How Does Vitamin D Contribute To Bone Mineralization?

You need to consume adequate calcium in your diet in order to have strong bones, but other nutrients are also important. Chief among these is vitamin D, which you need to absorb calcium. If you are deficient in vitamin D, no amount of calcium in your diet can protect you from losing bone mass and developing osteoporosis, a condition that can lead to fractures.

Minerals and Bones

Bone tissue breaks down and re-forms throughout your life. Osteoclasts are cells that break down old bone, and osteoblasts are cells that build new bone. Osteoblasts help form a matrix made of collagen fibers and crystalline salts. The crystalline salts, made primarily of calcium and phosphate, give bones strength. As much as 99 percent of your body's calcium is stored in your bones and teeth. Adequate calcium in the blood is vital to muscle function, nerve transmission, secretion of hormones and contraction and dilation of blood vessels. If needed, your body takes calcium from your bones to keep the blood levels stable.

Vitamin D and Calcium

Without adequate vitamin D, you absorb 10 to 15 percent of the calcium in your food. With enough, you absorb 30 to 40 percent. When calcium levels are adequate, your blood calcium stays at a level optimal for health. Your body stores calcium that is over and above what is needed for bodily functions by depositing it in your bones. These calcium deposits strengthen the bone matrix. Without adequate vitamin D for absorption, however, your blood calcium falls, your body pulls calcium from your bones and your bones become weaker over time.

Vitamin D and Blood Levels

Vitamin D goes through three stages to reach its active form. When exposed to sunlight, your skin makes vitamin D-3, and you can get it in fortified foods or supplements. Your liver converts vitamin D-3 to 25-hydroxyvitamin D. The kidneys perform the final step by converting 25-hydroxyvitamin D to the active form, 1,25 dihydroxyvitamin D. Commonly, all forms are called vitamin D. A test for blood levels of 25-hydroxyvitamin D is the best determinant of vitamin D status. A level between 50 nmol/L and 125 nmol/L is needed for strong bones and general health.

Doses

Recommendations for vitamin D intake are based on an assumption of minimal sun exposure. From age 1 to age 70, you should get at least 600 IU of vitamin D daily; over age 70, that goes up to 800 IU. If tests indicate a deficiency, you may be prescribed much higher doses until your level is adequate.

Sources

Sunlight triggers your skin to make vitamin D, but with age it becomes less efficient at doing so. And if you live in a northern climate, you can't get enough sunlight in winter to make it. Vitamin D is present in few foods naturally, with the best source being fatty fish, such as salmon, mackerel and tuna. Foods commonly fortified with vitamin D include cereals, milk, orange juice, yogurt and margarine. Check labels to verify vitamin D content.