The Relationship Between Calcium, Vitamin D, & Bones

Your bones, which provide your body with its shape and structure, consist of both living and non-living material. The living portion of the bones consists of blood vessels, nerves, a protein known as collagen and cells known as osteoblasts and osteoclasts. The non-living part of the bones consists of the minerals and salts that make bones strong. Your body needs calcium, the most abundant mineral in the body, to make bones strong, but without vitamin D, you cannot absorb calcium.

Bone Formation

One type of living cell in the bones, known as osteoclasts, breaks down old bone material, while another type of cell, known as osteoblasts, forms new bone. To form new bone, calcium combines with phosphate and hydroxide to create hydroxyapatite crystals. The osteoblasts deposit this crystalline salt to the bone matrix, which also contains collagen fibers. The collagen fibers give the bone the strength to endure great stretching forces, while the calcium salts give the bone compressional strength to endure squeezing forces. Without enough calcium, the bones become weak and susceptible to fracture.

Calcium

The National Institutes of Health Office of Dietary Supplements says that your body uses 99 percent of the calcium in your body to build strong bones and teeth. The remaining 1 percent also serves vital functions, including transmitting electrical impulses important for muscle contraction and maintaining a regular heartbeat. Foods in the dairy food group, including milk, yogurt and cheese, serve as good sources of calcium, but other foods like sardines, salmon and dark green leafy vegetables also contain calcium. To maintain healthy bones and reduce the risk of osteoporosis -- a condition characterized by weak and porous bones, you should eat a diet that includes calcium-rich foods. To effectively absorb the calcium from foods, however, you must also get enough vitamin D.

Vitamin D

Although your body does not directly use vitamin D to build bone, vitamin D facilitates the absorption of calcium. Your body must maintain your calcium level in a narrow range. If calcium levels fall, the parathyroid gland releases parathyroid hormone, which increases the activity of an enzyme necessary to produce the active form of vitamin D. The increased level of vitamin D increases the absorption of calcium through the intestines and decreases the amount of calcium lost in the urine. Although few foods naturally contain vitamin D, many foods like breakfast cereals and milk are fortified with vitamin D. The cells in your skin also produce vitamin D when stimulated by the ultraviolet rays of the sun.

Recommended Intake

Failing to consume adequate amounts of calcium and vitamin D can lead to osteoporosis, which affects nearly 10 million adults in the United States, with another 34 million at risk for developing the disease, according to the National Osteoporosis Foundation. To prevent the onset of disease, The Institute of Medicine sets the dietary reference intake, the amount of the nutrient needed to meet the requirements of most people within the given group, for both calcium and vitamin D. Adult men ages 19 to 70 should consume 1,000 mg of calcium per day and 15 mcg or 600 IU of vitamin D per day. Although more women suffer from osteoporosis than men, men can also develop the disease as they age. For this reason, men ages 71 and older should increase their calcium intake to 1,200 mg per day and their vitamin D intake to 20 mcg or 800 IU per day to keep their bones strong. Adult women between 19 and 50 should consume 1,000 mg of calcium, but as they hit menopause, around the age of 50, they should increase their calcium intake to 1,200 mg per day. Like men, adult women should get 15 mcg or 600 IU of vitamin D per day until the age of 71, when they should increase their intake to 20 mcg or 800 IU per day.