Vitamin D is fat-soluble and occurs in two forms: D-2 and D-3. Vitamin D3 occurs naturally and is made in the skin under direct sunlight and plays a major role in the development and hardening of bones. Low vitamin D or problem with its use leads to weakening of the bone. The liver is important in the processing of vitamin D; several diseases that affect the liver also affect the processing of vitamin D.
The Liver
The liver play a major role in processing vitamin D. When vitamin D is initially made, it is inactive. The liver converts inactive vitamin D to hydroxyvitamin D that is converted to active vitamin D in the kidneys. Diseases such as hepatitis and liver cirrhosis affect the liver's ability to convert inactive vitamin D to hydroxyvitamin D.
Complication
When the liver can't process inactive vitamin D, it causes a deficiency of active vitamin D in the blood. Low blood calcium is a major complication of vitamin D deficiency. Low blood phosphate can also occur in vitamin D deficiency and is the result of increased parathyroid hormone release. The parathyroid hormone is made by the parathyroid gland; it is made in response to low calcium in the blood. In children, vitamin D deficiency causes rickets; children with rickets have abnormal bone development and softening of the bones. In adults the softening of bones is called osteomalacia, which also results from vitamin D deficiency.
Associated Symptoms
Muscle aches and weakness occur in vitamin D deficiency. Low blood calcium often leads to tetany, a condition of uncontrollable muscle contractions. Tetany may cause abnormal sensations in the tongue, lips and fingers. Facial spasms can occur as well. A newborn may experience tetany, if her mother was deficient in vitamin D during pregnancy. Low blood calcium may also lead to seizures.
Assessment and Diagnosis
A simple blood test, ordered by the physician, is needed to diagnose vitamin D deficiency. Adequate history taken by the physician should also provide clues to vitamin D deficiency. The blood is tested for the concentration of active vitamin D or 25OHD. A normal concentration of 25OHD should be above 30 nanograms per milliliter, or ng/mL; if less than 30 ng/mL it is abnormal. A 25OHD concentration less than 20 ng/mL is defined as vitamin D deficiency.
Management
When disease causes vitamin D deficiency, treatment should include addressing the disease, vitamin D supplementation and if possible dietary and lifestyle changes. Vitamin D-3 supplementation is preferred since it exists naturally.
Vitamin D-3 is more effective in elevating active vitamin D, or 25OHD, in the blood. The U.S. Department of Health & Human Services recommends supplementation of vitamin D-3 at doses of 700 to 800 IU per day; it should also be done in conjunction with calcium at doses of 500 to 1,200 mg per day. Dietary modifications should include intake of eggs, fish, vitamin D-fortified milk and cod liver oil; they are abundant sources of vitamin D.
