about 99%). Nerve cells, body tissues, blood, and other body fluids contain the remaining calcium.Overview & Functions
Calcium is one of the most important minerals for the growth, maintenance, and reproduction of the human body. Calcium helps form and maintain healthy teeth and bones. Proper levels of calcium over a lifetime can help prevent osteoporosis. Calcium helps with blood clotting, nerve signaling, muscle contraction and relaxation, and the release of certain hormones. It is also needed for a normal heartbeat.Food Sources
Many foods contain calcium, but dairy products are the most significant source. Milk and dairy products such as yogurt, cheeses, and buttermilk contain an efficiently absorbed form of calcium.Whole milk (4% fat) is recommended for children age 1 to 2. The fat content of dairy products is a concern for adults and children over the age of 2. You can easily reduce the fat content while maintaining the calcium content by selecting low-fat (2% or 1%) or skim milk and other diary products. The calcium is not contained in the fat portion of milk, so removing the fat will not affect the calcium content. In fact, when you replace the fat portion that has been removed with an equal part of skimmed milk, you are actually increasing the calcium content. Therefore, one cup of skim or non-fat milk will have more calcium than one cup of whole milk because almost the entire cup of skim milk is made up of the calcium-containing portion. Other dairy products such as yogurt, most cheeses, and buttermilk are excellent sources of calcium and are available in low-fat or fat-free versions. Milk is also a good source of phosphorus and magnesium, which help the body absorb and use the calcium more effectively. Vitamin D is essential for efficient utilization of calcium. Milk is fortified with vitamin D for this reason. Green leafy vegetables such as broccoli, collards, kale, mustard greens, turnip greens, and bok choy or Chinese cabbage are good sources of calcium.
Other sources of calcium are salmon and sardines canned with their soft bones. Shellfish, almonds, Brazil nuts, and dried beans are also sources of calcium. It is difficult, however, to eat adequate quantities of these foods to achieve optimal calcium intake. Calcium is added to several food products, such as breads and orange juice, to make them a significant source of calcium for persons who do not eat a lot of dairy products.
Recommendations
The Food and Nutrition Board at the Institute of Medicine recommends the following dietary intake for calcium:Infants
- 0 - 6 months: 210 milligrams per day (mg/day)
- 7 - 12 months: 270 mg/day
- 1 - 3 years: 500 mg/day
- 4 - 8 years: 800 mg/day
- 9 - 13 years: 1300 mg/day
- Males age 14 to 18 years: 1300 mg/day
- Males age 19 to 50 years: 1000 mg/day
- Males 51 and over: 1200 mg/day
- Females age 14 to 18 years: 1300 mg/day
- Females age 19 to 50 years: 1000 mg/day
- Females 51 and over: 1200 mg/day
Up to 2,000 - 2,500 mg a day of calcium from dietary sources and supplements appears to be safe. The preferred source of calcium is calcium-rich foods such as dairy products.
The following list can help you determine how much calcium you are getting from food:
- 8-ounce glass of milk = 300mg of calcium
- 2 ounces of Swiss cheese = 530mg of calcium
- 6 ounces of yogurt = 300 mg of calcium
- 2 ounces of sardines with bones = 240mg of calcium
- 6 ounces of cooked turnip greens = 220mg of calcium
- 3 ounces of almonds = 210mg of calcium
Side Effects
Increased calcium for a limited periods does not normally cause side effects. However, receiving a large amount of calcium over a long period of time raises the risk of kidney stones in some people.Those who do not receive enough calcium over a long period of time can develop calcium deficiency. This condition leads to osteoporosis, loss of the jaw bone (osteonecrosis), hypertension, and other disorders. Persons with lactose intolerance have trouble digesting lactose, the sugar in milk. There are over-the-counter products available that make it easier to digest lactose. You can also buy lactose-free milk at most grocery stores. In rare instances, some people have a true allergy to the protein in milk. Such persons must avoid all dairy products and may need to take calcium supplements.
