Calcium, according to the Linus Pauling Institute, is the most abundant mineral in the body, with 99 percent of calcium stored in bones and teeth, and the remainder found in blood and soft tissue. Calcium aids with muscle contraction, secretion of hormones and structural support in the body. A daily intake of 1,000 to 1,300 milligrams of calcium a day is recommended for most individuals, with about 500 to 800 milligrams for young children, according to the Centers for Disease Control.
Where is Calcium Found?
Calcium, according to the Centers for Disease Control, cannot be produced by the body, so must be consumed through meals. Calcium is primarily found in dairy products such as milk, yogurt, and cheese, but is also found in dark green vegetables such as spinach and broccoli, nuts, and calcium fortified products such as orange juice, cereals, tofu, and soy milk. The Linus Pauling Institute reports that one cup of milk or yogurt, or 1.5 ounces of cheese, will provide about 300 milligrams of calcium.
How is Calcium Absorbed in the Body?
According to the Office of Dietary Supplements, absorption of calcium is affected by several factors. Calcium absorption efficiency decreases as we age, with adults having a 15 percent to 20 percent absorption efficiency compared to 60 percent in infants and young children.
Another factor that affects calcium absorption are oxalates and phytic acids, which, according to the National Institutes of Health, bind to calcium and inhibit its absorption. Oxalates are found in foods such as spinach, collard greens, and beans, while phytic acid is found in whole-grain foods and nuts. These foods should not be depended upon as a source of calcium in the diet.
Vitamin D intake, obtained through sunlight exposure and fortified foods, has been found to increase calcium absorption efficiency in the body.
Calcium and Bone
Calcium is an important structural component in the body. According to the National Institute of Child Health and Human Development, the body is constantly removing and replacing small amounts of calcium from the bones. When more bone is removed than replaced, the bones become weak. Young children and teens should build up their calcium stores since peak bone mass occurs at around age 30, according to the National Institutes of Health. Beyond this point, no more calcium can be stored in the bones.
Bone Disease
Perhaps the most commonly known bone disease is osteoporosis, or porous bone, which involves low bone mass and deterioration of bone tissue. When low bone mass, or osteopenia, is diagnosed through a bone mineral density test, an implementation of weight-bearing exercises and calcium supplementation in the diet may prevent development of osteoporosis. Once osteoporosis develops, individuals are more at risk for developing fractures in bones such as the hip, wrist, and pelvis. The National Institutes of Health reports an estimated 1.5 million fractures each year due to osteoporosis.
Individuals at Risk for Calcium Deficiency
According to the National Institutes of Health, postmenopausal women are at risk for calcium deficiency since decreases in estrogen production lead to decreased calcium absorption. Hormone replacement therapy has shown to be effective in increasing calcium levels.
Individuals with lactose intolerance are also at risk of calcium deficiency due to their inability to digest the milk sugar lactase, which in turn prevents them from consuming many calcium-rich dairy products. Like vegetarians who also avoid consumption of dairy products, such individuals should consume foods such as leafy greens, soy milk, and calcium-fortified foods to obtain their calcium. In some cases, calcium supplementation may be necessary for individuals in these high-risk groups.
References
- Linus Pauling Institute: Calcium
- National Institutes of Health: Office of Dietary Supplements: Dietary Supplement Fact Sheet: Calcium
- National Institutes of Health: Eunice Kennedy Shriver: National Institute of Child Health and Human Development: Bone Health
- Centers for Disease Control: Calcium and Bone Health
