Vitamin D is essential in the growth and formation of healthy bones and teeth. Without it, children can develop a bone-malformation condition known as rickets, and adults can develop osteomalacia, which is characterized by weakness, softness or fractures of the bones. Vitamin D also helps regulate levels of calcium, phosphorus and magnesium in the blood, and has been shown to influence the growth of other tissues in the body as well as the regulation of the immune system. Vitamin D deficiency has been implicated in the development of conditions such as cancer, heart disease‚ osteoporosis and multiple sclerosis.
The body gets vitamin D from two sources: dietary intake through foods and supplements (exogenous), and through production in the skin upon exposure to sunlight (endogenous). Although vitamin D is found naturally in only a few foods, in the United States, many products are supplemented with it, including milk, breakfast cereals and juices. Those at risk of vitamin D deficiency include individuals who are elderly; obese; have dark skin; are institutionalized, homebound or have limited sun exposure; have undergone gastric bypass surgery; and have conditions such as cystic fibrosis and Crohn’s disease that interfere with fat absorption.
The Vitamin D 25-Hydroxy Blood Test is often ordered for individuals that have symptoms of vitamin D deficiency. It may also be ordered before an individual begins osteoporosis drug therapy. Low levels may indicate a dietary deficiency, malabsorption or lack of exposure to sunlight.