What Is the Role of Calcium in the Bones?

Nicole Etolen

Calcium is an important mineral for the development and maintenance of strong, healthy bones. It is a major component in bone remodeling, a life-long process in which old bone is removed from the body and replaced with new bone. Calcium in the bones makes up more than 90 percent of the body’s supply of the mineral, and a deficiency can lead to potentially serious conditions.

Milk is a good source of calcium.
Milk is a good source of calcium.

Calcium is the most abundant mineral in the body and plays a role in muscle function, nerve transmission, and hormonal secretion. Only one percent of the body’s overall calcium supply is used for these processes. Calcium in the bones and teeth make up the remaining 99 percent, where it is used to support bone remodeling and maintain the strength of the structures.

Calcium in the bones is absorbed from the gastrointestinal tract with the help of Vitamin D.
Calcium in the bones is absorbed from the gastrointestinal tract with the help of Vitamin D.

During the bone remodeling process, bone-making cells called osteoblasts deposit new bone and osteoclasts, special cells that break down bone tissue, absorb the old bone. Having enough calcium in the bones is vital to the deposition part of the process, as the mineral binds with phosphate ions to create hydroxyapatite crystals, which form the new bone. During the absorption process, the osteoclasts release enzymes that digest the bone, which in turn releases the stored calcium back into the blood stream. Hormones in the body control the entire process.

Osteoporosis occurs when there is not enough calcium in the bones to support the remodeling process. This condition causes the bones to become thinner and more brittle over time, and reduces the overall bone mass in the body. It is most common in women older than age 50 and men older than age 70. The primary cause is a drop in estrogen and testosterone levels. Low levels of vitamin D can also contribute to osteoporosis.

Calcium in the bones is absorbed from the gastrointestinal tract with the help of Vitamin D. Maintaining an adequate amount of this vitamin in the body is just as essential to healthy bone development as calcium is. The skin makes vitamin D from the ultra-violet rays in sunlight, and the body stores the vitamin for later use. Those who cannot spend time out in the sum may need to take supplements to ensure an adequate supply of the vitamin.

Although the body can reuse calcium from broken-down bone material, it cannot make the mineral on its own. Calcium comes from dietary sources, primarily dairy products such as milk and cheese. The amount of calcium required by the body depends on age and sex. Infants younger than six months need about 210 milligrams (mg) each day if breastfed, and 350 mg daily if bottle-fed. Both male and female adolescents, and women between ages 19 and 50 require about 1,000 mg per day. After age 50 for women and 70 for men, the daily recommended intake rises to about 1,300 mg per day.

If getting enough calcium from the diet is not possible due to lactose intolerance or other issues, supplements may be recommended. A physician can recommend the best supplement and the amount that should be taken each day. While it is important to get enough calcium, it is also important to not take too much, as excess amounts of calcium can cause gastrointestinal issues, such as constipation and bloating.

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