Calcium is an important mineral for the human body. It is essential for muscle contraction, but also essential to the structure and health of the bones. Bones are continually remodeling and reforming, and calcium is a vital part of this process. People therefore need a certain daily amount of this mineral, since without it the bones become thin.
Structure of Bone
Bones are structured to provide strength and protection but also to allow for movement. In addition, the structure allows the bones to serve as a reservoir for several minerals, including calcium, because calcium quickly moves between the bone and the blood. Approximately 30 percent of bone is called the organic or living material and is made of collagen and protein, writes Elizabeth Corwin, Ph.D., in "Handbook of Pathophysiology." The other 70 percent is mainly made of calcium and phosphate, although there is some potassium, sodium and magnesium.
Bone Remodeling
Bones are continually remodeling and this process involves two types of cells. The osteoblasts build the organic material of the bone when sent the signal to do so. A few days later, calcium and phosphate start to make the new area hard. At the same time, there is a breakdown of bone by the osteoclasts, as explained by Corwin. These cells break down a small section and leave, then the osteoblasts arrive to fill in the area with new bone. New strong bone, which is mainly calcium, continually replaces areas of old, weak bone.
Calcium is Regulated
More than 99 percent of the calcium in the adult body is found in the skeleton, according to F. Richard Bringhurst, M.D., associate professor of medicine at Harvard Medical School, in "Harrison's Principles of Internal Medicine." Because calcium is so essential to the structure and health of the bones, as well as to the contraction of muscles and the reaction time of several processes, its metabolism and levels are tightly regulated by the parathyroid hormone, calcitonin hormone and vitamin D.
Calcium Levels
According to the National Institutes of Health, people who are 19 to 50 years old should have 1,000 mg of calcium every day. Those over 50 should have 1,200 mg on a daily basis. To be able to use calcium, the human body also must have enough vitamin D, because vitamin D stimulates the osteoblasts to build bone and stimulates the absorption of calcium from the intestines. Having large amounts of vitamin D without enough calcium can increase the breakdown of bone because the body will try to increase calcium levels.
Low Calcium and Bone
Osteoporosis is a bone disease in which people slowly develop less bone density. The bones become thin, which can result in fractures with only a minimal amount of trauma. Most people with this disease are postmenopausal women and elderly men. A deficiency of the estrogen hormone is an important cause in women and men, writes Lawrence Raisz, M.D., director of the University of Connecticut Center for Osteoporosis, in The Merck Manual for Healthcare Professionals. Low calcium dietary levels and low levels of vitamin D also can cause osteoporosis.
References
- "Handbook of Pathophysiology"; Elizabeth Corwin, MSN, Ph.D., FNP; 2000
- "Harrison's Principles of Internal Medicine"; Anthony Fauci, M.D., Dennis Kasper, M.D., Dan Longo, M.D. et al.; 2008
- The Merck Manual for Healthcare Professionals: Osteoporosis
- National Institutes of Health: Dietary Supplement Fact Sheet: Calcium
