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What Causes Vitamin D Deficiency?

written by: Leigh A. Zaykoski • edited by: Leigh A. Zaykoski • updated: 1/31/2010

Understanding what causes vitamin D deficiency will help you recognize the symptoms of this condition and seek medical treatment when necessary. Learn about vitamin D deficiency in adults and children to understand how to manage this condition.

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    Vitamin D

    Vitamin D occurs naturally in very few foods, so food manufacturers add the vitamin to milk and some other food products. Your body also produces its own vitamin D when you receive UV light from the sun. This vitamin plays an important role in the absorption of calcium and the normal balance of phosphorus and calcium. The bones need vitamin D for growth and repair, as well as protection from osteoporosis and other bone diseases.

    While most people think of vitamin D as a vitamin for the bones, it also plays an important role in reducing inflammation and controlling neuromuscular function. Vitamin D also modulates some of the genes that regulate cell growth, differentiation and programmed cell death.

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    Identifying Toxicity

    The 25-Hydroxyvitamin D blood test identifies abnormal concentrations of vitamin D in the blood. A result of less than 10 to 11 ng/mL (nanograms per milliliter) indicates an increased risk for Rickets in children and softening of the bones in adults, according to the NIH Office of Dietary Supplements. A result of less than 10 to 15 ng/mL in healthy individuals indicates vitamin D deficiency. A normal vitamin D level is 15 ng/mL or above. It is possible to have too much vitamin D in the blood, leading to low calcium levels and high phosphorus levels. If your vitamin D level is consistently above 200 ng/mL, you may have vitamin D toxicity.

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    What Causes Vitamin D Deficiency?

    Vitamin D deficiency occurs as the result of several factors. If you do not consume enough of the vitamin in your diet, or you limit your sun exposure, your blood levels of vitamin D will decrease. Strict vegetarians are at an increased risk for this condition, as vitamin D is found in eggs, liver, fish and cheese. Low vitamin D levels also occur as the result of absorption and conversion problems. Crohn’s disease, celiac disease and other digestive conditions impair your ability to absorb the vitamin in your digestive tract. Since the kidneys convert vitamin D to its active form, kidney damage and kidney diseases also contribute to low vitamin D levels.

    If you don’t have any of these problems, you may still be wondering what causes vitamin D deficiency. The answer may surprise you. Since the fat cells extract vitamin D from the blood, obesity contributes to vitamin D deficiency. WebMD reports that people with a BMI (body mass index) of 30 or greater are at an increased risk of vitamin D deficiency.

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    Risks

    In addition to increased risk for soft bones and osteoporosis, low vitamin D levels increase the risk for cognitive impairment, death from cardiovascular disease, cancer and severe asthma in children. This vitamin may also play a role in controlling hypertension, multiple sclerosis, glucose intolerance and diabetes.